A trip killer, also known as a hallucinogen antidote or hallucinogen antagonist, is a

drug A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via insufflation (medicine), inhalation, drug i ...

that aborts or reduces the effects of a

hallucinogen Hallucinogens, also known as psychedelics, entheogens, or historically as psychotomimetics, are a large and diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mo ...

experience Experience refers to Consciousness, conscious events in general, more specifically to perceptions, or to the practical knowledge and familiarity that is produced by these processes. Understood as a conscious event in the widest sense, experience i ...

(or 'trip'). As there are different types of hallucinogens that work in different ways, there are different types of trip killers. They can completely block or reduce the effects of hallucinogens, or they can simply provide anxiety relief and

sedation Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure. Examples of drugs which can be used for sedation include isoflurane, diethyl ether, ...

. Examples of trip killers, in the case of

serotonergic psychedelic Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary mental states (known as psychedelic experiences or "trips") and a perceived "expansion of consciousness". Also referred to as classic halluci ...

s, include

serotonin receptor antagonist A serotonin antagonist, or serotonin receptor antagonist, is a drug used to inhibit the action of serotonin and serotonergic drugs at serotonin receptor, serotonin (5-HT) receptors. Types 5-HT2A antagonists Antagonists of the 5-HT2A, 5-HT2A re ...

s, such as

antipsychotic Antipsychotics, previously known as neuroleptics and major tranquilizers, are a class of Psychiatric medication, psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), p ...

s like

risperidone Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder, as well as aggressive and self-injurious behaviors associated with autism spectrum disorder. It is t ...

and

quetiapine Quetiapine ( ), sold under the brand name Seroquel among others, is an atypical antipsychotic medication used in the treatment of schizophrenia, bipolar disorder, bipolar depression, and major depressive disorder. Despite being widely prescri ...

and certain

antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...

s like

trazodone Trazodone is an antidepressant medication used to treat major depressive disorder, anxiety disorders, and insomnia. It is a phenylpiperazine compound of the serotonin antagonist and reuptake inhibitor (SARI) class. The medication is taken or ...

and

mirtazapine Mirtazapine, sold under the brand name Remeron among others, is an atypical antidepressant, atypical tetracyclic antidepressant, and as such is used primarily to treat Depression (mood), depression. Its effects may take up to four weeks but ca ...

, and

benzodiazepine Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant, depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed t ...

s, for instance

diazepam Diazepam, sold under the brand name Valium among others, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is used to treat a range of conditions, including anxiety disorder, anxiety, seizures, alcohol withdrawal syndr ...

and

alprazolam Alprazolam, sold under the brand name Xanax among others, is a fast-acting, potent tranquilizer of moderate duration within the triazolobenzodiazepine group of chemicals called benzodiazepines. Alprazolam is most commonly prescribed in the ...

. Trip killers can be used clinically to manage effects of hallucinogens, like hallucinogenic effects, anxiety, and

psychomotor agitation Psychomotor agitation is a symptom in various disorders and health conditions. It is characterized by unintentional and purposeless motions and restlessness, often but not always accompanied by emotional distress and is always an indicative for ...

, for instance in the

emergency department An emergency department (ED), also known as an accident and emergency department (A&E), emergency room (ER), emergency ward (EW) or casualty department, is a medical treatment facility specializing in emergency medicine, the Acute (medicine), ...

and in the setting of psychedelic therapy. They are also sometimes used by recreational psychedelic users as a form of

harm reduction Harm reduction, or harm minimization, refers to a range of intentional practices and public health policies designed to lessen the negative social and/or physical consequences associated with various human behaviors, both legal and illegal. H ...

to manage "

bad trip A bad trip (also known as challenging experiences, acute intoxication from hallucinogens, psychedelic crisis, or emergence phenomenon) is an acute adverse psychological reaction to the effects of Psychoactive drug, psychoactive substances, namely ...

s" or challenging experiences, for instance emotionally difficult experiences with prominent

anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...

. While used for harm-reduction purposes, this use of trip killers has raised concerns about

safety Safety is the state of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. Meanings The word 'safety' entered the English language in the 1 ...

and possible

adverse effect An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term compli ...

Serotonergic psychedelic antidotes

Serotonin 5-HT_2A receptor antagonists

Serotonergic psychedelic Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary mental states (known as psychedelic experiences or "trips") and a perceived "expansion of consciousness". Also referred to as classic halluci ...

s, such as

psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...

(found in

psilocybin mushroom Psilocybin mushrooms, or psilocybin-containing mushrooms, commonly known as magic mushrooms or as shrooms, are a type of hallucinogenic mushroom and a polyphyletic informal group of fungi that contain the prodrug psilocybin, which turns into t ...

s),

lysergic acid diethylamide Lysergic acid diethylamide, commonly known as LSD (from German ; often referred to as acid or lucy), is a Semisynthesis, semisynthetic, Hallucinogen, hallucinogenic compound derived from ergot, known for its powerful psychological effects and ...

(LSD),

mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...

(found in

peyote The peyote (; ''Lophophora williamsii'' ) is a small, spineless cactus which contains psychoactive alkaloids, particularly mescaline. is a Spanish word derived from the Nahuatl (), meaning "caterpillar cocoon", from a root , "to glisten". p. ...

cactii), and

dimethyltryptamine Dimethyltryptamine (DMT), also known as ''N'',''N''-dimethyltryptamine (''N'',''N''-DMT), is a Psychedelic drug, serotonergic hallucinogen and Investigational New Drug, investigational drug of the substituted tryptamine, tryptamine family tha ...

(DMT) (found in

ayahuasca AyahuascaPronounced as in the UK and in the US. Also occasionally known in English as ''ayaguasca'' (Spanish-derived), ''aioasca'' (Brazilian Portuguese-derived), or as ''yagé'', pronounced or . Etymologically, all forms but ''yagé'' descen ...

), mediate their hallucinogenic effects by acting as

agonist An agonist is a chemical that activates a Receptor (biochemistry), receptor to produce a biological response. Receptors are Cell (biology), cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an R ...

s of the

serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...

5-HT_2A receptor. As a result, serotonin 5-HT_2A receptor

antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain. Accordingly, the serotonin 5-HT_2A receptor antagonists

ketanserin Ketanserin, sold under the brand name Sufrexal, is an antihypertensive agent which is used to treat arterial hypertension and vasospasm, vasospastic disorders. It is also used in scientific research as an antiserotonergic medication, agent in th ...

, an

antihypertensive agent Antihypertensives are a class of medication, drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke, heart failure, kidney failure and myo ...

, and

, an

, have been shown to block the effects of serotonergic psychedelics in

clinical studies Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietar ...

. This includes the effects of psilocybin, LSD, mescaline, and ayahuasca. Ketanserin is under formal clinical investigation as a "neutralizer" or "off-switch" for psychedelics. The more selective serotonin 5-HT_2A receptor antagonist pimavanserin is also being studied as a blocker of the effects of psychedelics. Other potent serotonin 5-HT_2A receptor antagonists that may block or reduce the effects of serotonergic psychedelics besides the above-listed drugs include other antipsychotics like

olanzapine Olanzapine, sold under the brand name Zyprexa among others, is an atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. It is also sometimes used off-label for treatment of chemotherapy-induced nausea and vomitin ...

aripiprazole Aripiprazole, sold under the brand name Abilify, among others, is an atypical antipsychotic primarily used in the treatment of schizophrenia, bipolar disorder, and irritability associated with autism spectrum disorder; other uses include as ...

, and pipamperone, antidepressants like

, mianserin, nefazodone, and etoperidone, and the antimigraine agent pizotifen, among others. The

typical antipsychotic Typical antipsychotics (also known as major tranquilizers, and first generation antipsychotics) are a class of antipsychotic drugs first developed in the 1950s and used to treat psychosis (in particular, schizophrenia). Typical antipsychotics m ...

chlorpromazine Chlorpromazine (CPZ), marketed under the brand names Thorazine and Largactil among others, is an antipsychotic medication. It is primarily used to treat psychotic disorders such as schizophrenia. Other uses include the treatment of bipolar d ...

, which has significant but less-potent serotonin 5-HT_2A receptor antagonism than many other antipsychotics, has shown incomplete and inconsistent effects in reversing psychedelic effects in clinical studies, while the typical antipsychotic

haloperidol Haloperidol, sold under the brand name Haldol among others, is a typical antipsychotic medication. Haloperidol is used in the treatment of schizophrenia, tics in Tourette syndrome, mania in bipolar disorder, delirium, agitation, acute psychos ...

, which is a

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...

D₂ receptor antagonist but not a significant serotonin 5-HT_2A receptor antagonist, is ineffective and has actually been found to increase anxiety and

dysphoria Dysphoria (; ) is a profound state of unease or dissatisfaction. It is the semantic opposite of euphoria. In a psychiatric context, dysphoria may accompany depression, anxiety, or agitation. In psychiatry Intense states of distress and uneas ...

in the setting of psychedelic experiences. In spite of variably acting as serotonin 5-HT_2A receptor antagonists,

tricyclic antidepressant Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants. TCAs were discovered in the early 1950s and were marketed later in the decade. They are named after their chemical structure, which contains ...

s (TCAs), including desipramine,

imipramine Imipramine, sold under the brand name Tofranil, among others, is a tricyclic antidepressant (TCA) mainly used in the treatment of depression. It is also effective in treating anxiety and panic disorder. Imipramine is taken by mouth. Common s ...

, and

clomipramine Clomipramine, sold under the brand name Anafranil among others, is a tricyclic antidepressant (TCA). It is used in the treatment of various conditions, most notably obsessive–compulsive disorder but also many other disorders, including hyper ...

, have paradoxically been reported to potentiate the effects of serotonergic psychedelics rather than diminish them, albeit based on very limited data.

Cyproheptadine Cyproheptadine, sold under the brand name Periactin among others, is a first-generation antihistamine, first-generation antihistamine with additional anticholinergic, antiserotonergic, and local anesthetic properties. It was patented in 1959 a ...

, a non-selective

including of the serotonin 5-HT_2A receptor, is used as an antidote in the treatment of

serotonin syndrome Serotonin syndrome (SS) is a group of symptoms that may occur with the use of certain Serotonin, serotonergic medications or Recreational drug use, drugs. The symptoms can range from mild to severe, and are potentially fatal. Symptoms in mild c ...

(serotonin toxicity) caused by serotonergic drugs, including the toxicity of serotonergic psychedelics like the

NBOMe The 25-NB (25''x''-NB''x'') series, or NBOMe series, also known as the ''N''-benzylphenethylamines, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C (psychedelics), 2C family. The most c ...

drugs. Certain other serotonin receptor antagonists, like chlorpromazine, have also been used for such purposes. Non-hallucinogenic partial agonists of the serotonin 5-HT_2A receptor with sufficiently low

intrinsic activity Intrinsic activity (IA) and efficacy (Emax) refer to the relative ability of a drug- receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind ...

, such as 2-bromo-LSD (bromolysergide; BOL-148) and

lisuride Lisuride, sold under the brand name Dopergin among others, is a monoaminergic medication of the ergoline family which is used in the treatment of Parkinson's disease, migraine, and high prolactin levels. It is taken by mouth. Side effects of l ...

, are effective in blocking the hallucinogenic-related effects of psychedelics in animals and/or humans as well. However, it has been argued that lisuride may actually be a psychedelic or hallucinogen itself at sufficiently high doses in humans. Serotonergic psychedelics are being developed as novel treatments for

psychiatric disorder A mental disorder, also referred to as a mental illness, a mental health condition, or a psychiatric disability, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. A mental disorder is ...

s and other conditions such as depression. A practical limitation in terms of clinical use of many major psychedelics, for instance psilocybin, LSD, and mescaline, is their long durations of action (4–12hours), which may require a whole day of clinical monitoring. In relation to this, shorter-acting psychedelics, like DMT,

5-MeO-DMT 5-MeO-DMT (5-methoxy-''N'',''N''-dimethyltryptamine), also known as ''O''-methylbufotenin or mebufotenin (), is a naturally occurring psychedelic of the tryptamine family. It is found in a wide variety of plant species, and is also secreted by ...

(mebufotenin), and bretisilocin (5-fluoro-MET; GM-2505), are also being investigated for potential therapeutic use. However, an alternative approach that is being investigated is use of serotonin 5-HT_2A receptor antagonists like ketanserin as trip killers to shorten the experiences of psychedelics. In a

clinical trial Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...

, ketanserin given 1hour after LSD shortened its duration from 8.5hours to 3.5hours (by ~60%). It did not modify the

pharmacokinetics Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to describing how the body affects a specific su ...

of LSD, and its

side effect In medicine, a side effect is an effect of the use of a medicinal drug or other treatment, usually adverse but sometimes beneficial, that is unintended. Herbal and traditional medicines also have side effects. A drug or procedure usually use ...

s, such as

nasal congestion Nasal congestion is the partial or complete blockage of nasal passages, leading to impaired nasal breathing, usually due to membranes lining the nose becoming swollen from inflammation of blood vessels. Background In about 85% of cases, nasal ...

, were minimal.

GABA_A receptor positive allosteric modulators

Benzodiazepine Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant, depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed t ...

s, such as

and

, are sometimes used to manage the effects of serotonergic psychedelics, including clinically. They act as

positive allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that ...

s of the GABA_A receptor, and do not specifically antagonize hallucinogenic effects (i.e., are not

antidote An antidote is a substance that can counteract a form of poisoning. The term ultimately derives from the Greek term φάρμακον ἀντίδοτον ''(pharmakon antidoton)'', "(medicine) given as a remedy". An older term in English which is ...

s), but instead have

anxiolytic An anxiolytic (; also antipanic or anti-anxiety agent) is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxie ...

sedative A sedative or tranquilliser is a substance that induces sedation by reducing irritability or Psychomotor agitation, excitement. They are central nervous system (CNS) Depressant, depressants and interact with brain activity, causing its decelera ...

, and memory-impairing effects that can lessen the negative effects of psychedelic experiences.

Alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

, which is also a GABA_A receptor positive allosteric modulator with similar effects, has been used for such purposes as well.

Other agents

Besides serotonin 5-HT_2A receptor antagonists, chronic use of other serotonergic drugs may also diminish the effects of serotonergic psychedelics. Examples include serotonin 5-HT_1A receptor agonists like

buspirone Buspirone, sold under the brand name Buspar among others, is an anxiolytic, a medication primarily used to treat anxiety disorders, particularly generalized anxiety disorder (GAD). It is a serotonin 5-HT1A receptor, 5-HT1A receptor partial ag ...

serotonin reuptake inhibitor A serotonin reuptake inhibitor (SRI) is a type of drug which acts as a reuptake inhibitor of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) by blocking the drug action, action of the serotonin transporter (SERT). This in turn lea ...

s such as

selective serotonin reuptake inhibitor Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions. SSRIs primarily work by blo ...

s (SSRIs) like

fluoxetine Fluoxetine, sold under the brand name Prozac, among others, is an Antidepressant, antidepressant medication of the selective serotonin reuptake inhibitor (SSRI) class used for the treatment of major depressive disorder, Anxiety disorder, anx ...

paroxetine Paroxetine ( ), sold under the brand name Paxil among others, is an Antidepressant, antidepressant medication of the selective serotonin reuptake inhibitor (SSRI) class used to treat major depressive disorder, obsessive-compulsive disorder, o ...

, and

sertraline Sertraline, sold under the brand name Zoloft among others, is an Antidepressant, antidepressant medication of the selective serotonin reuptake inhibitor (SSRI) class used to treat major depressive disorder, generalized anxiety disorder, socia ...

and

serotonin–norepinephrine reuptake inhibitor Serotonin–norepinephrine reuptake inhibitors (SNRIs) are a class of antidepressant medications used to treat major depressive disorder (MDD), anxiety disorders, social phobia, chronic neuropathic pain, fibromyalgia syndrome (FMS), and menopaus ...

s (SNRIs) like

venlafaxine Venlafaxine, sold under the brand name Effexor among others, is an antidepressant medication of the serotonin–norepinephrine reuptake inhibitor (SNRI) class. It is used to treat major depressive disorder, generalized anxiety disorder, pani ...

duloxetine Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, obsessive–compulsive disorder, fibromyalgia, neuropathic pain, central sensitization, and ...

, and

milnacipran Milnacipran (trade names Ixel, Savella, Dalcipran, Toledomin) is a serotonin–norepinephrine reuptake inhibitor (SNRI) used in the clinical treatment of fibromyalgia, Major depressive disorder, and Neuropathic pain. In the US, it is solely appr ...

, and

monoamine oxidase inhibitor Monoamine oxidase inhibitors (MAOIs) are a drug class, class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressa ...

s (MAOIs) such as

phenelzine Phenelzine, sold under the brand name Nardil among others, is a non-selective and irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine family which is primarily used as an antidepressant and anxiolytic to treat depression and a ...

tranylcypromine Tranylcypromine, sold under the brand name Parnate among others, is a monoamine oxidase inhibitor (MAOI). More specifically, tranylcypromine acts as nonselective and irreversible inhibitor of the enzyme monoamine oxidase (MAO). It is used a ...

, and

moclobemide Moclobemide, sold under the brand names Amira, Aurorix, Clobemix, Depnil and Manerix among others, is a reversible inhibitor of monoamine oxidase A (RIMA) drug primarily used to treat Clinical depression, depression and social anxiety. It is not ...

. Buspirone, a

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given Receptor (biochemistry), receptor, but have only partial Intrinsic activity, efficacy at the receptor relative to a full agonist. They may also be considered Ligand (bio ...

of the serotonin 5-HT_1A receptor, has specifically been found to markedly attenuate the visual and certain other effects of psilocybin, although it did not completely block the hallucinogenic effects of psilocybin. The reduced effects of psychedelics in the case of concomitant drugs that elevate serotonin levels may be due to desensitization of serotonin 5-HT_2A receptors. In contrast to earlier studies however, other more recent studies have found that SSRIs like

escitalopram Escitalopram ( ), sold under the brand names Lexapro and Cipralex, among others, is an antidepressant medication of the selective serotonin reuptake inhibitor (SSRI) class. It is mainly used to treat major depressive disorder, generalized ...

may not diminish the hallucinogenic effects of psychedelics like psilocybin and DMT. Instead, in one study, escitalopram resulted in greater

mystical experience A religious experience (sometimes known as a spiritual experience, sacred experience, mystical experience) is a subjective experience which is interpreted within a religious framework. The concept originated in the 19th century, as a defense ag ...

, emotional breakthrough, and

ego dissolution Ego death is a "complete loss of subjective self-identity". The term is used in various intertwined contexts, with related meanings. The 19th-century philosopher and psychologist William James uses the synonymous term "self-surrender", and Jungi ...

scores with DMT than in people not on escitalopram. Although MAOIs can diminish the effects of serotonergic psychedelics, it must be noted that some serotonergic psychedelics, such as DMT, are highly susceptible

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

s for

monoamine oxidase Monoamine oxidases (MAO) () are a family of enzymes that catalyze the oxidation of monoamines, employing oxygen to clip off their amine group. They are found bound to the outer membrane of mitochondria in most cell types of the body. The fi ...

(MAO), and hence can simultaneously be greatly potentiated by MAOIs (as in ayahuasca). The 2C drugs, such as 2C-B,

2C-I 2C-I, also known as 2,5-dimethoxy-4-iodophenethylamine, is a phenethylamine of the 2C family with psychedelic effects. It was first synthesized by Alexander Shulgin, and is described in Shulgin's book ''PiHKAL'' (1991). The substance is con ...

, and

2C-E 2C-E is a Psychedelic drug, psychedelic phenethylamines, phenethylamine of the 2C (psychedelics), 2C family. It was first synthesized by Alexander Shulgin and documented in his book ''PiHKAL''. Like the other substances in its family, it produces ...

, are also notable substrates of both

MAO-A Monoamine oxidase A, also known as MAO-A, is an enzyme ( E.C. 1.4.3.4) that in humans is encoded by the ''MAOA'' gene. This gene is one of two neighboring gene family members that encode mitochondrial enzymes which catalyze the oxidative deamin ...

and

MAO-B Monoamine oxidase B (MAO-B) is an enzyme that in humans is encoded by the ''MAOB'' gene. The protein encoded by this gene belongs to the flavin monoamine oxidase family. It is an enzyme located in the outer mitochondrial membrane. It catalyze ...

, and may likewise be greatly potentiated by MAOIs. High-dose

nicotinic acid Nicotinic acid, or niacin, is an organic compound and a vitamer of vitamin B3, an essential human nutrient. It is produced by plants and animals from the amino acid tryptophan. Nicotinic acid is also a prescription medication. Amounts f ...

(niacin, a B₃

vitamer A vitamer () is any of the related forms in which some vitamin occurs. Each vitamer of a particular vitamin is a compound that performs the functions of that vitamin and prevents the symptoms of deficiency of the vitamin. Early research identifi ...

) was reported to reduce and block the effects of LSD in one early clinical study. However, a subsequent clinical study attempting to replicate the findings found that it was not effective for this purpose. Azacyclonol, a claimed ataractive (i.e., non-antipsychotic

hallucination A hallucination is a perception in the absence of an external stimulus that has the compelling sense of reality. They are distinguishable from several related phenomena, such as dreaming ( REM sleep), which does not involve wakefulness; pse ...

-suppressing medication) that is no longer marketed, likewise seems to be ineffective. Other non-serotonergic drugs that may block or reduce the effects of serotonergic psychedelics based on

animal studies Animal studies is a recently recognised field in which animals are studied in a variety of cross-disciplinary ways. Scholars who engage in animal studies may be formally trained in a number of diverse fields, including art history, anthropology ...

include

AMPA receptor The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA receptor, AMPAR, or quisqualate receptor) is an ionotropic receptor, ionotropic glutamate receptor (iGluR) and predominantly sodium ion channel that mediates fast excitator ...

antagonists, metabotropic glutamate mGlu₂ and mGlu₃ receptor agonists,

μ-opioid receptor The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins. They are also referred to as μ(''mu'')-opioid peptide (MOP) receptors. The prototypical ...

agonists, and

adenosine Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9- glycosidic bond. Adenosine is one of the four nucleoside build ...

A₁ receptor agonists. Some drugs that have been reported to potentiate rather than inhibit the effects of serotonergic psychedelics include

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

reserpine Reserpine is a drug that is used for the treatment of hypertension, high blood pressure, usually in combination with a thiazide diuretic or vasodilator. Large clinical trials have shown that combined treatment with reserpine plus a thiazide diur ...

, pindolol, and methysergide. Pindolol, a

beta blocker Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms ( arrhythmia), and to protect the heart from a second heart attack after a first heart attack ( secondary prevention ...

and serotonin 5-HT_1A receptor antagonist, has been reported to potentiate the hallucinogenic effects of DMT by 2- to 3-fold in humans. A high rate of

seizure A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

s has been reported with the combination of lithium and psychedelics.

Use by recreational psychedelic users

Recreational psychedelic users sometimes employ trip killers to abort psychedelic trips. The most commonly encountered putative trip killers in a 2024 online study of

Reddit Reddit ( ) is an American Proprietary software, proprietary social news news aggregator, aggregation and Internet forum, forum Social media, social media platform. Registered users (commonly referred to as "redditors") submit content to the ...

social media Social media are interactive technologies that facilitate the Content creation, creation, information exchange, sharing and news aggregator, aggregation of Content (media), content (such as ideas, interests, and other forms of expression) amongs ...

postings were the

and

, the antipsychotic

, the

, and

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

. Others used less frequently included the benzodiazepines

lorazepam Lorazepam, sold under the brand name Ativan, Tavor among others, is a benzodiazepine medication. It is used to treat anxiety (including anxiety disorders), insomnia, severe agitation, active seizures including status epilepticus, alcoh ...

clonazepam Clonazepam, sold under the brand name Klonopin among others, is a benzodiazepine medication used to prevent and treat anxiety disorders, seizures, bipolar mania, agitation associated with psychosis, obsessive–compulsive disorder (OCD), and ...

, and etizolam, the antipsychotic

, and the antidepressant

, among others. While employed by recreational users for harm-reduction purposes, the use of trip killers to abort the effects of psychedelics is not fully characterized and could pose medical risks. In addition, doses of trip killers used by recreational psychedelic users may be non-optimal or excessive and increase risks.

Antidotes of other hallucinogens

Cannabinoid Cannabinoids () are several structural classes of compounds found primarily in the ''Cannabis'' plant or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoact ...

CB₁ receptor

antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.rimonabant Rimonabant (also known as SR141716; trade names Acomplia, Zimulti) is an anorectic antiobesity drug approved in Europe in 2006 but was withdrawn worldwide in 2008 due to serious psychiatric side effects; it was never approved in the United State ...

, drinabant, surinabant, and selonabant have been found to block or reduce the psychoactive effects of

cannabinoid Cannabinoids () are several structural classes of compounds found primarily in the ''Cannabis'' plant or as synthetic compounds. The most notable cannabinoid is the phytocannabinoid tetrahydrocannabinol (THC) (delta-9-THC), the primary psychoact ...

s in clinical studies and could be useful as antidotes against

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...

. Likewise, the hallucinogenic and other effects of

κ-opioid receptor The κ-opioid receptor or kappa opioid receptor, abbreviated KOR or KOP for its ligand ketazocine, is a G protein-coupled receptor that in humans is encoded by the ''OPRK1'' gene. The KOR is coupled to the G protein Gi/G0 and is one of four re ...

s like

salvinorin A Salvinorin A is the main active psychotropic molecule in '' Salvia divinorum''. Salvinorin A is considered an atypical dissociative hallucinogen. It is structurally distinct from other naturally occurring hallucinogens (such as DMT, psil ...

(found in ''

Salvia divinorum ''Salvia divinorum'' (; also called ska maría pastora, seer's sage, yerba de la pastora, magic mint or simply salvia) is a species of plant in the sage genus ''Salvia'', known for its transient psychoactive properties when its leaves, or e ...

''),

butorphanol Butorphanol is a morphinan-type synthetic agonist–antagonist opioid analgesic developed by Bristol-Myers. Butorphanol is most closely structurally related to levorphanol. Butorphanol is available as the tartrate salt in injectable, tablet, and ...

, and

pentazocine Pentazocine, sold under the brand name Talwin among others, is an analgesic medication used to treat moderate to severe pain. It is believed to work by activating (agonizing) κ-opioid receptors (KOR) and μ-opioid receptors (MOR). As such it i ...

have been shown to be blocked by the non-selective opioid receptor antagonist

naltrexone Naltrexone, sold under the brand name Revia among others, is a medication primarily used to manage alcohol use or opioid use disorder by reducing cravings and feelings of euphoria associated with substance use disorder. It has also been ...

in clinical studies. Although clinical management of

antimuscarinic A muscarinic acetylcholine receptor antagonist, also simply known as a muscarinic antagonist or as an antimuscarinic agent, is a type of anticholinergic drug that blocks the activity of the muscarinic acetylcholine receptors (mAChRs). The muscarin ...

deliriant Deliriants are a subclass of hallucinogen. The term was coined in the early 1980s to distinguish these drugs from psychedelics such as LSD and dissociatives such as ketamine, due to their primary effect of causing delirium, as opposed to th ...

intoxication and

poisoning Poisoning is the harmful effect which occurs when Toxicity, toxic substances are introduced into the body. The term "poisoning" is a derivative of poison, a term describing any chemical substance that may harm or kill a living organism upon ...

, for instance due to

scopolamine Scopolamine, also known as hyoscine, or Devil's Breath, is a medication used to treat motion sickness and postoperative nausea and vomiting. It is also sometimes used before surgery to decrease saliva. When used by injection, effects begin a ...

, is usually supportive,

acetylcholinesterase inhibitor Acetylcholinesterase inhibitors (AChEIs) also often called cholinesterase inhibitors, inhibit the enzyme acetylcholinesterase from breaking down the neurotransmitter acetylcholine into choline and acetate, thereby increasing both the level an ...

s, such as

physostigmine Physostigmine (also known as eserine from ''éséré'', the West African name for the Calabar bean) is a highly toxic parasympathomimetic alkaloid, specifically, a reversible cholinesterase inhibitor. It occurs naturally in the Calabar bean and ...

, have sometimes been used in this context as well.

s and

s have also been used in such situations. Although trip killers exist for certain types of hallucinogens,

s do not exist for all types of hallucinogens, for instance

NMDA receptor antagonist NMDA receptor antagonists are a class of drugs that work to receptor antagonist, antagonize, or inhibit the action of, the NMDA, ''N''-Methyl-D-aspartate receptor (NMDA receptor, NMDAR). They are commonly used as anesthetics for humans and anima ...

dissociative Dissociatives, colloquially dissos, are a subclass of hallucinogens that distort perception of sight and sound and produce feelings of detachment – dissociation – from the environment and/or self. Although many kinds of drugs are capable of ...

s like

ketamine Ketamine is a cyclohexanone-derived general anesthetic and NMDA receptor antagonist with analgesic and hallucinogenic properties, used medically for anesthesia, depression, and pain management. Ketamine exists as its S- (esketamine) a ...

and

phencyclidine Phencyclidine or phenylcyclohexyl piperidine (PCP), also known in its use as a street drug as angel dust among other names, is a dissociative anesthetic mainly used recreationally for its significant mind-altering effects. PCP may cause hall ...

(PCP).

NMDA receptor The ''N''-methyl-D-aspartate receptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and predominantly Ca2+ ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other ...

agonists, which theoretically could reverse the effects of NMDA receptor antagonists, can produce excitotoxic

neurotoxicity Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specifical ...

and

convulsion A convulsion is a medical condition where the body muscles contract and relax rapidly and repeatedly, resulting in uncontrolled shaking. Because epileptic seizures typically include convulsions, the term ''convulsion'' is often used as a synony ...

s, which restricts their potential medical use. In any case, benzodiazepines can be useful in managing dissociative intoxication, but can also augment

and associated risks. As with NMDA receptor antagonists, there is no antidote for ''

Amanita muscaria ''Amanita muscaria'', commonly known as the fly agaric or fly amanita, is a basidiomycete fungus of the genus ''Amanita''. It is a large white-lamella (mycology), gilled, white-spotted mushroom typically featuring a bright red cap covered with ...

'' intoxication, in which the hallucinogenic GABA_A receptor

muscimol is the active constituent.

Entactogen Entactogens, also known as empathogens or connectogens, are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, connectedness, emotional openness—that is, empathy—as particularly observe ...

s like

MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...

and MDA are generally only mildly hallucinogenic at best, but use of "trip killers" to reverse the effects of these drugs has also been described. Entactogens act primarily as

serotonin releasing agent A serotonin releasing agent (SRA) is a type of drug that induces the release of serotonin into the neuronal synaptic cleft. A selective serotonin releasing agent (SSRA) is an SRA with less significant or no efficacy in producing neurotransmitter ...

s that indirectly activate

serotonin receptor 5-HT receptors, 5-hydroxytryptamine receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels found in multiple tissues including the central and peripheral nervous systems. They mediate both ex ...

s and require entry into serotonergic

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

s via the

serotonin transporter The serotonin transporter (SERT or 5-HTT) also known as the sodium-dependent serotonin transporter and solute carrier family 6 member 4 is a protein that in humans is encoded by the SLC6A4 gene. SERT is a type of monoamine transporter protein t ...

(SERT) to induce their entactogenic effects.

Serotonin reuptake inhibitor A serotonin reuptake inhibitor (SRI) is a type of drug which acts as a reuptake inhibitor of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) by blocking the drug action, action of the serotonin transporter (SERT). This in turn lea ...

s (SRIs), for instance

s (SSRIs) like

and

citalopram Citalopram, sold under the brand name Celexa among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used to treat major depressive disorder, obsessive compulsive disorder, panic disorder, and soci ...

and

s (SNRIs) like

, can markedly block or abolish the serotonin release induced by entactogens by preventing their transport into these neurons, and thus can strongly reduce most of their subjective effects in humans. The serotonin 5-HT_2A receptor

antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.ketanserin Ketanserin, sold under the brand name Sufrexal, is an antihypertensive agent which is used to treat arterial hypertension and vasospasm, vasospastic disorders. It is also used in scientific research as an antiserotonergic medication, agent in th ...

has also been found to partially reduce some of the subjective effects of MDMA, particularly its perceptual effects, whereas the serotonin 5-HT_1A receptor antagonist pindolol was largely ineffective. Non-selective

s like

cyproheptadine Cyproheptadine, sold under the brand name Periactin among others, is a first-generation antihistamine, first-generation antihistamine with additional anticholinergic, antiserotonergic, and local anesthetic properties. It was patented in 1959 a ...

have been used in the clinical management of serotonin toxicity induced by MDMA, for instance in

overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended. Retrieved on September 20, 2014.

or precipitated by

drug interaction In pharmaceutical sciences, drug interactions occur when a drug's mechanism of action is affected by the concomitant administration of substances such as foods, beverages, or other drugs. A popular example of drug–food interaction is the effect ...

s like with

s (MAOIs).

References

External links

Reddit Says Xanax Is the Best “Trip Killer,” But Is It Safe? - Double Blind Magazine

How To Stop A Psychedelic Trip: The Promise of Ketanserin - Psychedelic Science Review (PSR)

Stopping Bad LSD Trips with “Off-Switch” Technology - Psychedelic Science Review (PSR)

Using ‘trip killers’ to cut short bad drug trips is potentially dangerous - The Conversation
{{Recreational drug use Hallucinogen antidotes

Serotonergic psychedelic antidotes

Serotonin 5-HT2A receptor antagonists

GABAA receptor positive allosteric modulators

Other agents

Use by recreational psychedelic users

Antidotes of other hallucinogens

See also

References

External links

Serotonin 5-HT_2A receptor antagonists

GABA_A receptor positive allosteric modulators