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 prescribed as a sleep aid due to its tranquillizing effects, the benefits of such use may not outweigh the risk of undesirable side effects. It is taken orally.

Common side effects include sedation, fatigue, weight gain, constipation, and dry mouth. Other side effects include low blood pressure with standing, seizures, high blood sugar, tardive dyskinesia, and neuroleptic malignant syndrome. In older people with dementia, its use increases the risk of death. Use in the third trimester of pregnancy may result in a movement disorder in the baby for some time after birth. Quetiapine is believed to work by blocking a number of receptors, including those for serotonin and dopamine.

Quetiapine was developed in 1985 and was approved for medical use in the United States in 1997. It is available as a generic medication. In 2022, it was the most prescribed antipsychotic and 82nd most commonly prescribed medication in the United States, with more than 8million prescriptions. It is on the World Health Organization's List of Essential Medicines.

The drug is typically among two antipsychotics (the other being olanzapine) to have superior efficacy for the treatment of bipolar disorder. Quetiapine is currently one of only two antipsychotics (the other of which is cariprazine) that produce equal efficacy as a standalone therapy for mixed manic-depressive mood swings as it is when used in combination with an SSRI antidepressant. However, quetiapine is less potent than clozapine, amisulpride, olanzapine, risperidone, and paliperidone, respectively, in alleviating psychotic symptoms or treating schizophrenia.

Medical uses

Quetiapine is primarily used to treat schizophrenia or bipolar disorder. Quetiapine targets both positive and negative symptoms of schizophrenia.

Schizophrenia

A 2013 Cochrane review compared quetiapine to typical antipsychotics:

In a 2013 comparison of 15 antipsychotics in effectiveness in treating schizophrenia, quetiapine demonstrated standard effectiveness. It was 13–16% more effective than ziprasidone, chlorpromazine, and asenapine and approximately as effective as haloperidol and aripiprazole.

There is tentative evidence of the benefit of quetiapine versus placebo in schizophrenia; however, definitive conclusions are not possible due to the high rate of attrition in trials (greater than 50%) and the lack of data on economic outcomes, social functioning, or quality of life.

It is debatable whether, as a class, typical or atypical antipsychotics are more effective. Both have equal drop-out and symptom relapse rates when typicals are used at low to moderate dosages. While quetiapine has lower rates of extrapyramidal side effects, there is greater sleepiness and rates of dry mouth.

A Cochrane review comparing quetiapine to other atypical antipsychotic agents tentatively concluded that it may be less efficacious than olanzapine and risperidone; produce fewer movement related side effects than paliperidone, aripiprazole, ziprasidone, risperidone and olanzapine; and produce weight gain similar to risperidone, clozapine and aripiprazole. They concluded that it produces suicide attempt, suicide; death; QTc prolongation, low blood pressure; tachycardia; sedation; gynaecomastia; galactorrhoea, menstrual irregularity and decline in white blood cell count at a rate similar to first generation antipsychotics.

Bipolar disorder

In those with bipolar disorder, quetiapine is used to treat depressive episodes; acute manic episodes associated with bipolar I disorder (as either monotherapy or adjunct therapy to lithium; valproate or lamotrigine); acute mixed episodes; and maintenance treatment of bipolar I disorder (as adjunct therapy to lithium or divalproex).

Major depressive disorder

Quetiapine is effective when used by itself and when used along with other medications in major depressive disorder (MDD). However, sedation is often an undesirable side effect.

In the United States, the United Kingdom and Australia (while not subsidised by the Australian Pharmaceutical Benefits Scheme for treatment of MDD), quetiapine is licensed for use as an add-on treatment in MDD.

Alzheimer's disease

Quetiapine does not decrease agitation among people with Alzheimer's disease. Quetiapine worsens intellectual functioning in the elderly with dementia and therefore is not recommended.

Insomnia

The use of low doses of quetiapine for insomnia, while common, is not recommended; there is little evidence of benefit and concerns regarding adverse effects. A 2022 network meta-analysis of 154 double-blind, randomized controlled trials of drug therapies vs. placebo for insomnia in adults found that quetiapine did not demonstrate any short-term benefits in sleep quality. Quetiapine, specifically, had an effect size ( standardized mean difference) against placebo for treatment of insomnia of 0.05 (95% –1.21 to 1.11) at 4weeks of treatment, with the certainty of evidence rated as very low. Doses of quetiapine used for insomnia have ranged from 12.5 to 800mg, with low doses of 25 to 200mg being the most typical. Regardless of the dose used, some of the more serious adverse effects may still possibly occur at the lower dosing ranges, such as dyslipidemia and neutropenia. These safety concerns at low doses are corroborated by Danish observational studies that showed use of specifically low-dose quetiapine (prescriptions filled for tablet strengths >50 mg were excluded) was associated with an increased risk of major cardiovascular events as compared to use of Z-drugs, with most of the risk being driven by cardiovascular death. Laboratory data from an unpublished analysis of the same cohort also support the lack of dose-dependency of metabolic side effects, as new use of low-dose quetiapine was associated with a risk of increased fasting triglycerides at 1-year follow-up.

Others

It is sometimes used off-label, often as an augmentation agent, to treat conditions such as Tourette syndrome, musical hallucinations and anxiety disorders.

Quetiapine and clozapine are the most widely used medications for the treatment of Parkinson's disease psychosis due to their relatively low extrapyramidal side-effect liability. Owing to the risks associated with clozapine (e.g. agranulocytosis, diabetes mellitus, etc.), clinicians often attempt treatment with quetiapine first, although the evidence to support quetiapine's use for this indication is significantly weaker than that of clozapine.

Adverse effects

Sources for incidence lists:

;Very common (>10% incidence) adverse effects
* Dry mouth
* Dizziness
* Headache
* Somnolence (drowsiness; of 15 antipsychotics quetiapine causes the 5th most sedation. Extended release (XR) formulations tend to produce less sedation, dose-by-dose, than the immediate release formulations.)

;Common (1–10% incidence) adverse effects

* High blood pressure
* Orthostatic hypotension
* High pulse rate
* High blood cholesterol
* Elevated serum triglycerides
* Abdominal pain
* Constipation
* Increased appetite
* Vomiting
* Increased liver enzymes
* Backache
* Asthenia
* Insomnia
* Lethargy
* Tremor
* Agitation
* Nasal congestion
* Pharyngitis
* Fatigue
* Pain
* Dyspepsia (Indigestion)
* Peripheral oedema
* Dysphagia

* Extrapyramidal disease: Quetiapine and clozapine are noted for their relative ''lack'' of extrapyramidal side effects.
* Weight gain: SMD 0.43 kg when compared to placebo. Produces roughly as much weight gain as risperidone, less weight gain than clozapine, olanzapine and zotepine and more weight gain than ziprasidone, lurasidone, aripiprazole and asenapine. As with many other atypical antipsychotics, this action is likely due to its actions at the H₁ histamine receptor and 5-HT_2C receptor.

;Rare (<1% incidence) adverse effects

* Prolonged QT interval (had an odds ratio for prolonging the QT interval over placebo of 0.17)
* Sudden cardiac death
* Syncope
* Diabetic ketoacidosis
* Restless legs syndrome
* Hyponatraemia, low blood sodium.
* Jaundice, yellowing of the eyes, skin and mucous membranes due to an impaired ability of the body to clear bilirubin, a by product of haem breakdown.
* Pancreatitis, pancreas swelling.
* Agranulocytosis, a potentially fatal drop in white blood cell count.
* Leukopenia, a drop in white blood cell count, not as severe as agranulocytosis.
* Neutropenia, a drop in neutrophils, the cell of the immune cells that defends the body against bacterial infections.
* Eosinophilia
* Anaphylaxis, a potentially fatal allergic reaction.
* Seizure
* Hypothyroidism, underactive thyroid gland. Common among bipolar patients; quetiapine increases incidence.
* Myocarditis, swelling of the myocardium.
* Cardiomyopathy
* Hepatitis, swelling of the liver.
* Suicidal ideation
* Priapism. A prolonged and painful erection.
* Stevens–Johnson syndrome. A potentially fatal skin reaction.

* Neuroleptic malignant syndrome a rare and potentially fatal complication of antipsychotic drug treatment. It is characterised by the following symptoms: tremor, rigidity, hyperthermia, tachycardia, mental status changes (e.g. confusion), etc.
* Tardive dyskinesia. A rare and often irreversible neurological condition characterised by involuntary movements of the face, tongue, lips and rest of the body. Most commonly occurs after prolonged treatment with antipsychotics. It is believed to be particularly uncommon with atypical antipsychotics, especially quetiapine and clozapine

Both typical and atypical antipsychotics can cause tardive dyskinesia. According to one study, rates are lower with the atypicals at 3.9% as opposed to the typicals at 5.5%. Although quetiapine and clozapine are atypical antipsychotics, switching to these atypicals is an option to minimize symptoms of tardive dyskinesia caused by other atypicals.

Weight gain can be a problem for some, with quetiapine causing more weight gain than fluphenazine, haloperidol, loxapine, molindone, olanzapine, pimozide, risperidone, thioridazine, thiothixene, trifluoperazine, and ziprasidone, but less than chlorpromazine, clozapine, perphenazine, and sertindole.

As with some other anti-psychotics, quetiapine may lower the seizure threshold, and should be taken with caution in combination with drugs such as bupropion.

Discontinuation

The British National Formulary recommends a gradual withdrawal when discontinuing antipsychotics to avoid acute withdrawal syndrome or rapid relapse. Symptoms of withdrawal commonly include nausea, vomiting, and loss of appetite. Other symptoms may include restlessness, increased sweating, and trouble sleeping. Less commonly there may be a feeling of the world spinning, numbness, or muscle pains. Symptoms generally resolve after a short period of time.

There is tentative evidence that discontinuation of antipsychotics can result in psychosis. It may also result in reoccurrence of the condition that is being treated. Rarely tardive dyskinesia can occur when the medication is stopped.

Pregnancy and lactation

Placental exposure is least for quetiapine compared to other atypical antipsychotics. The evidence is insufficient to rule out any risk to the foetus but available data suggests it is unlikely to result in any major foetal malformations. It is secreted in breast milk and hence quetiapine-treated mothers are advised not to breastfeed.

Abuse potential

In contrast to most other antipsychotic drugs, which tend to be somewhat aversive and often show problems with patient compliance with prescribed medication regimes, quetiapine is sometimes associated with drug misuse and abuse potential, for its hypnotic and sedative effects. It has a limited potential for misuse, usually only in individuals with a history of polysubstance abuse and/or mental illness, and especially in those incarcerated in prisons or secure psychiatric facilities where access to alternative intoxicants is more limited. To a significantly greater extent than other atypical antipsychotic drugs, quetiapine was found to be associated with drug-seeking behaviors, and to have standardised street prices and slang terms associated with it, either by itself or in combination with other drugs (such as "Q-ball" for the intravenous injection of quetiapine mixed with cocaine). The pharmacological basis for this distinction from other second generation antipsychotic drugs is unclear, though it has been suggested that quetiapine's comparatively lower dopamine receptor affinity and strong antihistamine activity might mean it could be regarded as more similar to sedating antihistamines in this context. While these issues have not been regarded as sufficient cause for placing quetiapine under increased legal controls, prescribers have been urged to show caution when prescribing quetiapine to individuals with characteristics that might place them at increased risk for drug misuse.

Overdose

Most instances of acute overdosage result in only sedation, hypotension and tachycardia, but cardiac arrhythmia, coma and death have occurred in adults. Serum or plasma quetiapine concentrations are usually in the 1–10 mg/L range in overdose survivors, while postmortem blood levels of 10–25 mg/L are generally observed in fatal cases. Non-toxic levels in postmortem blood extend to around 0.8 mg/kg, but toxic levels in postmortem blood can begin at 0.35 mg/kg.

Pharmacology

Pharmacodynamics

Quetiapine has the following pharmacological actions:

* Dopamine D₁, D₂, D₃, D₄, and D₅ receptor antagonist 5-HT_1A receptor partial agonist, 5-HT_2A, 5-HT_2B, 5-HT_2C, 5-HT₃, 5-HT₆, and 5-HT₇ receptor antagonist

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