pharmacology Pharmacology is the science of drugs and medications, including a substance's origin, composition, pharmacokinetics, pharmacodynamics, therapeutic use, and toxicology. More specifically, it is the study of the interactions that occur betwee ...

, partial agonists are drugs that bind to and activate a given

receptor Receptor may refer to: * Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and respond ...

, but have only partial

efficacy Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as '' effectiveness'', and it has often been used synonymously, although in pharmacology a distinction is now often made betwee ...

at the receptor relative to a

full agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agoni ...

. They may also be considered

ligands In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...

which display both agonistic and

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.competitive antagonist A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of recep ...

, competing with the full agonist for receptor occupancy and producing a net decrease in the receptor activation observed with the full agonist alone. Clinically, partial agonists can be used to activate receptors to give a desired submaximal response when inadequate amounts of the endogenous ligand are present, or they can reduce the overstimulation of receptors when excess amounts of the endogenous ligand are present. Some currently common drugs that have been classed as partial agonists at particular receptors include

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 ...

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 ...

, buprenorphine,

nalmefene Nalmefene, sold under the brand name Revex among others, is a medication that is used in the treatment of opioid overdose and alcohol dependence. Nalmefene belongs to the class of opioid antagonists and can be taken by mouth, administered by ...

and norclozapine. Examples of ligands activating

peroxisome proliferator-activated receptor gamma Peroxisome proliferator-activated receptor gamma (PPAR-γ or PPARG), also known as the glitazone reverse insulin resistance receptor, or NR1C3 (nuclear receptor subfamily 1, group C, member 3) is a type II nuclear receptor functioning as a transc ...

as partial agonists are

honokiol Honokiol is a lignan Bark isolate, isolated from the bark, seed cones, and leaves of trees belonging to the genus ''Magnolia''. It has been identified as one of the chemical compounds in some traditional Eastern herbal medicines along with magnolo ...

and

falcarindiol Falcarindiol is a polyyne found in carrot roots which has antifungal activity. Falcarindiol is the main compound responsible for bitterness in carrots. Falcarindiol and other falcarindiol-type polyacetylenes are also found in many other plants of ...

. Delta 9-tetrahydrocannabivarin ( THCV) is a partial agonist at CB2 receptors and this activity might be implicated in ∆9-THCV-mediated

anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation, fever or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs reduce pain by inhibiting mechan ...

effects. Additionally, Delta-9-Tetrahydrocannabinol ( THC) is a partial agonist at both the CB1 and CB2 receptors, with the former being responsible for its psychoactive effects.

References

Pharmacodynamics {{pharmacology-stub

See also

References