A dopamine receptor agonist is a compound that activates dopamine receptors. Dopamine receptor agonists activate signaling pathways through trimeric G-proteins and ?-arrestins, ultimately leading to changes in gene transcription.
Today, for several dopamine receptor subtypes (D1, D2, D3) agonists are known, that differentially address these signalling pathways. They are called biased agonists.
Video Dopamine agonist
Uses
Some medical drugs act as dopamine agonists and can treat hypodopaminergic (low dopamine) conditions; they are typically used for treating Parkinson's disease (PD), Attention deficit hyperactivity disorder (in the form of stimulants) and certain pituitary tumors (prolactinoma), and may be useful for restless legs syndrome (RLS). Both ropinirole and pramipexole are FDA-approved for the treatment of RLS. There is also an ongoing clinical trial to test the effectiveness of the dopamine agonist ropinirole in reversing the symptoms of SSRI-induced sexual dysfunction. Additionally, a systematic review and meta-analysis concluded that prophylactic treatment with cabergoline reduces the incidence, but not the severity, of ovarian hyperstimulation syndrome (OHSS), without compromising pregnancy outcomes, in females undergoing stimulated cycles of in vitro fertilization (IVF).
Maps Dopamine agonist
Side effects
Some of the common side effects of dopamine agonists include:
- Euphoria
- Pericardial effusion
- Fibrous thickening of lining that covers some of the internal organs including the heart or the lungs (fibrotic reaction)
- Hallucinations
- Causing or worsening psychosis
- Orthostatic hypotension
- Increased orgasmic intensity
- Weight loss
- Anorexia (symptom)
- Nausea and possible vomiting
- Insomnia
- Unusual tiredness or weakness
- Dizziness
- Drowsiness
- Possible Narcolepsy manifestations (Sleep attacks)
- Lightheadedness
- Raynaud's phenomenon (common side effect of ergot derivatives)
- Syncope
- Twitching, twisting, or other unusual body movements
- Pathological addiction (gambling, shopping, internet pornography, hyper-sexuality) - specifically D3-preferring agonists
- After long-term use of dopamine agonists, a withdrawal syndrome may occur, during dose reduction or discontinuation, with the following possible side effects: anxiety, panic attacks, dysphoria, depression, agitation, irritability, suicidal ideation, fatigue, orthostatic hypotension, nausea, vomiting, diaphoresis, generalized pain, and drug cravings. For some individuals, these withdrawal symptoms are short-lived and make a full recovery, for others a protracted withdrawal syndrome may occur with withdrawal symptoms persisting for months or years.
Examples
Examples of dopamine agonists include:
Partial agonist
- Aripiprazole (Partial agonist of the D2 family receptors - Trade name "Abilify" in the United States; atypical antipsychotic)
- Phencyclidine (a.k.a. PCP; partial agonist. Psychoactivity mainly due to NMDA antagonism)
- Quinpirole (Partial agonist of the D2 and D3 family of receptors)
- Salvinorin A (chief active constituent of the psychedelic herb salvia divinorum, the psychoactivity of which is mainly due to Kappa-opioid receptor agonism; partial agonist at the D2 with an Intrinsic activity of 40-60%, binding affinity of Ki=5-10nM and EC50=50-90nM)
Agonists of full/unknown efficacy
- Apomorphine (Apokyn - used to treat Parkinson's disease/Restless leg syndrome) - G-protein bias at the D1 receptor.
- Bromocriptine (Parlodel - used to treat PD/RLS)
- Cabergoline (Dostinex - used to treat PD/RLS)
- Ciladopa (used to treat PD/RLS)
- Dihydrexidine (used to treat PD/RLS)
- Dinapsoline (used to treat PD/RLS)
- Doxanthrine (used to treat PD/RLS)
- Epicriptine (used to treat PD/RLS)
- Lisuride (used to treat PD/RLS)
- Pergolide (used to treat PD/RLS) - previously available as Permax, but removed from the market in the USA on March 29, 2007.
- Piribedil (Pronoran and Trivastal - used to treat PD/RLS)
- Pramipexole (Mirapex and Sifrol - used to treatPD/RLS)
- Propylnorapomorphine (used to treat PD/RLS)
- Quinagolide (Norprolac - used to treat PD/RLS)
- Ropinirole (Requip - used to treat PD/RLS)
- Rotigotine (Neupro - used to treat PD/RLS)
- Roxindole (used to treat PD/RLS)
- Sumanirole (used to treat PD/RLS)
Some, such as fenoldopam, are selective for dopamine receptor D1.
Indirect agonists
There are two classes of drugs that act as indirect agonists of dopamine receptors: dopamine reuptake inhibitors and dopamine releasing agents.
The most commonly prescribed indirect agonists of dopamine receptors include:
- Amphetamine and/or dextroamphetamine (used to treat ADHD, narcolepsy, and obesity)
- Bupropion (used to facilitate smoking cessation and treat nicotine addiction and clinical depression)
- Lisdexamfetamine (used to treat ADHD and binge eating disorder)
- Methylphenidate or dexmethylphenidate (used to treat ADHD and narcolepsy)
Other examples include:
- Cathinone (no medical uses)
- Cocaine (no medical uses as a central nervous system stimulant)
- Methamphetamine (used in rare circumstances to treat ADHD and obesity)
- Phenethylamine (endogenous trace amine with no medical uses)
- p-Tyramine (endogenous trace amine with no medical uses)
See also
- Dopamine antagonist
- Dopamine reuptake inhibitor
- Receptor agonist
- GABA receptor agonist
- Dopaminergic
- Serotonin agonist
- Adrenergic agonist (sympathomimetic)
- Parasympathomimetic drug (acetylcholine agonist)
- Histamine agonist
References
- Avanzi M, Uber E, Bonfa F. Pathological gambling in two patients on dopamine replacement therapy for Parkinson's disease. Neurol Sci 2004; 25:98-101[Medline]
External links
- Dopamine Agonists at the US National Library of Medicine Medical Subject Headings (MeSH)
Source of article : Wikipedia
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