A dopamine agonist is a compound that activates dopamine receptors in the absence of that receptor's physiological ligand, the neurotransmitter dopamine. Dopamine agonists activate signaling pathways through the dopamine receptor and trimeric G-proteins, ultimately leading to changes in gene transcription.
Some medical drugs act as dopamine agonists and can treat hypodopaminergic (low dopamine) conditions; they are typically used for treating Parkinson's disease, attention deficit/hyperactivity disorder (in the form of stimulants) and certain pituitary tumors (prolactinoma), and may be useful for restless legs syndrome (RLS). Both Requip (Ropinirole) and Mirapex (Pramipexole) are FDA-approved for the treatment of RLS. There is also an ongoing clinical trial to test the effectiveness of the dopamine agonist Requip (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).
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
Examples of dopamine agonists include:
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)
Apomorphine (Apokyn) (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Bromocriptine (Parlodel) (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Cabergoline (Dostinex) (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Ciladopa (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Dihydrexidine (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Dinapsoline (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Doxanthrine (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Epicriptine (Similar to those of Bromocriptine) (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Lisuride (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Pergolide (Dopamine Agonist for Parkinson's disease/Restless leg syndrome) (Permax) - Removed from the market in the USA March 29, 2007.
Piribedil (Dopamine Agonist for Parkinson's disease/Restless leg syndrome) (Pronoran and Trivastal)
Pramipexole (Dopamine Agonist for Parkinson's disease/Restless leg syndrome) (Mirapex and Sifrol)
Propylnorapomorphine (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Quinagolide (Norprolac) (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Ropinirole (Dopamine Agonist for Parkinson's disease/Restless leg syndrome) (Requip)
Rotigotine (Dopamine Agonist for Parkinson's disease/Restless leg syndrome) (Neupro)
Roxindole (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Sumanirole (Dopamine Agonist for Parkinson's disease/Restless leg syndrome)
Some, such as fenoldopam, are selective for dopamine receptor D1.
