Dopamine Agonists
Examples
- Non ergot derivative - ropinirole, pramipexole, rotigotine
- Ergot derivative - cabergoline, pergolide, bromocriptine
In general, non-ergot derivatives are preferred due to a better side effect profile.
Indications
Parkinson's disease - first line or as an adjunct
Treatment of galactorrhoea and prolactinomas
Contraindications
Contraindications
- Hypersensitivity to ergot alkaloids
- Valvular heart disease
Mechanism
Dopamine receptor agonists bind to dopaminergic post-synaptic receptors in the central nervous system and thereby increase dopaminergic neurotransmission.
Oral and transdermal dopamine agonists can be split into ergot dopamine agonists (cabergoline, pergolide, bromocriptine) and non-ergot dopamine agonists (ropinirole, pramipexole, and rotigotine).
They can both be helpful in treating 'off' periods because they have a longer half life than levadopa.
Administration
Oral and transdermal (certain drugs only).
Adverse Reactions
- Nausea, vomiting
- Hypotension
- Psychiatric symptoms - hallucinations, delusions, nightmares
- Sleep disturbance and sudden onset of sleep
- Impulse control disorders - compulsive sexual activity, overeating, gambling.
- Ergot preparations can lead to valvulopathies and pericardial, pulmonary or retroperitoneal fibrotic disease. Patients require an echocardiogram prior to commencing these medications. Consider a doing a chest x-ray and monitoring ESR and creatinine.
Some of these side effects can be treated by giving domperidone (a peripheral dopamine blocker).
Interactions
As a general rule, medications which can cause Parkinsonism (see Management of Parkinson's Disease) should be avoided in Parkinson's disease - this would be a pharmacodynamic interaction.
Education
All patients should be warned of the potential side effect of sudden onset of sleep. This has important implications for driving or operating heavy machinery. Hypotension may also be a problem initially.
Impulse control disorders - patients need to be warned of the potential side effects of compulsive sexual activity, overeating and gambling. If they have had problems with these issues in the past they may decide against using these medications.
Fibrotic changes - patients should be aware that they need to report symptoms of dyspnoea, cough, chest pain, chest or abdominal pain or signs of heart failure.
Drug therapy should not be stopped suddenly due to the small risk of neuroleptic malignant syndrome.
Pharmacokinetics
Nil relevant.
