Dopamine Receptor Agonists in Parkinson's

Dopamine-receptor agonists work by stimulating post-synaptic dopamine receptors in the nigrostriatal system.¹ They are however associated with increased treatment withdrawal and poorer motor scores. Acute adverse effects are similar to levodopa and occur at the start of treatment and abate over several days to weeks.
The drugs in this group are cabergoline, pergolide, pramipexole,² ropinirole,³ bromocriptine and lisuride (the last two are now used less frequently).⁴

Apomorphine is considered in a separate article.

See Parkinson's Disease Management for further details on drug choice and drug combinations.

• In people with response fluctuations to levodopa, adjuvant dopamine agonists reduce 'off' time, improve motor impairment and activities of daily living and reduce levodopa dose. Dopaminergic adverse effects and dyskinesias are however increased.
• A considerable body of evidence supports their use as first-line therapy, particularly in young people (under 50).

• History of fibrotic disorders - cabergoline,¹⁰ pergolide, bromocriptine and lisuride are all associated with pulmonary, retroperitoneal, and pericardial fibrotic reactions
• Pergolide - cardiac valve disease⁶
• Other drugs - this is a disparate group of drugs - see individual drug monographs for further details

• Fibrotic reactions - see 'Initiation and Monitoring'
• Aggravation of dyskinesia
• Warn patients some drugs in this group can cause sudden onset sleep or low blood pressure in early days (dizziness, care with driving, operating machinery, etc).
• Pregnancy - see individual drug monographs
• Breast feeding - many in this group may suppress lactation
• Previous pituitary tumour (lisuride and bromocriptine)^9,11
• See also individual drugs for warnings which are not group-specific

• The effectiveness of these drugs are diminished by neuroleptics and other centrally active dopamine antagonists (such as phenothiazines, butyrophenones, thioxanthenes, metoclopramide), so concomitant use should be avoided.^3,10
• See individual drug monographs for other interactions

Adverse effects similar to levodopa, occur early in treatment, and abate over several days or weeks. They include nausea, vomiting, hypotension, and psychiatric symptoms (including hallucinations and hypersexuality).

• Early referral to specialist before prescribing is now considered good practice , in view of diagnostic difficulties, complicated list of contraindications, cautions, and long-term risks of aggravating rather than helping condition long-term.
• Once initiated, increase gradually. If treatment withdrawal necessary, tail off gradually.

• Cabergoline, pergolide, bromocriptine, lisuride - monitor for signs/symptoms of fibrotic reactions - dyspnoea, persistent cough, chest pain, cardiac failure, and abdominal pain or tenderness. Lung function tests may be needed long-term.
• Monitor early to check for postural hypotension