Clinical review and treatment of select adverse effects of dopamine receptor agonists in Parkinson's disease.

Dopamine receptor agonists provide a viable alternative or adjunct to levodopa therapy in Parkinson's disease and are associated with fewer motor complications and dyskinesia. However, all available dopamine agonists may cause profound adverse effects in some patients. In many cases, these adverse effects amplify non-motor symptoms that people with Parkinson's disease may already be experiencing. Nausea from dopamine agonists generally lessens with time and may be responsive to both antiemetic therapy and complementary remedies, such as ginger, peppermint and chamomile. Unfortunately, compulsive behaviours, as well as peripheral oedema caused by dopamine agonists, are poorly responsive to pharmacological therapy and require a reduction or discontinuation of agonist therapy. Somnolence and associated sleep attacks generally require elimination of the agonist or the use of a stimulating agent. The necessity of treatment for hallucinations and psychosis associated with dopamine agonists must be thoroughly evaluated prior to initiating therapy. If a medication is initiated for hallucinations or psychosis, quetiapine or clozapine are agents of choice. Orthostatic hypotension, though not always symptomatic, responds well to nonpharmacological strategies and medications, including indometacin, midodrine and fludrocortisone. Care must be taken to educate patients with Parkinson's disease about the common adverse effects of dopamine agonists and what can be done to lessen them.