Apomorphine

General information

Apomorphine, a very potent non-selective dopamine agonist, which acts on both D1 and D2 receptors, has been used with some success in Parkinson’s disease, particularly in patients with severe long-term adverse effects of levodopa. Because of first-pass metabolism it has to be used subcutaneously, sublingually, or intranasally. Its adverse effects resemble those of levodopa.

Yawning, somnolence, nausea, and vomiting can all result from the use of apomorphine; they respond to naloxone.

Local reactions to subcutaneous infusion of apomorphine in the nose and throat include swelling of the nose and lips, stomatitis, and buccal mucosal ulceration. Persistent nodules cause major problems in about 10% of patients after 3 or more years. One solution is to give the drug intravenously using an indwelling cannula. Six patients, who had responded well to subcutaneous apomorphine before nodules developed, had such cannulae inserted [ ]. The apomorphine was given at a mean rate of 9.0 mg/hour to a total mean dose of 257 mg/day, very similar to the subcutaneous dosage. The intravenous therapy virtually abolished “off” periods, reduced oral antiparkinsonian drug dosages by 59%, and produced a marked (but unquantified) reduction in dyskinesias and an improved quality of life. However, there were major problems. Two patients receiving high doses of apomorphine (450 and 290 mg/day, in the latter case a deliberate overdose) developed thromboembolic complications, following crystal formation, in one case to the right lung and in the other with obstruction to the superior vena cava. Both required surgical intervention. Both recovered fully, but the authors understandably commented that this therapeutic approach still needs further development.

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