The pharmacokinetic properties of apomorphine in patients with Parkinson's disease are described. Apomorphine is lipophilic; it has a large volume of distribution and is rapidly cleared from plasma, with an elimination half life of 33 minutes. It is rapidly absorbed following subcutaneous injection, with peak levels achieved within 5-10 minutes in most patients. There is a large variation in absorption between patients but is more constant within patients following repeated dosing. Apomorphine rapidly equilibrates between plasma and brain. Like levodopa, the response tends to be largely "all or none"; larger doses produce a longer duration of effect within a 30-90 minute range. Apomorphine may be administered intranasally and sublingually; of these routes, the former is more quickly and completely absorbed. Other routes of administration, including rectally, are not as well absorbed but may also be used effectively.