Apomorphine directly activates postsynaptic dopamine receptors in the striatum. In contrast to levodopa it is independent of the presynaptic dopaminergic terminals for storage and release1.
Apomorphine is a strong lipophilic compound and its positive motor effect depends on its concentration in the cerebrospinal fluid. Due to the high first pass effect of apomorphine, the bioavailability of the oral formulation is very low. Apomorphine is a substance with a high hepatic clearance, only 3-4% is eliminated unmodified with urine.2
After a subcutaneous injection, the absorption rate depends on the local blood circulation at the injection site and amounts to almost 100%.
Apomorphine is NOT morphine and is NOT addictive.
1 Hagell P, Odin P: Apormorphine in the Treatment of Parkinson's Disease. Journal of Neuroscience Nursing 2001.
2 Neef C, Van Laar T. Pharmacokinetic-pharmacodynamic relationship of apomorphine in patients with Parkinson's disease. Clin Pharmacokinet 1999.