The chemical messenger dopamine plays a critical role in relaying signals in the brain. Damage to the dopamine signaling system causes Parkinson's disease, a progressive neurological disorder that disrupts normal movement and muscle control. Doctors treat Parkinson's disease with drugs that restore function of the dopamine system. Intravenous, or IV, administration of a dopamine-like substance called apomorphine can help some patients with Parkinson's disease, but there are limitations and side effects to consider.
Limited Use
Patients with Parkinson's disease use daily pills to control their symptoms. Often the pills produce "on-off" effects, meaning that they are effective for a time, and then fail to control symptoms. During the "off" periods, patients can suffer severe symptoms and require brief intensive treatments called rescue therapy. Doctors often use apomorphine for rescue therapy. Apomorphine, sold under the brand name Apokyn, mimics the actions of dopamine in the body. Unlike other treatments for Parkinson's disease, doctors give apomorphine directly into the bloodstream over time through an intravenous line known as a "drip." Apomorphine acts very quickly--within 5 to 10 minutes, according to The Merck Manuals Online Medical Library--to restore normal movement, but its effects also wear off very quickly--within 60 to 90 minutes. Patients can receive up to five doses of apomorphine per day.
Pretreatment
Apomorphine causes severe nausea and vomiting, so doctors must give their patients antiemetic drugs to protect against nausea before administering apomorphine. The Merck Manuals Online Medical Library recommends that patients take the antiemetic medication trimethobenzamide three times a day for 3 days before starting apomorphine. Patients must continue taking the antiemetic throughout their treatment with apomorphine.
Blood Pressure
Like other dopamine mimics, apomorphine can cause a significant drop in blood pressure, especially when the patient stands up. The effect can be especially severe with apomorphine because it flows directly into the bloodstream. The Merck Manuals Online Medical Library recommends that doctors give a small test dose of apomorphine and then check blood pressure 20, 40 and 60 minutes later when the patient is lying down and standing up, and then decide on an appropriate dosage to control symptoms, or stop treatment if blood pressure falls too much.
Psychological Effects
Apomorphine and other dopamine-like drugs can cause hallucinations and impulsive behaviors, according to The Merck Manuals Online Medical Library. Patients have been known to have problems with pathological gambling, inappropriate sexual behaviors, hypersexuality and binge eating after apomorphine treatment. Reducing the apomorphine dose can help some patients with these side effects, but others continue to have problems even after they stop treatment.
Other
Other potential side effects of apomorphine include suddenly falling asleep during the day, excessive yawning and dizziness, falling, slow movements, nausea and chest pain. Apomorphine might also increase the risk of melanoma, a form of skin cancer, and fibrosis, or hardening of the lungs.
