After an initial screening, potential participants will undergo a test to verify that they can tolerate and respond to apomorphine. Those who meet all of the requirements will be randomized to receive the study drug via injections (shots) using an injector pen or a portable infusion pump. Apomorphine will be given either continuously using the portable pump during the waking day or intermittently by injection, for 6 months. The pump will be carried on a belt and connected by a tube to a small needle under the skin. Injections of apomorphine under the skin will be self-administered by the participants or administered by friends or family members using injector pens.