Aripiprazole (Abilify), an antipsychotic drug approved by the FDA in 2002, holds special interest because of the unique way it works and the possibility that it will have a low rate of side effects. It works neither like the older conventional antipsychotics such as haloperidol (Haldol) and chlorpromazine (Thorazine), nor like the novel drugs — clozapine (Clozaril), risperidone (Risperdal), and others — that are replacing them.
Aripiprazole prevents hallucinations and delusions by acting in the limbic system, the part of the brain that is a center for emotions. It also prevents the development of movement disorders — including akathisia (compulsive pacing and fidgeting) and parkinsonism (tremors, stiff posture, a hesitant walk, and an expressionless face) — by acting in the extrapyramidal system.
So far, aripiprazole seems to be free of some of the side effects that create problems for many patients taking other antipsychotic drugs. In tests to date, it has had little effect on heart rhythms or blood sugar regulation. And it has not caused much weight gain or raised levels of the hormone prolactin, which can cause breast development in men and sexual problems in men and women.
In clinical trials involving nearly 6,000 patients, the most common side effects of the drug have been headache, anxiety, insomnia, nausea, and constipation. It may cause some people to feel dizzy when standing or sitting up (orthostatic hypotension). But side effects have not caused patients taking aripiprazole to drop out of studies at a higher rate than those taking a placebo.
In a year-long study, aripiprazole proved to be more effective than haloperidol for negative schizophrenic symptoms — apathy, restricted emotional range, and inability to feel pleasure. But most clinical trials have been short-term, lasting several months at most. The long-term risks and benefits of aripiprazole will become clearer when patients and the people who care for them have more everyday experience with it.