The only exception is Eli Lilly and Co.'s Zyprexa, which may be better than the other medicines. Apart from being the most expensive drug, the study found Zyprexa users experienced dramatic weight gain and developed a higher risk of diabetes.
Financed by the National Institute of Mental Health and slated for publication in Thursday's New England Journal of Medicine
Results should help doctors choose the best therapy for the 3.2 million Americans suffering from schizophrenia, the tough-to-treat mental illness marked by delusions, hallucinations and confused thoughts.
Because the effectiveness of a drug may vary from person to person, side effects could force patients to stop taking medication or cause doctors to switch between medicines, altering dosages to find the best, most tolerable treatment.
The study gauged a drug's effectiveness based on the amount of time patients stayed on it. In all, 74 percent of the 1,432 volunteers at 57 study sites stopped taking the medication they were originally assigned.
Only those taking Zyprexa, also known as olanzapine, stuck with it significantly longer than the other four. But even 64 percent stopped taking it after 18 months.
The discontinuation rate was higher among the other four drugs: Seroquel (quetiapine) from AstraZeneca Plc; Risperdal (risperidone) from Janssen Pharmaceutica; Geodon (ziprasidone) from Pfizer Inc., and perphenazine, which has been around since the 1950s and is available in generic form.
Researchers also found that people on Zyprexa were less likely to be hospitalized for a psychotic relapse.
While 15 to 20 percent of patients taking the other drugs ended up in a hospital because their condition worsened, the rate was only 11 percent for Zyprexa recipients.
The study found perphenazine's side effects were surprisingly uncommon. These included tremor, rigidity, stiff movements and muscle restlessness. Patients tolerated it just as well as some of the newer drugs, and it was no less effective. It is also far cheaper.
At the average doses used in the study, a month's supply of perphenazine capsules costs about $50 -- compared with roughly $390 for Geodon, $425 for Risperdal, $475 for Seroquel, and $660 for Zyprexa.
