Haloperidol, thioridazine and placebo in mentally subnormal patients – serum levels and clinical effects

A randomized cross-over trial was conducted in 30 restless mentally subnormal patients by increasing the dosage of haloperidol from 10 to 60 mg and that of thioridazine from 100 to 600 mg daily. The clinical effects of drug holidays on placebo and serum drug levels were also examined. There were more relative drug-responders than nonresponders or negative responders. Correlation between clinical response and drug serum levels was poor, probably owing to the heterogeneity of disorders treated. Mesoridazine and other metabolites had 5-6 times higher serum levels than the parent compound, and relatively high serum levels are achieved already with moderate doses. The observed differences between haloperidol and thioridazine treatment were surprisingly few. Serum cholesterol was higher (P less than 0.05) at the end of thioridazine than of the haloperidol administration.