Relationships between psychotropic drug dosage, plasma drug concentration,and prolactin levels in nursing home residents

This study aimed to characterize the relationships between administered dos ages of psychotropic drugs, plasma drug concentration, and prolactin levels in a group of elderly nursing home residents. Tn a randomized, placebo-con trolled, double-blind crossover design study, blood samples were drawn from 47 nursing home residents at least 6 hours after taking either haloperidol , thioridazine, or lorazepam. Correlations between drug dosage and plasma d rug levels were significant for haloperidol and thioridazine, but not for l orazepam. Plasma drug levels were below the levels of detection for most of those taking haloperidol. Lorazepam was detected in the blood of 4 of the participants even after 3 weeks of downward titration to placebo and 6 week s of placebo. Prolactin level was related to administered dosage only in th ose who were taking haloperidol. For those taking haloperidol or thioridazi ne, prolactin levels decreased when participants were on placebo. When an o lder person is taken off lorazepam, the possibility of residual drug in the ir bodies even 6 weeks after termination of drug use should be considered. Haloperidol may be clinically active in the brain despite no currently dete ctable plasma drug concentration.