Effect of oral administration of haloperidol on plasma thyrotropin concentrations in men

To investigate the effects of neuroleptics on plasma thyrotropin (TSH) concentrations, haloperidol tablets were administered orally to 34 normal male volunteers. Seventeen of the subjects received 4 mg; the other 17 received 10 mg. Plasma samples were collected at baseline and 1, 3, 4, 6, 14, 24, 36, 48, 72 and 96 hr after drug administration. Plasma TSH was assayed by a double antibody radioimmunoassay procedure. A significant change in plasma TSH occurred for all subjects (p less than 0.001). By multivariate analysis of variance, the dose x time interaction was not significant. However, a significant dose x time interaction was detected in a univariate analysis. After haloperidol 10 mg a statistically significant rise in TSH occurred at 3-4 hr, which corresponded to the time of attainment of maximal plasma haloperidol concentrations. A significant but modest correlation between plasma haloperidol and TSH was present at 3 hr (0.373; p less than 0.05). TSH concentrations at 14 hr after the 10 mg dose were not significantly correlated with simultaneous or peak plasma haloperidol concentrations. Consequently, only the release of TSH occurring at 3-4 hr after the 10 mg dose was attributed to the drug's effects.