Interaction of haloperidol plasma level and antipsychotic effect in early phases of acute psychosis treatment.

The definition of the best combination of "when" and "how much" of haloperidol dosing during acute psychotic illness still represents a challenge. Randomized controlled trials can hardly account for the high variability of dose x timing of dose increase strategies that can be applied in everyday practice. We conducted an observational study in order to study and evaluate the naturalistic strategies of haloperidol oral administration in a sample of 101 acutely ill psychotic patients. Out of this sample, 82 patients had complete data on PANSS scores and 50 patients had data on the haloperidol plasma levels. In accordance with previous evidence, we found that improvement during the first two weeks of treatment was a significant predictor of response (t=6.94, p=2.11E-08). On this note, increasing the haloperidol doses over 6.64+/-2.08 mg/day on average from the second to the third week of treatment in those patients who did not respond to treatment during the first two weeks of treatment was of no use for further amelioration. This cutoff was associated with treatment efficacy but not with the incidence of side effects. In conclusion a moderate dose of haloperidol is suggested in the first two weeks, in case of non response a dose increase is of no further benefit. This finding could contribute to tailor more individualized treatment and highlights the need for early detection of non-responders.