Influence of route of administration on haloperidol plasma levels in psychotic patients.

Haloperidol plasma concentrations were determined in psychotic patients to whom the drug was given by three different routes of administration (i. v. perfusion, intramuscularly and orally). When measured 15 hours after the last administration, a significant difference (p < 0,001) was found in the steady state plasma concentration between the oral and the i.m. route. The values were higher after intramuscular administration and were subject to less interindividual fluctuation than after the oral. The reduction in plasma levels after oral administration in respect to i.m. were in accordance with the bioavailability of haloperidol. The opportunity of switching from oral to intramuscular treatment is discussed.