• dose-proportionality;
  • long-acting injectable;
  • paliperidone palmitate;
  • schizophrenia


Paliperidone palmitate (PP) is a long-acting injectable (LAI) antipsychotic, developed for monthly intramuscular (i.m.) administration into deltoid/gluteal muscle, approved for the treatment of schizophrenia in many countries. To assess the options for i.m. injection sites, dose-proportionality of PP was investigated after injection of a single dose (25–150 mg eq.) of PP in either gluteal (n = 106) or deltoid (n = 95) muscle of schizophrenic patients. Overall, mean (geometric) area under plasma concentration–time curve from time zero to infinity (AUC) of paliperidone increased proportionally with increasing PP doses, regardless of injection site. Mean maximum plasma concentration (Cmax) was slightly less than dose-proportional for both injection sites at PP doses >50 mg eq. Mean Cmax was higher after injection in the deltoid compared with the gluteal muscle, except for the 100 mg eq. dose, while AUC for both injection sites was comparable at all doses. Median time to reach Cmax (tmax) ranged from 13–14 days after deltoid and 13–17 days after gluteal injection across all doses. Single PP injections in deltoid and gluteal muscles in the dose range of 25–150 mg eq. were generally tolerable both locally and systemically.