Risperidone long-acting injection: pharmacokinetics following administration in deltoid versus gluteal muscle in schizophrenic patients

Abstract

Long-acting injectable (LAI) risperidone for intramuscular injection into the gluteal muscle every 2 weeks is approved for schizophrenia. The deltoid muscle provides a more accessible injection site and could therefore facilitate patient acceptance of an injectable medication. Two studies in chronic schizophrenic subjects evaluated the pharmacokinetics and tolerability of LAI risperidone administered into the deltoid muscle. The pharmacokinetics following deltoid injection and bioequivalence between deltoid and gluteal administration were assessed in an open-label, single-dose, crossover, fully powered bioavailability study. Tolerability and safety of deltoid LAI risperidone were investigated in an open-label multiple-dose study in subjects who were previously being treated with gluteal injections of LAI risperidone. Patients received 4 sequential intramuscular injections of LAI risperidone, administered every 2 weeks into the deltoid muscle. Deltoid and gluteal injections of LAI risperidone were shown to be bioequivalent at equal doses with respect to peak and total plasma exposure and exhibited dose-proportional pharmacokinetics, independent of injection site. In addition, deltoid injection was safe and well tolerated. Injection of LAI risperidone into the deltoid muscle can be considered an alternative route of administration, because deltoid and gluteal injections are interchangeable in terms of drug exposure, with no additional safety or tolerability issues.