Formulation, in vitro and in vivo evaluation of transdermal patches containing risperidone

The efficacy of oral risperidone treatment in prevention of schizophrenia is well known. However, oral side effects and patient compliance is always a problem for schizophrenics. In this study, risperidone was formulated into matrix transdermal patches to overcome these problems. The formulation factors for such patches, including eudragit RL 100 and eudragit RS 100 as matrix forming polymers, olive oil, groundnut oil and jojoba oil in different concentrations as enhancers and amount of drug loaded were investigated. The transdermal patches containing risperidone were prepared by solvent casting method and characterized for physicochemical and in vitro permeation studies through excised rat skin. Among the tested preparations, formulations with 20% risperidone, 3:2 ERL 100 and ERS 100 as polymers, mixture of olive oil and jojoba oil as enhancer, exhibited greatest cumulative amount of drug permeated (1.87 +/- 0.09 mg/cm(2)) in 72 h, so batch ROJ was concluded as optimized formulation and assessed for pharmacokinetic, pharmacodynamic and skin irritation potential. The pharmacokinetic characteristics of the optimized risperidone patch were determined using rabbits, while orally administered risperidone in solution was used for comparison. The calculated relative bioavailability of risperidone transdermal patch was 115.20% with prolonged release of drug. Neuroleptic efficacy of transdermal formulation was assessed by rota-rod and grip test in comparison with control and marketed oral formulations with no skin irritation. This suggests the transdermal application of risperidone holds promise for improved bioavailability and better management of schizophrenia in long-term basis.