Dopamine D2 receptor occupancy (D2RO) significantly influences the clinical effectiveness and safety of many antipsychotic drugs. Maintaining a D2RO range of 65%-80% provides the best antipsychotic effects while minimizing adverse reactions. Data from a Phase III trial were used to establish an exposure-response relationship for monthly intramuscular Risperidone ISM (75 and 100 mg) or placebo administered to adults with schizophrenia. Pharmacodynamic analysis was based on an Emax model for Positive and Negative Syndrome Scale (PANSS) developed in NONMEM. Plasma concentrations of the active moiety were derived using a previously developed population pharmacokinetic model, which was used for D2RO simulations in conjunction with a published Emax model. The optimal D2RO range (65%-80%) was reached for the median within hours following the first injection of both Risperidone ISM doses. At steady state, median D2RO for both doses remained above 65% throughout the 28-day dosing period and demonstrated lower variability than oral risperidone. PANSS response did not differ significantly between dose groups, most likely because active moiety concentrations had already reached the plateau of the concentration-response relationship. The pharmacokinetic/pharmacodynamic analysis showed a profound placebo effect (-11.7%), and an additional maximal drug effect (-6.6%) resulting in a total PANSS improvement over time of -18.3%. Pharmacokinetic/pharmacodynamic modeling quantified a PANSS improvement over time after Risperidone ISM administration. The response was not significantly different in either dose group, likely because D2RO was already above the proposed efficacy threshold (65%) within 1 h after the first Risperidone ISM injection and remained above this level following repeated administrations.

This study characterized the pharmacokinetics, safety, and tolerability of Risperidone ISM, a new long-acting intramuscular formulation, for monthly administration without oral supplementation. Patients with schizophrenia received multiple intramuscular injections of 75 mg in the gluteal or deltoid muscle at 28-day intervals. Of the 70 randomized patients, 67 received at least one dose of study medication. The mean Cmax of the active moiety was achieved 24–48 h (tmax) after each administration, regardless of injection site. They ranged over four consecutive doses from 39.6 to 53.2 and 54.1 to 61 ng/ml, when given in gluteal or deltoid muscle, respectively. Active moiety achieved therapeutic levels by 2 h after dose, and the levels were maintained throughout the 4-week dosing period. No significant changes across the study were observed on either Positive and Negative Syndrome Scale or Extrapyramidal Symptoms Scale. Overall, 63 (94%) patients experienced at least one treatment-emergent adverse event (TEAE). One serious TEAE (dystonia) was related to study treatment. The most frequently reported TEAEs were hyperprolactinaemia (57.7%) and injection site pain (32.8%). Risperidone ISM achieved therapeutic levels from the first hours after drug administration and provided a sustained release throughout the 4-week dosing period over multiple intramuscular injections and was found to be safe and well tolerated.

The aim of this study was to characterize the pharmacokinetics and to evaluate the safety of risperidone ISM in patients with schizophrenia or schizoaffective disorder after a single gluteal intramuscular injection at three different dose strengths (50, 75, and 100 mg). A total of 36 patients were randomized and blood samples were collected to measure the plasma concentrations. The pharmacokinetic of the active moiety was biphasic for all three dose groups, and the mean plasma concentration was 21.45, 24.60, and 29.68 ng/ml in the 50, 75, and 100 mg group, respectively, 24 h after dose administration; 22.81, 24.57, and 31.41 ng/ml in the 50, 75, and 100 mg group, respectively, 48 h after dose administration, and 12.26, 17.31, and 20.01 ng/ml in the 50, 75, and 100 mg group, respectively, 30 days after dose administration. Overall, 34 patients experienced at least one treatment-emergent adverse event (TEAE). Two patients experienced a serious TEAE and no deaths occurred. There were no extrapyramidal symptoms-related serious TEAEs and no significant changes in any Columbia Suicide Severity Rating Scale parameter were observed during the study. Risperidone ISM provided a sustained release of risperidone that achieved therapeutic plasma levels within the first day. Risperidone ISM was safe, well tolerated, and should be suitable for a 4-weekly administration without oral supplementation.

INTRODUCTION:Aging and renal impairment may prolong the half-life and lead to accumulation of low molecular weight heparins. Correct dosing is critical to prevent bleeding or thrombosis.MATERIALS AND METHODS:Open, parallel study. Healthy adult [n=13] and elderly (>65yrs) [n=12] volunteers; and subjects with mild (ClCr≥50 to ≤80mL/min, n=8), moderate (ClCr≥30 to <50mL/min, n=7), and severe (ClCr<30mL/min, n=8) renal impairment received four prophylactic doses (3,500IU/24h) and a single therapeutic dose (115IU/kg) of bemiparin with an interim washout period. Anti-FXa activity and the potential need for dose adjustment were evaluated.RESULTS:There were statistically significant differences in the severe renal impairment group vs. adult volunteers in all anti-FXa related parameters, but no significant differences in any of the anti-FXa related parameters between the adult and the elderly. Anti-FXa simulations after 10 prophylactic doses predicted mean Amax=0.59IU/mL in subjects with severe renal impairment and 0.33-0.39IU/mL in the rest. Simulations in the severe renal impairment group with dose adjustment (2,500IU/24h) predicted all individual Amax<0.60IU/mL (mean Amax=0.42IU/ml). Simulations after 10 therapeutic doses predicted mean Amax=1.22IU/mL in severe renal impairment group and 0.89-0.98IU/mL in the rest. Simulations in the severe renal impairment group with 75% dose adjustment predicted individual Amax≤1.60IU/mL (mean Amax=0.91IU/mL).CONCLUSIONS:No dose adjustments are required in elderly with preserved renal function. A dose adjustment of bemiparin is only advisable in patients with severe renal impairment when using prophylactic or therapeutic doses.