Pharmacokinetics, safety, and tolerability of four 28-day cycle intramuscular injections for risperidone-ISM 75 mg in patients with schizophrenia: A phase-2 randomized study (PRISMA-2)

Introduction

Risperidone-ISM is a new long acting intramuscular formulation of risperidone, for monthly administration without oral supplementation.

Objective

To characterize the pharmacokinetic of risperidone over multiple intramuscular injections in patients with schizophrenia.

Method

A multicenter, open label, two-arm, parallel design clinical trial was performed. Each patient received 4 intramuscular injections of 75 mg of risperidone-ISM in either, gluteal or deltoid muscle at 28-day intervals.

Results

A total of 70 patients were randomized, 67 received at least one dose of study medication. Preliminary data show that mean Cmax of the active moiety was achieved 24-48 hours (Tmax) after each administration and ranged over four consecutive doses from 39.6-53.2 ng/mL and 54.1-61 ng/mL, when given in gluteal or deltoid, respectively. All subjects achieved therapeutic levels (> 7.5 ng/mL for the active moiety) between 2-8 hours after drug administration. The mean concentrations were maintained above therapeutic levels throughout the 4-week dosing period. No significance changes across the study were observed, either on Positive and Negative Syndrome Scale or Extrapyramidal Symptoms Scale. Overall, 63 subjects (94%) experienced at least 1 Treatment Emergent Adverse Event (TEAE) during the study. One serious TEAE (dystonia) was related to study treatment. One death not related to study medication was informed. The most frequently reported TEAEs were hyperprolactinaemia (57.7%) and injection site pain (32.8%).

Conclusions

Risperidone-ISM achieved therapeutic levels from the first hours after drug administration and provided a sustained release throughout the 4-weeks dosing period over multiple intramuscular injections independently of the injection site. Risperidone-ISM was found to be safe and well tolerated.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Population pharmacokinetic modeling and simulations of dopamine Dd2 receptor occupancy of long-acting intramuscular risperidone-ISM

Introduction

Risperidone-ISM is a new long-acting intramuscular formulation intended to achieve sustained plasma concentrations over 4 weeks without oral supplementation. The clinical efficacy to risperidone has been associated with 65–80% occupancy of dopamine D2 receptor (D2RO) and a mean Cmax between 7.5 ng/mL and 80 ng/mL.

Aim

Use a population PK/PD model to predict the PK and the D2RO for Risperidone-ISM in schizophrenic patients and to characterize the relationship among doses, in order to guide dose selection for a future Phase-III trial.

Methods

A population PK/PD analysis for Risperidone-ISM using Monolix software was conducted based on 6641 plasma samples from two Phase-I studies (17 healthy subjects and 31 schizophrenic subjects, respectively) and 1 Phase-II study (60 schizophrenic subjects). Simulations were subsequently undertaken predicting the steady state PK and D2RO after multiple Risperidone-ISM doses administered every 28 days for 12 weeks.

Results

Doses of 75 and 100 mg, administered either in gluteal or deltoid muscle, were predicted to result in median Cmax and Ctrough that stayed between 7.5 ng/mL and 80 ng/mL. At steady state 75 mg and 100 mg dose (gluteal) achieved a D2RO average [min–max] of 70.8% [61.4–80.4] and 74.3% [66.2–82.1], respectively; a 75-mg and 100-mg dose (deltoid) achieved a D2RO average [min–max] of 69.3% [56.5–80.3] and 73.0% [61.8–82.1], respectively. The model estimated that the 65% D2RO occurs within first 8 h after treatment.

Conclusions

Simulations were carried out supporting doses of 75 mg and 100 mg Risperidone-ISM to show the greatest efficacy and safety potential to be assessed in the future Phase-III trial.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Transmitted drug resistance to rilpivirine in newly diagnosed antiretroviral naive adults

We characterized transmitted drug resistance to rilpivirine and the predicted efficacy of first-line rilpivirine-containing regimens in antiretroviral-naive Spanish patients. International Antiviral Society-USA mutations were detected in 138 of 2781 patients (4.9%), E138A (3.4%) being the most prevalent. Using the Stanford Algorithm, 121 patients (4.4%) showed low-level or intermediate resistance. No differences in the predicted efficacy of first-line non-nucleoside reverse transcriptase inhibitor-based regimens were observed. As rilpivirine becomes more widely used in clinical practice, the evolution of its transmitted drug resistance will need to be monitored. In addition, the exact role of E138A singletons on rilpivirine activity as part of first-line regimens merits further evaluation.

Opsonophagocytosis versus complement bactericidal killing as effectors following Neisseria meningitidis group C vaccination

BACKGROUND

Opsonophagocytosis and complement-mediated Neisseria meningitidis killing after vaccination were investigated.

METHODS

Twelve seronegative healthy volunteers received one dose of polysaccharide A/C vaccine and were followed for 3 years. Ex vivo serum killing rates with polymorphonuclear cells (PMN) and/or complement were performed at 0, 1.5, 6, 12, 18, 24, 30 and 36 months.

RESULTS

High mean total and median bactericidal antibodies were detected over time in all subjects. Considerable reduction of the initial inoculum was obtained only in the presence of complement, with or without PMN (with significant differences compared to curves without complement) a long time after vaccination.

CONCLUSION

PMN did not increase post-vaccination bacterial killing, suggesting that antibody complement-mediated killing, and not opsonophagocytosis, is the main immune effector of the vaccine protection against N. meningitidis.

In vitro bactericidal activity of peak serum concentrations of co-amoxiclav, amoxicillin and vancomycin against methicillin-resistant Staphylococcus aureus

In order to explore the bactericidal activity of concentrations similar to the peak serum concentrations obtained after a single i.v. dose of 2,000/200 mg co-amoxiclav and 500 mg vancomycin, killing curves with co-amoxiclav (69/10 microg/ml), amoxicillin (69 microg/ml), clavulanic acid (10 microg/ml), and vancomycin (15 microg/ml) were performed against two isogenic (ss-lactamase positive and negative) methicillin-resistant Staphylococcus aureus strains in cation-supplemented Mueller-Hinton broth with 2% NaCl incubated at 35 degrees C. Colony counts were performed at 0, 1, 2, 3 and 4 hours in Mueller- Hinton plates supplemented with 4% NaCl and 25 microg/ml oxacillin to measure the resistant population. Similar initial inocula reductions were obtained for amoxicillin-clavulanic acid and vancomycin for both strains, and significant differences were found in comparison to the control. Clavulanic acid decreased the growth rate of the ss-lactamase negative strain when compared to control curves. The penicillin-binding protein 2a affinity of old ss-lactams in conjunction with clavulanic acid overcoming ss-lactamase resistance may explain these results.