Bioavailability of three formulations of intravenous diazepam

Physiologically-Based Pharmacokinetic and Pharmacodynamic Modeling of Diazepam: Unbound Interstitial Brain Concentrations Correspond to Clinical Endpoints

Benzodiazepines induce a series of clinical effects by modulating subtypes of GABA_A receptors in the central nervous system. The brain concentration-time profiles of diazepam that correspond to these effects are unknown, but can be estimated with physiologically-based pharmacokinetic (PBPK) modeling. In this study, a PBPK model for the 1,4-benzodiazepines diazepam and nordiazepam was developed from plasma concentration time-courses with PK-Sim^® software to predict brain concentrations. The PBPK model simulations accurately parallel plasma concentrations from both an internal model training data set and an external data set for both intravenous and peroral diazepam administrations. It was determined that the unbound interstitial brain concentration-time profiles correlated with diazepam pharmacodynamic endpoints. With a 30 mg intravenous diazepam dose, the peak unbound interstitial brain concentration from this model is 160 nM at 2 minutes and 28.9 nM at 120 minutes. Peak potentiation of recombinant GABA_A receptors composed of α1β2γ2s, α2β2γ2s, and α5β2γ2s subunit combinations that are involved in diazepam clinical endpoints is 108%, 139% and 186%, respectively, with this intravenous dose. With 10 mg peroral administrations of diazepam delivered every 24 hours, steady-state peak and trough unbound interstitial brain diazepam concentrations are 22.3 ± 7.5 nM and 9.3 ± 3.5 nM. Nordiazepam unbound interstitial brain concentration is 36.1 nM at equilibrium with this diazepam dosing schedule. Pharmacodynamic models coupled to the diazepam unbound interstitial brain concentrations from the PBPK analysis account for electroencephalographic drug effect, change in 13-30 Hz electroencephalographic activity, amnesia incidence, and sedation score time-courses from human subjects. This article is protected by copyright. All rights reserved.

Bioequivalence and tolerability assessment of a novel intravenous ciclosporin lipid emulsion compared to branded ciclosporin in Cremophor ® EL

BACKGROUND

Ciclosporin is used as an immunosuppressant in current clinical practice but recent research implies novel indications for the drug, such as neuro- and cardioprotection. The intravenous formulation currently on the market, Sandimmune(®) Injection (Sandimmune(®)), uses Cremophor(®) EL as emulsifying excipient. Cremophor(®) EL is known to cause hypersensitivity reactions in some patients, ranging from skin reactions to potentially fatal anaphylactic shock.

OBJECTIVES

The primary objective was to assess if CicloMulsion(®), a Cremophor(®) EL-free lipid emulsion of ciclosporin for intravenous administration, is bioequivalent to Sandimmune(®), and the secondary objective was to compare the tolerability profiles of the two preparations.

METHODS

This was a single-centre, open-label, subject-blind, laboratory-blind, single-dose, randomized, two-treatment, two-period, two-sequence crossover study of the pharmacokinetics of two formulations of intravenous ciclosporin. Fifty-two healthy volunteer subjects were administered 5 mg/kg of each of the two formulations of ciclosporin as a 4-h intravenous infusion. The last blood sample was acquired 48 h after the end of the infusion. Bioequivalence assessments according to current guidelines were performed.

RESULTS

The geometric mean ratios for CicloMulsion(®)/Sandimmune(®) (90 % confidence interval [CI]) were 0.90 (0.88, 0.92) for AUC(0-last) (area under the blood concentration-time curve from time zero to time of last measurable concentration) and 0.95 (0.92, 0.97) for C(max) (maximum blood concentration). For all additional variables analysed, the 90 % CIs were also within the accepted bioequivalence range of 0.80-1.25. One anaphylactoid and one anaphylactic reaction, both classified as serious adverse events, were reported after treatment with Sandimmune(®). No serious adverse events were recorded after treatment with CicloMulsion(®).

CONCLUSION

We have assessed the pharmacokinetics and tolerability of a new Cremophor(®) EL-free lipid emulsion of ciclosporin, CicloMulsion(®), compared to Sandimmune(®). The proportion of adverse events was significantly higher for the Cremophor(®) EL-based product Sandimmune(®). We conclude that CicloMulsion(®) is bioequivalent to Sandimmune(®) and exhibits fewer adverse reactions.

A randomized comparison of midazolam and diazepam injectable emulsion in cataract surgery

The purpose of this study was to compare the psychomotor recovery of patients sedated with either midazolam or Diazemuls using the digit symbol substitution test and the Trieger test. Sixty patients were allocated in random double-blind fashion to receive either midazolam or diazepam in oil emulsion (Diazemuls) as intravenous sedation for cataract surgery. Both groups received fentanyl 0.5 micrograms.kg-1 IV. Tests of cognition were performed by the patients prior to sedation and at half-hourly intervals for three hours after cataract surgery. In a dose ratio of 1:4, midazolam was found to produce better sedation but more prolonged recovery than Diazemuls. Anterograde amnesia was comparable in the two groups, while more patients in the Diazemuls group developed episodes of apnoea and venous irritation.