A freeze-dried injectable form of flurbiprofen: development and optimisation using response surface methodology

Solubilization of ibuprofen for freeze dried parenteral dosage forms

Ibuprofen, a weakly acidic non-steroidal anti-inflammatory drug having poor aqueous solubility, is a challenging drug for the development of pharmaceutical formulations, resulting in numerous research attempts focusing on improvement of its solubility and consequently bioavailability. Most studies have been done for solid dosage forms, with very little attention paid to parenterals. Hence, the main purpose of the present study was to enhance ibuprofen solubility as a result of formulation composition and the freeze drying process. Moreover, the purpose was to prepare a freeze dried dosage form with improved ibuprofen solubility that could, after simple reconstitution with water for injection, result in an isotonic parenteral solution. Solubility of ibuprofen was modified by various excipients suitable for parenteral application. Drug interactions with selected excipients in the final product/lyophilisate were studied by a combined use of XRPD, DSC, Raman and ss-NMR. Analyses of lyophilized samples showed solubility enhancement of ibuprofen and in situ formation of an ibuprofen salt with the alkaline excipients used.

A pH-independent instantaneous release of flurbiprofen: a study of the preparation of complexes, their characterization and in vitro/in vivo evaluation

In this study, furbiprofen/hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complexes were prepared to improve the drug dissolution and facilitate its application in hydrophilic gels. Inclusion complexes were prepared using a supercritical fluid processing and a conventional optimized co-lypholization method was employed as a reference. The entrapment efficacy and drug loading of both methods were investigated. Evaluation of drug dissolution enhancement was conducted in deionized water as well as buffer solutions of different pH. Carbopol 940 gels of both flurbiprofen and flurbiprofen/HPβCD inclusion complexes, with or without penetration enhancers, were prepared and percutaneous permeation studies were performed using rat abdominal skin samples. Formation of flurbiprofen/HPβCD inclusion complexes was confirmed by Fourier transform-infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. The results obtained showed that SCF processing produced a higher EE (81.91 ± 1.54%) and DL (6.96 ± 0.17%) compared with OCL with values of 69.11 ± 2.23% and 4.00 ± 1.01%, respectively. A marked instantaneous release of flurbiprofen/HPβCD inclusion complexes prepared by SCF processing (103.04 ± 2.66% cumulative release within 5 min, a 10-fold increase in comparison with flurbiprofen alone) was observed. In addition, this improvement in dissolution was shown to be pH-independent (the percentage cumulative release at pH 1.2, 4.5, 6.8 and 7.4 at 5 min was 95.19 ± 1.71, 101.75 ± 1.44, 105.37 ± 4.58 and 96.84 ± 0.56, respectively). Percutaneous permeability of flurbiprofen-in-HPβCD-in-gels could be significantly accelerated by turpentine oil and was related to the water content in the system. An in vivo pharmacokinetic study showed a 2-fold increase in C_max and a shortened T_max as well as a comparable relative bioavailability when compared with the commercial flurbiprofen Cataplasms (Zepolas^®). With their superior dissolution, these flurbiprofen/HPβCD inclusion complexes prepared by SCF processing could provide improved applications for flurbiprofen.

Influence of preparation methodology on solid-state properties of an acidic drug-cyclodextrin system

We have investigated the influence of processing variables on the solid-state of a model drug, flurbiprofen, in cyclodextrin-based systems and its effect on dissolution behaviour of the drug. The interaction between flurbiprofen and hydroxypropyl β-cyclodextrin (HP-β-CyD) was studied by NMR spectroscopy and phase solubility studies. Binary systems containing flurbiprofen and HP-β-CyD or povidone (polyvinylpyrrolidone) K30, prepared by various processes, were characterized by FTIR, DSC, XRD and dissolution studies. HP-β-CyD enhanced the solubility of flurbiprofen and increased dissolution rates from binary systems. It was found to be superior to povidone K30 in producing higher dissolution rates. The method of preparation of the binary systems and the agents used were found to have a major influence on the final solid-state of flurbiprofen. Solvents and processing conditions favouring greater interaction between flurbiprofen and the cyclodextrin during the preparation process resulted in greater extent of drug-cyclodextrin association and/or greater amorphization of the drug. Use of ammonia during the preparation of binary systems yielded solids from which very rapid drug dissolution was achieved, due to a higher extent of molecular dispersion of the drug. Processing variables therefore could significantly influence the solid-state of a drug in cyclodextrin-based formulations and thereby affect its dissolution behaviour. This could lead to significant effects on the in-vivo performance of the formulation.

Formulation Studies and In Vivo Evaluation of a Flurbiprofen-Hydroxypropyl β-Cyclodextrin System

The purpose of this study was 1) to investigate in vivo advantages of a flurbiprofen (FPN)-hydroxypropyl beta-cyclodextrin (HPbetaCD) solid dispersion (SD) in rats, 2) to study factors affecting the drug release from SD formulations, and 3) to evaluate the pharmacokinetic profile of the drug when administered as SD, in humans. The solubility of FPN in water and dissolution media was evaluated as a function of HPbetaCD concentration. The SD was prepared by coevaporation from dilute aqueous NH3 and evaluated in rats. The release of the drug from tablet formulations and capsules of SD was studied in simulated gastric fluid and phosphate buffer, pH 7.2. The bioavailability of drug when administered as SD was evaluated in humans. HPbetaCD enhanced the solubility of the drug, and SD improved bioavailability and reduced ulcerogenicity of the drug in rats. The type of excipient used affected drug release from tablets. Presence of microcrystalline cellulose, a hydrophilic polymeric excipient, resulted in uptake of water and stabilization of the resulting gels-like structure of HPbetaCD-containing tablets. This adversely affected drug release. The release from capsules filled with SD was comparable to that obtained from plain SD powder. The drug-HPbetaCD association constant in water was much lower than the values reported in literature. The bioavailability (which could suffer in case of higher association constant) was enhanced on administration of SD-filled capsules to humans.