Topical corticosteroid delivery into human skin using hydrofluoroalkane metered dose aerosol sprays.

Drug loaded hydrofluoroalkane (HFA) sprays can generate effective pharmaceutical formulations, but a deeper understanding of the manner in which these dynamic systems drive the process of in situ semi-solid dosage form assembly is required. The aim of this study was to investigate the effect of the matrix assembly and composition on drug localisation in human skin. Comparing the characteristics of sprays constituting HFA 134a, ethanol (EtOH), poly(vinyl pyrrolidone) K90, isopropyl myristate (IPM), and poly(ethylene glycol) (PEG) demonstrated that the addition of non-volatile solvents acted to delay EtOH evaporation, control the degree of drug saturation (DS) and enhance the corticosteroid delivery from HFA spray formulations.

Transient drug supersaturation kinetics of beclomethasone dipropionate in rapidly drying films.

Supersaturation is an effective method to enhance the delivery of active compounds into the skin, however the long-term instability of the drug in these formulations that exceed thermodynamic unity prevents clinical use. The creation of supersaturation in situ by volatile solvent evaporation after application may overcome this. The aim of this study was to determine how altering the kinetics of transient supersaturation and recrystallisation would effect the rate of beclomethasone dipropionate (BDP) release from metered dose aerosols (MDA) that also consisted of hydrofluoroalkane 134a, ethanol (EtOH), and poly(vinyl pyrrolidone) (PVP) K90.

An investigation into solvent-membrane interactions when assessing drug release from organic vehicles using regenerated cellulose membranes.

The influence of organic solvents on artificial membranes when assessing drug release from topical formulations is, generally, poorly characterised yet current guidelines require no characterisation of the membrane before, during or after an experiment. Therefore, the aim of this study was to determine the effect of solvent-membrane interactions when using in-vitro Franz cell methods for the assessment of corticosteroid release and to assess compliance or otherwise with Higuchi's equation. The rate of beclometasone dipropionate monohydrate (BDP) and betamethasone 17-valerate (BMV) release across a regenerated cellulose membrane (RCM), from both saturated solutions and commercial formulations, was determined.

Manipulation of corticosteroid release from a transiently supersaturated topical metered dose aerosol using a residual miscible co-solvent.

Purpose: The creation of supersaturation transiently after application overcomes the issue of drug instability. However, if the solvents used to drive supersaturation evaporate too quickly, drug recrystallisation or rapid film drying can occur which will inhibit drug release. As such the effects of a residual solvent, poly(ethylene glycol) 400 (PEG), on the release, mobility and supersaturation kinetics of a transiently supersaturated formulation were studied.

Determining degree of saturation after application of transiently supersaturated metered dose aerosols for topical delivery of corticosteroids.

A transiently supersaturated drug delivery system has the potential to enhance topical drug delivery via heightened thermodynamic activity. The aim of this work was to quantify the degree of saturation (DS) for transiently supersaturated formulations using three traditional and one novel in vitro assessment methods. Metered dose aerosols (MDA) were formulated containing saturated levels of beclomethasone dipropionate monohydrate (BDP) or betamethasone 17-valerate (BMV) within a pressurised canister, and included ethanol (EtOH), hydrofluoroalkane 134a propellant and poly(vinyl pyrrolidone).