In vivo assessment of percutaneous local anaesthetic preparations.

This study has demonstrated greater efficacy of a new percutaneous amethocaine preparation relative to Eutectic Mixture of Local Anaesthetics (EMLA). Initially, a double-blinded trial was undertaken on each preparation individually against placebo, as the recommended method of application was different for EMLA (2.5 g applied for 60 min under an occlusive dressing) and the amethocaine formulation (0.5 g applied for 30 min). Thereafter, the two preparations were compared directly, in a double-blinded study using a standardized application for both formulations. The results indicated that both preparations provided significant (chi-square; P less than 0.001) percutaneous local anaesthesia when compared with placebo. The amethocaine preparation produced significant anaesthesia (chi-square, P less than 0.001) after 30 min application. Furthermore, the amethocaine formulation demonstrated both increased rapidity of action and increased duration of effect, as determined by a two-tailed unpaired t test, in comparison with EMLA when application times of both 30 and 60 min were used for each preparation. The results of this study indicate that the amethocaine preparation provided more rapid and prolonged anaesthesia than EMLA.

Comparative in vivo and in vitro assessment of the percutaneous absorption of local anaesthetics.

The percutaneous absorption of local anaesthetics in a standard formulation has been compared in vitro and in vivo. In vitro data were obtained with a modified Sartorius absorption system and silastic as a lipophilic barrier membrane. With this system the greatest steady-state flux values and permeability coefficients were obtained with amethocaine and lignocaine. These drugs also performed best in an in vivo volunteer trial. However, statistical analysis revealed that amethocaine was significantly better at producing full-depth anaesthesia to the challenge of insertion of a sterile needle. An optimized amethocaine formulation may therefore be expected to meet most closely the ideal profile for a percutaneous local anaesthetic preparation.

A comparative assessment of a new antacid formulation based on magaldrate.

A new antacid formulation (Dynese) based on magaldrate, a discrete chemical entity with marked antacid properties, has been compared in vitro with several commercially available antacid preparations. All preparations were tested for their ability to maintain gastric pH within acceptable limits and to effectively bind bile acids. Sodium concentrations were also determined. Dynese was shown to compare very favourably with existing preparations in that it had a prolonged even neutralization profile, efficient bile acid binding properties and a low sodium content.