Validation of data on the use of twin mix in minor oral surgery: comparative evaluation of efficacy of twin mix versus 2 % lignocaine with 1:200000 epinephrine based on power analysis and an UV spectrometry study for chemical stability of the mixture.

INTRODUCTION: There is convincing evidence supporting the addition of dexamethasone to lignocaine and its administration as an intra-space injection to achieve benefit of a single dose steroid after third molar surgery. This study was undertaken to validate the existing data on the use of twin mix in minor oral surgery based on power analysis, statistical sample size estimation and an ultraviolet (UV) spectrometry study for chemical stability of the mixture. MATERIAL AND METHODS: A prospective, randomized, double-blind trial was designed to validate the pilot study on the efficacy of twin mix and 2 % lignocaine with 1:200,000 epinephrine in the surgical removal of impacted mandibular third molars. Clinical parameters of anaesthetic latency, anaesthetic duration, efficacy of twin mix as an anaesthetic and post-operative patient discomfort were assessed. The stability of active ingredients in the solution was assessed using a double beam UV-visible spectrophotometery. RESULTS: The results of the study showed better post-operative outcome with administration of dexamethasone and lignocaine as an intra-space injection in decreasing the post-operative patient discomfort. The anaesthetic efficacy of the twin-mix admixture was found statistically similar to the control solution of 2 % lignocaine with 1:200,000 epinephrine. The λmax recorded for dexamethasone and local anaesthetic individually was obtained with the twin-mix solution, which indicated no change in the active pharmacological compounds. DISCUSSION: Clinical anaesthetic efficacy of twin mix is comparable to 2 % lignocaine with 1:200,000 epinephrine when administered in the pterygomandibular space with the additional advantage of a single prick co-administration of dexamethasone with local anaesthetic, lesser sting of the local anaesthetic injection, shorter anaesthetic latency, prolonged duration of the soft tissue anaesthesia and decrease in post-operative discomfort after the oral surgical procedure.

A fundamental investigation into the effects of eutectic formation on transmembrane transport.

Eutectic systems enhance the permeation of therapeutic agents across biological barriers, but the mechanism by which this occurs has not previously been elucidated. Using human skin it has proven difficult to isolate the fundamental effects of eutectic formation on molecule diffusion and partition from those that arise as a consequence of the simultaneous application of two agents. The aim of this work was to employ a model hydrophobic membrane to understand the fundamental permeation characteristics of two agents when applied as a eutectic mixture. Lidocaine and prilocaine were selected as model agents and infinite-dose permeation studies were carried out using pre-calibrated Franz diffusion cells with two thicknesses of silicone membrane. Membrane solubility was determined by HCl solution extraction and the membrane diffusion coefficients were calculated from the permeation lag-times. The maximum permeation enhancement was achieved using a eutectic mixture at a 0.7:0.3 prilocaine/lidocaine ratio. A higher solubility of both agents in silicone membrane, enhanced diffusivity of prilocaine and superior release of both drugs, all contributed to produce enhanced permeation from the eutectic mixtures. Deconvolution of the transmembrane transport process suggests that the eutectic enhancement phenomena is a consequence of more favorable permeation characteristics of the two molecules in the absence of a formulation vehicle which competes in the transport process.

Effect of temperature and some common metals on the stability of volatile anaesthetic-Entonox mixtures.

Thermal stability of pressurised ready-to-use volatile liquid anaesthetic mixtures (halothane, isoflurane and enflurane) in Entonox (commercially available premixed 50% N2O, 50% O2 mixture) were investigated at temperatures of 20, 258, 400, 503 and 602 degrees C on glass, stainless steel, copper and aluminium by gas chromatography and GC-MS. It was found that most of the decomposition products formed were halogenated compounds and the observed thermal stabilities in glass, stainless steel and copper allowed a thermal treatment up to 250 degrees C without any decomposition problem. Aluminium was found to be the most effective metal at causing decomposition of the anaesthetic mixtures even at lower temperatures.