| Menthol is a cyclic terpene alcohol made synthetically or obtained from corn mint, peppermint or other mint oils. It is used frequently as a penetration enhancer in various topical and transdermal formulations. Its ability to chemically trigger cold sensitive TRPM8 receptors in the skin is responsible for the well-known cooling sensation it provokes when inhaled, eaten, or applied to the skin. TRPM8 (Transient receptor potential cation channel subfamily M member 8), also known as the cold and menthol receptor 1 (CMR1), is an ion channel that upon activation allows the entry of Na+ (sodium) and Ca 2+(calcium) ions to the cell that leads to depolarization and the generation of an action potential. Also, extracellular calcium ions concentration plays a significant role in the expression of cadherin (calcium dependent adhesion molecules) responsible for cell adhesion.;The purpose of this thesis is to evaluate whether these calcium related properties of Menthol also plays a. role in its percutaneous enhancing effects by using Verapamil as a calcium blocker. In Dr. Stagni's laboratory, it was recently demonstrated that indeed the presence of a calcium channel blocker almost nullifies the capability of menthol to enhance the penetration of two basic drugs: Diphenhydramine and Lidocaine. This thesis work investigates whether the same effect is noticeable for an acid drug, e.g., Ibuprofen. Four gel formulations were prepared containing: (A) ibuprofen, (B) ibuprofen and menthol, (C) ibuprofen, menthol, and verapamil, and (D) ibuprofen and verapamil. Verapamil and menthol were in equal molar proportions. In vitro studies were performed in triplicates with jacketed diffusion Franz cells with cellulose membrane to identify any physical interactions.;In order to quantify Verapamil and Ibuprofen in the same sample, a modified HPLC method for the detection of Ibuprofen and Verapamil was validated. The separation was achieved with a C 18-column at room temperature (25 °C) with the detection wavelength set at 230 nm. The mobile phase consisted of Acetonitrile : Deionized water (55:45), pH: 2.6 +/- 0.01; Flow rate was 1.2 m1/min; run time was 10 minutes and injection sample was 20 microl. The method has a LLOQ of 0.5 microg/m1 and a linearity range of 0.5 to 500 microg/ml.;Cumulative amounts of drug diffused across the membrane were 0.239 +/- 0.0002mg, 0.244 +/- 0.7* 10-7mg, 0.138 +/- 0.0002mg, and 0.081 +/- 0.002mg for gels A,B,C, and D respectively. Drug flux across the membrane were 0.116 +/- 0.006 microg/cm2/min, 0.123 +/- 0.002 microg/cm2/min, 0.066 +/- 0.007 microg/cm 2/min, and 0.048 +/- 0.006 microg/cm2/min for gels A, B, C, and D respectively. One-way ANOVA analysis shows that both Flux and Cumulative amount of drug released were statistically lowered (p<0.05) by the presence of verapamil showing a possible physical interaction between Ibuprofen and Verapamil. In conclusion, Ibuprofen is not a suitable candidate to further study in-vivo mechanism of interaction between Menthol and the calcium channel blocker Verapamil. |
