Dimenhydrinate is an over-the-counter medication that is used to relieve nausea, vomiting, and vertigo caused by motion sickness. It has a short elimination half-life, possibly due to its first-pass metabolism. The current study aimed to prepare and evaluate new transdermal formulations of dimenhydrinate to prolong the drug’s release and improve its cutaneous permeation. First, the patches were fabricated and evaluated to determine their properties. The results were statistically investigated and considered significant at the p < 0.05 level. Additionally, the quantitative analysis of the drug-release data and kinetic modeling was performed by using the DDSolver software to decide the candidate formula dependably. The effect of the penetration enhancers on the permeability of dimenhydrinate from the selected patch was then studied ex vivo compared to the control sample, and the patch’s safety was evaluated in rabbits, using the skin-irritation test.
The aim of this study was to predict the blood/plasma drug concentration profiles for five brand of nifedipine present on the Saudi Arabia market by using the numerical convolution method and to estimate the pharmacokinetic parameters (Cmax, Tmax, Ka, K and Vd) by the application of the residual method to the predicted plasma drug concentration profiles. Results showed that the higher Cmax was 118.95ng/ml for brand A2 and the lower Cmax was 72.29ng/ml for brand A3. The Tmax was ranged from 2.3 hr to 4.9 hr for brands A2 and A3 respectively. The total area under plasma drug concentration curve (AUCinf.) was in lower value equal to 585.59 ng x hr/ml for brand A2 and the higher value was for brand A5 equal to 743.52ng x hr/ml. The volume of distribution was also increased from 52.5 L for free nifidipine to 72 L for brand A1. The predicted first order elimination rate constant was decreased from 0.34 hr-1 for free nifedipine to 0.17 hr-1 for brand A3. The half-life of nifedapine was increased from 2 hours for free drug to 3.93 hours for brand A3. From this study it can be concluded that brands present in the market that shows similarity in accordance to the Dissimilarity factor f1 are not always guaranty that they will be bioequivalent in vivo and vice versa. Also, this study indicates that the method of convolution is a useful tool for prediction of bioequivalence of different brands present on the market.
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