Relative contribution of rat CYP isoforms responsible for stereoselective metabolism of carvedilol

Antiretroviral Treatment and Antihypertensive Therapy

The presence of hypertension among the population with human immunodeficiency virus (HIV) has become a new threat to the health and well-being of people living with this disease, in particular, among those who received antiretroviral therapy. The estimated prevalence of high blood pressure in HIV-infected patients is significantly higher than the rate observed in HIV-uninfected subjects. The approach to the HIV-positive patient requires the assessment of individual cardiovascular risk and its consideration when designing the individualized target. On the other hand, the numerous pharmacological interactions of antiretroviral (ARV) drugs are essential elements to take into account. Serum levels of any kind of antihypertensive drugs may be influenced by the coadministration of protease inhibitors, non-nucleoside reverse transcriptase inhibitor, or other antiretroviral. Similarly, plasma concentrations of antiretroviral drugs can be increased by the concomitant use of calcium channel blockers or diuretics. In this regard, the treatment of high blood pressure in HIV patients should be preferentially based on ACE inhibitors or thiazide/thiazide-like diuretics or their combination.

Determination and Comparison of the Solubility, Oil-Water Partition Coefficient, Intestinal Absorption, and Biliary Excretion of Carvedilol Enantiomers

Carvedilol is administered as a racemic mixture for the therapy of hypertension and heart failure. S-enantiomer is the dominant conformation of pharmacodynamics, but its further development was obstructed by its poor bioavailability. In this study, carvedilol and its enantiomers were compared in terms of solubility, permeability, and biliary excretion, and reasons for the poor bioavailability were discussed. Equilibrium solubility and log P were measured by a shake flask method at a wide pH range (1.2-8.0), and intestinal absorption and biliary excretion were evaluated using a single-pass rat intestinal perfusion model. According to BCS guidance, carvedilol and its R/S enantiomers are considered highly soluble at pH value less than 5.0 and low soluble at neutral or weak alkaline conditions. RS-carvedilol showed significantly lower solubilities at pH 1.2-5.0 and higher solubilities at pH 6.0-8.0 than its enantiomers. In addition, carvedilol and its enantiomers possessed similar log P values at pH 1.2-8.0. High intestinal permeabilities of carvedilol and its enantiomers were observed, and S-carvedilol showed higher absorption than R-carvedilol and RS-carvedilol. The biliary excretion about two major metabolites, 1-hydroxycarvedilol O-glucuronide and 8-hydroxycarvedilol O-glucuronide, of RS-carvedilol, S-carvedilol, and R-carvedilol were 66.4%, 73.5%, and 54.3%, respectively. In conclusion, there are significant differences amongst carvedilol and its R/S enantiomers in terms of solubility, intestine absorption, and biliary excretion abilities. The first pass effect is the primary reasons for the low bioavailability of S-carvedilol. Therefore, pharmaceutical strategies or parenteral routes should be considered to avoid the first pass metabolism.