Cyclosporin is thought to be exclusively metabolised in the liver. We instilled cyclosporin into the small bowel of 2 patients during the anhepatic phase of liver transplantation; cyclosporin metabolites were readily detected in portal venous blood. Our findings indicate that the small intestine is a major site of cyclosporin breakdown: such intestinal metabolism might help to explain the poor oral bioavailability and drug interactions of cyclosporin.

The majority of medications can be coadministered with the 3D regimen of OBV, PTV/r, and DSV without dose adjustment, or with clinical monitoring or dose adjustment. Although no dose adjustment is necessary for the 3D regimen when coadministered with 17 of the 20 medications, coadministration with gemfibrozil, carbamazepine, or ethinyl estradiol-containing contraceptives is contraindicated.

Lopinavir, an HIV protease inhibitor, is coformulated with ritonavir to enhance the bioavailability and pharmacokinetics of lopinavir. The original solid oral formulation of lopinavir/ritonavir, a soft-gelatin capsule (SGC), requires refrigerated storage, is taken as 6 capsules daily at the recommended adult dose, and is administered with food to maximize the bioavailability of lopinavir. Melt extrusion technology was used to produce a tablet formulation reducing the number of dosage units administered per day and simplifying storage requirements. Three studies assessed the bioavailability of tablet doses of lopinavir/ritonavir at 800/200 mg or 400/100 mg under different meal conditions compared with equal doses of the SGC after a moderate-fat meal. The tablet was bioequivalent to the SGC after a moderate-fat meal with respect to lopinavir and ritonavir areas under the concentration-time curve. Compared with the SGC formulation, the tablet formulation resulted in more consistent lopinavir and ritonavir exposures within and across studies and across meal conditions. The diminished food effect and decreased variability of the tablet are likely to result in more consistent lopinavir and ritonavir exposures, minimizing the likelihood of extreme high or low values compared with the SGC.

We have developed a new semi-physiological platelet model for describing fast drop of platelets after initial navitoclax administration and long-term decline of platelets after continuous administration of navitoclax.

Levothyroxine (LT4) has a narrow therapeutic index. Consequently, precise standards for assessing the bioequivalence of different LT4 products are vital. We examined the methodology that the Food and Drug Administration (FDA) recommends for comparing the bioavailability of LT4 products, as well as three modifications to correct for endogenous, thyroxine (T4) levels, to determine if the methodology could distinguish LT4 products that differ by 12.5%, 25%, or 33%. With no baseline correction for the endogenous T4 pool, differences in administered LT4 doses that differed by 25%-33% could not be detected (450 microg and 400 microg doses versus 600 microg dose, respectively). The three mathematical correction methods could distinguish the doses that differed by 25% and 33%. None of the correction methods could distinguish dosage strengths that differed by 12.5% (450 microg versus 400 microg). Dose differences within this range are known to result in clinically relevant differences in safety and effectiveness. Methods of analysis of bioequivalence data that do not consider endogenous T4 concentrations confound accurate quantitation and interpretation of LT4 bioavailability. As a result, products inappropriately deemed bioequivalent may put patients at risk for iatrogenic hyperthyroidism or hypothyroidism. More precise methods for defining bioequivalence are required in order to ensure that LT4 products accepted as bioequivalent will perform equivalently in patients without the need for further monitoring and retitration of their dose.