The purpose of this study was to determine the permeability and solubility of seven beta-blockers (acebutolol, atenolol, labetalol, metoprolol, nadolol, sotalol, and timolol) and to classify them according to the Biopharmaceutics Classification System (BCS). Apparent permeability coefficients (Papp) were measured using the Caco-2 cell line, and the solubility was determined at 37 degrees C over a pH range of 1.0-7.5. The permeability coefficients ranged from 1.0x10(-7) to 4.8x10(-5) cm/s. On the basis of the in vitro permeability and solubility data observed in the study, labetolol, metoprolol, and timolol can be categorized as BCS Class I drugs, whereas acebutolol, atenolol, and nadolol belong to BCS Class III. The permeability coefficients in Caco-2 cells were consistent with the reported extent of intestinal absorption in humans for all drugs except sotalol. Sotalol displayed low permeability in the Caco-2 cell line, but the extent of intestinal absorption in humans is over 90%. The low permeability through the Caco-2 monolayers might be largely related to its low lipophilicity. In addition, the difference between the tightness of the intercellular junction in vivo and in vitro may partially contribute to this disparity in the sotalol permeability of in vivo and in vitro.

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The American Medical Association has questioned whether expiration dating markedly underestimates the actual shelf life of drug products. Results from the shelf life extension program (SLEP) have been evaluated to provide extensive data to address this issue. The SLEP has been administered by the Food and Drug Administration for the United States Department of Defense (DOD) for 20 years. This program probably contains the most extensive source of pharmaceutical stability data extant. This report summarizes extended stability profiles for 122 different drug products (3,005 different lots). The drug products were categorized into five groups based on incidence of initial extension failures and termination failures (extended lot eventually failed upon re-testing). Based on testing and stability assessment, 88% of the lots were extended at least 1 year beyond their original expiration date for an average extension of 66 months, but the additional stability period was highly variable. The SLEP data supports the assertion that many drug products, if properly stored, can be extended past the expiration date. Due to the lot-to-lot variability, the stability and quality of extended drug products can only be assured by periodic testing and systematic evaluation of each lot.

We used 17O NMR imaging techniques to measure the H2(17)O concentration in a 0.8-ml voxel in the cat brain following injection of an arterial bolus of enriched H2(17)O and during inhalation of enriched 17O2. We also measured the H2(17)O concentration in arterial blood during 17O2 inhalation. The data from the first measurement were used to calculate the blood flow in the voxel. The data from all three measurements were combined to calculate the oxygen consumption in the voxel. The values of cerebral blood flow and oxygen consumption calculated with 17O NMR techniques agree reasonably well with values calculated for a similar region of the cat brain using autoradiographic techniques.