New method for calculating the intrinsic absorption rate of drugs.
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Biomedical subjects
Publications and source records attributed to J C Loo.
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Two betamethasone tablet formulations, and betamethasone phosphate solution were compared in a plasma level study. The tablet formulations (A and B) and a solution of betamethasone phosphate (C) were administered in single 2 mg doses to nine volunteers according to a three times repeated Latin square design. Plasma samples were obtained over 72 h following each dose and plasma was analysed for betamethasone by radioimmunoassay. Pharmacokinetic evaluation of the data, obtained according to the one-compartment open model, indicated that there were no significant differences between the extent of absorption, and the first-order elimination rate constants. As would be expected, the solution (C) gave a faster absorption rate than tablets A and B.
Following the oral co-administration of isonicotinic acid hydrazide and norethindrone to minipigs, the hydrazone of norethindrone was detected in plasma as its p-methoxybenzaldehyde derivative, using a high performance liquid chromatographic technique. The suspected precursor of the hydrazone of norethindrone was isonicotinyl hydrazone of norethindrone, a reaction product probably formed between norethindrone and isonicotinic acid hydrazide in the acid environment of the stomach. An in vitro liver metabolite of isonicotinyl hydrazone of norethindrone was isolated following derivatization with p-methoxybenzaldehyde and characterized by high resolution mass spectrometric and radiochemical techniques. The results demonstrated that the hydrazone of norethindrone is a metabolite of isonicotinyl hydrazone of norethindrone.
Pharmacokinetic and bioavailability parameters of propranolol were estimated in 10 healthy adult subjects after single oral doses of two commercial tablet formulations of propranolol hydrochloride (2 X 40 mg). Plasma concentrations of propranolol were determined by a high-performance liquid-chromatographic (HPLC) assay. Peak plasma concentrations of propranolol glucuronide were 6-8 times those of the corresponding peak propranolol plasma concentrations. The mean resident time (MRT) of propranolol and of propranolol glucuronide was determined for each subject for both formulations. The MRT of the parent drug was found to be longer than the MRT of the glucuronide metabolite for each of the subjects examined. Statistical moment analysis indicated that this phenomenon is attributable to extensive presystemic glucuronidation of the parent drug.
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The pediatric cardiology vernacular is replete with ambiguous and erroneous terminology. This article discusses several examples in a plea to bring the accuracy and precision of the scientific method to the clinical pediatric cardiology vernacular.