Plasma concentrations of orphenadrine were measured by a specific gas chromatographic method in 5 healthy male volunteers after a single oral dose of orphenadrine hydrochloride 100mg. The single dose pharmacokinetic profile of orphenadrine was evaluated from these data. The elimination half-life ranged from 13.2-20.1h after the commercial tablet formulation. Plasma concentrations, determined in volunteers and patients under different conditions of repeated oral administration of the same formulation of orphenadrine hydrochloride exceeded the theoretical values, predicted from the single dose pharmacokinetics, by a factor 2 to 3. The elimination half-lives after discontinuation of treatment showed a 2 to 3-fold increase over the single dose values. This demonstrates a clear discrepancy between the multiple and single dose pharmacokinetics of orphenadrine. Experiments in dogs suggested competition for biotransformation between orphenadrine and its metabolite N-demethylorphenadrine. Product inhibition of this type could explain the observed discrepancy.
The production of sweeteners from starch by enzymes has been commercially successful for many years. However, the real need for improving the current industrial processes for bioconversion of starch, which is chiefly obtained from the wet milling of corn, into the monosaccharides glucose and fructose still exists. Currently, most starch processing in the corn wet milling industry is achieved by using the enzymes α‐amylase, amyloglucosidase and glucose isomerase. This lecture deals with the production of glucose from dextrins by means of amyloglucosidase systems. The amyloglucosidase preparations commonly applied in industry are mixtures containing various enzymes. The maximum obtainable conversion of dextrins into glucose is determined by the thermodynamic and kinetic behaviour of the enzymes present in the amyloglucosidase mixtures. Therefore, knowledge of the composition and properties of the enzymes may lead to the decision to alter the composition of the enzyme system as a possible means of improving the glucose production process. In the search for various amylolytic components advanced chromatography techniques were applied and the enzymes found were used in saccharification studies.
The bioavailability of orphenadrine hydrochloride after a single intramuscular injection was compared to that after a single oral dose by following serial plasma concentration estimations of the unchanged drug. Eight subjects received 40 mg orphenadrine HCl intramuscularly and 50 mg orally on separate occasions 1 week apart. The bioavailability of orphenadrine from the intramuscular dosage form proved to be equal to or even greater than that from the tablet. The first hour plasma concentrations after intramuscular doses were significantly higher than those after oral doses, supporting the clinical use of the intramuscular route in those indications where rapid effects of the drug are required.
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