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The extent of absorption of sulfanilamide, bretylium tosylate, sulfisoxazole acetyl, and riboflavin was determined in rats exposed to 850 rad of cobalt-60 gamma-radiation of sham irradiated. The drug were administered orally at 1 or 5 days postirradiation, and the amount of drug excreted in the urine was used as the measure of absorption. Following intravenous drug administration, there was no difference between irradiated and control animals in the amount of drug excreted in the urine. At 1 day postirradiation, the absorption of sulfanilamide and bretylium was not affected by radiation; the absorption of sulfisoxazole acetyl and riboflavin was increased. The fraction of sulfanilamide excreted in the urine as N4-conjugate was increased at 1 day postirradiation. At 5 days postirradiation, there was no detectable difference between irradiated and control animals in the extent of drug absorption. The effects of radiation on the extent of absorption of orally administered drugs were most pronounced immediately following irradiation. Irradiation apparently does not affect the absorption of drugs that are normally well absorbed or poorly absorbed due to slow transport across the GI mucosa. Following irradiation, there may be an increase in the extent of absorption of drugs that are poorly absorbed due to low aqueous solubility or that are absorbed by a saturable transport mechanism.

Lorapride has been determined in plasma, red blood cells, and urine by HPLC. The detection was performed at a short wavelength (226 nm), resulting in a detection limit of 10 ng/mL (amount injected was 3.5 ng). Reproducibility of analytical and chromatographic methods through statistical coefficients of variation was 4%. By TLC, only levels in urine were determined. Urine samples were spotted directly on the plate; lorapride was determined after spraying the plate with the Bratton-Marshall reagent, and measurements were carried out in the simultaneous reflectance and transmittance mode (540 nm). The detection limit was 10 ng spotted. Lorapride amounts in urine determined by the two methods were compared by statistical analysis. Examples of kinetics after intravenous and oral administration (100 mg) in humans are given.

A high-pressure liquid chromatographic method for the separation and quantitative determination of sulfamethazine, sulfathiazole, and their N4-acetylated metabolites on an amino-bonded reversed-phase column was developed. The method is suitable for the analysis of these compounds in pure solutions as well as in cattle urine. Retention times were reproducible. Injection volumes containing 0.2 mug of individual sulfonamides or their acetyl derivatives were successfully quantitated; coefficients of variation ranged from 0 to 0.073 for individual sulfonamides.