Use of the analogue computer to examine the quantitative relation between urinary pH and kidney reabsorption of drugs partially ionized at physiological pH

A method, involving the use of an analogue computer, is described for determining a quantitative relation between measured urinary pH and the kidney tubular reabsorption of certain drugs under normal conditions of fluctuating urinary pH. The method is based on the use of drug excretion versus time profiles under normal conditions and of absorption, metabolism and excretion rate constants, determined under conditions of controlled urinary pH, e.g. constant acidic pH (<5) in the case of basic drugs. In support of the theoretical treatment, experimental results, using amphetamine as a model drug, are presented. The implications of the method are discussed with respect to the evaluation of drug formulations under normal urinary pH conditions.

Application of the analogue computer to pharmacokinetic and biopharmaceutical studies with amphetamine-type compounds

The kinetics of absorption, metabolism, and excretion of (+)-amphetamine and (+)-methylamphetamine, after oral administration of “free” dosage forms to man, under controlled acidic urine conditions, have been examined using an electronic analogue computer. This device has also been used to determine the in vivo rate of release of the drugs from hard gelatin capsule dosage forms and prolonged-release preparations. In vivo drug release from the prolonged-release preparations was correlated with in vitro drug release data.

Routine detection and identification in urine of stimulants and other drugs, some of which may be used to modify performance in sport

A general procedure for the analysis in urine of basic drugs (and their metabolites), some of which may be misused as stimulants in sport, has been developed. The techniques used include gas-liquid and thin-layer chromatography and linked gas-liquid chromatography—mass spectroscopy. It is recommended that international control of drug-taking in sport be based primarily upon urine analysis by gas-liquid chromatography systems and also derivative formation followed by gas-liquid chromatography. The principles outlined in the procedure can be applied in a much wider forensic context.