An ultra‐violet spectrophotometric method is described for the determination of thalidomide in blood, plasma or urine. Thalidomide is extracted from the sample with chloroform, and the drop in extinction measured when solutions are treated with alkali. The method has been used to determine the amount of drug present in animal and human blood.

1. The absorption, metabolism and excretion of isamoxole, (2-methyl-N-butyl-N-(4-methyloxazol-2-yl)propanamide), a compound with anti-allergy properties, has been studied in the rat and guinea-pig. 2. The compound was well-absorbed by both species after oral doses of 50 to 150 mg/kg. It underwent extensive first-pass metabolism in the liver, and was excreted as a mixture of metabolites, predominantly in the urine, within 48 h. 3. Three major routes of metabolism were involved, namely deacylation, oxidative ring scission and alkyl oxidation. 4. A major plasma and urine metabolite was 1-butyl-3-(1-carboxyethyl)urea, and this was accompanied by low levels of its cyclized product 3-butyl-5-methylhydantoin.