A quick and convenient method has been developed for the micro estimation of antihistamine drugs. 1-5 mg of sample is allowed to react with 10 ml of 0.02 M, N-bromosaccharin solution. Unconsumed reagent can be accurately titrated with 5 ml of 15% KI and 0.02N sodium thiosulphate solution using starch as indicator. SD and CV was calculated for reproducible and accurate result. The accuracy of the method is within + 1 % and possible course of reaction was suggested on the basis of stoichiometry as well as find reaction product.