A 20 years old nulliparous woman is an oral contraceptives pills. She is currently diagnosed as having pulmonary tuberculosis which antituberculous drug decreases the effect of OCP.
Ans. is 'd' i.e.,. Rifampicin (Ref KDT in, 11/01, p. 754).There is not much to explain in this one as you know refampicin is a microsomal enzyme inducer which enhances its own metabolism as well as that of many drugs like - Warfarin*OCP* in) Digitoxin*Sulfonylureas*Steroids*
INH
Pyrazinamide
Ethambutol
Rifampicin
Pharmacology in Gynaecology