smear-positive pulmonary tuberculosis. His backgroundhistory included chronic essential hypertension which waswell-controlled with amlodipine 10mg daily. However, hisblood pressure became suboptimal one week intoantitubercular treatment, necessitating escalation ofantihypertensive therapy up to six medications. Followingcompletion of antitubercular treatment, his blood pressureimproved markedly. The number of antihypertensives wasable to be reduced to only two after a month. We postulatethat rifampicin has attenuated the therapeutic effect ofamlodipine via potent induction of hepatic CYP3A4 but thefailure to control the blood pressure even with medicationsunrelated to cytochrome P450 pathways raises the spectreof an additional interaction.