<prompt> A known sputum positive pulmonary tuberculosis patient currently on INH, rifampicin, pyrizinamide and ethambutol is found to be HIV positive. His CD4 count is 100 dl and viral load is more than 50,000 copiesml. Which of the following antiretroviral drug should be avoided in this patient?IndinavirLamivudinRitonavirEirenz  <response>: Ritonavir a protease inhibitor should be avoided from the treatment of HIV, in a patient receiving rifampicin as a pa of antituberculosis treatment regime. Rifampin is a potent hepatic enzyme inducer. When this is co administered with a protease inhibitor, it decrease the availability of the drug upto 80. This resulting low concentration of the drug promotes the development of drug resistance and treatment failure. Ref: Antiretroviral Therapy By Erik De Clercq, Page 347 