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What is A known sputum positive pulmonary tuberculosis patient currently on INH, rifampicin, pyrizinamide and ethambutol is found to be HIV positive. His CD4 count was 100/ L and viral load was more than 50,000 copies/ml. Which of the following antiretroviral drug should be avoided - and explain in detail?
Rifampicin is a potent inducer of enzymes of the cytochrome p450 system, lowers serum levels of many HIV protease inhibitors and some nonucleoside reverse transcriptase inhibitors.
In such cases rifabutin which has much less enzyme inducing activity has been recommended in place of rifampin.
Thus, for the patient in question, level of both indinavir and Ritonavir will be reduced as both are protease inhibitors. So which drug should be avoided

According to Harrison
"Both rifampicin and rifabutin should be avoided in patients on Ritonavir."

In general the standard t/t regimens are equally efficacous in HIV negative and HIV positive. However adverse drug affect may be more pronounced in HIV infected patients.