Rifapentine, a rifamycin derivative, is the basis of the once-weekly 12-week regimen (with isoniazid) for latent tuberculosis. The property that permits such infrequent dosing compared with rifampicin is:

• A Absence of hepatic enzyme induction
• B Activity restricted to dormant bacilli only
• C Complete lack of interaction with cytochrome P450 substrates
• D The longest plasma half-life among the rifamycins ✓

Explanation

Rifapentine has the longest half-life of any rifamycin (roughly 13 to 15 hours versus about 3 hours for rifampicin), permitting once-weekly administration with isoniazid for 12 weeks in the treatment of latent TB. Like rifampicin, it remains a potent inducer of cytochrome P450 enzymes, which is exactly why it must be avoided with protease inhibitors and many other antiretrovirals, ruling out options A and C.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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