Prescription ·Strong evidence ·Reviewed May 2026
Rifampin is a bactericidal rifamycin antibiotic used most often as a cornerstone of multidrug tuberculosis therapy and for eradicating meningococcal carriage. It is also one of the most potent inducers of hepatic and intestinal drug-metabolizing enzymes and transporters, which is why it dramatically lowers the blood levels of many co-administered drugs. Through enzyme induction it can also accelerate the catabolism of vitamin D and reduce circulating 25-hydroxyvitamin D, contributing to disturbances in calcium and bone metabolism with prolonged use.
The bottom line
Evidence rating strong. Most-documented uses: treatment of active and latent mycobacterium tuberculosis infection as part of combination therapy, eradication of neisseria meningitidis nasopharyngeal carriage (meningococcal prophylaxis), treatment of leprosy in combination regimens. 3 sources indexed (1980–2018), with 5 interaction records on file.
Core mechanism
Rifampin inhibits bacterial DNA-dependent RNA polymerase by binding to its beta subunit, blocking the initiation of RNA transcription and thereby halting protein synthesis in susceptible organisms, which produces bactericidal activity against Mycobacterium tuberculosis and many gram-positive and selected gram-negative bacteria. In the human host it is a powerful agonist of the pregnane X receptor (PXR), which upregulates cytochrome P450 enzymes (notably CYP3A4, CYP2C9, and CYP2C19), phase II conjugating enzymes (UGTs), and efflux transporters such as P-glycoprotein. This broad induction accelerates the metabolism and elimination of numerous substrates, including vitamin D (via increased 25-hydroxyvitamin D catabolism), oral contraceptives, warfarin, many antiretrovirals, and immunosuppressants, accounting for its extensive drug-interaction profile.2,1
Best absorbed on an empty stomach, taken 1 hour before or 2 hours after a meal, because food (especially high-fat meals) delays and modestly reduces absorption. It is well absorbed orally and widely distributed, including into CSF when meninges are inflamed.
Nutrients this medication can lower over time, and what to replace.
Rifampin induces hepatic enzymes that accelerate vitamin D catabolism during prolonged therapy.
By inducing hepatic cytochrome P450 enzymes, rifampin accelerates the metabolism and clearance of vitamin K, which can reduce vitamin K-dependent clotting factor activity. The effect is most clinically apparent in patients with marginal intake or those on vitamin K antagonist anticoagulants.
Rifampin lowers active vitamin D metabolites through PXR-mediated CYP induction, which secondarily reduces intestinal calcium absorption. Chronic therapy has been associated with disturbed calcium and phosphate homeostasis and, in susceptible patients, drug-induced osteomalacia.
St. John's Wort and rifampin are both strong induction concerns for drug-metabolizing enzymes and transporters; the main danger is failure of other concomitant drugs, not loss of rifampin exposure.
Recommendation: Avoid combining unless the full medication list has been reviewed; monitor or adjust affected concomitant drugs such as anticoagulants, antiretrovirals, transplant drugs, hormonal contraceptives, and azole antifungals.
Rifampin can accelerate vitamin D catabolism during prolonged therapy and may contribute to low vitamin D or bone risk.
Recommendation: Monitor 25-hydroxyvitamin D in prolonged therapy or high-risk patients; supplement based on labs rather than guessing.
Rifampin can alter vitamin K dependent anticoagulation control and prolonged antibiotic therapy may affect vitamin K status.
Recommendation: Coordinate vitamin K intake and INR monitoring if anticoagulated; do not make abrupt supplement changes.
Rifampin can lower exposure to orally administered curcumin, while curcumin may inhibit some enzymes and transporters; the net effect is reduced and unpredictable curcumin bioavailability when taken with rifampin.
Recommendation: Do not rely on curcumin supplements to produce consistent effects during rifampin therapy, as its already-low bioavailability may be further reduced. There is no need to stop curcumin for safety, but expect diminished and variable effect.
Rifampin is hepatotoxic and silymarin from milk thistle is often taken for liver support; combining them can obscure or complicate interpretation of liver enzyme changes, and rifampin may reduce silymarin exposure through enzyme induction.
Recommendation: If using milk thistle during rifampin therapy, continue routine liver function monitoring and do not interpret normal results as proof of liver safety. Report any signs of hepatotoxicity such as jaundice, dark urine, or right upper quadrant pain to a clinician.
Numbered references. Citations throughout the page link here.
Rifampin induces CYP3A4, CYP2C9, CYP2C19, UGTs, and P-glycoprotein, reducing plasma concentrations of numerous substrate drugs.
Documents the mechanism of action against RNA polymerase, the empty-stomach dosing recommendation, hepatotoxicity, and extensive enzyme-induction drug interactions.
Enzyme induction by rifampin increased catabolism of 25-hydroxyvitamin D, lowering circulating concentrations and affecting calcium metabolism.
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