How would you manage methotrexate therapy in an active rheumatoid arthritis patient undergoing treatment for latent TB with rifampin?

There are no easy answers as both rifampin and INH combined with methotrexate are associated with enhanced hepatotoxicity. Monotherapy regimens, while generally well tolerated can cause hepatotoxicity leading to dose modification/interruption in about 5-10%.

All approved regimens can be tried depending on shared and informed decision process - I generally avoid combination regimens and go with 6 or 9 m INH or 4 months rifampin.

General caution with Tylenol and alcohol; stop for bili > 3mg% or ALT >5.

Liver toxicity is generally totally reversible.

Monitor liver profile ALT bili regularly. We have most data on 6-9 months INH and 4 months rifampin. I am not aware of published data on combo INH rifampin/rifamycin and MTX.