Rifampicin

Mechanism of action

• binds to DNA dependent RNA polymerase

• inhibits initiation of RNA synthesis

Activity

• bactericidal for Mycobacterium tuberculosis

• very active against aerobic gram positive cocci (inc. staphylococi, streptococci)

Resistance

• can develop rapidly so usually used in combination

• mutation in beta-subunit of RNA polymerase

• Gram-negative intrinsically resistant due to decreased uptake

Adverse reactions

• Hepatitis

• GI upsets

• thrombocytopenia

• colours bodily secretions orange

Interactions

• enzyme induction enhances metabolism of

  • warfarin

  • oral contraceptive pill

  • phenytoin

  • sulponylureas

  • corticosteroids

Also

Rifabutin

• similar properties - particularly active against Mycobacterium avium