rifampicin

introduction

rifampicin is a rifamycin antibiotic which inhibits DNA dependent RNA polymerase activity in susceptible cells
it is mainly used for:
- Rx of tuberculosis (TB)
- Rx of leprosy
- prophylaxis for meningitis and Haemophilus influenza type B
particularly active against rapidly growing extracellular organisms
has bactericidal activity intracellularly and against slow and intermittently growing Mycobacterium tuberculosis

jaundice
HS to rifamycin
concurrently with the combination of saquinavir/ ritonavir
PH rifampicin induced thrombocytopenia, purpura, haemolytic anaemia or renal failure

may cause or increase risk of drug-induced hepatitis, eg when used with isoniazid
competes with bilirubin for excretory pathways in liver cells thuis may cause jaundice during start of Rx
resistance may rapidly occur
rifampicin syrup contains sodium metabisulfite which may cause allergic reactions is some people
urine, faeces, saliva, sputum, sweat and tears may be coloured red-orange - avoid in patients with soft contact lenses which may become permantly stained
has enzyme induction properties that can enhance the metabolism of endogenous substrates
may exacerbate porphyrias
category C in pregnancy
- bleeding attributable to hypoprothrombinaemia has been reported in newborn infants and in mothers after the use of rifampicin during late pregnancy. If rifampicin is used during the last few weeks of pregnancy, vitamin K should be given to the mother and the newborn infant.
avoid in lactation as passes into breast milk
avoid in newborn infants as liver enzymes not adequately developed

increase risk of drug-induced hepatitis, eg when used with:
- isoniazid
- halothane
- combination saquinavir/ ritonavir
warfarin - may need to increase warfarin dose
drugs metabolised by cytochrome P450
women using combined oral contraceptive pill (OCP) should be advised to change to nonhormonal methods of birth control during rifampicin therapy