Effect of activated charcoal on rifampicin absorption in man

The effect of activated charcoal (AC) on rifampicin excretion was investigated in six healthy volunteers. On three occasions, at weekly intervals, each subject received a 600 mg rifampicin with 350 ml of water; b+c one and two weeks later, 600 mg of rifampicin plus 7.5 and 15 g AC, respectively, in 350 ml of water as a charcoal slurry. Urinary levels of rifampicin were measured form 1-36 hr after ingestion. Treatment with AC led to 1.2 per cent urinary recovery of rifampicin; decreased excretion rate; and a much lower plateau indicative of reduced absorption.