Effect of oral charcoal and urine pH on sotalol pharmacokinetics

The effects of orally given activated charcoal, sodium bicarbonate and ammonium chloride on the pharmacokinetics of sotalol were studied in 7 volunteers in a randomized, cross-over study. Serum and urine concentrations of sotalol were determined by HPLC up to 72 h. Activated charcoal, 50 g, given within 5 min of sotalol hydrochloride (160 mg), reduced its absorption by 99%. When given in repeated doses from 6 h on, 50 g followed by 12.5 g at 6 h intervals, charcoal shortened the half-life after sotalol in serum from 9.4 +/- 0.4 h to 7.6 +/- 0.3 h and in urine from 9.4 +/- 0.4 h to 7.3 +/- 0.3 h (p less than 0.01). The excretion of unchanged sotalol into urine was 65% of the dose during the control phase but neither acidification nor alkalinization of urine for 3 days did increase its urinary excretion. Thus, activated charcoal seems to be effective in prevention of the absorption of sotalol when ingested without delay. Given in repeated oral doses charcoal moderately increases the rate of sotalol elimination, probably by interrupting its enterohepatic or enteroenteric circulation.