Prevention of gastrointestinal absorption of phenobarbital by activated carbon beads as an oral adsorbent.

The in vitro adsorption characteristics of activated carbon beads suitable for oral administration and the original fine powder were examined, using phenobarbital as the test drug. The extent and rate of drug adsorption on carbon in the beads were almost equal to those on the powder. In three healthy volunteers, 10 g of activated carbon beads administered orally 20 min after 120 mg of phenobarbital, reduced the total bioavailability by 57% (p less than 0.005), based on the salivary AUC-value during 96 h and the achieved peak concentration of the drug in salvia by 51%. These results demonstrated the potency of activated carbon beads as a gastrointestinal adsorbent in acute intoxications from phenobarbital.