Pharmacokinetics of phenobarbital during certain enhanced elimination modalities to evaluate their clinical efficacy in management of drug overdose.

This work was performed to study the pharmacokinetics of phenobarbital during renal clearance enhancement, intestinal clearance enhancement, and a combination of both to determine which method is clinically more effective in the management of drug poisoning. Thirty young patients with phenobarbital overdose were enrolled in the study. They were classified according to the method of treatment to enhance the elimination of phenobarbital into three equal groups: those treated with multiple-dose activated charcoal (MDAC) alone; those treated with urinary alkalinization alone; and those treated with a combination of the two methods. All patients received the required supportive care at the same time as the elimination procedures. Plasma phenobarbital levels were determined on admission and at 6, 12, 18, 24, 30, 36, 42, and 48 hours after admission by the enzyme multiplied immunoassay technique. The results showed that the decrease in plasma phenobarbital levels with MDAC was significantly greater than with either urinary alkalinization or the combined use of both. The results also revealed statistically significant greater total body clearance for phenobarbital and consequently a shorter half-life with MDAC treatment versus either urinary alkalinization alone or the combined use of both. Thus, the authors conclude that the management of drug overdose in the case of weak acidic drugs that have small volumes of distribution should include the sole use of MDAC and supportive care, without urinary alkalinization.