Introduction: Barbiturates are potent drugs for treatment of alcohol withdrawal symptoms, but they entail a risk of over-dosage and respiratory depression. The purpose of the present study was to investigate the correlation between phenobarbital dose and phenobarbital blood concentration in patients withdrawing from long-term alcohol intoxication.
Material and methods: A total of 497 patients who were hospitalized for treatment of alcohol withdrawal symptoms during an 18-month period were enrolled in the study. Phenobarbital 200 mg was administered orally every 30 or 60 minutes in response to the observed symptoms. Within the first 24 hours after admission, i.e. at 8 AM, blood was collected for determination of phenobarbital concentration, and the cumulated dose of phenobarbital at the time of the blood sampling was registered.
Results: The mean cumulated phenobarbital dose at the time of the blood sampling was 877 mg +/- 557 mg, while the mean plasma phenobarbital concentration was 104 micromol/l +/- 62 micromol/l. A statistically significant linear correlation between phenobarbital dose and concentration was found for both males and females as 83% and 84% of the variation in drug concentration, respectively, could be explained by the phenobarbital dose. We observed no serious complications of the phenobarbital treatment--including respiratory problems or severe sedation.
Discussion: The strong linear correlation between phenobarbital dose and concentration suggests that absorption of plasma phenobarbital from the gastrointestinal system is highly predictable.