Individualization of theophylline dosage: a Bayesian method evaluated in patients with once-daily dosing.

A Bayesian drug dosing program was prospectively evaluated in 16 hospitalized patients with obstructive respiratory disease treated with a novel sustained-release preparation Euphylong. Theophylline was given as a single evening dose. By means of the Bayesian method, the early morning peak was predicted from a steady-state theophylline serum level determined at 8:00 a.m. The prediction errors were in all cases within a clinically acceptable range (mean prediction error +/- standard deviation: -0.2 +/- 1.3 mg/L). The results were compared with predictions based on steady state theophylline serum levels at 8:00 p.m. The prediction errors observed were on average greater than the prediction errors based on the serum levels at 8:00 a.m. (-0.6 +/- 2.5 mg/L). These findings suggest that the Bayesian method is useful for dosage predictions in patients treated once a day with Euphylong.