To the Editor: In their study of the effect of food on the bioavailability of a sustained-release verapamil preparation (Isoptin-SR, Knoll AG, 240-mg tablet), Conway et al. reported that food had no appreciable effect on Cmax, which was found to be 92 ± 79 ng/mL (mean ± SD) when subjects (n = 12) had fasted and 63 ± 27 ng/mL when they were dosed following breakfast. The AUC0–∞ values were also similar: 1270 ± 556 and 1306 ± 483 h · ng/mL under fasting and fed conditions, respectively. In their discussion, the authors suggested that dietary precautions may be unnecessary. In contrast, the Isoptin–SR package insert describes a twofold increase in Cmax (to 164 from 79 ng/mL) when fasting subjects are compared with fed subjects. The insert states that the AUC0–24 determined in fasting subjects was 1478 h·ng/mL compared with 841 h · ng/mL in fed subjects. The manufacturer recommends that the product be taken with food.