To the Editor.— Modification of the gastrointestinal absorption of one drug by another may be an important factor in patients receiving multiple drug therapy, especially with the increasing use of over-the-counter medications. We report the influence of administration of antacids on the release of aspirin from an entericcoated formulation. Enteric-coated aspirin (Ecotrin) was administered to six healthy subjects (aged 21 to 32 years) with and without coadministration of a magnesium and aluminum hydroxide oral suspension (Maalox) in a crossover manner. At least one week separated each study. After an overnight fast and one hour prior to the administration of the aspirin, 15 ml of antacid suspension was taken with 85 ml of water. At the time of aspirin administration, 15 ml of antacid suspension was again administered with 85 ml ofwater. The control studies consisted of administration of 100 ml of water one hour prior to and concomitantly with