SummaryA study was carried out in 15 healthy volunteers to investigate the absorption of erythromycin after oral administration when given on an empty stomach or together with food. Plasma concentrations were measured from capillary blood samples collected at various times after administration of a single 500 mg tablet dose of erythromycin stearate to subjects who had fasted overnight and received no food for a further 3 hours. The measurements were repeated, 1 week later, when the subjects took the test dose immediately before a standardized breakfast. In a third series, measurements were taken at steady state. The volunteers had taken their first tablet on Day 7 with food, having received 1 tablet (500 mg) 8 hourly from Day 1. The results showed that the single dose taken on an empty stomach produced the lowest peak plasma concentration. Peak plasma concentration was not only significantly higher but was reached 1 hour earlier when the test dose was taken immediately before a meal, and the findings were not significantly different in the steady state series. It is recommended, therefore, that patients being treated with erythromycin stearate should be instructed to take their tablets just before a meal and not, as previously advised, 1 hour before or 2 hours afterwards.