Relative Bioavailability of Enteric Coated Pellets, Stearate and Ethylsuccinate Formulations of Erythromycin

In a randomized three-phase crossover study, 12 healthy male volunteers were given three 12-hourly 500-mg doses of erythromycin base, as enteric coated pellets in capsules (2 × 250 mg), erythromycin stearate tablet (1 × 500 mg), or erythromycin ethylsuccinate sachet (1 × 500 mg). The reaction time after administration of the pellets is significantly longer than after the stearate or ethylsuccinate formulations. The peak serum concentrations are higher for the pellets after both the 1st and 3rd dose. The time to reach peak concentrations is significantly longer for the pellets than for the stearate and ethylsuccinate formulations. The area under the serum concentration/time curve during 0–8 h after both doses is highest for the pellets. In conclusion, these findings indicate that despite the longer lag (1.8–1.2 h), the extent of gastrointestinal absorption and bioavailability of erythromycin is apparently greater for the base pellets than for the stearate and ethylsuccinate formulations.