Pharmacokinetics of a new, microencapsulated erythromycin base after repeated oral doses

Pharmacokinetics of a new preparation of microencapsulated erythromycin base was studied in 16 healthy subjects. They received 250 mg base 6-hourly or 500 mg 12-hourly for 7 days. The mean maximal serum peaks (+/- SD) after morning doses on days 1, 2, 3, and 7 were 1.4 +/- 0.9, 3.2 +/- 1.1, 3.6 +/- 0.6, 3.5 +/- 1.2 mg/l after the 250-mg dose and 3.2 +/- 1.5, 3.7 +/- 2.1, 3.6 +/- 1.8, and 3.0 +/- 2.0 mg/l after the 500-mg dose. The mean 24-hour urine recoveries were 1.8 and 1.2%, the serum half-lives were (days 1-7) 1.4-2.1 h and 1.9-2.8 h for the 250-mg and 500-mg doses. The mean areas under the serum concentration curves (+/- SD) were 5.8 +/- 2.2, 11.9 +/- 2.2, and 15.3 +/- 5.1 mg . h . 1(-1) after 250 mg and 14.2 +/- 4.9, 16.4 +/- 7.6, and 14.3 +/- 9.0 mg . h . 1(-1) after 500 mg on days 1, 2, and 7. The inter- and intrasubject variability was larger after the 500-mg dose. The pharmacokinetic results indicate that both dosage alternatives are suitable and result in similar steady-state peak levels, but the initial dose should be 500 mg.