A comparison of the pharmacokinetics and tissue penetration of spiramycin and erythromycin.

The pharmacokinetics of two orally administered macrolides, spiramycin and erythromycin, were compared in six healthy male volunteers in a single dose cross-over study. Penetration of these antimicrobial agents into inflammatory fluid was studied. Spiramycin was administered in a 2 g dose and erythromycin in a 500 mg dose. Spiramycin (Tmax = 3.3 h) and erythromycin (Tmax = 1.2 h) were well absorbed reaching mean plasma Cmax of 3.1 mg/l and 2.1 mg/l, respectively. The relative bioavailability of erythromycin compared to spiramycin appeared to be three- to four-fold greater. The mean plasma elimination half-life was 3.8 h for spiramycin and 1.6 h for erythromycin. The percentage penetration of the antibiotics into inflammatory fluid was good, being 66% for spiramycin and 54% for erythromycin. Both antimicrobial agents attained inflammatory fluid Cmax of 0.7 mg/l by 4-4.8 h. Spiramycin persisted in the inflammatory fluid with a mean elimination half-life of 7.7 h compared to 2.2 h for erythromycin. Twenty-four hour urinary recovery of the administered dose of each antimicrobial agent was less than 5%.