9-O-[[(5S)-5α-(ジメチルアミノ)テトラヒドロ-6β-メチル-2H-ピラン]-2-イル]ロイコマイシンV

The mechanism of action of macrolides has been a matter of controversy for some time. Spiramycin, a 16-membered macrolide, inhibits translocation by binding to bacterial 50S ribosomal subunits with an apparent 1 : 1 stoichiometry. This antibiotic is a potent inhibitor of the binding to the ribosome of both donor and acceptor substrates. The primary mechanism of action is done by stimulation of dissociation of peptidyl-tRNA from ribosomes during translocation.I

The extent of absorption of Spiramycin was shown to be incomplete. Oral bioavailability ranges from 30-39%. Spiramycin has slower rate of absorption than Erythromycin. It has a high pKa (7.9) which could be a result of high degree of ionization in acidic medium of the stomach.

Fecal-biliary route is the primary route of elimination. The secondary route is renal-urinary route.

The tissue distribution of spiramycin is extensive. The volume of distribution is in excess of 300 L, and concentrations achieved in bone, muscle, respiratory tract and saliva exceed those found in serum. Spiramycin showed high concentrations in tissues such as: lungs, bronchi, tonsils, and sinuses.

80% of the administered dose excreted in the bile, which makes the fecal-biliary route is the most important route of elimination. Enterohepatic recycling could also occur. Only 4 to 14% of an administered dose is eliminated through renal-urinary excretion route.