Spiramycin

Antibacterial antibiotic belonging to the macrolides family.

Antibacterial activity spectrum

Critical concentrations differentiate sensitive from moderate strains, and both from resistant ones: S <1 mg/l and R >4 mg/l

For certain species, the prevalence of acquired resistance may vary according to place and time. It is useful, therefore, to have information on the prevalence of local resistance, particularly when treating severe infections.

These data can only provide an indication of the sensitivity of a bacterial strain to this antibiotic.

When the variability in the prevalence of resistance for a given species of bacteria is known in France, it is shown in the table below:

Absorption

Spiramycin is rapidly but incompletely absorbed and is not modified by food intake.

Distribution

After oral administration of 6 million IU of spiramycin, the peak serum concentration is 3.3 μg/ml. Plasma half-life is about 8 hours.

Spiramycin does not enter the CSF and is excreted into breast milk.

Plasma protein binding is low (10%).

Tissue and saliva diffusion is excellent (lungs: 20-60 μg/g, tonsils: 20-80 μg/g, infected sinuses: 75-110 μg/g, bones: 5-100 μg/g).

Ten days after the end of treatment, there is 5 to 7 μg/g of active substance in the spleen, liver and kidneys.

Macrolides penetrate and accumulate in phagocytes (polynuclear neutrophils, monocytes, peritoneal and alveolar macrophages).

Intra-phagocyte concentrations are high in man.

These properties explain macrolides activity against intra-cellular bacteria.

Metabolism

Spiramycin is metabolised in the liver with the formation of chemically unknown but active metabolites.

Excretion

Urine: 10% of the administered dose.

Extensive biliary excretion: concentrations 15 to 40 times higher than serum concentrations.

Small amounts of spiramycin are present in feces.

Not relevant.