spiramycin

Spiramycin is a macrolide antibiotic produced by the bacterium Streptomyces ambofaciens. It belongs to the spiramycin group of 16-membered ring macrolides and is marketed as a mixture of closely related compounds, notably spiramycin A and spiramycin B.

Spiramycin exerts its effect by binding to the 50S subunit of the bacterial ribosome, inhibiting peptide chain elongation and translocation. This action reduces bacterial protein synthesis and helps to control susceptible organisms.

The antimicrobial spectrum of spiramycin is primarily against Gram-positive cocci such as Streptococcus species and Staphylococcus aureus, along with some Gram-positive rods and certain anaerobes. It has limited activity against many Gram-negative bacteria and Enterobacteriaceae. Clinically, it is used for various infections including respiratory tract infections, gynecologic and soft tissue infections where susceptible organisms are involved. In some countries, spiramycin is used for the prevention of vertical transmission of toxoplasmosis during pregnancy, typically when preferred therapies are unsuitable.

Spiramycin is usually given orally, with absorption that can be variable. It concentrates in tissues and placental tissues, and is eliminated primarily via biliary routes with some renal excretion. Dosing regimens vary by indication and formulation.

Adverse effects are generally similar to other macrolides and include gastrointestinal upset (nausea, vomiting, diarrhea) and hypersensitivity. Rare liver function abnormalities may occur. Drug interactions are possible, and coadministration with other medications that affect the cytochrome P450 system or the QT interval should be monitored.

Spiramycin is used in several countries around the world and is not approved by the United States FDA for human use.