Quick Facts
| CAS Number | 8025-81-8 |
|---|---|
| Molecular Formula | C43H74N2O14 (Spiramycin I, major component) |
| Molecular Weight | 843.05 (Spiramycin I) |
| Pharmacopoeia | EP/CEP |
| Packaging | 25 KG/DRUM |
Product Overview
Spiramycin was discovered in 1954 at the Rhone-Poulenc laboratories in France, isolated from a new strain of soil actinomycete collected near Peronne in the Somme region: Streptomyces ambofaciens. It was the first 16-membered macrolide antibiotic, structurally distinct from the 14-membered erythromycin discovered just two years earlier. The larger lactone ring confers spiramycin with its most clinically valuable property: exceptional tissue penetration. Spiramycin achieves concentrations in lung parenchyma, bronchial secretions, udder tissue, and alveolar macrophages that are 20-30 times higher than simultaneous serum levels — a distribution advantage outstanding by erythromycin, clarithromycin, or azithromycin.
The mechanism behind this tissue penetration is active cellular uptake. Spiramycin is avidly concentrated inside phagocytic cells (macrophages and neutrophils) through a process known as lysosomal trapping — the weakly basic macrolide diffuses into acidic lysosomes where it becomes ionized and trapped. These drug-loaded phagocytes then migrate to sites of infection, delivering high spiramycin concentrations directly into infected tissue and abscesses. This "Trojan horse" delivery mechanism makes spiramycin particularly effective against intracellular pathogens (Mycoplasma, Toxoplasma) and pathogens sequestered in biofilms and abscesses, where passive diffusion-limited antibiotics fail to reach therapeutic levels.
Spiramycin is not a single molecule but a natural mixture of three structurally related components: spiramycin I (approximately 63%), II (approximately 24%), and III (approximately 13%), which differ by the acylation pattern on the mycarose sugar residue. All three are microbiologically active, and the natural ratio is the result of the biosynthetic pathway in S. ambofaciens. The EP monograph controls this component ratio as an acceptance criterion to ensure batch-to-batch consistency. Spiramycin potency is typically expressed in international units (IU) per milligram, with pharmaceutical-grade spiramycin base typically exceeding 4,500 IU/mg on the dried basis.
As of mid-2026, spiramycin occupies a specialized position in the veterinary macrolide market alongside tylosin and tilmicosin. Its unique advantage — extraordinary tissue penetration without the cardiotoxicity risk of tilmicosin — makes it the preferred macrolide for intramammary mastitis preparations, toxoplasmosis control, and respiratory disease where intracellular pathogen clearance matters. China is the dominant global producer of spiramycin base, with fermentation-based manufacturing concentrated in Shandong, Hebei, and Ningxia provinces. KingWish supplies GMP-certified spiramycin base meeting EP specifications, including CEP certification for the EU market.
Quality Specifications
| Potency (HPLC/Microbiological) | ≥ 4,500 IU/mg (dried basis), per EP monograph |
|---|---|
| Component Ratio | Spiramycin I ≥ 80%, Spiramycin II ≤ 10%, Spiramycin III ≤ 10% (EP) |
| Related Substances | Individual impurity ≤ 2.0%, total impurities ≤ 3.0% (EP) |
| Residual Solvents | Compliant with ICH Q3C; methanol and acetone typically the main process solvents |
| Heavy Metals | ≤ 20 ppm |
| GMP Status | Manufactured under ICH Q7 GMP conditions; CEP certified for EU supply |
Veterinary Applications
Respiratory Disease (Poultry & Swine)
Water-soluble spiramycin for CRD complex in broilers. Feed medication for mycoplasmal pneumonia in swine. Lung tissue concentrations exceed plasma by 20-30x, achieving therapeutic levels against Mycoplasma spp.
Mastitis (Dairy Cattle)
Intramammary spiramycin for Gram-positive mastitis (Staph. aureus, Strep. agalactiae). Excellent udder tissue penetration, short milk withdrawal, and no cardiotoxicity risk — a key advantage over some other macrolides in lactating animals.
Therapeutic Areas
- Poultry: Chronic respiratory disease (CRD), Mycoplasma gallisepticum and M. synoviae infections
- Swine: Mycoplasmal pneumonia (M. hyopneumoniae), enzootic pneumonia, bacterial enteritis
- Cattle: Gram-positive mastitis, respiratory infections, neonatal calf diarrhea
- Sheep & Goats: Toxoplasmosis prevention and treatment
- Companion Animals: Toxoplasmosis, susceptible bacterial infections
Sourcing Spiramycin Base: Key Checks
Documentation
Request CoA with HPLC component ratio data (I/II/III), potency in IU/mg, residual solvent statement (ICH Q3C), heavy metals, and GMP certificate. For EU supply, CEP is the key document. For feed applications, confirm whether pharmaceutical or feed-grade specification applies.
Red Flags
Component ratios outside EP limits (especially elevated spiramycin II/III), low potency below 4,500 IU/mg, atypical HPLC impurity profile, and missing component ratio data on CoA. Fermentation-derived APIs require consistent component profiles between batches.
Packaging & Logistics
Standard: 25 KG/DRUM with PE liner. Store at room temperature in airtight containers, protected from moisture. Spiramycin is a fermentation product — ensure stability data supports the proposed storage conditions and shelf life. Standard lead time 4-8 weeks.
Market Context
Spiramycin competes with tylosin and tilmicosin in the veterinary macrolide market. Its key differentiators are superior tissue penetration and absence of cardiotoxicity (tilmicosin carries a fatal human cardiotoxicity warning). CEP certification differentiates pharmaceutical-grade suppliers from commodity fermentation producers for the EU market.