Why is erythromycin thiocyanate used in feed rather than newer macrolides like tylosin or tilmicosin?

Three practical reasons: (1) Cost — erythromycin thiocyanate is typically 30–50% less expensive per kg than tylosin and substantially cheaper than tilmicosin, making it the most cost-effective macrolide for large-scale feed medication; (2) established safety record — erythromycin has over 70 years of clinical use data across species; (3) familiarity — many feed mills and integrators have decades of formulation experience with erythromycin thiocyanate premixes. However, tylosin and tilmicosin offer advantages in specific applications — tylosin has better activity against Lawsonia intracellularis (ileitis) in swine, and tilmicosin concentrates in lung tissue for respiratory disease in cattle.

What quality parameters are critical when sourcing erythromycin thiocyanate?

Critical parameters: (1) potency (microbiological assay) — not less than 750 ug/mg erythromycin base equivalent per TS3004; (2) pH of aqueous suspension — typically 7.0–9.0; (3) loss on drying — not more than 6.0%; (4) thiocyanate content — verified by ion chromatography or titrimetric method; (5) related substances — erythromycin A content not less than 93% of total erythromycins; (6) residual solvents — compliant with feed-grade requirements; (7) heavy metals and arsenic — within feed additive limits. For premix manufacturers, particle size distribution and bulk density are critical for homogeneous blending in feed.

Erythromycin Thiocyanate | CAS 7704-67-8 | Veterinary API Supplier China

Name: Erythromycin Thiocyanate
SKU: 7704-67-8
Availability: InStock

Erythromycin Thiocyanate molecular structure

Quick Facts

CAS Number	7704-67-8
Molecular Formula	C₃₇H₆₇NO₁₃·HSCN
Molecular Weight	793.02
Pharmacopoeia	TS3004
Packaging	25 KG/DRUM

GMP Certified TS3004 Standard

Product Overview

Erythromycin was discovered in 1952 by Dr. J.M. McGuire and colleagues at Eli Lilly and Company, isolated from a soil sample collected in the Philippines containing the actinobacterium Saccharopolyspora erythraea (formerly Streptomyces erythreus). It was the first macrolide antibiotic ever discovered, establishing an entirely new antibiotic class distinguished by a 14-membered macrocyclic lactone ring. Erythromycin entered clinical use in 1953 under the brand name Ilotycin (originally Ilotycin) and quickly became the standard alternative for penicillin-allergic patients. Over the following decades, the macrolide scaffold gave rise to second-generation (clarithromycin, azithromycin) and third-generation (telithromycin) derivatives with improved pharmacokinetics.

Erythromycin thiocyanate is the thiocyanate salt form of erythromycin designed specifically for veterinary feed additive applications. This salt was developed because erythromycin base is unstable in feed matrices — the free amine form is susceptible to acid-catalyzed degradation in the gastric environment and oxidation during feed processing. The thiocyanate counterion improves chemical stability during pelleting and storage while providing favorable dissolution kinetics in the intestinal tract where absorption and antimicrobial activity are desired. Potency is expressed as erythromycin base equivalents, typically not less than 750 ug/mg.

In veterinary medicine, erythromycin's clinical niche centers on Mycoplasma and Campylobacter infections — two pathogen groups where many other antibiotic classes show limited or inconsistent activity. In poultry, erythromycin thiocyanate has been a mainstay treatment for chronic respiratory disease (CRD) caused by Mycoplasma gallisepticum for over 50 years. In swine, it is used for bacterial enteritis and as part of respiratory disease combination protocols. An important secondary benefit is its activity against Campylobacter jejuni, making it useful in flock-level Campylobacter reduction programs — increasingly relevant as food safety regulations tighten around this zoonotic pathogen.

As of mid-2026, erythromycin thiocyanate remains a cost-effective macrolide option for large-scale poultry and swine operations, particularly in Asia, Latin America, and Africa where its established safety record and lower cost relative to tylosin and tilmicosin are competitive advantages. China is the dominant global producer of erythromycin thiocyanate API. KingWish supplies GMP-certified erythromycin thiocyanate meeting TS3004 standards, supporting feed premix manufacturers and veterinary pharmaceutical companies worldwide.

Quality Specifications

Potency (Microbiological Assay)	≥ 750 ug/mg erythromycin base equivalent, per TS3004
pH (Aqueous Suspension)	7.0–9.0
Loss on Drying	≤ 6.0%
Erythromycin A Content	≥ 93% of total erythromycins by HPLC
Heavy Metals	≤ 20 ppm; arsenic ≤ 2 ppm (feed additive limits)
GMP Status	Manufactured under ICH Q7 GMP conditions

Veterinary Applications

Poultry Feed Medication

Feed additive for prevention and treatment of CRD (Mycoplasma gallisepticum), infectious synovitis (M. synoviae), and necrotic enteritis (C. perfringens). Typical inclusion: 100–200 g/ton feed for 5–7 days.

Swine Respiratory Disease

Feed or water medication for bacterial respiratory infections and enteritis. Often combined with tetracyclines for broader coverage. Effective against Lawsonia intracellularis at higher doses.

Therapeutic Areas

Poultry: Chronic respiratory disease (CRD), mycoplasma infections, necrotic enteritis, Campylobacter control
Swine: Respiratory disease complex, bacterial enteritis, ileitis
Cattle: Respiratory disease, foot rot (Fusobacterium necrophorum), calf diphtheria

Sourcing Erythromycin Thiocyanate: Key Checks

Documentation

Request CoA with microbiological potency assay and HPLC erythromycin A content. Verify thiocyanate content by titrimetric method. Confirm residual solvent compliance. For premix manufacturers, request particle size and bulk density data.

Red Flags

Low potency (<750 ug/mg) suggests degradation or substandard fermentation. Elevated loss on drying (>6%) indicates moisture damage. Low erythromycin A content (<93%) means higher inactive erythromycin B and C analogs. Unusual color or odor.

Packaging & Logistics

Standard: 25 KG/DRUM with moisture barrier. Store in cool, dry conditions below 25°C, protected from light and moisture. Feed-grade material has typical shelf life of 24–36 months in unopened original packaging.

Market Context

Erythromycin thiocyanate remains the most cost-effective macrolide for large-scale feed medication in Asia, Latin America, and Africa. Price advantage of 30–50% vs tylosin. China dominates global API production. Market report

Frequently Asked Questions

Erythromycin thiocyanate (CAS 7704-67-8) is the thiocyanate salt of erythromycin, specifically designed for veterinary feed additive applications. Unlike erythromycin base (CAS 114-07-8) used in human pharmaceuticals, the thiocyanate salt offers improved stability in feed matrices, better handling characteristics for premix manufacturing, and optimized release kinetics in the gastrointestinal tract of livestock. The thiocyanate counterion does not contribute to antimicrobial activity — potency is expressed as erythromycin base equivalents, typically not less than 750 ug/mg per TS3004 standard.

In poultry, erythromycin thiocyanate is primarily used against: (1) Mycoplasma gallisepticum — the cause of chronic respiratory disease (CRD), the most economically significant respiratory disease in broilers and layers; (2) Mycoplasma synoviae — infectious synovitis and airsacculitis; (3) Clostridium perfringens — necrotic enteritis; (4) Campylobacter jejuni — for flock-level control programs increasingly important for food safety compliance; and (5) Gram-positive cocci including Staphylococcus and Streptococcus species involved in secondary respiratory infections.

Three practical reasons: (1) Cost — erythromycin thiocyanate is typically 30–50% less expensive per kilogram of active than tylosin and substantially cheaper than tilmicosin, making it the most cost-effective macrolide for large-scale feed medication programs; (2) established safety record — erythromycin has over 70 years of clinical use data across multiple species; (3) formulation familiarity — many feed mills and poultry integrators have decades of experience with erythromycin thiocyanate premix manufacturing and inclusion. However, tylosin has superior activity against Lawsonia intracellularis (porcine ileitis), and tilmicosin provides concentrated lung tissue levels for bovine respiratory disease — the choice depends on the specific production system and target pathogens.

Critical parameters: (1) potency by microbiological assay — not less than 750 ug/mg erythromycin base equivalent per TS3004; (2) pH of aqueous suspension — typically 7.0–9.0; (3) loss on drying — not more than 6.0% (higher values suggest moisture damage during storage); (4) erythromycin A content by HPLC — not less than 93% of total erythromycins (lower values mean higher proportions of less active erythromycin B and C); (5) thiocyanate content verified by ion chromatography or titrimetric method; (6) residual solvents compliant with feed-grade requirements; (7) heavy metals and arsenic within feed additive safety limits. For premix manufacturers, consistent particle size distribution and bulk density are critical for homogeneous blending during feed production.

Standards: TS3004 | CAS: 7704-67-8 | Quality data verified against pharmacopoeia monograph COA and MSDS available | DrugBank | July 2026