Sulfachlorpyridazine Sodium
Sulfachlorpyridazine sodium
Also known as: Vetisulid · cluricol · sulphachlorpyridazine
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Enteric bacterial infections (E. coli) | Mix 1/4 teaspoonful per liter of water and use as only supply of drinking water | PO | continuous | 5-10 days | 🌎 NA |
| Enteric bacterial infections (E. coli) | Mix 3/4 teaspoonsful per 2 quarts of water | PO | continuous | — | 🌎 NA |
| E. coli and coccidiosis in pigeons | 1200 mg per gallon of drinking water | PO | continuous | — | 🌎 NA |
- Enteric bacterial infections (E. coli): Using the oral powder. May be effective for many E. coli enteric infections.
- Enteric bacterial infections (E. coli): Using the oral powder. Fairly effective for enteric infections, particularly E. coli. Reserved for clients who are unable to give other medications by mouth or parenterally.
- E. coli and coccidiosis in pigeons: Very effective for E. coli and it is a good coccidiostat.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Diarrhea caused or complicated by E. coli in calves less than one month of age | 33-49.5 mg/kg PO, or IV twice daily | PO/IV | q12h | 1-5 days | 🌎 NA |
- Diarrhea caused or complicated by E. coli in calves less than one month of age: Suggest initiating therapy with intravenous preparation and then changing to oral if possible
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Colibacillosis | 44-77 mg/kg PO per day (divide dose and give twice daily if treating individual animals) | PO | q12h or q24h | 1-5 days | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Sulfachlorpyridazine sodium is a short- to intermediate-acting, low lipid-soluble sulfonamide antimicrobial agent. In veterinary medicine, it is primarily indicated for the treatment of enteric infections, particularly diarrhea caused or complicated by E. coli in calves (under one month of age) and colibacillosis in swine. It is also utilized parenterally as a general-purpose sulfonamide in adult cattle and other species.
Clinical Pearls:
- As a time-dependent, bacteriostatic antibiotic, maintaining consistent dosing intervals is crucial for efficacy.
- While resistance to sulfonamides is an increasing and widespread phenomenon, sulfachlorpyridazine remains a valuable tool for specific herd health applications.
- It is highly soluble in urine at usual physiological pH levels, though crystalluria remains a risk in dehydrated patients or those with highly concentrated, acidic urine.
Mechanism of action
Sulfonamides are generally bacteriostatic agents. They act as structural analogues of para-aminobenzoic acid (PABA).
- They competitively inhibit the bacterial enzyme dihydropteroate synthase.
- This blocks the incorporation of PABA into dihydropteroic acid → preventing the biosynthesis of tetrahydrofolic acid (the active form of folic acid).
- Because mammalian cells utilize preformed dietary folic acid and do not synthesize their own, they are generally unaffected by this mechanism.
- Efficacy is significantly reduced in the presence of pus, necrotic tissue, or extensive cellular debris, as these environments are rich in PABA which outcompetes the drug.
Safety & warnings
Contraindications
- Hypersensitivity to sulfonamides, thiazides, or sulfonylurea agents
- Severe renal impairment
- Severe hepatic impairment
Adverse effects
- Crystalluria
- Hematuria
- Renal tubule obstruction
- Keratoconjunctivitis sicca (KCS) in dogs
- Bone marrow depression
- Hypersensitivity reactions (rashes, dermatitis)
- Focal retinitis
- Fever
- Vomiting
- Nonseptic polyarthritis
- Muscle weakness, blindness, ataxia, and collapse (with rapid IV injection)
- Tissue irritation and necrosis (with IM or SC injection)
- Temporary depression of normal cellulytic function in the ruminoreticulum
Precautions
Caution: Use with care in patients with diminished renal or hepatic function, or urinary obstruction.
- Hydration: Ensure adequate urine flow to prevent crystalluria. Alkalinization of urine may prevent crystalluria but decreases tubular reabsorption.
- Administration: Avoid too-rapid IV injection to prevent acute neurological and muscular adverse effects. Avoid IM or SC routes due to the alkaline nature of the solution causing tissue irritation and necrosis.
- Pregnancy: Potentially teratogenic at high doses; crosses the placenta. Weigh risk vs. benefit.
- Lactation: Distributed into milk. Safe use during lactation cannot be assumed; use with caution.
- Laboratory: May cause false-positive results for urine glucose determinations when using the Benedict's method.
Drug interactions
May decrease the oral bioavailability of sulfonamides if administered concurrently
Monitoring
- Clinical efficacy (resolution of diarrhea/infection)
- Adverse effects
- Hydration status and urine output
Pharmacokinetics
Absorption
Readily absorbed from the GI tract of non-ruminants. Food delays the rate, but usually not the extent of absorption. Peak levels occur within 1-2 hours in non-ruminant (and young pre-ruminant) animals. Adult ruminants may have significant delays before oral absorption.
Distribution
Well distributed throughout the body; some reach significant levels in the CSF. Highest levels in liver, kidney, and lung; lower in muscle and bone. Highly bound to serum proteins (species and drug dependent); protein-bound fraction is inactive.
Metabolism
Principally metabolized in the liver via acetylation and glucuronidation, though extra-hepatic metabolism is also involved. Acetylated metabolites may be less soluble, increasing the risk of crystalluria.
Elimination
Renally excreted via both tubular secretion and glomerular filtration. Protein-bound drug is not filtered. The serum half-life of sulfachlorpyridazine is approximately 1.2 hours in cattle.
Overdose
Acute toxicity secondary to overdoses apparently occurs only rarely in veterinary species.
- Signs of Toxicity: In addition to standard adverse effects, CNS stimulation and myelin degeneration have been noted after very high dosages.
- Treatment: Treatment is largely supportive and symptomatic. Ensure aggressive fluid therapy to maintain urine output and prevent crystalluria.
Available products
Formulations
- Oral powder
- Oral suspension
- Injection
- Oral boluses
Veterinary
- Sulfachlorpyridazine Sodium Oral powder: 54 grams per bottle (Vetisulid Powder)
- Sulfachlorpyridazine Sodium Oral Suspension: 50 mg/mL in 180 mL bottles (Vetisulid Oral Suspension)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Injection: Store at room temperature and protect from light; avoid freezing. Oral suspension: Store at room temperature; avoid freezing. Oral boluses and powder: Store at room temperature; avoid excessive heat (above 40°C; 104°F).
Client information
- Water is Crucial: To help reduce the possibility of drug crystals forming in the urine (crystalluria), ensure your animal has free and unrestricted access to fresh drinking water at all times. Avoid dehydration.
- Proper Administration: Give the medication exactly as prescribed by your veterinarian for the full duration, even if the animal seems to feel better.
- Monitor for Side Effects: Contact your veterinarian if you notice decreased urination, blood in the urine, unusual weakness, or if the diarrhea worsens.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.