Sulfadimethoxine
4-Amino-N-(2,6-dimethoxy-4-pyrimidinyl)benzenesulfonamide
Also known as: Albon · Di-Methox · Amtech · solfadimetossina · solfadimetossipirimidina · sulphadimethoxine · Chemiosalfa · Deltin · Risulpir · Ritarsulfa · SDM · Sulfadren · Sulfastop · Sulfasol · Sulfathox
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
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 25 mg/kg PO, IV, or IM once daily | PO, IV, IM | q24h | — | 🌎 NA |
| Susceptible infections | 100 mg/kg PO, IV or IM once daily | PO, IV, IM | q24h | — | 🌎 NA |
| Susceptible infections | 55 mg/kg PO, or IV, or SC initially, then 27.5 mg/kg once daily thereafter | PO, IV, SC | q24h | — | 🌎 NA |
| Coccidiosis | 55 mg/kg PO initially on the first day of therapy, then 27.5 mg/kg PO once daily for 9 days | PO | q24h | 10 days total | 🌎 NA |
| Coccidiosis | 50 mg/kg once daily for 10-14 days | PO | q24h | 10-14 days | 🌎 NA |
| Coccidiosis (Infant period 2-6 weeks) | 50 mg/kg PO on the first day followed by a daily dose of 25 mg/kg PO until symptoms regress | PO | q24h | Until symptoms regress | 🌎 NA |
- Coccidiosis: Will eliminate oocyst excretion in most dogs
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 25 mg/kg PO, IV, or IM once daily | PO, IV, IM | q24h | — | 🌎 NA |
| Susceptible infections | 100 mg/kg PO, IV or IM once daily | PO, IV, IM | q24h | — | 🌎 NA |
| Susceptible infections | 55 mg/kg PO, or IV, or SC initially, then 27.5 mg/kg once daily thereafter | PO, IV, SC | q24h | — | 🌎 NA |
| Coccidiosis | 50 mg/kg once daily for 10-14 days | PO | q24h | 10-14 days | 🌎 NA |
- Coccidiosis: Will eliminate oocyst excretion in most cats
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections (Rabbits) | 10-15 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| Coccidiosis (Rabbits) | 25 mg/kg PO once daily | PO | q24h | — | 🌎 NA |
| Susceptible infections (Hedgehogs) | 2-20 mg/kg/day IM, SC or PO | IM, SC, PO | q24h | — | 🌎 NA |
| Coccidiostat (Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas) | 50 mg/kg PO once, then 25 mg/kg PO once daily for 10-20 days or 75 mg/kg PO for 7-14 days | PO | q24h | 10-20 days or 7-14 days | 🌎 NA |
Ferrets
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 25 mg/kg PO, SC or IM once daily | PO, SC, IM | q24h | — | 🌎 NA |
| Coccidiosis | 25 mg/kg PO once daily for 14 days | PO | q24h | 14 days | 🌎 NA |
Reptiles
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Coccidia | 90 mg/kg PO on day one and then 45 mg/kg PO on 5 successive days; may also be given IM or IV | PO, IM, IV | q24h | 6 days total | 🌎 NA |
- Coccidia: Maintain adequate hydration.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 55 mg/kg, PO or IV q12h | PO, IV | q12h | — | 🌎 NA |
| Susceptible infections | 55 mg/kg IV or PO initially, then 27.5 mg/kg q24h IV | IV, PO | q24h | — | 🌎 NA |
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections | 110 mg/kg PO or IV once daily | PO, IV | q24h | — | 🌎 NA |
| Susceptible infections | 55 mg/kg IV initially, then 27.5 mg/kg IV once daily | IV | q24h | — | 🌎 NA |
| Susceptible infections | 110 mg/kg, PO q24h | PO | q24h | — | 🌎 NA |
| Susceptible infections | 55 mg/kg PO or IV initially, then 27.5 mg/kg q24h | PO, IV | q24h | — | 🌎 NA |
| Susceptible infections | 55 mg/kg IV or PO initially, then 27.5 mg/kg q24h IV or PO for up to 5 days. If using sustained release boluses: 137.5 mg/kg PO every 4 days | IV, PO | q24h (or q4d for SR) | Up to 5 days | 🌎 NA |
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Coccidiosis (Camelids - E. alpacae, E. lamae, E. punoensis, E. peruviana) | 15 mg/kg PO twice daily for 5 days | PO | q12h | 5 days | 🌎 NA |
| Coccidiosis (Camelids - E. macusaniensis) | 110 mg/kg PO q24h | PO | q24h | 10-15 days | 🌎 NA |
- Coccidiosis (Camelids - E. alpacae, E. lamae, E. punoensis, E. peruviana): Monitor for signs of polioencephalomalacia.
- Coccidiosis (Camelids - E. macusaniensis): Administer directly to animal, not in water supply.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Sulfadimethoxine is a long-acting, broad-spectrum sulfonamide antimicrobial agent used widely in veterinary medicine.
Key Clinical Highlights:
- Primary Uses: FDA-approved for respiratory, genitourinary, enteric, and soft tissue infections in dogs, cats, horses, and cattle. It is also heavily utilized (though off-label in some species) for the treatment of coccidiosis.
- Spectrum of Activity: Effective against many gram-positive bacteria (e.g., Streptococcus, Staphylococcus, Nocardia) and some gram-negative bacteria. It also has notable activity against protozoa like Coccidia and Toxoplasma.
- Limitations: Bacteriostatic when used alone. Efficacy is significantly reduced in the presence of pus, necrotic tissue, or extensive cellular debris. Bacterial resistance is increasingly common.
- Species Specifics: Highly protein-bound and well-distributed. In dogs, it relies heavily on renal excretion rather than hepatic metabolism, and extensive renal tubular reabsorption gives it a long half-life.
Mechanism of action
Sulfonamides are bacteriostatic agents that disrupt bacterial folic acid synthesis.
- Mechanism: Sulfadimethoxine acts as a structural analog of para-aminobenzoic acid (PABA).
- Pathway: It competitively inhibits the bacterial enzyme dihydropteroate synthase → blocks the incorporation of PABA into dihydropteroic acid → prevents the biosynthesis of tetrahydrofolic acid (active folic acid).
- Result: Without tetrahydrofolic acid, susceptible bacteria and protozoa cannot synthesize purines, pyrimidines, and ultimately DNA/RNA, halting replication.
- Note: Mammalian cells are unaffected because they utilize preformed dietary folic acid rather than synthesizing it de novo.
Safety & warnings
Contraindications
- Hypersensitivity to sulfonamides, thiazides, or sulfonylurea agents
- Severe renal or hepatic impairment
- Doberman Pinschers (highly susceptible to poly-systemic immune complex disease)
- Dehydrated patients (increased risk of crystalluria)
Adverse effects
- Crystalluria, hematuria, and renal tubule obstruction (especially with acidic/concentrated urine)
- Keratoconjunctivitis sicca (KCS or 'dry eye') in dogs
- Hypersensitivity reactions (rashes, dermatitis, fever)
- Bone marrow depression
- Nonseptic polyarthritis (especially in Doberman Pinschers)
- Focal retinitis
- Vomiting and diarrhea (due to altered gut flora)
- Muscle weakness, blindness, ataxia, and collapse (if injected IV too rapidly)
- Tissue irritation and necrosis (if injected IM or SC)
Precautions
Breed Warning: Doberman Pinschers are highly susceptible to sulfonamide-induced poly-systemic immune complex disease (presenting as polyarthritis, fever, uveitis, glomerulonephropathy). Use is generally contraindicated in this breed.
- Renal/Hepatic: Use with extreme caution in patients with diminished renal or hepatic function, or urinary obstruction.
- Hydration: Maintain adequate hydration and urine flow to prevent crystalluria and renal tubular obstruction.
- Tissue Irritation: Because solutions are highly alkaline, IM or SC injections can cause significant tissue irritation and necrosis.
- Ruminants: Oral administration can temporarily depress normal cellulytic function of the ruminoreticulum.
- Pregnancy: Potentially teratogenic at high doses. Weigh risk vs. benefit. Crosses the placenta and is distributed into milk.
Drug interactions
May decrease the oral bioavailability of sulfonamides if administered concurrently.
Monitoring
- Clinical efficacy and resolution of infection/coccidiosis
- Hydration status and urine output
- Schirmer Tear Test (STT) in dogs (monitor for KCS, especially with prolonged use)
- Complete Blood Count (CBC) if used long-term (monitor for bone marrow depression)
- Signs of hypersensitivity (fever, joint pain, rash)
Pharmacokinetics
Half-life
Absorption
Readily absorbed in dogs, cats, swine, and sheep.
Distribution
Well distributed. Highly protein bound. Relative volumes of distribution range from 0.17 L/kg (sheep) to 0.35 L/kg (cattle and horses). Crosses the placenta and is distributed into milk.
Metabolism
In most species, acetylated in the liver to acetylsulfadimethoxine. In dogs, the drug is not appreciably hepatically metabolized.
Elimination
In dogs, renal excretion is the basis for the majority of elimination. Long elimination half-lives are a result of appreciable reabsorption in the renal tubules.
Overdose
Acute toxicity secondary to overdoses occurs only rarely in veterinary species. In addition to standard adverse effects (crystalluria, GI upset, hypersensitivity), CNS stimulation and myelin degeneration have been noted after very high dosages.
Available products
Formulations
- Injection (400 mg/mL)
- Oral Tablets (125 mg, 250 mg, 500 mg)
- Oral Suspension (50 mg/mL)
- Oral Boluses (5 g, 15 g)
- Sustained-Release Oral Boluses (12.5 g)
- Soluble Powder (94.6 g/packet)
- Concentrated Solution (12.5%)
Veterinary
- Sulfadimethoxine Injection: 400 mg/mL (40%) (Albon, Di-Methox)
- Sulfadimethoxine Oral Tablets: 125 mg, 250 mg, 500 mg (Albon)
- Sulfadimethoxine Oral Suspension: 50 mg/mL (Albon)
- Sulfadimethoxine Oral Boluses: 5 g, 15 g (Albon)
- Sulfadimethoxine Oral Boluses Sustained-Release: 12.5 g (Albon SR)
- Sulfadimethoxine Soluble Powder: 94.6 grams/packet (Albon)
- Sulfadimethoxine 12.5% Concentrated Solution (Albon)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature and protect from light. If crystals form due to exposure to cold temperatures, either warm the vial or store at room temperature for several days to resolubilize the drug; efficacy is not impaired by this process.
Client information
Important Guidelines for Pet Owners:
- Water is Crucial: Ensure your pet has access to plenty of fresh drinking water at all times while on this medication. This helps prevent the drug from forming crystals in the kidneys.
- Watch the Eyes: In dogs, this medication can occasionally decrease tear production, leading to 'dry eye'. Contact your veterinarian if you notice your dog squinting, rubbing their eyes, redness, or a thick yellow/green eye discharge.
- Monitor for Reactions: Stop the medication and contact your vet immediately if your pet develops a skin rash, unexplained fever, joint stiffness/limping, or severe vomiting.
- Administration: Can be given with or without food. If your pet vomits after receiving the dose on an empty stomach, try giving future doses with a small meal or treat.
- Pregnancy: Inform your veterinarian if your pet is pregnant or nursing, as this drug can cross the placenta and enter the milk.
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.