Sulfadimethoxine: veterinary dose and monograph

At a glance

Drug class

Antibiotic

Also known as

Albon, Bactrovet, Di-Methox

Species with doses

Dogs, Cats, Cattle, Horses, Rabbits, Ferrets, Guinea pigs, Reptiles, Camelids, Chinchillas, Hamsters, Rats, Mice and Gerbils

General dose range

25–55 mg/kg PO q24h — check the species tables for the indication

Routes

PO, IV

Last reviewed

1 October 2026

Indications

• Canine / feline coccidiosis (Isospora / Cystoisospora)
• Susceptible bacterial UTI
• Bovine respiratory disease / foot rot
• Equine protozoal myeloencephalitis (EPM) — with pyrimethamine
• Avian coccidiosis

Sulfadimethoxine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Coccidiosis (label): Plumb’s p.1092: coccidiosis 55 mg/kg PO on day 1, then 27.5 mg/kg once daily for 9 days (Matz); label for infections 55 mg/kg then 27.5 mg/kg q24h. Papich 5e: 55 mg/kg loading then 27.5 mg/kg q12h. Monitor Schirmer tear tests on longer courses (KCS).
• Coccidiosis maintenance (Day 2+): Plumb’s p.1092: 27.5 mg/kg PO once daily for 9 days after the 55 mg/kg loading dose (Matz); alternatively 50 mg/kg once daily for 10–14 days eliminates oocyst shedding in most dogs and cats (Marks); puppies 2–6 weeks 50 mg/kg day 1 then 25 mg/kg daily (Macintire). Papich 5e: 27.5 mg/kg q12h.

Cats

• Coccidiosis: Plumb’s p.1092: label 55 mg/kg PO (or IV/SC) initially then 27.5 mg/kg once daily; coccidiosis 50 mg/kg once daily for 10–14 days (Marks). Papich 5e: 55 mg/kg loading then 27.5 mg/kg q12h. Ensure hydration; monitor CBC on longer courses.
• Coccidiosis maintenance (Day 2+): Plumb’s p.1092 (label): 27.5 mg/kg once daily after the loading dose; or continue 50 mg/kg once daily for 10–14 days (Marks). Papich 5e: 27.5 mg/kg q12h.

Cattle

• BRD / foot rot (label): Papich 5e and Plumb’s p.1092 (Albon label): 55 mg/kg IV or PO initially, then 27.5 mg/kg q24h for up to 5 days; sustained-release bolus 137.5 mg/kg PO every 4 days; 110 mg/kg PO or IV q24h (Upson; Burrows). Withdrawals differ between injectable, oral and bolus products — follow the product label.

Horses

• Susceptible infection (label): Plumb’s p.1092 (Albon label): 55 mg/kg IV or PO initially, then 27.5 mg/kg q24h IV; Upson 1988: 55 mg/kg PO or IV q12h. (EPM regimens in the references use sulfadiazine or sulfamethoxazole with pyrimethamine, not sulfadimethoxine.)

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• BRD / foot rot (label): Papich 5e and Plumb’s p.1092 (Albon label): 55 mg/kg IV or PO initially, then 27.5 mg/kg q24h for up to 5 days; sustained-release bolus 137.5 mg/kg PO every 4 days; 110 mg/kg PO or IV q24h (Upson; Burrows). Withdrawals differ between injectable, oral and bolus products — follow the product label.

Birds

• No reference dose for this species: The previous 25–50 mg/kg PO bird row had no source; neither Papich 5e nor Plumb’s gives an avian sulfadimethoxine dose. Poultry products are dosed per their water/feed label.

Rabbits

• Susceptible infection / coccidiosis: Plumb's p.1092: rabbits 10–15 mg/kg PO q12h (Ivey & Morrisey 2000); coccidiosis 25 mg/kg PO once daily (Burke 1999). Sulfonamides are safe in rabbits (unlike penicillins/macrolides).

Ferrets

• Coccidiosis: Plumb's p.1092 (Williams 2000; Johnson 2006): 25 mg/kg PO/SC/IM once daily; coccidiosis 25 mg/kg PO q24h ×14 days.

Guinea pigs

• Coccidiosis: Plumb's p.1092 (Adamcak & Otten 2000): Mice/Rats/Gerbils/Hamsters/Guinea pigs/Chinchillas coccidiostat 50 mg/kg PO once, then 25 mg/kg PO q24h ×10–20 days (or 75 mg/kg PO ×7–14 days).

Reptiles

• Coccidia: Plumb's p.1092 (Lewbart 2001): 90 mg/kg PO day 1, then 45 mg/kg PO on 5 successive days; may also give IM/IV. Maintain hydration.

Camelids

• Coccidiosis (Eimeria): Plumb's p.1092: 15 mg/kg PO q12h ×5 days (Walker 2009); or 110 mg/kg PO q24h for Eimeria in clinically affected animals. Monitor for polioencephalomalacia.

Chinchillas

• Coccidiosis: Plumb's p.1092: 50 mg/kg PO once then 25 mg/kg PO q24h.

Hamsters

• Coccidiosis: Plumb's p.1092: 50 mg/kg PO once then 25 mg/kg PO q24h.

Rats

• Coccidiosis: Plumb's p.1092: 50 mg/kg PO once then 25 mg/kg PO q24h.

Mice

• Coccidiosis: Plumb's p.1092: 50 mg/kg PO once then 25 mg/kg PO q24h.

Gerbils

• Coccidiosis: Plumb's p.1092: 50 mg/kg PO once then 25 mg/kg PO q24h.

Contraindications

Hypersensitivity to sulfonamides. Severe hepatic/renal impairment. Dehydration. Cats more susceptible to sulfonamide toxicity. Dobermans/Rottweilers predisposed to polyarthropathy. Pregnancy (teratogenic). Not for use with methenamine.

Species-specific warnings

Dogs: KCS (potentially permanent) and polyarthropathy. Schirmer test at baseline + 1–2 weeks. AVOID in Doberman Pinschers. Adequate hydration to prevent crystalluria.

Cats: More sensitive to sulfa effects — neurological signs at high doses. Use lower end of range.

Rabbits: One of FEW antibiotics SAFE orally in rabbits at 50 mg/kg PO q24h × 5 d. Useful for coccidiosis.

Cattle: Approved for cattle coccidiosis and respiratory. Strict withdrawal: 5–10 d meat / 60 h milk.

Horses: TMS (with trimethoprim) is widely used in horses. Plain sulfa less common.

Birds: Poultry coccidiosis: 0.05% in drinking water × 6 days. Egg withdrawal periods vary by jurisdiction.

Adverse effects

• Crystalluria (ensure hydration)
• Keratoconjunctivitis sicca / KCS (dogs — may be irreversible)
• Hepatotoxicity
• Haemolytic anaemia, thrombocytopenia, leukopenia
• Polyarthritis / skin eruptions (Dobermans, Rottweilers predisposed)
• Hypothyroidism (chronic use)

Drug interactions

• Trimethoprim: SYNERGISTIC — sequential block of folate pathway = bactericidal (TMS combinations)
• NSAIDs: increased sulfonamide blood levels (displaced from protein binding)
• Anticonvulsants (phenobarbital, phenytoin): may displace sulfa from binding sites
• Warfarin: potentiates anticoagulation (sulfa displaces from protein binding)
• Methotrexate, methenamine: increased crystalluria risk
• Antacids: reduce sulfa absorption — separate by 2 h
• Sulfonamide cross-allergy: avoid in patients with known sulfa hypersensitivity (KCS, polyarthropathy, skin reactions)

Pregnancy and lactation

Crosses placenta. Last-trimester use can displace bilirubin from albumin → fetal kernicterus risk. Use with caution and avoid near term. Excreted in milk in low amounts. Generally avoided in pregnant breeding stock when alternatives exist.

Monitoring

• Schirmer tear test BASELINE + at 1–2 weeks for dogs on TMS — KCS is the most insidious adverse effect
• Urinalysis: check pH, crystals, casts — alkalinise if acidic
• CBC every 2 weeks on prolonged courses — thrombocytopenia, neutropenia
• Thyroid function (T4) — sulfa-induced hypothyroidism on chronic use
• Joint pain / lameness — discontinue immediately if observed (polyarthropathy)
• Withdrawal periods: cattle 5–10 d slaughter / 60 h milk; poultry 10 d
• Adequate hydration to prevent crystalluria

Toxicity and overdose

KERATOCONJUNCTIVITIS SICCA (KCS) in dogs — dose-dependent and idiosyncratic; can be permanent. POLYARTHROPATHY (immune-mediated) especially in Doberman Pinschers. Hepatotoxicity, hypothyroidism, blood dyscrasia (thrombocytopenia, neutropenia), CRYSTALLURIA in acidic urine → renal tubular damage. Sulfa hypersensitivity — fever, dermatitis, vasculitis, Stevens-Johnson syndrome. Cats: more sensitive — keratoconjunctivitis, neurological signs.

Management: Discontinue. ALKALINISE URINE (sodium bicarbonate 1 mEq/kg IV q4–6h) to prevent crystalluria — target urine pH >7.5. Aggressive IV fluid diuresis. KCS: SCHIRMER TEAR TEST baseline + at 1–2 weeks of therapy; treat with cyclosporine ophthalmic drops + tear replacement, KCS may be permanent. Polyarthropathy: discontinue, NSAID/steroid for inflammation. Anaphylaxis: standard protocol.

Clinical pearls

• Coccidiosis (calves, lambs, kids, kits, poultry): 55 mg/kg PO day 1, then 27.5 mg/kg PO q24h × 5–14 days
• Coccidiosis (dogs, cats): 55 mg/kg PO day 1, then 27.5 mg/kg PO q24h × 14–21 days
• Rabbits coccidiosis: 50 mg/kg PO q24h × 5 days (one of the few antibiotics safe orally in rabbits)
• Cattle / sheep / goat respiratory: 55 mg/kg PO/IV day 1, then 27.5 mg/kg q24h × 4 days
• Trimethoprim-sulfa combination (TMS, Tribrissen, Septra): synergistic bactericidal for UTI, soft tissue, prostatitis
• NEVER in dehydrated patients — crystalluria → AKI risk
• Schirmer tear test at baseline + 1–2 weeks in dogs — KCS develops insidiously
• AVOID in Doberman Pinschers — polyarthropathy risk
• Strict withdrawal periods in food animals — verify per jurisdiction

Mechanism of action

Long-acting sulfonamide antibiotic. Competitive inhibitor of para-aminobenzoic acid (PABA) in bacterial folate synthesis — blocks dihydropteroate synthase, preventing dihydrofolate formation. Bacteriostatic. Spectrum: many Gram-positive cocci, Gram-negative aerobes, Eimeria (coccidia — the primary indication in cattle, sheep, poultry, rabbits). Long half-life allows single daily dosing. Combination with trimethoprim (potentiated sulfa) gives synergistic bactericidal activity via sequential block of folate pathway.

Formulations and products

• Albon oral suspension 50 mg/mL
• Albon tablet 125 mg
• Albon tablet 250 mg
• Albon tablet 500 mg
• Albon injection 400 mg/mL

Storage

Tablets / boluses: 15–30 °C, dry, protected from light. Oral suspension: 15–25 °C, shake well. Injection: 15–25 °C, protect from light. Some sulfonamides crystallise on cooling — warm before injection.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other antibiotics

• Silver Sulfadiazine
• Spectinomycin
• Streptomycin (Dihydrostreptomycin)
• Sulfadiazine
• Sulphadimidine (Sulfamethazine)
• Tiamulin
• Tildipirosin
• Tilmicosin

Frequently asked questions