Sulfadimethoxine

Sulfadimethoxine is a relatively long-acting sulfonamide used for susceptible bacterial infections and selected coccidial disease. Veterinary applications span companion animals, livestock and poultry, depending on the product. It is also used in potentiated combinations, whose antimicrobial behavior differs from single-agent treatment. The useful spectrum is determined by organism susceptibility and formulation.

Group

Sulfonamide antibacterial

Mechanism of Action

Sulfadimethoxine acts as a competitive antagonist of para-aminobenzoic acid in microbial folate synthesis. Inhibition of dihydropteroate synthase reduces folate availability for nucleic-acid production and suppresses growth of susceptible bacteria or coccidia. Its action is generally static rather than directly destructive of all parasite stages. Pharmacokinetic persistence supports longer exposure in some species.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection — Loading	55 mg/kg	PO, IV, SC	Once
Susceptible infection — Maintenance	27.5 mg/kg	PO	Every 12 h	Preserves the supplied q12h regimen; not silently replaced by a different schedule.
Susceptible infection alternative	25 mg/kg	PO, IV, IM	Every 24 h
Susceptible infection alternative	100 mg/kg	PO, IV, IM	Every 24 h
Susceptible infection — Maintenance	27.5 mg/kg	PO	Every 24 h	Once-daily alternative; do not combine with a twice-daily schedule.
Coccidiosis — Initial	55 mg/kg	PO	Once
Coccidiosis — Maintenance	27.5 mg/kg	PO	Every 24 h	Up to 9 days
Infant coccidiosis — Initial	50 mg/kg	PO	Once	Puppies 2-6 weeks.
Infant coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Until signs regress.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection — Loading	55 mg/kg	PO, IV, SC	Once
Susceptible infection — Maintenance	27.5 mg/kg	PO	Every 12 h	Preserves the supplied q12h regimen; not silently replaced by a different schedule.
Susceptible infection alternative	25 mg/kg	PO, IV, IM	Every 24 h
Susceptible infection alternative	100 mg/kg	PO, IV, IM	Every 24 h
Susceptible infection — Maintenance	27.5 mg/kg	PO	Every 24 h	Once-daily alternative; do not combine with a twice-daily schedule.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Pneumonia and susceptible infections — Loading	55 mg/kg	PO	Once
Pneumonia and susceptible infections — Maintenance	27 mg/kg	PO	Every 24 h	Up to 5 days
Sustained-release antibacterial treatment	137.5 mg/kg	PO	Once	Albon-SR formulation only.
Susceptible infection	110 mg/kg	PO, IV	Every 24 h
Susceptible infection — Loading	55 mg/kg	IV	Once
Susceptible infection — Maintenance	27.5 mg/kg	PO, IV	Every 24 h	Up to 5 days
Sustained-release antibacterial treatment	137.5 mg/kg	PO	Every 96 h	Albon sustained-release bolus specifically.

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	25 mg/kg	PO, SC, IM	Every 24 h
Coccidiosis	25 mg/kg	PO	Every 24 h	Up to 14 days

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	10–15 mg/kg	PO	Every 12 h
Coccidiosis	25 mg/kg	PO	Every 24 h

Hedgehog

Use / stage	Dose	Route	Schedule	Instructions
Susceptible infection	2–20 mg/kg	IM, SC, PO	Every 24 h

Mice

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	50 mg/kg	PO	Once
Coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Up to 20 days; Reported 10-20 days.

Rats

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	50 mg/kg	PO	Once
Coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Up to 20 days; Reported 10-20 days.

Gerbils

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	50 mg/kg	PO	Once
Coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Up to 20 days; Reported 10-20 days.

Hamsters

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	50 mg/kg	PO	Once
Coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Up to 20 days; Reported 10-20 days.

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	50 mg/kg	PO	Once
Coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Up to 20 days; Reported 10-20 days.

Chinchillas

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	50 mg/kg	PO	Once
Coccidiosis — Maintenance	25 mg/kg	PO	Every 24 h	Up to 20 days; Reported 10-20 days.

Horses

Use / stage	Dose	Route	Schedule
Susceptible infection	55 mg/kg	PO, IV	Every 12 h
Susceptible infection — Loading	55 mg/kg	PO, IV	Once
Susceptible infection — Maintenance	27.5 mg/kg	IV	Every 24 h

Llamas

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis	15 mg/kg	PO	Every 12 h	Up to 5 days; Monitor neurological signs.
Eimeria infection	110 mg/kg	PO	Every 24 h	Up to 15 days; E. macusaniensis reports use 10-15 days; dose directly rather than through uncertain water intake.

Alpacas

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis	15 mg/kg	PO	Every 12 h	Up to 5 days; Monitor neurological signs.
Eimeria infection	110 mg/kg	PO	Every 24 h	Up to 15 days; E. macusaniensis reports use 10-15 days; dose directly rather than through uncertain water intake.

Reptiles

Use / stage	Dose	Route	Schedule	Instructions
Coccidiosis — Initial	90 mg/kg	PO	Once
Coccidiosis — Maintenance	45 mg/kg	PO	Every 24 h	Up to 5 days; Maintain hydration; source also describes parenteral alternatives, not product-specific compatibility.

Indications

Treatment of selected susceptible bacterial respiratory, urinary, enteric or soft-tissue infections in dogs and cats.
Treatment of intestinal coccidiosis in dogs, cats or selected other veterinary species with a supported regimen.
Treatment of susceptible livestock respiratory disease, calf diphtheria or foot rot with a corresponding product.
Treatment of selected poultry coccidiosis, fowl cholera or infectious coryza where included in the product indication.
Treatment of selected susceptible equine bacterial respiratory infections.

Contraindications

Sulfonamide hypersensitivity
Doberman pinschers may have greater susceptibility to reactions.

Interactions

Warfarin, methenamine, dapsone, etodolac, methotrexate and pyrimethamine may interact; cyclosporine exposure may fall.
IV trimethoprim-sulfonamide combinations with equine detomidine can provoke arrhythmias; this warning is not a general oral interaction.

Adverse effects

Hypersensitivity, cytopenias, hepatopathy, keratoconjunctivitis sicca, arthropathy and thyroid suppression with prolonged therapy.

Toxicity

Massive exposure can cause CNS stimulation in addition to sulfonamide hypersensitivity, renal, hepatic or marrow effects.

Preparations

Preparation	Form	Strength	Route
Sulfadimethoxine 125 mg	Tablet	125 mg / tablet	PO
Sulfadimethoxine 250 mg	Tablet	250 mg / tablet	PO
Sulfadimethoxine 500 mg	Tablet	500 mg / tablet	PO
Sulfadimethoxine suspension 50 mg/mL	Oral Liquid	50 mg / mL	PO
Sulfadimethoxine sterile injection 400 mg/mL Sterile injectable preparation only; never inject oral suspension. Exact product authorizations differ.	Injection	400 mg / mL	IV

Monitoring and Administration

Assess clinical and microbiological response; monitor CBC, hepatic signs, tear production and thyroid interpretation during prolonged treatment. A combination dose must not be treated as a single sulfonamide component dose.