Sulfadiazine

Name

• Trimethoprim/Sulfonamide.

Class of drug

• Potentiated sulfonamide antibiotic.

Uses

Action

• Trimethoprim and sulfonamides block sequential steps in the synthesis of tetrahydrofolate, a co-factor required for the synthesis of many molecules including nucleic acids.
• Sulfonamides block the synthesis of dihydropetoic acid and subsequently dihydrofolic acid by competing with para-aminobenzoic acid and trimethoprim inhibits the enzyme dihydrofolate reductase, preventing the production of dihydrofolic acid.
• This two-step mechanism ensures that bacterial resistance develops more slowly than to either agent alone.

Indications

• Many organisms are susceptible including Nocardia    , Brucella , Gram-negative bacilli, some Gram-positive organisms ( Streptococci spp    , Pneumocystis carinii    , Toxoplasma gondii    and coccidial species    .
• Pseudomonas spp    and Leptospira spp    are usually resistant.
• Trimethoprim/sulfonamide is useful in the management of urinary, respiratory tract and prostatic infections,but are ineffective in the presence of necrotic tissue.
• Trimethoprin alone may be used for urinary, prostatic, systemic salmonella and respiratory tract infections.
• Fewer adverse effects are seen with trimethoprin alone.

Adverse reactions

Other reported reactions

• Anorexia.
• Leukopenia.
• Anemia.
• Hypersalivation.
  Dog
  
• Acute hepatitis, vomiting, cholestasis.
• Immune-mediated thrombocytopenia.
• Immune-mediated polyarthritis.
• Acute hypersensitivity reactions are possible with sulfonamide products, they may manifest as a type III hypersensitivity reaction.
• Dermatological reactions (eg toxic epidermal necrolysis) have been associated with the use of sulfonamides in some animals, in particular the Doberman.
• Keratoconjunctivitis sicca (KCS) has been reported in dogs treated with sulfapyridine and other sulfonamides.

• May reversibly suppress thyroid function causing iatrogenic hypothyroidism.
• Hematological effects (anemias, agranulocytosis) in dogs.
• Sulfonamide crystal formation can occur in the urinary tract especially in animals producing very concentrated acidic urine. Ensure animals receiving sulfonamides are well hydrated and not receiving urinary acidifiers.