Sulfavet Injection

Indications

• Bacterial infections
• Urinary tract infections
• Respiratory tract infections
• Gastrointestinal infections
• Skin and soft tissue infections

Dosage

Children: Refer to BNF for Children for specific paediatric dosing recommendations.

Adults: Refer to BNF for specific adult dosing recommendations.

Mechanism of action

Sulfadimidine inhibits the enzymatic conversion of pteridine and p-aminobenzoic acid (PABA) to dihydropteroic acid by competing with PABA for binding to dihydrofolate synthetase. This inhibition affects the synthesis of tetrahydrofolic acid (THF), which is vital for the production of purines and deoxythymidine monophosphate (dTMP), leading to reduced bacterial growth.

Pharmacodynamics

Sulfadimidine is classified as a bacteriostatic agent, which means it inhibits the growth of bacteria rather than killing them outright. By obstructing the synthesis of dihydrofolic acid, sulfadimidine decreases the availability of nucleotides necessary for DNA synthesis, ultimately leading to a reduction in bacterial proliferation.

Pharmacokinetics

Sulfadimidine is absorbed well from the gastrointestinal tract, and its bioavailability is influenced by factors such as pH and the presence of food. The drug is distributed widely throughout body tissues and fluids, including the central nervous system. It undergoes hepatic metabolism and is primarily excreted unchanged in the urine, with a half-life that can vary based on the individual's renal function.

Contra-indications

• Hypersensitivity to sulfonamides
• Severe liver or kidney impairment
• Porphyria

Adverse effects

• Rash
• Nausea
• Vomiting
• Diarrhea
• Hematological reactions such as agranulocytosis or aplastic anemia
• Hypersensitivity reactions including Stevens-Johnson syndrome
• Renal impairment

Interactions

• May enhance the effects of anticoagulants such as warfarin
• May interact with oral hypoglycemic agents
• Interactions with other drugs that affect renal function

Precautions

• Use with caution in patients with renal or hepatic impairment
• Monitor for signs of blood dyscrasias
• Ensure adequate hydration to avoid crystalluria

Pregnancy

Not recommended during pregnancy, especially in the third trimester due to the risk of kernicterus in the newborn.

Breast-feeding

Use with caution, as it may be excreted in breast milk and could affect the nursing infant.

Storage

Store in a cool, dry place, away from light. Keep out of reach of children.

Formulations

• Tablets
• Oral suspension

Mechanism of action

Sulfonamides inhibit the enzymatic conversion of pteridine and p-aminobenzoic acid (PABA) to dihydropteroic acid by competing with PABA for binding to dihydrofolate synthetase, an intermediate of tetrahydrofolic acid (THF) synthesis. THF is required for the synthesis of purines and dTMP and inhibition of its synthesis inhibits bacterial growth. Pyrimethamine and trimethoprim inhibit dihydrofolate reductase, another step in THF synthesis, and therefore act synergistically with the sulfonamides.

Pharmacodynamics

Sulfamethazine is a sulfonamide drug that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA) for binding to dihydropteroate synthetase (dihydrofolate synthetase). Sulfamethazine is bacteriostatic in nature. Inhibition of dihydrofolic acid synthesis decreases the synthesis of bacterial nucleotides and DNA.