Sulpha-300 wsp

Indications

• Bacterial infections of the urinary tract
• Respiratory tract infections
• Certain skin infections
• Other infections caused by susceptible organisms

Dosage

Children: Refer to the BNF for Children for appropriate dosing based on the child's age and weight.

Adults: Refer to the BNF for specific dosing recommendations based on the type and severity of infection.

Mechanism of action

Sulfonamides, including sulphadimidine, inhibit the enzymatic conversion of pteridine and p-aminobenzoic acid (PABA) to dihydropteroic acid by competing with PABA for binding to dihydrofolate synthetase. This inhibition reduces the synthesis of dihydrofolate, which is required for the synthesis of tetrahydrofolic acid (THF). THF is crucial for the synthesis of purines and deoxythymidine monophosphate (dTMP), thereby inhibiting bacterial growth.

Pharmacodynamics

Sulphadimidine is bacteriostatic, meaning it inhibits bacterial growth by preventing the synthesis of dihydrofolic acid. This, in turn, decreases the synthesis of bacterial nucleotides and DNA, effectively limiting the ability of bacteria to reproduce and proliferate within the host.

Pharmacokinetics

Sulphadimidine is well absorbed from the gastrointestinal tract and reaches peak plasma concentrations within a few hours after administration. It is distributed widely throughout body tissues and fluids, including the central nervous system. The drug is metabolized in the liver and excreted primarily via the kidneys in the urine, with a half-life that can vary based on patient factors such as renal function.

Contra-indications

• Hypersensitivity to sulfonamides
• Severe liver or kidney disease
• Porphyria
• Pregnancy at term

Adverse effects

• Rash
• Nausea
• Vomiting
• Diarrhea
• Hematological reactions such as agranulocytosis and aplastic anemia
• Hepatotoxicity
• Renal toxicity

Interactions

• May enhance the anticoagulant effect of warfarin
• May interact with methotrexate, increasing its toxicity
• May decrease the efficacy of oral contraceptives

Precautions

• Use with caution in patients with G6PD deficiency
• Monitor renal function regularly during prolonged therapy
• Use cautiously in patients with asthma or other allergic conditions

Pregnancy

Not recommended in pregnancy, especially during the third trimester due to potential risks to the fetus.

Breast-feeding

Use with caution, as it may pass into breast milk and affect the nursing infant.

Storage

Store in a cool, dry place away from direct light.

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.