Phthalylsulfathiazole

Oral
Bowel decontamination before surgery, Susceptible infections

Dose reduction may be necessary.

Pregnancy (prior to delivery); infants within 1-2 mth of birth; porphyria; severe renal or hepatic failure; blood disorders; hypersensitivity; SLE.

Adequate hydration is necessary to reduce the risk of crystalluria. Discontinue immediately if rash appears. Renal or hepatic failure; asthma or history of allergy; elderly; G6PD deficiency; AIDS patients (especially those on trimethoprim).

GI effects, hypersensitivity reactions, nephrotoxic reactions, blood disorders, hepatic disorders, CV effects, hypoglycaemia, hypothyroidism, neurological reactions, pseudomembranous colitis and kernicterus in premature neonates.
Potentially Fatal: Toxic epidermal necrolysis, Stevens-Johnson syndrome, anaphylaxis.

Potentiates effect of oral anticoagulants, methotrexate and phenytoin; possible failures of hormonal contraceptives; enhanced antidiabetic effect of sulfonylurea compounds; antagonism with PABA and its derivatives; associated with decrease in plasma-ciclosporin concentrations.

Urea, creatinine and urinary glucose and urobilinogen.

Description:
Mechanism of Action: Phthalylsulfathiazole is a sulfonamide with properties similar to those of sulfamethoxazole. Sulfonamides have a similar structure to p-aminobenzoic acid (PABA) and interfere with the nucleic acid synthesis in sensitive microorganisms by blocking the conversion of PABA to the reduced form of folic acid, co-enzyme dihydrofolic acid. Primarily bacteriostatic, it may exert bactericidal effects where concentrations of thymine are low in surrounding medium. It is used to treat infections and for bowel decontamination before surgery.
Pharmacokinetics:
Absorption: Poorly absorbed, approx 95% remaining in the intestine.
Metabolism: Slowly hydrolysed to sulfathiazole.

Sulphonamides