Drug information of Sulfadiazine

Sulfadiazine

Drug group: sulfonamide

Sulfadiazine is a sulfonamide antibiotic . Treating and preventing certain bacterial infections.

Mechanism of effect

Sulfonamides competitively inhibit bacterial synthesis of folic acid (pteroylglutamic acid) from aminobenzoic acid. Resistant strains are capable of utilizing folic acid precursors or preformed folic acid.

Pharmacodynamic

Sulfonamides competitively inhibit bacterial synthesis of folic acid ( pteroylglutamic acid ) from aminobenzoic acid.

Pharmacokinetics

Sulfadiazine given orally is readily absorbed from the gastrointestinal tract.
When a dose of 100 mg/kg of body weight is given initially and followed by 50 mg/kg every 6 hours, blood levels of free Sulfadiazine are about 7 mg/100mL.
Protein binding is 38% to 48%. Sulfadiazine diffuses into the cerebrospinal fluid; free drug reaches 32% to 65% of blood levels and total drug 40% to 60%.
Sulfadiazine is excreted largely in the urine, where concentrations are 10 to 25 times greater than serum levels.
Approximately 10% of a single oral dose is excreted in the first 6 hours, 50% within 24 hours and 60% to 85% in 48 to 72 hours. Of the amount excreted in the urine, 15% to 40% is in the acetyl form.

Dosage

Usual Adult Dose for Rheumatic Fever Prophylaxis
Secondary prophylaxis of rheumatic fever, if patient is intolerant of penicillin:
1 g orally once a day.
The optimal duration has not been definitely determined. The American Heart Association recommends that prophylaxis be continued for at least 5 years or until the patient reaches age 21 (whichever is longer) for rheumatic fever without carditis, and for 10 years in patients with carditis but no valvar heart disease.
Prophylaxis is recommended for at least 10 years since the last episode or until the patient reaches age 40 for carditis and persistent valvar disease; lifelong prophylaxis may be required.
Usual Adult Dose for Toxoplasmosis
• Toxoplasmic encephalitis :
• Initial dose: Pyrimethamine 200 mg orally once
• Maintenance dose :
<60 kg: Sulfadiazine 1 g orally every 6 hours plus pyrimethamine 50 mg orally once a day.
>=60 kg: Sulfadiazine 1500 mg orally every 6 hours plus pyrimethamine 75 mg orally once a day.
In addition, leucovorin 10 to 20 mg/day orally (may increase up to 50 mg/day).
Corticosteroids and anticonvulsants may be given if indicated.
Duration: At least 6 weeks, followed by chronic suppressive therapy.
Usual Adult Dose for Toxoplasmosis – Prophylaxis
Secondary prophylaxis after acute treatment of toxoplasmic encephalitis:
Sulfadiazine, 500 to 1000 mg orally every 6 hours plus pyrimethamine 25 to 50 mg orally once a day plus leucovorin 10 to 25 mg orally once a day.
Duration: Lifelong in HIV-infected patients. Discontinuation may be considered if the patient has maintained CD4+ T-lymphocyte counts >200 cells/microL following HAART (e.g., >6 months) and has no symptoms of toxoplasmosis. Some experts would also recommend an MRI of the brain.
Usual Pediatric Dose for Rheumatic Fever Prophylaxis
Secondary prophylaxis of rheumatic fever, if patient is intolerant of penicillin:
> 2 months and <=27 kg: 500 mg orally once a day.
>27 kg: 1 g orally once a day.
The optimal duration has not been definitely determined. The American Heart Association recommends that prophylaxis be continued for at least 5 years or until the patient reaches age 21 (whichever is longer) for rheumatic fever without carditis, and for 10 years in patients with carditis but no valvar heart disease.
Prophylaxis is recommended for at least 10 years since the last episode or until the patient reaches age 40 for carditis and persistent valvar disease; lifelong prophylaxis may be required.
Usual Pediatric Dose for Toxoplasmosis
• Congenital toxoplasmosis :
Initial dose: Pyrimethamine 2 mg/kg orally once a day for 2 days
• Maintenance dose: Sulfadiazine 50 mg/kg orally twice a day plus pyrimethamine 1 mg/kg orally once a day plus leucovorin 10 mg orally or IM once a day.
• Duration: 12 months. After 2 to 6 months, decrease pyrimethamine to 1 mg/kg orally 3 times a week.
Acute acquired toxoplasmosis :
• Initial dose: Pyrimethamine 2 mg/kg (maximum 50 mg) orally once a day for 3 days.
• Maintenance dose: Sulfadiazine 25 to 50 mg/kg (maximum 1 to 1.5 g/dose) orally every 6 hours plus pyrimethamine 1 mg/kg (maximum 25 mg) orally once a day plus leucovorin 10 to 25 mg orally once a day.
• Duration: At least 6 weeks, followed by chronic suppressive therapy.
Usual Pediatric Dose for Toxoplasmosis – Prophylaxis
• Secondary prophylaxis after acute treatment of toxoplasmic encephalitis:
Sulfadiazine 85 to 120 mg/kg/day (maximum adult dose, 4 to 6 g/day) orally in 2 to 4 divided doses plus pyrimethamine, 1 mg/kg or 15 mg/m2 (maximum dose 25 mg) orally once a day plus leucovorin 5 mg orally every 3 days .
• Duration : Lifelong in HIV-infected patients.

Alerts

• The sulfonamides should not be used for the treatment of group A betahemolytic streptococcal infections.
• In an established infection, they will not eradicate the streptococcus and, therefore, will not prevent sequelae such as rheumatic fever and glomerulonephritis.
• Deaths associated with the administration of sulfonamides have been reported from hypersensitivity reactions, agranulocytosis, aplastic anemia and other blood dyscrasias.
• The presence of such clinical signs as sore throat, fever, pallor, purpura or jaundice may be early indications of serious blood disorders.
• The frequency of renal complications is considerably lower in patients receiving the more soluble sulfonamides.

Points of recommendation

Patients should be instructed to drink an eight ounce glass of water with each dose of medication and at frequent intervals throughout the day.
Caution patients to report promptly the onset of sore throat, fever, pallor, purpura or jaundice when taking this drug, since these may be early indications of serious blood disorders.

Related drugs

Triplesulfa , Cotrimoxazole


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