Pyrimethamine

These indications are based on manufacturer information for both originator and generic products. For product specific registered indications, please refer to product specific manufacturer information

Registered South African indications:

• Toxoplasmosis caused by Toxoplasma gondii , in combination with a sulphapyrimidine-type sulphonamide 

Contraindications

• Hypersensitivity to the active ingredient or any of its excipients
• Should not be given to individuals with a history of pyrimethamine allergy
• Should not be given to patients with conditions associated with folate deficiency such as megaloblastic anaemia

Cautions

• Pregnancy
• Breastfeeding
• Renal impairment
• Hepatic impairment
• Megaloblastic anaemia
• Dehydration
• Patients predisposed to folate deficiency
• History of seizures
• Galactose intolerance
• Lapp lactase deficiency 
• Glucose-galactose malabsorption

Forms avail. in SA and covered in this monograph: tab

Infections caused by: Toxoplasma gondii

General dosing range (additional agent required)

• Oral (tab): Initial: 50-200mg, dly for 1-2 days; Maintenance: 25-75mg; Treatment duration: Immunocompetent: 3-6 weeks; Immunocompromised: Minimum 6 weeks

Pyrimethamine should be given concurrently with sulphadiazine or another appropriate antibiotic

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

Toxoplasma gondii encephalitis in immunocompromised patients
Isospora belli diarrhoea

• Oral (tab): Initial: 200mg as a single dose, dly; Maintenance: 50mg, dly; Treatment duration: 6 weeks

Toxoplasma gondii treatment in immunocompetent patients

• Oral (tab): Initial: 50-200, 6hrly for 1-2 days; Maintenance: 25-50mg, 6hrly; Treatment duration: 2-4 weeks

Must always be used in combination with folinic acid

Paed. forms avail. in SA and covered in this monograph: tab

Infections caused by: Toxoplasma gondii

General dosing range (additional agent required)

• Oral (tab): 0.5-1mg/kg, dly

Specific doses based on individual indications

Please note that the dosages below should be used in combination with regional guidelines, taking into account local antibiotic sensitivities

Congenital toxoplasmosis (Additional agent required)

• Oral (tab): 1mg/kg, dly for 1-3 days; Then 0.5mg/kg, dly; Treatment duration: 6 months if no signs of infection present; 12 months if signs of infection present

Acquired toxoplasmosis (Additional agent required)

• Oral (tab): 1mg/kg, dly for 1-3 days; Then 0.5mg/kg, dly; Treatment duration: 4-6 weeks

Pregnancy

• Caution

Breastfeeding

• Caution; not recommended

Renal Impairment

• Caution; no dose adjustment recommended

Hepatic Impairment

• Caution; no dose adjustment recommended

Elderly

• No dose adjustment recommended

Central Nervous System Disorders

• Headache
• Dizziness
• Convulsions 

Respiratory Disorders

• Pneumonia with cellular and eosinophilic pulmonary infiltration 

Gastrointestinal Disorders

• Nausea and vomiting 
• Diarrhoea
• Colic
• Buccal ulceration

Skin and Subcutaneous Tissue Disorders

• Rash
• Abnormal skin pigmentation
• Dermatitis

Immune, Blood and Lymphatic System Disorders

• Anaemia
• Leucopenia
• Thromboctopenia
• Pancytopenia
• Fever

• Folate inhibitors 
• Daunorubicin
• Cytosine arabinoside 
• Trimethoprim 
• Methotrexate
• Antimalarial agents
• Quinine 
• Warfarin
• Lorazepam
• Antacid salts 
• Kaolin

• Full blood count
• Hepatic function
• Renal function

Pyrimethamine binds to and reversibly inhibits the protozoa enzyme dihydrofolate reductase. This depletes folate, an essential cofactor in biosynthesis of nucleic acids.

Spectrum of activity: Toxoplasma gondii

Tablet 25mg

• Daraprim (GSK) originator

COMBINATION PREPARATIONS

Sulfadoxine/ Pyrimethamine

Tablet 500mg/25mg

• Fansidar (Roche) originator