Pyrimethamine

CLINICAL USE

Antiprotozoal agent:Malaria Toxoplasmosis

DOSE IN NORMAL RENAL FUNCTION

Malaria: used in dual drug combinations Malaria prophylaxis: 25 mg weekly Toxoplasmosis: 100–200 mg daily for 2–3 days then 25–100 mg daily for 2–6 weeks (in combination with sulfadiazine)

PHARMACOKINETICS

Molecular weight :248.7

%Protein binding :80–90

%Excreted unchanged in urine : 15–30

Volume of distribution (L/kg) :2

half-life – normal/ESRD (hrs) :35–175/Unchanged

DOSE IN RENAL IMPAIRMENT

GFR (mL/MIN)

20 to 50 : Dose as in normal renal function

10 to 20 : Dose as in normal renal function

<10 : Dose as in normal renal function

DOSE IN PATIENTS UNDERGOING RENAL REPLACEMENT THERAPIES

CAPD :Not dialysed. Dose as in normal renal function

HD :Not dialysed. Dose as in normal renal function

HDF/high flux :Unknown dialysability. Dose as in normal renal function

CAV/VVHD :Not dialysed. Dose as in normal renal function

IMPORTANT DRUG INTERACTIONS

Potentially hazardous interactions with other drugsIncreased antifolate effect with sulphonamides, trimethoprim and methotrexate

Anti-epileptics: anticonvulsant effect antagonised; increased antifolate effect with phenytoin

Antimalarials: avoid concomitant use with artemether/lumefantrine; increased antifolate effect with proguanil

ADMINISTRATION

Reconstition

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Route

Oral

Rate of Administration

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Comments

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OTHER INFORMATION

Pyrimethamine should always be administered with a folate supplement to reduce the risk of bone marrow depression.

See how to identify renal failure stages according to GFR calculation

See how to diagnose irreversible renal disease

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