Title: Pyrimethamine
CAS Registry Number: 58-14-0
CAS Name: 5-(4-Chlorophenyl)-6-ethyl-2,4-pyrimidinediamine
Additional Names: 2,4-diamino-5-(p-chlorophenyl)-6-ethylpyrimidine
Manufacturers' Codes: RP-4753
Trademarks: Daraprim (GSK); Malocide (Aventis)
Molecular Formula: C12H13ClN4
Molecular Weight: 248.71
Percent Composition: C 57.95%, H 5.27%, Cl 14.25%, N 22.53%
Literature References: Dihydrofolate reductase inhibitor; generally used in combination with other antimicrobial agents. Prepn: P. B. Russell, G. H. Hitchings, J. Am. Chem. Soc. 73, 3763 (1951); G. H. Hitchings et al., US 2576939 (1951 to Burroughs Wellcome); W. Logemann et al., Ber. 87, 435 (1954); R. M. Jacob, US 2680740 (1954 to Rhône-Poulenc). Review of antimicrobial activity and mechanism of action: Burchall in Antibiotics vol. 3, J. W. Corcoran, F. E. Hahn, Eds. (Springer-Verlag, New York, 1975) pp 312-320. Comprehensive description: M. A. Loutfy, H. Y. Aboul-Enein, Anal. Profiles Drug Subs. 12, 463-482 (1983). LC-MS determn in plasma: B. A. Sinnaeve et al., J. Chromatogr. A 1076, 97 (2005). Clinical evaluations in toxoplasmosis in AIDS patients: C. Leport et al., Am. J. Med. 84, 94 (1988); B. Dannemann et al., Ann. Intern. Med. 116, 33 (1992). Review of clinical experience in malaria: H. M. McIntosh et al., Ann. Trop. Med. Parasitol. 93, 265-270 (1998); C. V. Plowe et al., Br. Med. J. 328, 545 (2004).
Properties: Crystals, mp 233-234° (capillary); mp 240-242° (copper block). Practically insol in water. Slightly sol in ethanol, (about 9 g/l), in dil HCl (about 5 g/l); sol in boiling ethanol (about 25 g/l). Very sparingly sol in propylene glycol and dimethylacetamide at 70°.
Melting point: mp 233-234° (capillary); mp 240-242° (copper block)
Derivative Type: Combination with sulfadoxine
CAS Registry Number: 37338-39-9
Trademarks: Fansidar (Roche)
Therap-Cat: Antiprotozoal (Toxoplasma); antimalarial.
Therap-Cat-Vet: Antiprotozoal (Toxoplasma).
Keywords: Antimalarial; Antiprotozoal (Toxoplasma).
Pyrimethanil Pyrimidine Pyriminil Pyrimithate Pyrinoline

Systematic (IUPAC) name
5-(4-chlorophenyl)-6-ethyl- 2,4-pyrimidinediamine
Clinical data
Trade names Daraprim
AHFS/ monograph
MedlinePlus a601050
Pregnancy cat. B3 (AU) C (US)
Legal status Prescription only
Routes Oral
Pharmacokinetic data
Bioavailability well-absorbed
Protein binding 87%
Metabolism Hepatic
Half-life 96 hours
Excretion Renal
CAS number 58-14-0 YesY
ATC code P01BD01
QP51AX51 (combinations)
PubChem CID 4993
DrugBank DB00205
ChemSpider 4819 YesY
KEGG D00488 YesY
Chemical data
Formula C12H13ClN4 
Mol. mass 248.71 g/mol
 YesY (what is this?)  (verify)

Pyrimethamine (trade name Daraprim) is a medication used for protozoal infections. It is commonly used as an antimalarial drug (for both treatment and prevention of malaria), and is also used (combined with sulfadiazine) in the treatment of Toxoplasma gondii infections in immunocompromised patients, such as HIV-positive individuals. It is also currently being evaluated[1] in clinical trials as a treatment for ALS. In 2011, researchers have discovered that Pyrimethamine can increase ß-hexosaminidase activity, thus slowing down the progression of Late-Onset Tay–Sachs disease.