Basic information Pharmacology and mechanism of action Indications Side effects Contraindications and precautions Interactions Preparations References Safety Supplier Related
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Basic information Pharmacology and mechanism of action Indications Side effects Contraindications and precautions Interactions Preparations References Safety Supplier Related

Sulfadoxine Basic information

Product Name:
  • 4-amino-n-(5,6-dimethoxy-4-pyrimidinyl)-benzenesulfonamid
  • 6-(4-aminobenzenesulfonamido)-4,5-dimethoxypyrimidine
  • fanasil
  • sulforthomidine
  • 6-(4-aminobenzenesulfonamide)-4,5-dimethoxypyrimidine
  • 4-sulfanilamido-5,6-dimethoxypyrimidine
  • Sulfadoxine BP2000/USP25
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Mol File:

Sulfadoxine Chemical Properties

Melting point:
Boiling point:
298°C (rough estimate)
1.4006 (rough estimate)
refractive index 
1.6270 (estimate)
storage temp. 
Keep in dark place,Inert atmosphere,Room temperature
Soluble in ethanol & ammonium hydroxide (9:1) at 20mg/ml
Water Solubility 
209.8mg/L(temperature not stated)

Safety Information

Hazard Codes 
Risk Statements 
Safety Statements 
WGK Germany 
HS Code 
LD50 in mice (microcrystals, mg/kg): 5200 orally, 2900 s.c., 2900 i.p. (Bhni)



Sulfadoxine Usage And Synthesis

Pharmacology and mechanism of action

The efficacy of sulphadoxine for the treatment of human malaria was first reported in 1964 [1]. Soon thereafter it was found that potentiation took place when sulphadoxine was combined with pyrimethamine for treatment of malaria and monotherapy was abandoned.
Malaria parasites synthesize their folate co-factors and cannot use dietary folic acid as the human host can. Sulphadoxine competes with para-aminobenzoic acid (PABA) for binding to the enzyme dihydropteroate synthetase in the synthesis of dihydropteroate which is an essential substance for the formation of folic acid [2]. It is active against asexual blood forms of P. falciparum but less active against other species. The action is too slow to be used alone for malaria treatment [3].


Sulphadoxine is used only in combination with pyrimethamine for the treatment of falciparum malaria. It should generally not be used for malaria prophylaxis except perhaps in long-term travellers who have previously tolerated the combination.

Side effects

Sulphadoxine is usually well tolerated. Vomiting, skin rashes, pruritus and haematological reactions such as haemolysis and leucopenia occur [4]. Hypersensitivity pneumonitis is reported[5, 6]. Cases of liver injury alone (hepatitis of hepatocellular, mixed hepatocellular, or aggressive type) or as part of a generalized allergic syndrome are well known[4, 6], and one case of fatal hepatic failure has also been reported [7].
Severe cutaneous adverse reactions (erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis) have been reported in persons taking prophylactic doses of sulphadoxine/pyrimethamine[6, 8]. Sulphadoxine has been incriminated as the most probable cause of these reactions. They all occurred within 7 weeks after start of prophylaxis.
The reported incidence was 1/5,000–8,000 users in USA and approximately 1/10,000 users in Sweden with fatality rates of 1/11,000–25,000 and 1/50,000, respectively. In Mozambique, when sulphadoxine was given alone in a single dose for cholera prophylaxis to 149,000 inhabitants, a total of 22 cases of Stevens-Johnson syndrome was seen with 3 deaths [9].

Contraindications and precautions

The drug or its combination should not be given to patients allergic to sulphonamides. It should not be used in persons with severe blood, kidney or liver diseases.


Increased impairment of folic acid synthesis and consequent haematological adverse effects may occur if trimethoprim or its combination with sulphonamide is administered concurrently. Sulphadoxine potentiates the action of warfarin and thiopentone [10].


Sulphadoxine combined with pyrimethamine.  • Fansidar® (Roche). Tablets (sulphadoxine 500 mg+pyrimethamine 25 mg), solution for intramuscular injection (sulphadoxine 200 mg/ml+pyrimethamine 10 mg/ml).


1. Laing ABG (1964). Antimalarial effect of sulphorthodimethoxine (Fanasil). BMJ, 2, 1439–1440.
2. The biology of malaria parasites. Technical Report Series no. 743 (1987). (Geneva: World Health Organization).
3. Chemotherapy of Malaria. Monograph series No. 27, 2nd edn, (1986), (Geneva: World Health Organization).
4. Hoigné R, Malinverni R, Sonntag R (1992). Sulfonomides, other folic acid antagonists and miscellaneous antibacterial drugs. In: Meyler’s Side Effects of Drugs, 12th edn, edited by M.N.G.Dukes (Amsterdam: Elsevier), pp. 715–722.
5. Svanbom M, Rombo L, Gustafsson L (1984). Unusual pulmonary reaction during short term prophylaxis with pyrimethamine-sulphadoxine (Fansidar). BMJ, 1, 1876.
6. Hellgren U, Rombo L, Berg B, Carlson J, Wiholm B-E (1987). Adverse reactions to sulphadoxinepyrimethamine in Swedish travellers: implications for prophylaxis. BMJ, 295, 365–366.
7. Zitelli BJ, Alexander J, Taylor S (1987). Fatal hepatic necrosis due to pyrimethamine-sulphadoxine (Fansidar). Ann Intern Med, 106, 393–395. 25. Miller KD, Lobel HO, Satriale RF, Kirutsky JN, Stern R, Campell CC (1986). Severe cutaneous reactions among American travellers using pyrimethamine-sulphadoxine (Fansidar) for malaria prophylaxis. Am J Trop Hyg, 35, 451–458.
8. Hernberg A (1985). Stevens-Johnson syndrome after mass prophylaxis with sulphadoxine for cholera in Mozambique. Lancet, 2, 1072–1073.
9. Sulfadoxine. Therapeutic Drugs, edited by Sir Colin Dollery (1991), (London: Churchill Livingstone), pp. S115–S119.

Chemical Properties

White Crystalline Solid




Used as an antibacterial


ChEBI: A sulfonamide consisting of pyrimidine having methoxy substituents at the 5- and 6-positions and a 4-aminobenzenesulfonamido group at the 4-position. In combination with the antiprotozoal pyrimethamine (CHEBI:8673) it is used as an antimalarial.

Manufacturing Process

(a) α-methoxy-cyanoacetic acid methyl ester is condensed with thiourea, in the presence of sodium methylate, to form 2-thio-4-amino-5-methoxy-6- hydroxy-pyrimidine.
(b) The product thus obtained is methylated in a sodium methylate solution with methyl iodide to form 2-methylthio-4-amino-5-methoxy-6-hydroxypyrimidine of MP 203°C, from water.
(c) The latter product is methylated with phenyltrimethylammoniumtoluenesulfonate to form 2-methylthio-4-amino-5,6-dimethoxy-pyrimidine of MP 112° to 115°C, from 20% methanol.
(d) 0.9 gram of 2-methylthio-4-amino-5,6-dimethoxy-pyrimidine are dissolved in 3 ml of absolute pyridine. At 0°C, 1.2 grams of pacetylaminobenzenesulfonyl chloride are added thereto and the mixture is shaken until all the material is dissolved. The solution is allowed to stand for 22 hours at 0°C and the pyridine eliminated in vacuo at 20°C. To the resulting product are added 20 ml of water and 3 ml of glacial acetic acid, whereupon the whole mixture is heated to the boil, thus causing crystallization. The crude product obtained is dissolved in 40 ml of 2.5% soda solution, and the solution obtained is filtered and supersaturated with gaseous carbon dioxide. There is thus obtained 1.5 grams (85%) of 2-methylthio-4-(N4-acetyl-sulfanilamido)- 5,6-dimethoxy-pyrimidine of MP 220° to 221°C, from 50% ethanol.
(e) 1.3 grams of 2-methylthio-4-(N4-acetyl-sulfanilamido)-5,6-dimethoxypyrimidineare dissolved in 25 ml of water and 0.4 gram of anhydrous sodium carbonate, then refluxed for 3 ? hours in the presence of 6 to 7 grams of Raney nickel. Then, a solution of 1 gram of sodium hydroxide in 3 ml of water is added thereto and heating continued for another hour. The catalyst is filtered off and the filtrate acidified to Congo red with hydrochloric acid. The pH is then brought to 5 by means of ammonia, thus causing crystallization. There is thus obtained 0.51 gram of 4-sulfanilamido-5,6-dimethoxy-pyrimidine of MP 190° to 194°C, from 50% ethanol.

brand name

Fanasil (Hoffmann-LaRoche-International); Fanzil (Hoffmann-LaRoche).

Therapeutic Function


Antimicrobial activity

Its antibacterial activity is relatively poor. Used alone it has a slow and uncertain effect against malaria parasites. Resistance of malaria parasites to the combination with pyrimethamine is common in many endemic areas.

Pharmaceutical Applications

An ultra-long-acting sulfonamide. It is no longer prescribed alone, but is used in combination with pyrimethamine as the antimalarial agent Fansidar. It is poorly soluble in water.


Oral absorption :Extensive
Cmax 500 mg oral: c. 60 mg/L after 3–4 h
Plasma half-life:c.6 days
Volume of distribution:0.13 L/kg
Plasma protein binding:94%
The extremely long half-life allows administration at weekly intervals. The acetyl metabolite has a similarly long half-life, but sulfadoxine is less extensively metabolized than many other sulfonamides.


In terms of antibacterial action, this drug is analogous to other sulfanilamides; however, it possesses very prolonged action. Its half-life is from 120 to 200 h. Sulfadoxine is used for infectious diseases caused by microorganisms that are sensitive to the sulfanilamide drugs, such as infections of respiratory organs, gastric and urinary tracts; purulent infections of various localization, osteomyelitis, sinusitis, and other infections. It is used in combination with antimalarial drugs. Synonyms of this drug are sulfarmethoxine, fanasil, and fansidar.

Clinical Use

Sulfadoxine is used only in combination with pyrimethamine.

Side effects

Side effects are those common to the group. There have been many reports of Stevens–Johnson syndrome following its use and the combination with pyrimethamine is no longer recommended for the prophylaxis of malaria.

Chemical Synthesis

Sulfadoxine, 4,5-dimethoxy-6-sulfanilamidopyrimidine (33.1.33), is synthesized by the standard scheme from 4-acetylaminobenzenesulfonyl chloride and 4-amino-5,6-dimethoxypyrimidine. However, the synthesis of 4-amino-5,6- dimethoxypyrimidine (33.1.31) is itself curious—it is synthesized from methyl ester of methoxyacetic acid. Interacting this with dimethyloxalate in the presence of sodium methoxide gives the methoxy derivative (33.1.25), and the pyrolysis of this compound gives the dimethyl ester of methoxymalonic acid (33.1.26). Reacting this with ammonia gives the diamide of methoxymalonic acid (33.1.27). Heterocyclization of the resulting product by a reaction with formamide in the presence of sodium ethoxide gives 4,6- dioxy-5-methoxypyrimidine (33.1.28), which is then transformed to 4,6-dichloro-5- methoxypyrimidine (33.1.29). The resulting 4,6-dichloro-5-methoxypyrimidine (33.1.29) undergoes a reaction with ammonia to make 4-amino-6-chloro-5-methoxypyrimidine (33.1.30), and the resulting compound is then reacted with sodium methoxide to make the desired 5,6-dimethoxy-5-aminopyrimidine (33.1.31). Reacting this with 4-acetylaminobenzenesulfonyl chloride and subsequent hydrolysis of the acetyl group in (33.1.32) gives sulfadoxine.


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