dapsone

Dapsone
Systematic (IUPAC) name
4-[(4-aminobenzene)sulfonyl]aniline
Identifiers
CAS number	80-08-0
ATC code	J04BA02
PubChem	2955
DrugBank	APRD00345
ChemSpider	2849
Chemical data
Formula	C12H12N2O2S
Mol. mass	248.302 gmol-1
SMILES	eMolecules & PubChem
Pharmacokinetic data
Bioavailability	70 to 80%
Protein binding	70 to 90%
Metabolism	Hepatic (mostly CYP2E1-mediated)
Half life	20 to 30 hours
Excretion	Renal
Therapeutic considerations
Pregnancy cat.	B2(AU) C(US)
Legal status	℞-only (U.S.), POM (UK)
Routes	Oral
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Dapsone (diamino-diphenyl sulfone) is a pharmacological medication most commonly used in combination with rifampicin and clofazimine as multidrug therapy (MDT) for the treatment of Mycobacterium leprae infections (leprosy). It is also used to treat Pneumocystis carinii pneumonia (PCP) caused by Pneumocystis jiroveci (formerly P. carinii). Dapsone is used in combination with pyrimethamine in the treatment of malaria.^[1][2]

History

In the early 20th century the German chemist Paul Ehrlich was developing theories of selective toxicity based largely on the ability of certain dyes to kill microbes. Gerhard Domagk, who would later win a Nobel Prize for his efforts, made a major breakthrough in 1932 with the discovery of the antibacterial prontosil red. Further investigation into the active chemicals involved led to the discoveries both of dapsone and of the antibacterial sulfonamides.^[3]

Mechanism

As an antibacterial, dapsone inhibits bacterial synthesis of dihydrofolic acid.^[4] Though structurally distinct from dapsone, the sulfonamide group of antibacterial drugs also work in this way.

When used for the treatment of skin conditions in which bacteria do not have a role, the mechanism or action of dapsone is less well understood. In presumed cases of brown recluse spider bites, dapsone is often used effectively, but clinical trials do not demonstrate similar effectiveness^[5]; however, dapsone may be effective at treating many "spider bites" because many such cases are actually misdiagnosed microbial infections^[6].

Synthesis

Dapsone was first synthesized by Fromm and Wittmann in 1908. 4,4'-Dinitrodiphenyl sulfide was oxidized to the sulfone in a solution of potassium dichromate, glacial acetic acid, and sulfuric acid. The nitro- groups on the sulfone was reduced with tin and concentrated hydrochloric acid, and the free base was obtained by treatment with an alkali:^[7]

Indication

As well as being used in leprosy, dapsone can also be used to treat mucous membrane pemphigoid,^[8] an autoimmune blistering disease of skin and mucous membranes, dermatitis herpetiformis and Linear immunoglobulin A dermatosis both blistering skin diseases which are effectively treated with a long-time treatment with dapsone, as well as other skin conditions including lichen planus.

It is also sometimes used to prevent Pneumocystis pneumonia (PCP) in people who are immunosuppressed and to treat idiopathic thrombocytopenic purpura.

It is used prophylactically to prevent Pneumocystis pneumonia and toxoplasmosis in patients unable to tolerate trimethoprim with sulfamethoxazole.^[9]

Dapsone is also used to treat Brown recluse spider bites.^[10]

In December 2008, a 5% dapsone gel called Aczone was introduced to the prescription market as a treatment for moderate to severe acne.[1]

Administration

Dapsone is administered orally as a 100 mg tablet or alternatively as 25 mg tablets.

To deal with dapsone-resistant leprosy cases, multidrug therapy was introduced by WHO in 1981; dapsone is administered along with rifampin and clofazimine or other antileprotic drugs.

Adverse effects

Effects on the blood

The most prominent side effects of this drug are dose-related hemolysis (which may lead to hemolytic anemia) and methemoglobinemia.^[11] Agranulocytosis occurs rarely when dapsone is used alone but more frequently in combination regimens for malaria prophylaxis.^[12] Abnormalities in white blood cell formation, including aplastic anaemia, are rare but the cause of the majority of deaths due to dapsone therapy.^[13][14][15]

Effects on the liver

Toxic hepatitis and cholestatic jaundice have been reported by the manufacturer. Jaundice may also occur as part of the dapsone reaction or dapsone syndrome (see below). Dapsone is also known to inhibit the Cytochrome P450 system.

Other adverse effects

Other adverse effects include nausea, headache, and rash, which are common, and insomnia, psychosis and peripheral neuropathy. Effects on the lung occur rarely and may be serious though are generally reversible.^[16]

Dapsone reaction

Hypersensitivity reactions occur in some patients. This reaction may be more frequent in patients receiving multiple drug therapy.^[17][18][19]

The reaction always involves a rash and may also include fever, jaundice, and eosinophilia.^{[20][21][22][23][24]} These symptoms will generally occur within the first six weeks of therapy or not at all, and may be ameliorated by corticosteroid therapy.^[9]

Specific considerations

Certain patients are at higher risks of adverse effects when using dapsone. Some specific issues which should be considered are:^[9]

• Related to the blood (a full blood count should be obtained prior to initiating therapy):
  • Porphyria
  • Anaemia
  • Cardiac disease
  • Pulmonary disease
  • HIV infection
  • G6PD deficiency

• Related to the liver (obtain liver function tests before starting therapy):
  • Liver impairment

• Related to allergy:
  • Sulfonamide allergy is associated with dapsone allergy

References

External links

• MedlinePlus Drug Information