DAPSONE

By Gary M. White, MD

Note: This is a summary only. Please consult the latest information when prescribing.


Dapsone is a drug commonly used in dermatology to treat dermatitis herpetiformis.

Supplied

25 mg, 100 mg

Sig

Once daily

Half life

2-4 days Once daily dosing

Dose

One usually starts 50-100 mg/day. Alternatively, one may start low, even only 25 mg/day go up 25 per week.

Metabolized

Metabolized in the liver and excreted in the kidney. It may be prolonged by the enterohepatic circulation.

Baseline labs

G6PD, CBC, SGPT, SGOT

Monitoring

Contraindications

Heart condition, e.g. CHF, angina, G6PD deficient

SIDE EFFECTS--Note, this is only a partial list.

Agranulocytosis

Onset is usually 3-12 weeks after initiation of therapy with a typical dose being 100 mg/day. Patients usually presented with signs of acute infection. Fatalities have occurred.

Dapsone Syndrome

The constellation of findings in the dapsone syndrome often begin 5-6 weeks after initiation of the drug and include fever, lymphadenopathy, hepatosplenomegaly, hepatitis, and a rash. The rash may take the form of urticaria, erythroderma, maculopapular rash, EM or TEN. If this occurs, dapsone should be stopped and systemic steroids are indicated.

Hemolytic Anemia

Always occurs to some degree in every patient. Severe anemia may occur in patients with G6PD deficiency. It has been shown that vitamin E 800 Units/day can partially reduce the hemolysis associated with dapsone [AD 1992;128;210].

One usually tries to keep the H/H above 10/30.

Methemoglobinemia

Rare above 12-15%. It may be decreased by the addition of cimetidine 400 mg TID (BJD 1993;129;507). Symptoms of methemoglobinemia may occur at or above 3% and can include cyanosis, a grayish color, weakness, headache, tachycardia, nausea and abdominal pain.

Cyanosis of tongue: Dapsone-induced methemoglobinemia in a patient of leprosy. Indian J Dermatol 2015;60:108: At presentation and 2 weeks later after treatment.

Neuropathy

Neuropathy may occur distally and is both sensory and motor. It usually occurs within 5 years and at a dose of 300 mg/day. Sulfapyridine does not cause neuropathy and can be used in patients affected with this side effect.

Psychogenic Irritability

Apprehension, insomnia, irrational speech and a general sense of ill being are signs. The patient may have similar symptoms to sulfapyridine.

Hypoalbuminemia

Rare, but can be fatal.

Liver Function Abnormalities

Elevated LFTs may occur with dapsone therapy either in conjunction or separate [BJD 1999;141;172] from the dapsone syndrome. Sulphapyridine is an alternative in this situation.

Pregnancy

Dapsone has been used in pregnancy for e.g malaria, dermatitis herpetiformis, linear IgA bullous dermatosis and leprosy and appears relatively safe but caution must be taken and dapsone used only if clearly needed.

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