Brand name: Dapsone Aczone™
Description: Used to treat leprosy and skin infections.
Dapsone is a versatile drug. It is a synthetic sulfone
and is chemically similar to sulfonamides, but cross-sensitivity has
not been substantiated. It is used as an antiinfective (for leprosy,
Pneumocystis carinii pneumonia (PCP), and prophylaxis of malaria) and
as an immunosuppressive agent (for relapsing polychondritis and systemic
lupus erythematosus). Dapsone also has been used to treat various dermatologic
disorders such as actinomycotic mycetoma, dermatitis herpetiformis,
pemphigoid, subcorneal pustular dermatosis, granuloma annulare, and pyoderma
gangrenosum.
In addition, dapsone is commonly used to treat Loxosceles reclusa (e.g.,
brown recluse spider) bites; however, both human and animal data to
support its routine use are conflicting. A few case reports and small
case series
indicate efficacy in humans, but prospective human trials supporting
its use are not available. Furthermore, in addition to the lack of
evidence to support its use, dapsone can cause serious, life-threatening
toxicities
(e.g., hemolytic anemia, hepatitis, methemoglobinemia). A prospective
epidemiologic study found that patients treated with dapsone for suspected
loxoscelism experienced a nonsignificant increase in healing time and
scarring.
The benefits of administering dapsone for the treatment
of loxoscelism should be carefully balanced against the risks; supportive
therapy and wound care are the treatment modalities of choice in
patients presenting with loxoscelism.[8838] [8840] Dapsone is currently
the
agent of choice in the treatment of all forms of leprosy, unless the
organism
exhibits dapsone resistance. Dapsone can be used for prophylaxis
of PCP either as a single agent or in combination with pyrimethamine.
In
combination
with trimethoprim, dapsone is effective for treatment of PCP.[189]
In combination with pyrimethamine, dapsone is effective for prevention
of
toxoplasmosis in patients with AIDS.[191] Acedapsone is a long-acting
repository form. In Canada, a commonly used brand name of oral dapsone
is Alvosulfon.
Dapsone was originally approved by the FDA in 1955.
A 5% topical dapsone gel (Aczone™) was approved for use in treating
acne vulgaris on July 7, 2005.
Mechanism of Action: Similar to sulfonamides, dapsone inhibits dihyropteroate
synthase in susceptible organisms. Other proposed mechanisms for dapsone
include inhibition of the neutrophilic-cytotoxic system and interference
with the alternate pathway of the complement system. Although the mechanism
of dapsone in dermatologic disorders is unknown, it has been suggested
that it may act as an immunomodulator.
For many years, dapsone was the main therapy for leprosy (Mycobacterium
leprae). Unfortunately, years of monotherapy has lead to significant
resistance in this organism. Resistance to M. leprae develops in 2—10%
of patients after prolonged administration. Nevertheless, dapsone remains
a component of combination therapy for leprosy.
Pharmacokinetics:
Dapsone is administered orally and is almost completely
absorbed from the GI tract. Peak serum levels are reached in 2—8
hours. Dapsone is widely distributed and is retained in the skin, muscles,
kidneys, and liver. The drug also crosses the placenta and is distributed
into breast milk (see Contraindications).
