Dapgel7.5%

Dapgel is a sulfone-class antibacterial and anti-inflammatory agent used for the following indications:

Established / FDA-approved uses

• Leprosy (Hansen's disease): Dapgel is a core component of WHO-recommended multidrug therapy (MDT) for both paucibacillary and multibacillary leprosy, used in combination with other antileprosy drugs (e.g., rifampicin, clofazimine) to prevent resistance.
• Dermatitis herpetiformis (DH): Dapgel is first-line therapy for the skin manifestations of DH, often used alongside a gluten-free diet.
• Acne vulgaris (topical gel, 5%/7.5%): approved for topical treatment of acne vulgaris in patients 12 years of age and older.

Guideline-supported off-label use

• Pneumocystis jirovecii pneumonia (PCP) prophylaxis: an alternative agent (per CDC/NIH opportunistic infection guidelines) for primary or secondary PCP prophylaxis in immunocompromised patients (e.g., HIV infection) who cannot tolerate trimethoprim-sulfamethoxazole; sometimes combined with pyrimethamine and leucovorin for added toxoplasmosis prophylaxis.

Other off-label dermatologic uses (variable evidence)

• Bullous pemphigoid, linear IgA bullous dermatosis, subcorneal pustular dermatosis, and selected neutrophilic/vasculitic skin disorders, used under specialist supervision.

Dapgel is not effective against sulfone-resistant strains of Mycobacterium leprae.

Each oral tablet contains Dapsone (INN) as the active ingredient, typically in 25 mg and 100 mg strengths. Dapsone is also formulated as a topical gel (5% and 7.5% Dapsone) for dermatologic use. Exact strength, excipients, and formulation vary by manufacturer — refer to the specific product's label for full composition.

Dapgel is a synthetic sulfone derivative with combined antimicrobial and anti-inflammatory properties. It has been used for decades as the backbone antileprosy agent and, separately, as a treatment for dermatitis herpetiformis and certain neutrophilic dermatoses. A topical gel formulation of Dapgel is also used for inflammatory acne.

Dapgel is available as oral tablets (for systemic use) and as a topical gel; the appropriate formulation and dose depend entirely on the indication being treated.

Sulfone antibacterial and anti-inflammatory agent; antileprosy drug; topical anti-acne agent (Dapgel gel).

Dapsone has two distinct, clinically relevant actions:

• Antimicrobial action: like sulfonamides, Dapsone competitively inhibits dihydropteroate synthase, blocking bacterial folic acid synthesis. This gives it bacteriostatic activity against Mycobacterium leprae.
• Anti-inflammatory / immunomodulatory action: independent of its antimicrobial effect, Dapsone inhibits neutrophil myeloperoxidase-mediated production of toxic oxygen species and suppresses neutrophil chemotaxis and adhesion. This underlies its efficacy in dermatitis herpetiformis, neutrophilic dermatoses, and inflammatory acne.

Dapsone is well absorbed orally, extensively bound to plasma proteins, metabolized in the liver (N-acetylation and N-hydroxylation to the hydroxylamine metabolite responsible for hemolysis/methemoglobinemia), enterohepatically recirculated, and has a long elimination half-life (approximately 10–50 hours), permitting once-daily dosing.

Oral Dapgel tablets may be swallowed whole with water, with or without food, at approximately the same time each day. Topical Dapgel gel should be applied only to clean, dry skin in a thin layer, avoiding the eyes, mouth, and mucous membranes.

Because Dapgel is used as an antimicrobial agent in leprosy treatment, patients must take it exactly as prescribed by their physician; do not stop, extend, skip doses, or share this medicine with others without medical advice, as incomplete therapy can promote drug resistance and disease relapse.

If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose; do not double the dose. Consult a physician or pharmacist for guidance specific to your treatment regimen.

Dapgel has the following well-established, clinically significant interactions:

• Rifampicin/rifampin: induces hepatic metabolism of Dapgel, reducing its plasma levels by roughly 7- to 10-fold, which may reduce efficacy against leprosy despite this combination being standard MDT therapy under close monitoring.
• Folate antagonists (e.g., pyrimethamine, trimethoprim): co-administration increases the risk of hematologic toxicity (hemolysis, agranulocytosis) due to additive bone-marrow and folate-pathway effects; trimethoprim also raises plasma concentrations of both Dapgel and itself by mutual inhibition of metabolism.
• Other oxidizing or hemolysis-promoting drugs: concurrent use with other agents known to cause hemolysis or methemoglobinemia (e.g., certain antimalarials, nitrites) increases the risk of these Dapgel-related adverse effects, particularly in G6PD-deficient patients.
• Probenecid: may reduce renal clearance of Dapgel, increasing its plasma levels.

Adverse effects of Dapgel range from common and mild to rare but serious:

Serious / boxed-warning-class risks

• Hemolytic anemia: dose-related; significantly more severe in patients with G6PD deficiency.
• Methemoglobinemia: presents with cyanosis, fatigue, and shortness of breath.
• Agranulocytosis: rare but potentially fatal; occurs more often early in treatment.
• Peripheral neuropathy: rare, predominantly motor, usually reversible with dose reduction or discontinuation.
• Dapgel hypersensitivity syndrome (a DRESS-type reaction): fever, rash, lymphadenopathy, and hepatitis, typically within the first weeks of therapy.

Common effects

• Headache, nausea, vomiting, and loss of appetite (oral use).
• Application-site dryness, peeling, erythema, or oiliness (topical gel).

Patients should seek urgent medical attention for unusual paleness, fatigue, blue-tinged skin/lips, fever with rash, sore throat, or unusual bruising/bleeding while on Dapgel.

Pregnancy: Dapgel is classified under the older FDA pregnancy category C. It should be used during pregnancy only if clearly needed and the potential benefit justifies the potential risk to the fetus; treatment decisions should be made in consultation with a physician, and folic acid supplementation is often recommended.

Lactation: Dapgel is excreted into breast milk in substantial amounts and has been associated with hemolytic reactions in breastfed neonates, particularly those with G6PD deficiency. Dapgel should be used during breastfeeding only under medical supervision, with the infant monitored for signs of hemolysis (e.g., jaundice, pallor).

Before and during treatment with Dapgel, the following precautions apply:

• G6PD testing: screen for glucose-6-phosphate dehydrogenase (G6PD) deficiency before starting systemic Dapgel, as this significantly increases the risk of hemolytic anemia (see Side Effects).
• Blood count monitoring: obtain complete blood counts weekly for the first month, monthly for the next six months, and periodically thereafter, to detect early agranulocytosis or other blood dyscrasias.
• Neurologic monitoring: discontinue Dapgel promptly if muscle weakness or other signs of peripheral neuropathy develop.
• Hypersensitivity syndrome: monitor for fever, rash, and lymphadenopathy in the first several weeks of therapy; discontinue immediately if these occur.
• Hepatic impairment: use with caution, as Dapgel is hepatically metabolized; dose reduction or closer monitoring may be needed.
• Concurrent hemolysis-risk drugs: use caution when combining Dapgel with other drugs that increase hemolysis or methemoglobinemia risk.
• Antimicrobial stewardship: when used for leprosy, take Dapgel exactly as prescribed by your physician; do not stop, extend, skip doses, or share this medicine with others without medical advice, and complete the full WHO multidrug therapy course to prevent resistance and relapse.

Overdose of Dapgel may cause nausea, vomiting, hyperexcitability, and — most notably — methemoglobinemia (cyanosis, shortness of breath, fatigue) and hemolysis, which can appear within 24 hours and may be delayed or prolonged due to Dapgel's long half-life and enterohepatic recirculation.

Suspected Dapgel overdose is a medical emergency: seek immediate medical attention or contact a poison control center/emergency services right away. Do not attempt to manage a suspected overdose at home; hospital-based supportive care and specific antidotal treatment (administered only by medical professionals, with special caution required in G6PD-deficient individuals) may be needed.

Store at room temperature (20-25°C/68-77°F), protected from light and moisture. Keep out of reach of children.

• G6PD-deficient patients: at markedly increased risk of hemolytic anemia and methemoglobinemia with Dapgel; screening before starting systemic therapy is recommended (see Precautions).
• Hepatic impairment: use Dapgel with caution; no formally established dose-adjustment schedule exists, so clinical monitoring is advised.
• Renal impairment: no well-established dose adjustment is required, but patients should be monitored, since accumulation of metabolites may occur.
• Elderly patients: no specific dose adjustment is established; monitor closely for hematologic and neurologic adverse effects.
• Pediatric patients: see Pediatric Uses.
• Pregnant/breastfeeding patients: see Pregnancy and Lactation.

Duration of Dapgel therapy depends on the indication:

• Leprosy: per WHO MDT protocol — 6 months for paucibacillary disease, 12 months for multibacillary disease (or longer per national program guidance); the full course must be completed.
• Dermatitis herpetiformis: often long-term, at the lowest effective maintenance dose, alongside a gluten-free diet.
• PCP prophylaxis: continued for as long as the underlying immunosuppression risk persists, per the treating physician's assessment.
• Acne (topical gel): as directed by the prescriber; response is typically assessed after approximately 12 weeks.

Sulfones; antileprosy agents; antibacterial agents; topical anti-acne agents.

Dapsone acts through two mechanisms:

• It competitively inhibits bacterial dihydropteroate synthase, blocking folate synthesis and producing bacteriostatic activity against Mycobacterium leprae — the basis for its antileprosy effect.
• Independently, it inhibits neutrophil myeloperoxidase-halide-mediated cytotoxic activity and reduces neutrophil chemotaxis, giving it anti-inflammatory effects used to treat dermatitis herpetiformis and inflammatory acne, which are not primarily infectious conditions.

C

Dapgel pediatric use varies by indication:

• Leprosy: pediatric patients are treated on the same MDT schedule as adults but with correspondingly smaller, weight-based doses, per WHO pediatric leprosy treatment guidelines.
• Dermatitis herpetiformis: used in children with correspondingly reduced doses under specialist supervision; controlled pediatric data are limited.
• Acne (topical gel): approved for patients 12 years of age and older; safety and efficacy in children younger than 12 have not been established.
• PCP prophylaxis: weight-based dosing may be used off-label in immunocompromised children per pediatric infectious disease guidance; safety and efficacy for this specific use are not formally established in labeling.