Dapsone is a synthetic sulfone antimicrobial agent with a well-established history in dermatological and infectious disease therapeutics. Its primary mechanism of action involves inhibition of bacterial folate synthesis and potent anti-inflammatory effects, particularly through the suppression of neutrophil migration and function. This dual-action profile makes it a cornerstone treatment for a spectrum of conditions, from leprosy to refractory inflammatory dermatoses. Its utility extends to off-label uses where conventional therapies have failed, offering a critical option for managing complex patient cases.

Features

• Synthetic sulfone antimicrobial compound
• Available in 25 mg and 100 mg oral tablets
• Demonstrated bactericidal and bacteriostatic activity against Mycobacterium leprae
• Potent anti-inflammatory properties, specifically inhibiting neutrophil myeloperoxidase
• Standardized manufacturing under strict pharmaceutical quality controls

Benefits

• Provides effective first-line systemic treatment for all forms of leprosy (Hansen’s disease).
• Offers significant clinical improvement in dermatitis herpetiformis, often inducing remission of the intense pruritus and skin lesions.
• Serves as a steroid-sparing agent in the management of various neutrophilic dermatoses, such as linear IgA disease and autoimmune bullous disorders.
• Demonstrates efficacy in the treatment and prophylaxis of Pneumocystis jirovecii pneumonia, particularly in immunosuppressed patient populations.
• Provides a therapeutic option for patients with acne vulgaris that is severe and resistant to conventional antibiotic regimens.

Common use

Dapsone is indicated for the treatment of leprosy, caused by Mycobacterium leprae, and dermatitis herpetiformis, a chronic, intensely pruritic skin disorder associated with celiac disease. It is used in combination with other antileprotic drugs like rifampicin and clofazimine in multibacillary leprosy to prevent resistance. Its off-label applications are extensive and evidence-supported, including management of subcorneal pustular dermatosis, linear IgA bullous dermatosis, and other autoimmune blistering diseases. It is also utilized for prophylaxis against Pneumocystis jirovecii pneumonia in immunocompromised individuals, such as those with HIV/AIDS or undergoing immunosuppressive chemotherapy, who cannot tolerate first-line agents like trimethoprim-sulfamethoxazole.

Dosage and direction

Dosage is highly indication-specific and must be individualized based on patient diagnosis, clinical response, and tolerability. For leprosy, the adult dosage is 100 mg daily, unsupervised, in combination with other antileprosy drugs, often for prolonged periods (months to years). For dermatitis herpetiformis, the initial adult dose is typically 50 mg daily, which may be increased to a maximum of 300 mg daily or until symptoms are controlled, followed by a gradual reduction to the lowest effective maintenance dose. For P. jirovecii pneumonia prophylaxis in adults, the dose is 100 mg daily. Administration should be with food or water to minimize potential gastrointestinal upset. Dosing in pediatric populations is based on body weight and must be carefully calculated by a specialist. Regular monitoring of complete blood count (CBC) and liver function tests is mandatory, especially during the initial phase of therapy.

Precautions

The most significant precaution associated with dapsone therapy is the risk of hematological toxicity. All patients should be screened for glucose-6-phosphate dehydrogenase (G6PD) deficiency prior to initiation, as deficient individuals are at high risk for dose-related hemolysis and methemoglobinemia. A baseline CBC is essential. Patients should be monitored for signs of hemolysis (e.g., fatigue, pallor, dark urine), agranulocytosis, and methemoglobinemia (e.g., cyanosis, shortness of breath, fatigue). Use with caution in patients with pre-existing hepatic or severe renal impairment, as dosage adjustment may be required. A “dapsone hypersensitivity syndrome” may occur, characterized by fever, rash, lymphadenopathy, and hepatitis, typically within the first 6 weeks of therapy; this requires immediate drug discontinuation. Peripheral neuropathy, both motor and sensory, has been reported with long-term use.

Contraindications

Dapsone is absolutely contraindicated in patients with a known hypersensitivity to dapsone or any component of the formulation. Its use is also contraindicated in patients with severe anemia (especially if due to G6PD deficiency, which must be ruled out prior to treatment) and in those with a history of methemoglobinemia. Concomitant use with drugs that are known to cause hemolysis or suppress bone marrow function (e.g., primaquine) is generally contraindicated unless the potential benefit outweighs the significant risk.

Possible side effect

A wide range of adverse effects is possible, with severity varying from mild to life-threatening.

• Common: Hemolytic anemia (especially in G6PD-deficient individuals), headache, nausea, vomiting, abdominal pain, dizziness.
• Serious: Methemoglobinemia, agranulocytosis, aplastic anemia, peripheral neuropathy (may be irreversible), dapsone hypersensitivity syndrome (drug reaction with eosinophilia and systemic symptoms - DRESS), hepatitis, cholestatic jaundice, exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, phototoxicity, psychosis.
• Rare: Nephrotic syndrome, pulmonary eosinophilia, hypoalbuminemia without proteinuria.

Drug interaction

Dapsone has a substantial potential for pharmacokinetic and pharmacodynamic interactions.

• Probenecid: May increase dapsone levels by reducing renal excretion.
• Rifampin: Significantly induces the metabolism of dapsone, decreasing its plasma levels and efficacy.
• Trimethoprim: Increases levels of both dapsone and its hydroxylamine metabolite, potentiating the risk of hematologic toxicity.
• Didanosine: Coadministration may reduce the absorption of dapsone.
• Other hematotoxic drugs (e.g., zidovudine, pyrimethamine, clozapine): May have additive myelosuppressive effects.
• Methaemoglobin-inducing agents (e.g., nitrites, local anesthetics like benzocaine): Increased risk of clinically significant methemoglobinemia.

Missed dose

If a dose is missed, it should be taken as soon as it is remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped. Patients should never take a double dose to make up for a missed one. Maintaining a consistent dosing schedule is important for therapeutic efficacy, particularly in chronic conditions.

Overdose

Overdose can be severe and potentially fatal, primarily manifesting as exaggerated pharmacological effects: nausea, vomiting, hyperexcitability, convulsions, and severe methemoglobinemia leading to cyanosis, hemolysis, and Heinz body formation. Treatment is primarily supportive and symptomatic. Gastric lavage or activated charcoal may be considered if ingestion was recent. Methylene blue is the specific antidote for methemoglobinemia (1-2 mg/kg IV administered slowly over 5 minutes; may be repeated), but it is contraindicated in patients with G6PD deficiency due to the risk of precipitating hemolysis. In such cases, exchange transfusion may be necessary. Hemodialysis is not effective for dapsone removal.

Storage

Store dapsone tablets at controlled room temperature, 20°C to 25°C (68°F to 77°F), in a tight, light-resistant container. Keep the medication out of reach of children and pets. Do not use after the expiration date printed on the bottle. Do not flush unused medication or pour it down a drain; consult a pharmacist on proper disposal methods.

Disclaimer

This information is for educational and professional medical reference purposes only and is not a substitute for the professional judgment of a qualified healthcare provider in diagnosing and treating patients. The content does not cover all possible uses, directions, precautions, interactions, or adverse effects. The author and publisher are not responsible for any errors, omissions, or for any outcomes resulting from the use of this information. The reader is strongly advised to consult the full manufacturer’s prescribing information and other primary references before initiating or monitoring any therapy.

Reviews

“Dapsone remains an irreplaceable agent in my dermatology practice. For patients with debilitating dermatitis herpetiformis, the rapid and dramatic resolution of pruritus is often life-changing. While the monitoring requirements are non-negotiable, the benefit-to-risk profile in appropriately selected and managed patients is excellent.” – Dermatologist, 15 years of experience.

“In the context of leprosy management, dapsone’s role within multidrug therapy is foundational. It is effective and generally well-tolerated over the long treatment courses required. Vigilance for early signs of hypersensitivity is paramount.” – Infectious Disease Specialist, working in endemic regions.

“I utilize dapsone for PJP prophylaxis in transplant patients intolerant to TMP-SMX. It is a reliable second-line option. The main challenge is patient education regarding the signs of methemoglobinemia and the necessity of G6PD testing prior to initiation.” – Transplant Pharmacist.