Dapsone is a sulfone antibiotic medication primarily used to treat dermatitis herpetiformis and leprosy (Hansen’s disease). It functions through antibacterial and anti-inflammatory mechanisms, making it particularly valuable in managing chronic inflammatory dermatological conditions. This medication requires careful medical supervision due to its potential for serious side effects, particularly hematological complications. Proper dosing and monitoring are essential for safe and effective treatment outcomes.

Features

• Chemical class: Sulfone antibiotic
• Mechanism: Bacteriostatic action against Mycobacterium leprae; anti-inflammatory effects via inhibition of neutrophil migration and function
• Administration: Oral tablet formulation
• Available strengths: 25 mg and 100 mg tablets
• Prescription status: Rx-only medication
• Bioavailability: 70-80% following oral administration
• Half-life: 20-30 hours (permits once-daily dosing)
• Metabolism: Hepatic acetylation (genetic polymorphism affects metabolism rate)
• Excretion: Primarily renal

Benefits

• Provides rapid relief from the intense pruritus associated with dermatitis herpetiformis
• Effective bactericidal action against Mycobacterium leprae in all forms of leprosy
• Demonstrates significant anti-inflammatory properties beneficial for various dermatoses
• Allows for once-daily dosing regimen due to prolonged half-life
• Serves as second-line treatment for Pneumocystis jirovecii pneumonia prophylaxis in immunocompromised patients
• Offers therapeutic alternative for patients unresponsive to first-line treatments

Common use

Dapsone is primarily indicated for the treatment of dermatitis herpetiformis, a chronic blistering skin disorder associated with gluten sensitivity. It is equally fundamental in the multidrug therapy of leprosy, both paucibacillary and multibacillary forms, as recommended by the World Health Organization. Off-label uses include treatment of various autoimmune bullous diseases such as linear IgA dermatosis, subcorneal pustular dermatosis, and occasionally for acne vulgaris refractory to conventional treatments. It is also employed as prophylaxis against Pneumocystis jirovecii pneumonia in immunocompromised patients, particularly those with HIV/AIDS who cannot tolerate trimethoprim-sulfamethoxazole.

Dosage and direction

For dermatitis herpetiformis, the initial adult dosage is typically 50 mg daily, which may be increased to 300 mg daily or higher based on response and tolerance. Maintenance doses usually range between 50-150 mg daily. For leprosy treatment, dapsone is administered as part of multidrug therapy: 100 mg daily for adults and proportional weight-based dosing for children, continued for specified durations depending on leprosy classification (6 months for paucibacillary, 12 months for multibacillary leprosy). The medication should be taken with food to minimize gastrointestinal upset. Regular monitoring of complete blood count, liver function tests, and glucose-6-phosphate dehydrogenase (G6PD) levels is mandatory before and during therapy.

Precautions

Prior to initiating dapsone therapy, G6PD deficiency must be ruled out due to the risk of hemolytic anemia. Regular hematological monitoring is essential, particularly during the first month of treatment and periodically thereafter. Patients should be advised to report immediately any signs of infection, unusual fatigue, dark urine, or yellowing of skin/eyes. Hepatic and renal function should be assessed regularly, with dosage adjustments necessary in impairment. Dapsone may cause peripheral neuropathy with prolonged use, requiring neurological assessment. Photosensitivity reactions may occur, necessitating sun protection measures. Pregnancy category C: use only if potential benefit justifies potential risk to fetus.

Contraindications

Dapsone is contraindicated in patients with known hypersensitivity to sulfones or any component of the formulation. Absolute contraindications include severe G6PD deficiency (due to high risk of hemolysis), severe anemia, and methemoglobin reductase deficiency. Relative contraindications include significant hepatic impairment, severe renal impairment (CrCl <30 mL/min), and history of sulfonamide allergy. Concomitant use with trimethoprim-sulfamethoxazole is generally contraindicated due to additive adverse effects. Not recommended during lactation due to secretion in breast milk and risk of kernicterus in infants.

Possible side effect

Common adverse effects include hemolytic anemia (especially in G6PD deficiency), methemoglobinemia, nausea, vomiting, headache, dizziness, and blurred vision. Less frequent but serious side effects include agranulocytosis, peripheral neuropathy, hepatitis, cholestatic jaundice, hypersensitivity syndrome (fever, rash, lymphadenopathy), and exfoliative dermatitis. Rare but severe reactions include Stevens-Johnson syndrome, toxic epidermal necrolysis, and sulfone syndrome (fever, hepatitis, exfoliative dermatitis, and lymphadenopathy). Most hematological effects are dose-related and reversible upon discontinuation.

Drug interaction

Dapsone interacts significantly with rifampin, which decreases dapsone levels by increasing hepatic metabolism. Probenecid increases dapsone levels by reducing renal excretion. Trimethoprim increases dapsone levels and potentiates hematological toxicity. Activated charcoal and para-aminobenzoic acid (PABA) may reduce dapsone absorption. Dapsone may decrease the efficacy of oral contraceptives. Concurrent use with other hemolytic agents or drugs causing methemoglobinemia (nitrites, sulfonamides, phenacetin) increases toxic risks. Antacids may decrease dapsone absorption and should be administered separately.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next scheduled dose. In that case, the missed dose should be skipped, and the regular dosing schedule resumed. Doubling doses to make up for a missed dose is not recommended due to increased risk of adverse effects. Patients should be educated about maintaining regular dosing schedules and advised to contact their healthcare provider if multiple doses are missed for guidance on resumption of therapy.

Overdose

Dapsone overdose manifests primarily with methemoglobinemia (cyanosis, chocolate-brown colored blood, hypoxia), hemolytic anemia, nausea, vomiting, hyperexcitability, and convulsions. Massive overdose may cause hepatic necrosis, agranulocytosis, and neurotoxicity. Treatment is supportive and includes gastric lavage if presented early, activated charcoal, and methylene blue for methemoglobinemia (1-2 mg/kg IV slowly). Exchange transfusion may be necessary in severe cases. Hemodialysis is not effective due to high protein binding. Management should occur in a hospital setting with monitoring of methemoglobin levels and hematological parameters.

Storage

Store at controlled room temperature (20-25°C or 68-77°F) in a tight, light-resistant container. Keep away from moisture and excessive heat. Keep out of reach of children and pets. Do not use after the expiration date printed on the packaging. Do not transfer tablets to other containers that do not provide equivalent protection from light and moisture. Properly discard any unused medication after treatment completion or expiration.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Dapsone is a prescription medication that should be used only under the supervision of a qualified healthcare professional. The prescribing physician should be consulted for specific medical advice, diagnosis, and treatment. Individual response to medication may vary, and not all potential side effects or interactions are listed here. Patients should disclose their complete medical history and current medications to their healthcare provider before initiating therapy.

Reviews

Clinical studies demonstrate dapsone’s efficacy in dermatitis herpetiformis, with approximately 90% of patients experiencing significant improvement in itching within 48-72 hours and lesion clearance within several days to weeks. In leprosy treatment, multidrug therapy including dapsone has reduced prevalence rates dramatically worldwide. Dermatologists report excellent response in most autoimmune bullous diseases, though side effects require careful management. Patient reviews often mention dramatic improvement in quality of life due to control of debilitating itching, though some report gastrointestinal side effects and the inconvenience of required monitoring. The need for regular blood tests is frequently cited as a drawback by patients on long-term therapy.