Dapsone is a synthetic sulfone antimicrobial agent with a well-established history in clinical medicine, primarily recognized for its antibacterial and anti-inflammatory properties. Its unique dual mechanism of action makes it a cornerstone in the treatment of specific dermatological conditions and certain infectious diseases. This medication exerts its effects by inhibiting bacterial folate synthesis and suppressing neutrophil-mediated inflammation, providing a targeted therapeutic approach for complex conditions where conventional treatments may fall short. Its utility spans from managing leprosy to addressing refractory inflammatory skin disorders, underscoring its importance in specialized therapeutic regimens.

Features

• Synthetic sulfone antimicrobial and anti-inflammatory agent.
• Available in oral tablet formulations (e.g., 25 mg and 100 mg strengths).
• Mechanism of action: competitive inhibition of dihydropteroate synthase, disrupting folate synthesis in susceptible bacteria.
• Additional anti-inflammatory mechanism: inhibition of neutrophil migration and function via interference with the integrin-mediated respiratory burst.
• Typically administered once or twice daily, depending on the indication and patient-specific factors.

Benefits

• Provides effective bacteriostatic action against Mycobacterium leprae, making it a first-line agent in the multidrug therapy (MDT) for leprosy.
• Offers significant anti-inflammatory effects for managing dermatological conditions like dermatitis herpetiformis, reducing blister formation and pruritus.
• Serves as a second-line treatment option for acne vulgaris, particularly in cases demonstrating inflammatory papules and pustules resistant to other therapies.
• Used as a steroid-sparing agent in various immune-mediated conditions, potentially reducing the long-term adverse effects associated with systemic corticosteroid use.
• Demonstrates efficacy in the prophylaxis and treatment of Pneumocystis jirovecii pneumonia (PJP), particularly in sulfa-allergic patients, when combined with other agents like trimethoprim.
• Provides a targeted therapeutic option for a spectrum of neutrophilic dermatoses, including linear IgA disease and subcorneal pustular dermatosis.

Common use

Dapsone is indicated for the treatment of leprosy (Hansen’s disease), always as part of a multidrug regimen to prevent the development of resistance. It is also FDA-approved for the treatment of dermatitis herpetiformis, a chronic, intensely pruritic blistering skin disorder associated with celiac disease. Beyond these approved uses, it is widely employed off-label for a variety of conditions. This includes its use as an anti-inflammatory agent for acne vulgaris, particularly inflammatory types. It is also used in the management of other autoimmune bullous diseases (e.g., linear IgA disease, bullous lupus erythematosus) and neutrophilic dermatoses (e.g., Sweet’s syndrome). Furthermore, it plays a role in the prophylaxis against Pneumocystis jirovecii pneumonia in immunocompromised patients, such as those with HIV/AIDS or on immunosuppressive therapies.

Dosage and direction

Dosage is highly indication-specific and must be individualized based on patient response and tolerance. For leprosy, as part of MDT, the standard adult dose is 100 mg daily. For dermatitis herpetiformis, the initial adult dose typically ranges from 50 mg to 150 mg daily, often starting lower and titrating upward to the lowest effective dose that controls symptoms. For acne vulgaris, doses usually range from 50 mg to 100 mg daily. For PJP prophylaxis, a common regimen is dapsone 100 mg daily or 50 mg twice daily. Administration with food may minimize gastrointestinal upset. It is crucial to adhere strictly to the prescribing clinician’s instructions. Doses for pediatric patients are calculated based on body weight.

Precautions

Prior to initiation, screening for glucose-6-phosphate dehydrogenase (G6PD) deficiency is mandatory, as dapsone can cause dose-related hemolysis, which is severe in G6PD-deficient individuals. A complete blood count (CBC) should be obtained at baseline and monitored periodically during therapy to check for hemolytic anemia, methemoglobinemia, and agranulocytosis. Liver and renal function tests are also recommended at baseline. Patients should be advised that dapsone may cause peripheral neuropathy with prolonged use. Caution is advised in patients with pre-existing cardiac, pulmonary, hepatic, or renal impairment. Use during pregnancy should only be considered if the potential benefit justifies the potential risk to the fetus.

Contraindications

Dapsone is contraindicated in patients with a known hypersensitivity to dapsone or any component of the formulation. Its use is absolutely contraindicated in patients with severe G6PD deficiency due to the high risk of severe hemolysis. It is also contraindicated in patients with a history of severe dapsone-associated methemoglobinemia or agranulocytosis.

Possible side effect

The most common side effects are hemolytic anemia and methemoglobinemia, which are dose-related. Other potential adverse reactions include nausea, vomiting, abdominal pain, headache, dizziness, blurred vision, tinnitus, insomnia, and peripheral neuropathy. Rash and pruritus may occur. Idiosyncratic reactions include agranulocytosis, cutaneous hypersensitivity reactions (e.g., toxic epidermal necrolysis, Stevens-Johnson syndrome), and the “dapsone syndrome” (a mononucleosis-like reaction with fever, rash, and lymphadenopathy). Hepatitis, cholestatic jaundice, and psychiatric effects like psychosis have also been reported.

Drug interaction

Dapsone has significant interactions with several drug classes. Probenecid inhibits the renal excretion of dapsone, increasing its plasma levels and the risk of toxicity. Rifampin significantly induces the metabolism of dapsone, decreasing its plasma concentration and potentially reducing its efficacy. Trimethoprim increases dapsone levels and the risk of hematologic toxicity. Concurrent use with other drugs that cause hemolysis (e.g., primaquine) or methemoglobinemia (e.g., nitrites, local anesthetics like benzocaine) should be avoided due to additive risks. Dapsone may decrease the efficacy of oral contraceptives.

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 and the regular dosing schedule resumed. Patients should not double the dose to make up for a missed one. Consistent adherence to the prescribed schedule is important for maintaining therapeutic efficacy.

Overdose

Symptoms of overdose are primarily an exaggeration of its known adverse effects, including severe hemolytic anemia, methemoglobinemia (evidenced by cyanosis, chocolate-brown colored blood, shortness of breath, fatigue, and tachycardia), nausea, vomiting, and hyperexcitability. Agranulocytosis and hepatitis may also occur. In case of suspected overdose, seek immediate medical attention. Management is supportive and includes gastric lavage (if presented early), administration of activated charcoal, and specific treatments for methemoglobinemia (e.g., methylene blue intravenous infusion). Severe cases may require transfusion support.

Storage

Store dapsone tablets at room temperature (20°C to 25°C or 68°F to 77°F), in a tight, light-resistant container. The medication must be kept out of reach of children and pets. Do not store in bathrooms or other areas with high humidity. Do not use after the expiration date printed on the container.

Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting or altering any treatment regimen. Never disregard professional medical advice or delay in seeking it because of something you have read here. The content provided reflects information available at the time of writing and is subject to change as new research emerges.

Reviews

• “As a dermatologist, dapsone is an invaluable tool in my arsenal for managing difficult cases of dermatitis herpetiformis. The rapid relief from pruritus it provides is often remarkable for patients who have suffered for years.” – Dermatologist, 15 years experience.
• “In our infectious disease clinic, dapsone remains a critical component of the WHO-recommended multidrug therapy for leprosy. Its efficacy is well-proven, though vigilant monitoring for hematologic side effects is non-negotiable.” – Infectious Disease Specialist.
• “Prescribing dapsone for refractory inflammatory acne requires careful patient selection and counseling on the monitoring process. For the right patient, the improvement in papule and pustule count can be significant where other treatments have failed.” – Physician Assistant, Dermatology.
• “The utility of dapsone for PJP prophylaxis in my HIV-positive patients who are sulfa-allergic cannot be overstated. It provides a necessary alternative, though we always co-administer it with trimethoprim and monitor closely.” – HIV Specialist.