Dapsone is a sulfone antibiotic used to treat a variety of conditions, most notably leprosy and the chronic skin condition dermatitis herpetiformis [1.2.3, 1.8.1]. It functions by inhibiting the synthesis of dihydrofolic acid in bacteria [1.2.2]. While effective for many, dapsone carries significant risks for certain individuals. A thorough understanding of its contraindications is essential for patient safety.
Absolute and Relative Contraindications
Certain conditions outright preclude the use of dapsone (absolute contraindications), while others require caution and careful monitoring (relative contraindications).
Absolute Contraindications:
- Allergy to Dapsone: The primary contraindication for using dapsone is a known allergy to the drug itself [1.2.2, 1.3.2].
- Prior Hypersensitivity Reactions: Patients who have previously experienced severe reactions like dapsone hypersensitivity syndrome (DHS) or agranulocytosis (a sharp drop in white blood cells) should not take the medication [1.2.2, 1.4.2].
Relative Contraindications and High-Risk Groups:
- Sulfonamide Allergy: While dapsone is a sulfone, not a sulfonamide, caution is advised for those with allergies to 'sulfa drugs,' as cross-reactivity can occur [1.2.2, 1.3.1, 1.4.5].
- Severe Anemia: Dapsone can cause hemolysis (destruction of red blood cells), so individuals with pre-existing severe anemia should have their condition treated before starting dapsone [1.4.2, 1.10.4].
- Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency: This genetic disorder makes individuals highly susceptible to hemolysis when taking dapsone [1.2.2, 1.6.1]. Pre-treatment screening for G6PD deficiency is strongly recommended [1.2.3]. While considered a relative contraindication, many providers will choose an alternative treatment if G6PD levels are low [1.2.2].
- Methemoglobin Reductase Deficiency: Similar to G6PD deficiency, this condition increases the risk of methemoglobinemia, where the blood's ability to carry oxygen is dangerously reduced [1.2.2].
- Significant Cardiac or Pulmonary Disease: Because dapsone can affect the oxygen-carrying capacity of the blood, patients with severe heart or lung disease may require a lower dose and careful monitoring [1.3.2, 1.2.4].
- Severe Liver or Kidney Disease (Hepatopathy/Renal Impairment): Dapsone is metabolized by the liver and excreted by the kidneys [1.8.3]. Patients with severe liver or kidney impairment are at higher risk for adverse effects [1.2.2, 1.2.4]. Cases of toxic hepatitis, jaundice, and acute renal failure have been reported [1.8.1, 1.8.2].
Dapsone Hypersensitivity Syndrome (DHS)
DHS is a rare but severe and potentially fatal reaction with a mortality rate of up to 23% [1.2.2, 1.9.1]. It typically develops weeks to months after starting the drug and is characterized by a triad of fever, skin rash, and systemic organ involvement (often the liver or lungs) [1.2.2, 1.9.4]. Key features include:
- Fever and rash [1.2.2]
- Eosinophilia (high levels of eosinophils) [1.2.2]
- Lymphadenopathy (swollen lymph nodes) [1.9.1]
- Hepatic and pulmonary manifestations [1.2.2]
Prompt discontinuation of dapsone and administration of systemic steroids are crucial for management [1.2.2, 1.9.1]. Due to dapsone's long half-life, steroids must be tapered slowly over a month or more [1.2.2].
Comparison of High-Risk Patient Groups
Condition | Primary Risk with Dapsone | Recommended Action |
---|---|---|
G6PD Deficiency | Severe Hemolytic Anemia [1.6.1] | Pre-treatment screening; use with extreme caution or avoid [1.2.2, 1.2.3]. |
Severe Anemia | Worsening of anemia due to hemolysis [1.4.2] | Treat anemia before initiating dapsone therapy [1.4.2]. |
Liver Disease | Hepatotoxicity, Dapsone Syndrome [1.8.1] | Use with caution; monitor liver function tests [1.2.2, 1.8.1]. |
Kidney Disease | Potential for acute kidney injury; dose accumulation [1.8.2, 1.8.3] | Use with caution; dose may need adjustment [1.8.3]. |
Pregnancy | Potential for neonatal hemolysis and cyanosis [1.2.2] | Use only if benefit outweighs risk; Category C drug [1.2.2, 1.7.2]. |
Breastfeeding | Excreted in breast milk; risk of hemolytic anemia in infant [1.7.2] | A decision should be made to discontinue nursing or the drug [1.7.2]. |
Drug Interactions
Certain medications can increase the risks associated with dapsone. Patients should inform their doctor if they are taking:
- Drugs that induce methemoglobinemia: This includes certain anesthetics (like benzocaine), nitrates, and sulfa drugs [1.2.2, 1.5.3].
- Rifampin: Can increase the formation of a dapsone metabolite associated with hemolysis [1.5.1, 1.5.3].
- Trimethoprim: Increases dapsone levels in the blood, raising the risk of adverse effects [1.5.3, 1.5.4].
- Probenecid: A treatment for gout that should be avoided [1.3.4].
- Zidovudine: Can interact with dapsone [1.5.1].
Conclusion
While dapsone is a valuable medication for specific diseases, it is not suitable for everyone. Absolute contraindications include a known allergy to dapsone or a history of severe hypersensitivity. Relative contraindications requiring extreme caution and close medical supervision include G6PD deficiency, severe anemia, and significant heart, lung, liver, or kidney disease [1.2.2, 1.2.4]. Pre-treatment screening and ongoing monitoring of blood counts and organ function are critical safety measures to mitigate the risks of serious adverse events like hemolytic anemia and the potentially fatal Dapsone Hypersensitivity Syndrome [1.2.3, 1.9.1].
For more information from an authoritative source, you may consult the National Institutes of Health's page on Dapsone: https://www.ncbi.nlm.nih.gov/books/NBK548936/