Dapsone
Dapsone is a **sulfone antimicrobial** and **anti-inflammatory** agent. Historically known for treating human leprosy, its veterinary use is largely relegated to a **second-line or adjunctive therapy** for specific immune-mediated dermatoses (e.g., pemphigus, cutaneous vasculitis) and certain atypical infections (e.g., mycobacteriosis, *Pneumocystis jiroveci*). > **Clinical Pearl**: Due to a high risk of severe adverse effects—particularly **hepatotoxicity** and **blood dyscrasias**—dapsone is rarely a first-choice drug. It is considered **relatively contraindicated in cats** due to their high susceptibility to methemoglobinemia and hemolytic anemia.
Mecanismo: **Antimicrobial action**: Acts as a competitive antagonist of **para-aminobenzoic acid (PABA)**. It inhibits the enzyme **dihydropteroate synthase (DHPS)** → blocks the synthesis of **dihydrofolic acid** → disrupts nucleic acid synthesis in susceptible organisms (similar to sulfonamides). **Anti-inflammatory action**: Dapsone exerts potent immunomodulatory effects. It inhibits the **myeloperoxidase-H2O2-halide system** → suppresses the **neutrophil respiratory burst**. It also decreases **neutrophil chemotaxis**, complement activation, antibody production, and lysosomal enzyme synthesis, making it useful for sterile, neutrophil-driven inflammatory conditions like vasculitis or Brown Recluse spider bites.
Dosificación por especie
- Alternative to clofazimine for treating feline leprosy · 1 mg/kg once daily PO · PO · q24h · Caution: High risk of serious side effects. Intensive monitoring required.
- Treating mycobacteriosis · 8 mg/kg PO once daily for 6 weeks · PO · q24h · 6 weeks · Caution: High risk of serious side effects. Intensive monitoring required.
- Aural chondritis · 1 mg/kg PO q24h · PO · q24h · Caution: High risk of serious side effects. Intensive monitoring required.
- Alternative treatment for Pneumocystis carinii pneumonia · 3 mg/kg PO once daily (q24h) · PO · q24h · 56 days · From one case report of treatment of a foal.
- Alternative treatment for pemphigus · 1 mg/kg PO q8h; with sulfasalazine at 10-40 mg/kg q8h · PO · q8h
- Post-vaccination alopecia/vasculitis resistant to prednisone therapy · 1 mg/kg PO q8h · PO · q8h
- Treating mycobacteriosis · 1.1 mg/kg PO q6h until remission, then 0.3 mg/kg q8-12h after recovery · PO · q6h initially, then q8-12h · Until remission, then maintenance
- Adjunctive therapy of vasculitis · 1 mg/kg PO q8h · PO · q8h
- Adjunctive treatment of Brown Recluse spider (Loxosceles spp.) bite · 1 mg/kg PO three times daily for 10 days · PO · TID · 10 days
Vías de administración
Contraindicaciones
- Cats (relatively contraindicated due to high risk of neurotoxicity and hemolytic anemia)
- Hypersensitivity to dapsone or other sulfone drugs
- Patients with severe anemias or preexisting blood dyscrasias
- Preexisting hepatic dysfunction (use with extreme caution)
Efectos adversos
- Hepatotoxicity
- Dose-dependent methemoglobinemia
- Hemolytic anemia
- Thrombocytopenia
- Neutropenias
- Gastrointestinal effects (nausea, vomiting)
- Neuropathies
- Cutaneous drug eruptions
- Photosensitivity
- Potential carcinogen
Interacciones farmacológicas
- Probenecid · May decrease the renal excretion of active metabolites of dapsone.
- Pyrimethamine · May increase risk of hematologic reactions occurring with dapsone.
- Rifampin · May decrease plasma dapsone concentrations (7-10 fold).
- Trimethoprim · May increase plasma dapsone concentrations (and vice versa) and potentially increase each other's toxicity.
Monitoreo
- CBC with platelets every 2-3 weeks during first 4 months of treatment, then every 3-4 months
- Liver function tests
- Clinical signs of adverse effects (GI upset, drug eruptions, neurotoxicity, jaundice, cyanosis)
- Clinical efficacy
Sobredosis
Because of its toxicity potential, specific species differences in sensitivity, and pharmacokinetics, it is recommended to contact an animal poison control center in cases of dapsone overdoses. - **Clinical Signs**: In humans, overdoses generally cause nausea, vomiting, and hyperexcitability within minutes. **Methemoglobinemia** with associated depression, seizures, and cyanosis can occur. **Hemolysis** may be delayed, occurring 7-14 days after the overdose. - **Treatment**: Includes removal of drug from the gut (decontamination), **methylene blue** for methemoglobinemia, and sometimes hemodialysis to enhance removal of the drug and its monoacetyl metabolite.
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