Dapsone

# Dapsone ## Overview - **Classification**: Sulfone antibiotic, anti-inflammatory. - **Mechanism**: Inhibits bacterial folic acid synthesis by competing with PABA. Anti-inflammatory effects include inhibition of neutrophil myeloperoxidase. ## Primary Indications 1. **Leprosy (Hansen's Disease)** - Part of multi-drug therapy (MDT). 2. **Dermatitis Herpetiformis** - Chronic blistering skin condition. 3. **Pneumocystis Jirovecii Pneumonia (PJP) Prophylaxis/Treatment** - Alternative for sulfa-allergic patients. 4. **Toxoplasmosis Prophylaxis** - Alternative for sulfa-allergic patients. ## Adult Dosing ### Standard Dosing **Leprosy (Multi-drug Therapy)** - **Dose**: **100 mg** - **Frequency**: Once daily - **Route**: Oral - **Duration**: 6-12 months depending on classification **Dermatitis Herpetiformis** - **Dose**: Initial **50 mg**, titrate to **50-300 mg** - **Frequency**: Once daily - **Route**: Oral - **Duration**: Long-term, potentially lifelong **PJP Prophylaxis** (Alternative regimen) - **Dose**: **100 mg** - **Frequency**: Once daily - **Route**: Oral ### Dose Adjustments - **Renal Impairment**: Use with caution if CrCl < **10 mL/min**. Consider longer interval or reduced dose. Dapsone is dialyzable. - **Hepatic Impairment**: Use with caution. Consider lower doses and close monitoring due to hepatic metabolism. - **Elderly Patients**: Start at lower end of dosing range; monitor for adverse effects due to potential altered pharmacokinetics. ## Pediatric Dosing ### Neonates (0-28 days) - **Leprosy (off-label)**: **2 mg/kg/day** - **Frequency**: Once daily - **Maximum**: No clear maximum. - **Special Notes**: High risk of hemolysis/methemoglobinemia. Consult specialist. ### Infants (1-12 months) - **Leprosy**: **2 mg/kg/day** - **Frequency**: Once daily - **Maximum**: Not to exceed adult dose. ### Children (1-12 years) - **Leprosy**: **2 mg/kg/day** - **Frequency**: Once daily - **Maximum**: **100 mg/day** - **PJP Prophylaxis**: **2 mg/kg/day** (Max **100 mg/day**) or **4 mg/kg** twice weekly (Max **200 mg/week**). ### Adolescents (13-18 years) - **Dose**: Follows adult dosing guidelines based on indication. - **Maximum**: Adult maximum dose for the relevant indication. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to dapsone or its components. - **Absolute**: Severe anemia (Hb < **7-8 g/dL**). - **Absolute**: Acute porphyria. - **Relative**: Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency. ### Common Adverse Effects - **Very Common (>10%)**: Hemolytic anemia (dose-related), methemoglobinemia. - **Common (1-10%)**: Rash, pruritus, headache, nausea, vomiting, peripheral neuropathy. - **Serious but Rare**: Dapsone Hypersensitivity Syndrome (DHS), agranulocytosis. ### Key Drug Interactions - **Rifampin**: Decreases dapsone levels by enzyme induction. May require dapsone dose increase in leprosy. - **Trimethoprim**: Increases dapsone and methemoglobin levels. Increased risk of hematologic toxicity. - **Antimalarials (e.g., pyrimethamine)**: Increased risk of bone marrow suppression. Monitor CBC closely. - **Didanosine (DDI)**: Dapsone absorption may be reduced. Separate administration times. ## Monitoring & Follow-up - **Before Treatment**: Complete Blood Count (CBC) with differential, G6PD screen (if indicated), Liver Function Tests (LFTs). - **During Treatment**: CBC weekly for first month, then monthly for 6 months, then every 6-12 months. Monitor LFTs regularly. - **Clinical Signs**: Watch for pallor, jaundice, fatigue (anemia), cyanosis (methemoglobinemia), fever, rash, lymphadenopathy (DHS), numbness/tingling (neuropathy). ## Clinical Pearls - 💡 **Tip 1**: Always screen for **G6PD deficiency** prior to initiation, especially in high-risk populations (African, Mediterranean, Asian descent). - 💡 **Tip 2**: **Dapsone Hypersensitivity Syndrome (DHS)** is a severe, potentially fatal reaction. Educate patients to seek immediate care for fever, rash, lymphadenopathy, or hepatitis signs. - 💡 **Tip 3**: Methemoglobinemia is common and dose-dependent. Patients may appear cyanotic despite normal SpO2 readings (pulse oximetry saturation gap). - 💡 **Tip 4**: Administer with food to minimize gastrointestinal upset. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.