Doxycyclin

# Doxycyclin ## Overview - **Classification**: Tetracycline antibiotic. - **Mechanism**: Reversibly binds to the 30S ribosomal subunit, inhibiting bacterial protein synthesis. Bacteriostatic. ## Primary Indications 1. **Bacterial Infections**: Broad-spectrum (e.g., respiratory, urinary, skin, ophthalmic, GI). 2. **Sexually Transmitted Infections (STIs)**: Chlamydia, syphilis (alternative), gonorrhea (alternative). 3. **Malaria**: Prophylaxis and treatment for chloroquine-resistant strains. 4. **Acne Vulgaris**: Moderate to severe inflammatory acne. 5. **Lyme Disease**: Early localized and early disseminated disease. ## Adult Dosing ### Standard Dosing **General Bacterial Infections (e.g., Chlamydia)** - **Dose**: **100 mg** - **Frequency**: Twice daily (every 12 hours) - **Route**: Oral (PO) or Intravenous (IV) - **Duration**: Varies (e.g., 7 days for Chlamydia) **Lyme Disease (Early)** - **Dose**: **100 mg** - **Frequency**: Twice daily (every 12 hours) - **Route**: Oral (PO) - **Duration**: **10-21 days** (early localized), **14-28 days** (early disseminated). **Malaria Prophylaxis** - **Dose**: **100 mg** - **Frequency**: Once daily - **Route**: Oral (PO) - **Duration**: Start 1-2 days before, continue for 4 weeks after leaving endemic area. **Acne Vulgaris** - **Dose**: **50-100 mg** - **Frequency**: Once or twice daily - **Route**: Oral (PO) - **Duration**: Long-term, several weeks to months. ### Dose Adjustments - **Renal Impairment**: No dose adjustment needed. Doxycycline is primarily eliminated non-renally. - **Hepatic Impairment**: Use with caution in severe hepatic dysfunction. Monitor liver function. - **Elderly Patients**: No specific dose adjustment needed. Consider overall health and co-medications. ## Pediatric Dosing *(Note: Tetracyclines are generally avoided in children <8 years due to tooth discoloration, but are recommended for specific severe infections like tick-borne diseases when benefits outweigh risks).* ### Neonates (0-28 days) - **Dose**: Generally **not recommended/contraindicated**. - **Special Notes**: Reserve for life-threatening infections (e.g., anthrax) when alternatives are not feasible, due to risk of permanent tooth discoloration and bone growth inhibition. ### Infants (1-12 months) - **Dose**: Generally **not recommended/contraindicated**. - **Special Notes**: Reserve for life-threatening infections when alternatives are not feasible, due to risk of permanent tooth discoloration and bone growth inhibition. ### Children (1-12 years) *For specific indications like tick-borne diseases (e.g., Rocky Mountain Spotted Fever, Lyme Disease).* - **Dose**: **2.2 mg/kg/dose** - **Frequency**: Twice daily (every 12 hours) - **Maximum**: **100 mg/dose** or **200 mg/day** for children weighing > 45 kg. - **Special Notes**: Administer with food/milk to reduce GI upset and with plenty of water to prevent esophageal irritation. ### Adolescents (13-18 years) - **Dose**: **100 mg** - **Frequency**: Once or twice daily (follow adult dosing based on indication). - **Maximum**: **200 mg/day**. - **Special Notes**: Same considerations as adults. Ensure adequate hydration. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to tetracyclines. - **Absolute**: Pregnancy (causes tooth discoloration/bone effects in fetus). - **Absolute**: Breastfeeding (passes into milk, potential for infant tooth/bone effects). - **Absolute**: Children **< 8 years** (unless indicated for severe, life-threatening infection, e.g., Rocky Mountain Spotted Fever) due to permanent tooth discoloration and enamel hypoplasia. ### Common Adverse Effects - **Very Common (>10%)**: Nausea, vomiting, diarrhea, photosensitivity. - **Common (1-10%)**: Esophageal irritation/ulceration, abdominal pain, rash, headache. - **Serious but Rare**: Pseudotumor cerebri (idiopathic intracranial hypertension), severe photosensitivity, hepatotoxicity, Clostridioides difficile-associated diarrhea (CDAD). ### Key Drug Interactions - **Antacids/Iron/Calcium/Magnesium/Bismuth**: Reduce doxycycline absorption. - **Effect**: Separate administration by **2-3 hours before** or **4-6 hours after** doxycycline. - **Oral Contraceptives**: May reduce efficacy (less proven, but advise backup method). - **Monitoring**: Advise use of a backup contraceptive method. - **Warfarin**: May potentiate anticoagulant effect. - **Monitoring**: Increased INR/PT monitoring may be necessary. - **Retinoids (oral)**: Increased risk of pseudotumor cerebri. - **Contraindication**: Concomitant use **contraindicated**. ## Monitoring & Follow-up - **Before Treatment**: Baseline LFTs in patients with pre-existing hepatic impairment. - **During Treatment**: Monitor for GI upset, photosensitivity, and signs of superinfection. - **Clinical Signs**: Watch for severe headache (pseudotumor cerebri), severe skin reactions, or jaundice. ## Clinical Pearls - 💡 **Administration**: Take with a **full glass of water** while sitting upright for at least 30 minutes to prevent esophageal irritation. - 💡 **Food Intake**: Can be taken with food/milk to minimize GI upset, but avoid calcium-rich dairy within 2 hours of dose. - 💡 **Sun Protection**: Advise patients to use broad-spectrum sunscreen and protective clothing due to high photosensitivity risk. - 💡 **Pediatric Use**: For children <8 years with tick-borne illnesses (e.g., RMSF), doxycycline is the drug of choice despite age restrictions, due to superior efficacy and lower risk of long-term effects than the disease itself. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.