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# Mycoplasma (pathogen, not a drug)
## Overview
*Mycoplasma pneumoniae* is an atypical bacterium that lacks a cell wall, rendering it intrinsically resistant to all beta-lactams (e.g., penicillins, cephalosporins). Treatment focuses on antibiotics that inhibit protein synthesis (macrolides, tetracyclines) or DNA replication (fluoroquinolones).
## Primary Indications
* Community-acquired pneumonia (CAP).
* Tracheobronchitis.
* Systemic infections in immunocompromised hosts.
## Adult Dosing
* **Macrolides:** Azithromycin 500 mg PO on day 1, then 250 mg PO daily for 4 days OR Clarithromycin 500 mg PO BID for 7–10 days.
* **Tetracyclines:** Doxycycline 100 mg PO/IV BID for 7–10 days.
* **Fluoroquinolones (Respiratory):** Levofloxacin 750 mg PO/IV daily for 5 days OR Moxifloxacin 400 mg PO/IV daily for 7–10 days.
## Pediatric Dosing
* **Macrolides:** Azithromycin 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) on days 2–5.
* **Tetracyclines (Ages ≥8 years):** Doxycycline 2–5 mg/kg/day divided BID (max 100 mg/dose). *Note: Use for <8 years is restricted to short courses (≤21 days) due to theoretical tooth discoloration risk, per AAP/CDC guidelines.*
* **Fluoroquinolones:** Generally reserved for older adolescents or when no alternatives exist; consult pediatric infectious disease protocol.
## Dose Adjustments
* **Renal/Hepatic:** Fluoroquinolones require renal dose adjustment based on CrCl; tetracyclines generally do not require dose adjustment but should be used with caution in severe hepatic impairment. Macrolides require no adjustment in renal impairment, but caution is advised in severe hepatic disease (erythromycin).
## Contraindications
* **Hypersensitivity:** Known allergy to the selected antibiotic class.
* **Tetracyclines:** Pregnancy (second/third trimester) due to fetal bone/tooth toxicity.
* **Fluoroquinolones:** History of myasthenia gravis, aortic aneurysm risk, or significant QTc prolongation (depending on the agent).
## Adverse Effects
* **Macrolides:** GI upset (nausea, diarrhea), QTc prolongation, hepatotoxicity (rare).
* **Tetracyclines:** Photosensitivity, esophageal ulceration (take with full glass of water), teeth discoloration (pediatric).
* **Fluoroquinolones:** Tendonitis/tendon rupture, CNS effects (dizziness, seizures), peripheral neuropathy, QTc prolongation, *C. difficile* infection risk.
## Key Drug Interactions
* **QTc Prolongation:** Avoid concurrent use of macrolides or fluoroquinolones with other QTc-prolonging agents (e.g., Amiodarone, Ondansetron).
* **Divalent Cations:** Tetracyclines chelate with antacids, iron, magnesium, or calcium-containing products. Administer 2 hours before or 4–6 hours after these supplements.
* **Warfarin:** Macrolides and fluoroquinolones may potentiate the anticoagulant effect; monitor INR closely.
## Monitoring
* Monitor clinical response (e.g., fever, cough resolution) within 48–72 hours of initiation.
* Monitor for adverse event emergence (e.g., diarrhea, tendon pain).
* If using fluoroquinolones: Monitor ECG if baseline QTc is prolonged or if patient is elderly.
## Clinical Pearls
* **Macrolide Resistance:** Increasing resistance of *M. pneumoniae* to macrolides has been reported globally; consider doxycycline or respiratory fluoroquinolones as first-line therapy if resistance is suspected or if symptoms persist.
* **Static vs. Cidal:** Macrolides are bacteriostatic; ensure the patient is immunocompetent to clear the infection.
* **Local Policy:** Empiric treatment should always align with local institutional antibiograms and regional resistance patterns.
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**EDUCATIONAL DISCLAIMER:** This information is for educational purposes only. Always consult current institutional protocols, prescribing information (package inserts), and clinical decision-support software before prescribing or administering any medication. Clinical judgment should be prioritized based on individual patient factors.
