Clarithromycin

# Clarithromycin ## Overview - **Classification**: Macrolide antibiotic - **Mechanism**: Binds to the 50S ribosomal subunit, inhibiting bacterial protein synthesis. ## Primary Indications 1. **Community-Acquired Pneumonia (CAP)** - Treatment of susceptible bacterial infections. 2. **Pharyngitis/Tonsillitis** - Due to *Streptococcus pyogenes* (as an alternative to penicillin). 3. **Acute Bacterial Exacerbation of Chronic Bronchitis (ABECB)** - Treatment of susceptible infections. 4. **Acute Maxillary Sinusitis** - Treatment of susceptible bacterial infections. 5. **Skin and Soft Tissue Infections** - Uncomplicated infections. 6. **H. pylori Eradication** - Part of multi-drug regimens for peptic ulcer disease. 7. **Mycobacterium avium complex (MAC)** - Prophylaxis and treatment in immunocompromised patients. ## Adult Dosing ### Standard Dosing **Community-Acquired Pneumonia, Pharyngitis/Tonsillitis, ABECB, Acute Maxillary Sinusitis, Skin/Soft Tissue Infections** - **Dose**: **250 mg** to **500 mg** - **Frequency**: Every 12 hours (BID) - **Route**: Oral - **Duration**: 7 to 14 days (duration varies by indication) **H. pylori Eradication (as part of triple therapy)** - **Dose**: **500 mg** - **Frequency**: Every 12 hours (BID) - **Route**: Oral - **Duration**: 10 to 14 days **Mycobacterium avium complex (MAC) Treatment/Prophylaxis** - **Dose**: **500 mg** - **Frequency**: Every 12 hours (BID) - **Route**: Oral - **Duration**: Lifelong for prophylaxis or long-term for treatment (often with other agents) ### Dose Adjustments - **Renal Impairment**: - **CrCl <30 mL/min**: Reduce dose by **50%** or double dosing interval. - **Max dose**: **500 mg/day**. - **Hepatic Impairment**: Generally no adjustment needed for mild-moderate; use with caution in severe. - **Elderly Patients**: Monitor renal function; increased risk of adverse effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Special Notes**: Generally **avoided** due to association with infantile hypertrophic pyloric stenosis (IHPS), especially if exposed in first two weeks of life. Use only if no alternatives and with close monitoring. ### Infants (1-12 months) - **Dose**: **7.5 mg/kg/dose** - **Frequency**: Every 12 hours (BID) - **Maximum**: **500 mg/dose** - **Special Notes**: Oral suspension available; closely monitor for IHPS symptoms, especially under 6 weeks. ### Children (1-12 years) - **Dose**: **7.5 mg/kg/dose** - **Frequency**: Every 12 hours (BID) - **Maximum**: **500 mg/dose** (or **1 gram/day** total) - **Special Notes**: Oral suspension or tablets available. ### Adolescents (13-18 years) - **Dose**: Generally follow **adult dosing** guidelines. - **Maximum**: **500 mg/dose** (or **1 gram/day** total) ## Safety Information ### Contraindications - **Absolute**: History of QTc prolongation or ventricular arrhythmia. - **Absolute**: Hypokalemia or hypomagnesemia. - **Absolute**: Co-administration with colchicine (in patients with renal/hepatic impairment). - **Absolute**: Co-administration with simvastatin, lovastatin (risk of rhabdomyolysis). - **Absolute**: Co-administration with ticagrelor, ranolazine, ergot alkaloids, lurasidone, pimozide, cisapride. - **Absolute**: Severe hepatic impairment with concomitant renal impairment. ### Common Adverse Effects - **Very Common (>10%)**: Taste disturbance (dysgeusia), diarrhea. - **Common (1-10%)**: Nausea, vomiting, abdominal pain, dyspepsia, headache, rash. - **Serious but Rare**: QTc prolongation, Torsades de Pointes, hepatotoxicity (cholestatic/hepatocellular), Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), C. difficile-associated diarrhea (CDAD). ### Key Drug Interactions - **CYP3A4 Inhibitors**: Strong inhibitor; increases levels of many drugs (e.g., **statins** like simvastatin/lovastatin, **colchicine**, **warfarin/DOACs**, **antiarrhythmics** like digoxin, amiodarone, disopyramide, **immunosuppressants** like cyclosporine, tacrolimus, sirolimus). - **QTc Prolonging Drugs**: Increased risk of Torsades de Pointes (e.g., **quinidine, procainamide, sotalol, antipsychotics, tricyclic antidepressants**). - **Oral Hypoglycemics/Insulin**: May enhance hypoglycemic effect; monitor blood glucose. - **Rifamycins (rifampin, rifabutin)**: Can decrease clarithromycin levels; consider alternative. ## Monitoring & Follow-up - **Before Treatment**: Review patient's medication list for drug interactions, baseline electrolytes (K, Mg), liver function tests (LFTs) if risk factors. - **During Treatment**: - Monitor for signs of hepatotoxicity (dark urine, jaundice, right upper quadrant pain). - Monitor for QTc prolongation (ECG) if at risk or on interacting drugs. - Monitor for C. difficile symptoms (severe diarrhea). - **Clinical Signs**: Resolution of infection symptoms, development of adverse effects. ## Clinical Pearls - 💡 **Taste Disturbance**: A common side effect; patients describe a metallic or bitter taste, which usually resolves after stopping the drug. - 💡 **Administration**: Can be taken with or without food. Extended-release (XL) tablets should be taken with food. - 💡 **Formulation**: Oral suspension requires refrigeration once reconstituted. Shake well before each dose. - 💡 **Cardiac Risk**: Avoid in patients with known CAD due to a potential small increase in long-term cardiac mortality, especially after completion of treatment. Consider alternative macrolides or other classes if suitable. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.