1. Clinical & Scientific Overview
Clarithromycin & Erythromycin (TIP-MED-000148, Reference Code [8.20]) is classified under
Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08) as a Macrolide 50S Ribosomal Protein Synthesis Inhibitors — Potent CYP3A4 Inhibitors (Schedule H | NLEM 2022).
Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).
Representative Indian Market Examples (Edition 2.7 Ch 08 [8.20], p. 102): Clarithromycin: Claribid (Abbott), Clarithro (Alembic), Crixan (Sun), HP-Kit. Erythromycin Stearate/Estolate: Althrocin (Alembic), Erythrocin — Strengths & Dosage Forms: Clarithromycin Tablets: 250 mg, 500 mg, 500 mg XL; Dry Syrup: 125 mg/5mL, 250 mg/5mL. Erythromycin Tablets: 250 mg, 500 mg; Syrup: 125 mg/5mL
Clarithromycin Tablets: 250 mg, 500 mg, 500 mg XL; Dry Syrup: 125 mg/5mL, 250 mg/5mL. Erythromycin Tablets: 250 mg, 500 mg; Syrup: 125 mg/5mL
3. Mechanism of Action & Pharmacodynamics
Macrolide 50S Ribosomal Protein Synthesis Inhibitors — Potent CYP3A4 Inhibitors (Schedule H | NLEM 2022) acting on target receptor/enzyme pathways in Antimicrobials — Antibacterial & Antibiotic Agents (Ch 08): clinical efficacy is mediated via Macrolide 50S Ribosomal Protein Synthesis Inhibitors — Potent CYP3A4 Inhibitors (Schedule H | NLEM 2022) for Clarithromycin: H. pylori eradication triple/quadruple therapy (500 mg BD x 14 days), atypical community-acquired pneumonia, MAC infections. Erythromycin: Pertussis, diphtheria, chlamydia/syphilis in pregnancy, rheumatic fever prophylaxis in penicillin allergy, and gastroparesis prokinetic.
4. Therapeutic Indications & Evidence-Supported Uses
- Clarithromycin: H
- pylori eradication triple/quadruple therapy (500 mg BD x 14 days), atypical community-acquired pneumonia, MAC infections
- Erythromycin: Pertussis, diphtheria, chlamydia/syphilis in pregnancy, rheumatic fever prophylaxis in penicillin allergy, and gastroparesis prokinetic
🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: Clarithromycin: 250–500 mg PO BD (or 500 mg XL OD with food) for 7–14 days. Erythromycin: 250–500 mg PO QID (Children: 30–50 mg/kg/day in 3–4 doses)
Administration & Meal Timing: Clarithromycin IR may be taken with or without food (Clarithromycin XL MUST be taken with food). Take Erythromycin Stearate before meals | Clarithromycin: Morning & Evening (BD). Erythromycin: QID (q6h)
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Renal: Halve Clarithromycin dose (250 mg OD or BD) if CrCl <30 mL/min! Hepatic: Avoid in prior macrolide jaundice
Renal: Halve Clarithromycin dose (250 mg OD or BD) if CrCl <30 mL/min! Hepatic: Avoid in prior macrolide jaundice
Renal: Halve Clarithromycin dose (250 mg OD or BD) if CrCl <30 mL/min! Hepatic: Avoid in prior macrolide jaundice
7. Contraindications, Precautions & High-Risk Warnings
- CONTRAINDICATED with Simvastatin, Lovastatin, Atorvastatin (>20 mg), Colchicine (in CKD/hepatic disease), Ticagrelor, Ivabradine, Ranolazine, Quetiapine, Domperidone, Pimozide, and Ergot alkaloids! Contraindicated in QTc prolongation, hypokalaemia, and macrolide cholestatic jaundice
Key Clinical Precautions: Renal: Halve Clarithromycin dose (250 mg OD or BD) if CrCl <30 mL/min! Hepatic: Avoid in prior macrolide jaundice
8. Adverse Effects Profile
- Bitter/metallic dysgeusia (very common on Clarithromycin!), abdominal cramping, nausea, diarrhoea, headache
- QTc prolongation and fatal Torsades de Pointes, cholestatic hepatitis, rhabdomyolysis (from statin interaction!), acute kidney injury (from CCB hypotension!), C. difficile colitis
- Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- EXTREME CYP3A4 & P-gp INHIBITION: (1) Statins (Atorvastatin, Simvastatin) -> rhabdomyolysis (HOLD Statin during Clarithromycin course!); (2) CCBs (Amlodipine, Cilnidipine, Nifedipine, Diltiazem, Verapamil) -> severe hypotension & AKI; (3) Colchicine -> fatal pancytopenia; (4) Warfarin & DOACs -> major bleeding; (5) Sulfonylureas/Repaglinide -> severe hypoglycaemia; (6) Carbamazepine, Tacrolimus, Cyclosporine, & Digoxin -> acute toxicity!
10. Clinical Monitoring, Patient Counselling & Storage
Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.
Pharmacist Patient Counselling Points:
- Patient Counselling Checklist: THREE VITAL COUNTER RULES: (1) If you take Atorvastatin or Simvastatin, PAUSE your cholesterol tablet while taking Claribid and resume 2 days after finishing; (2) Never put reconstituted Claribid paediatric syrup in the fridge (store at room temp!); (3) Metallic taste in mouth is harmless
- Meal & Clock Timing Instruction: Clarithromycin IR may be taken with or without food (Clarithromycin XL MUST be taken with food). Take Erythromycin Stearate before meals (Clarithromycin: Morning & Evening (BD). Erythromycin: QID (q6h))
- Missed Dose Protocol: Take as soon as remembered unless close to next dose
- Geriatric Dispensing Pearl: High risk of fatal arrhythmias, CCB-induced hypotensive AKI, and statin rhabdomyolysis in older adults (prefer Azithromycin or Doxycycline if atypical cover is needed!)
Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Clarithromycin Tablets: 250 mg, 500 mg, 500 mg XL; Dry Syrup: 125 mg/5mL, 250 mg/5mL. Erythromycin Tablets: 250 mg, 500 mg; Syrup: 125 mg/5mL
11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)
12. Authoritative References, Regulatory Sources & Editorial Disclaimer
Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 08 [8.20] (p. 102)
Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)
Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT
Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.
13. Related Reference Monographs, Educational Guides & Visual Concept
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