Usage
Clarithromycin is a macrolide antibiotic prescribed for mild to moderate infections caused by susceptible bacteria. These infections commonly involve the respiratory tract (e.g., pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, community-acquired pneumonia), skin and soft tissue (e.g., impetigo, folliculitis, cellulitis, erysipelas), and H. pylori infections (in combination therapy for duodenal ulcers). It’s also used for the prophylaxis and treatment of disseminated Mycobacterium avium complex (MAC) infections in patients with advanced HIV infection.
Alternate Names
The active ingredient is clarithromycin. Brand names include Biaxin, Biaxin XL, Klacid, Fromilid, Klaricid, and others depending on the region.
How It Works
Pharmacodynamics: Clarithromycin inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit of susceptible bacteria. This prevents peptide bond formation and subsequent protein production, ultimately leading to bacterial growth inhibition or death.
Pharmacokinetics:
- Absorption: Clarithromycin is well-absorbed orally, although food can slightly delay absorption. It has good tissue penetration, including lung, tonsil, and skin tissue.
- Metabolism: Primarily hepatic via CYP3A4, forming an active metabolite, 14-hydroxyclarithromycin.
- Elimination: Excreted in urine and feces. Dosage adjustments may be required for patients with renal impairment.
Dosage
Standard Dosage
Adults:
- Immediate-release: 250-500 mg orally every 12 hours for 7-14 days.
- Extended-release: 1000 mg orally once daily for 7-14 days.
Children (6 months to 12 years):
- Immediate-release: 7.5 mg/kg orally every 12 hours for 5-10 days (max 500 mg/dose). Clarithromycin tablets are not typically recommended for children under 12.
- Suspension: For children who weigh less than 8 kg, the dose is 0.15 ml/kg twice daily. Clarithromycin suspension comes in two strengths: 125 mg/5 ml and 250 mg/5 ml. Dosing should be based on the specific product guidelines.
Special Cases:
- Elderly Patients: As for adults, but monitor for potential drug interactions and adverse effects.
- Patients with Renal Impairment (CrCl < 30 mL/min): Reduce dose by 50%. For severe renal impairment (CrCl < 30 mL/min), reduce dose by 75% or administer 250 mg once daily or twice daily in more severe infections. Do not exceed 14 days of treatment. Extended-release formulations are contraindicated in severe renal impairment.
- Patients with Hepatic Dysfunction: Use with caution. Dosage adjustments may be necessary.
- Patients with Comorbid Conditions: Consider potential drug interactions and adjust dosage if needed. For patients with HIV and CD4 lymphocyte counts < 75 cells/mm3, 500 mg twice daily is recommended for MAC prophylaxis.
Clinical Use Cases
The dosage for clinical use cases, such as Intubation, Surgical Procedures, Mechanical Ventilation, Intensive Care Unit (ICU) Use, and Emergency Situations, align with the standard dosage guidelines for adults and children mentioned above and may be adjusted according to patient-specific factors and severity of infection.
Side Effects
Common Side Effects:
Nausea, vomiting, diarrhea, abdominal pain, abnormal taste, headache.
Rare but Serious Side Effects:
- Hepatotoxicity (jaundice, elevated liver enzymes).
- QT prolongation and serious cardiac arrhythmias (including torsades de pointes).
- Clostridium difficile-associated diarrhea (CDAD).
- Severe allergic reactions (e.g., Stevens-Johnson syndrome).
- Exacerbation of myasthenia gravis.
Long-Term Effects:
Chronic complications from prolonged use are uncommon but may include antibiotic-associated colitis or fungal infections.
Adverse Drug Reactions (ADR):
Any of the rare but serious side effects listed above would be considered clinically significant ADRs requiring urgent medical attention.
Contraindications
- Hypersensitivity to clarithromycin or other macrolides.
- Concomitant use with cisapride, pimozide, terfenadine, ergot alkaloids, lovastatin, simvastatin, colchicine, or oral midazolam.
- History of QT prolongation or ventricular arrhythmias.
- Severe hepatic failure with renal impairment.
Drug Interactions
Clarithromycin is primarily metabolized by CYP3A4. Significant interactions can occur with:
- CYP3A4 Inhibitors: Increase clarithromycin levels.
- CYP3A4 Inducers: Decrease clarithromycin levels.
- Drugs affecting QT interval: Increase risk of arrhythmias.
- Statins (lovastatin, simvastatin): Increased risk of rhabdomyolysis.
- Colchicine: Increased risk of colchicine toxicity.
- Warfarin: Increased risk of bleeding.
- Oral hypoglycemic agents: Altered blood glucose control.
- Theophylline: Increased theophylline levels.
- Carbamazepine: Increased carbamazepine levels.
Pregnancy and Breastfeeding
Clarithromycin can be used during pregnancy if the potential benefit outweighs the risk. It is present in breast milk; hence, if the doctor or health visitor says your baby is healthy, clarithromycin can be used while breastfeeding, and potential side effects are usually minimal. The infant should be monitored for potential effects on gastrointestinal flora.
Drug Profile Summary
- Mechanism of Action: Inhibits bacterial protein synthesis.
- Side Effects: Nausea, vomiting, diarrhea, QT prolongation.
- Contraindications: Hypersensitivity to macrolides, concomitant use with certain drugs (see above).
- Drug Interactions: CYP3A4 inhibitors/inducers, QT prolonging drugs, statins.
- Pregnancy & Breastfeeding: Can be used with caution if benefits outweigh risks.
- Dosage: Adults: 250-500 mg BID or 1000 mg XL daily; Children: 7.5 mg/kg BID.
- Monitoring Parameters: Liver function tests, ECG (if indicated), clinical response.
Popular Combinations
- Triple therapy for H. pylori: Clarithromycin + amoxicillin + proton pump inhibitor (PPI) (e.g., lansoprazole, omeprazole).
- Dual therapy for H. pylori: Clarithromycin + PPI.
Precautions
Assess for hypersensitivity to macrolides, hepatic or renal dysfunction, and potential drug interactions. Monitor for adverse effects, especially QT prolongation, hepatotoxicity, and CDAD.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Clarithromycin?
A: Adults: 250-500 mg orally every 12 hours, or 1000 mg extended-release once daily. Children: 7.5 mg/kg orally every 12 hours (max 500 mg/dose). Adjustments are required for renal and hepatic impairment.
Q2: What are the common side effects of Clarithromycin?
A: Nausea, vomiting, diarrhea, abdominal pain, abnormal taste, and headache.
Q3: Is Clarithromycin safe during pregnancy?
A: Clarithromycin can be used if benefits outweigh risks. Discuss with a physician for appropriate assessment.
Q4: What are the serious side effects of Clarithromycin?
A: Hepatotoxicity, QT prolongation and cardiac arrhythmias, C. difficile infection, severe allergic reactions, and worsening of myasthenia gravis.
Q5: Can Clarithromycin be used in children?
A: Yes, for children 6 months and older. Dosage is weight-based (7.5mg/kg BID). Use tablets only in children older than 12 years.
Q6: What drugs interact with Clarithromycin?
A: CYP3A4 inhibitors/inducers, QT prolonging drugs, statins (lovastatin, simvastatin), colchicine, and others. Consult a drug interaction database for a complete list.
A: Primarily by the liver through CYP3A4, with an active metabolite 14-OH-clarithromycin.
Q8: How long should Clarithromycin be taken?
A: Usually 7-14 days, but duration depends on the infection type and severity.
Q9: Can you take Clarithromycin with food?
A: Yes, but food may slightly delay absorption.
Q10: What should patients be advised before starting Clarithromycin?
A: Report any allergies, pre-existing medical conditions (especially liver or kidney problems, heart conditions), and other medications they are taking (including OTC drugs and supplements). Advise them to immediately report any signs of adverse effects, such as jaundice, severe diarrhea, or changes in heart rhythm.
