Clarithromycin

1. Introduction

Clarithromycin is a macrolide antibiotic used to treat various bacterial infections. It works by inhibiting bacterial protein synthesis through binding to the 50S ribosomal subunit, thereby stopping bacterial growth. It is effective against a wide range of gram-positive and gram-negative bacteria and is particularly useful for respiratory tract infections, skin infections, and Helicobacter pylori eradication.

2. Indications

  • Approved Indications:
    • Respiratory tract infections (e.g., pneumonia, bronchitis, sinusitis, pharyngitis).
    • Skin and soft tissue infections.
    • Helicobacter pylori eradication in peptic ulcer disease (as part of triple or quadruple therapy).
    • Mycobacterium avium complex (MAC) infections in HIV patients.
    • Acute otitis media (children).
  • Off-Label Uses:
    • Prevention of pertussis (whooping cough) in contacts of infected individuals.

3. Dosage

  • Adults:
    • General infections: 250–500 mg every 12 hours for 7–14 days.
    • Severe infections: 500 mg every 12 hours.
    • Helicobacter pylori eradication: 500 mg twice daily, in combination with other antibiotics and a proton pump inhibitor, for 7–14 days.
  • Children:
    • 7.5 mg/kg twice daily (maximum 500 mg per dose), for 7–14 days.
  • For Mycobacterium avium complex (MAC):
    • Adults: 500 mg twice daily (used in combination therapy).
    • Children: Dose based on body weight, up to 15 mg/kg/day divided twice daily.
  • Maximum Dose:
    • Adults: 1000 mg/day.
    • Children: Not to exceed 1000 mg/day.

4. Administration

  • Can be taken with or without food.
  • Extended-release tablets should be taken with food and swallowed whole; do not crush or chew.
  • Oral suspension should be shaken well before use.

5. Forms Available

  • Tablets: 250 mg, 500 mg.
  • Extended-release tablets: 500 mg.
  • Oral suspension: 125 mg/5 mL, 250 mg/5 mL.

6. Side Effects

6.1. Common Side Effects

  • Nausea.
  • Diarrhoea.
  • Abdominal pain.
  • Altered taste (metallic or bitter taste).

6.2. Less Common Side Effects

  • Headache.
  • Rash.
  • Dizziness.

6.3. Rare but Serious Side Effects

  • Hepatotoxicity (jaundice, elevated liver enzymes).
  • QT prolongation, leading to arrhythmias.
  • Clostridioides difficile-associated diarrhoea.
  • Severe allergic reactions (e.g., anaphylaxis).

7. Warnings

  • Avoid in patients with a history of QT prolongation or ventricular arrhythmias.
  • Use cautiously in patients with severe hepatic impairment or renal impairment.
  • Do not use in patients with a known hypersensitivity to macrolides.

8. Precautions

  • Monitor for signs of hepatotoxicity, especially in prolonged use.
  • Use cautiously in patients taking drugs that prolong the QT interval or those at risk of arrhythmias.
  • Avoid unnecessary use to reduce the risk of antibiotic resistance.

9. Interactions

  • Drug-Drug Interactions:
    • Statins (e.g., simvastatin, atorvastatin): Increased risk of myopathy and rhabdomyolysis.
    • Warfarin: Enhanced anticoagulant effect, increasing bleeding risk.
    • Benzodiazepines (e.g., midazolam): Increased sedative effects.
    • CYP3A4 substrates (e.g., carbamazepine, theophylline): Increased plasma levels of these drugs.
  • Drug-Food Interactions:
    • No significant interactions, but taking extended-release tablets with food improves absorption.

10. Monitoring Parameters

  • Monitor for improvement in infection symptoms (e.g., reduced fever, pain, or inflammation).
  • Liver function tests in prolonged or high-dose therapy.
  • ECG monitoring in patients with a history of arrhythmias or prolonged QT interval.

11. Use in Children

  • Approved for children in appropriate weight-based doses.
  • Monitor closely for gastrointestinal side effects.

12. Use in Pregnancy

  • Category C: Use only if potential benefits outweigh risks.
  • Limited data; avoid unless necessary, especially during the first trimester.

13. Use in Elderly

  • Use with caution due to an increased risk of QT prolongation and drug interactions.

14. Use in Kidney Disease

  • Dose adjustment required in severe renal impairment (CrCl <30 mL/min): Reduce dose by 50%.

15. Use in Liver Disease

  • Avoid in patients with severe liver impairment.
  • Use with caution in mild to moderate hepatic dysfunction.

16. Patient Counselling Points

  • Complete the full course of treatment, even if symptoms improve early.
  • Report any unusual symptoms such as jaundice, severe diarrhoea, or heart palpitations immediately.
  • Avoid grapefruit juice as it may increase the risk of side effects by altering drug metabolism.
  • Extended-release tablets should be taken with food.
  • Shake the oral suspension well before use and measure doses with a calibrated spoon or syringe.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
BiaxinAbbott Laboratories$40–60 (14 tablets, 500 mg)
KlaricidAspen Pharmacare$30–50 (14 tablets, 500 mg)
Generic OptionsVarious$10–20 (14 tablets, 500 mg)

18. FAQs (15 Questions)

  1. What is clarithromycin used for?
    It is used to treat bacterial infections, including respiratory infections, skin infections, and Helicobacter pylori eradication.
  2. How does clarithromycin work?
    It inhibits bacterial protein synthesis, stopping bacterial growth.
  3. Can clarithromycin treat viral infections?
    No, clarithromycin is ineffective against viral infections such as the flu or common cold.
  4. What are the common side effects of clarithromycin?
    Nausea, diarrhoea, abdominal pain, and altered taste.
  5. Can clarithromycin be taken during pregnancy?
    It should only be used if the benefits outweigh the risks, particularly during the first trimester.
  6. Is clarithromycin safe for children?
    Yes, it is approved for children when dosed appropriately.
  7. How should clarithromycin be taken?
    Tablets can be taken with or without food, but extended-release tablets should be taken with food.
  8. Does clarithromycin interact with other medications?
    Yes, it interacts with statins, warfarin, benzodiazepines, and other drugs metabolised by CYP3A4.
  9. How long does clarithromycin take to work?
    Symptom improvement is typically seen within 2–3 days, but the full course should be completed.
  10. What should I do if I miss a dose?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double the dose.
  11. Can clarithromycin cause heart problems?
    Yes, it may cause QT prolongation, increasing the risk of arrhythmias in susceptible individuals.
  12. Can clarithromycin be used for Helicobacter pylori eradication?
    Yes, it is part of standard triple or quadruple therapy for H. pylori infections.
  13. Does clarithromycin cause liver problems?
    Rarely, it may cause hepatotoxicity. Report symptoms like jaundice or abdominal pain immediately.
  14. Can clarithromycin be taken with alcohol?
    It is advisable to avoid alcohol to minimise side effects like nausea or dizziness.
  15. How should clarithromycin be stored?
    Store tablets at room temperature and oral suspension in the refrigerator, discarding unused suspension after 14 days.