Description of Clarithromycin
Clarithromycin is a macrolide antibacterial antibiotic. It used in the treatment of various infection of bacteria origin. These infections include respiratory infections (Streptococcus pneumonia), skin and skin structure infections, Helicobacter pylori infection that causes ulcer, and several others. It is taken both orally and as an infusion and as a result comes in both liquid (suspension), solid (tablet) and Powder for solution for infusion dosage forms.
Pharmacology of Clarithromycin
How does Clarithromycin work?
Clarithromycin is a semi-synthetic derivative of erythromycin. Unlike erythromycin, it is acid-stable , rendering it safe from being acted upon by gastric acids. It exerts its antibacterial action by binding to the 50S ribosomal sub-unit of susceptible bacteria and suppresses protein synthesis. It is readily absorbed from the GIT, widely diffusing into most tissues and transported into the site of action.
It undergoes first-pass metabolism in the liver, yielding a systemic bioavailability of about 50% after a 250mg dose and elimination half-life of about 3 to 4 hours. Its major metabolites include an active metabolite,14-(R)-hydroxyclarithromycin and an inactive metabolite, N-desmethylclarithromycin. Clarithromycin (20-40) and the active metabolite (10-15%) are excreted in the urine.
Indications and Uses of Clarithromycin
Clarithromycin is used in the following conditions:
- lower respiratory tract infections like pneumonia, acute and chronic bronchitis
- upper respiratory tract infections like pharyngitis and acute maxillary sinusitis
- infections caused by Haemophilus influenza, haemophilus parainfluenzae, Moraxella catarrhalis or Streptococcus pneumonia, mycoplasma pneumonia.
- mycobaterial infection; treatment of disseminated infections caused by mycobacterium avium complex or mycobacterium intracellulare, (also used in combination with other antimycobacterial drugs like ethambutol)
- peptic ulcer disease: Clarithromycin is used in eradication of H.pylori in treatment of patients with active ulcer and/or Type B gastritis (admistered as combination therapy with Amoxillin and Omeprazole)
- skin and skin structure infections like acne vulgaris, furuncles, cellulitis caused by Streptococcus pyogenes
- for treatment of pertussis or post-exposure prophylaxis
- Lyme disease
- Legionnaires’ disease (type of lung infection)
- for bacterial endocarditis prophylaxis
Dosage and Administration of Clarithromycin
Oral Dosage Form
orally 12hourly with or without meals.
The dosage and length of treatment are usually based on your medical condition and severity.
In children, it is usually based on body weight.
- 250mg twice daily for 7 days for mild infections
- 500mg twice daily for 7 to 14 days for severe infections
- Extended release; 1000mg once daily for 7 to 14 days
15mg/kg/day divided every 12 hours for 10 days
When indicated for prophylaxis in endocarditis management
Adult: 500mg orally 30 to 60 mins before surgical procedure
Children: 15mg/kg orally 30 to 60 mins before surgical procedure, individual dose should not exceed 500mg.
For intravenous administration only.
Intravenous therapy may be given for 2 to 5 days in the very ill patient and should be changed to oral clarithromycin therapy whenever possible as determined by the physician.
The recommended dosage is 1.0 gram daily, divided into two 500mg doses.
Children older than 12 years:
As for adults.
Children under 12 years:
Clarithromycin 500 mg Powder for Solution for Infusion is not recommended for children under 12 years of age, who should use clarithromycin paediatric suspension (granules for oral suspension).
As for adults.
In patients with renal impairment with creatinine clearance less than 30ml/min, the dosage of clarithromycin should be reduced by one half, i.e. 250 mg once daily, or 250 mg twice daily in more severe infections. Treatment should not be continued beyond 14 days in these patients.
Method of administration:
Clarithromycin 500mg Powder for Solution for Infusion should be administered into one of the larger proximal veins as an IV infusion over 60 minutes, using a solution concentration of about 2mg/ml. Clarithromycin should not be given as a bolus or an intramuscular injection.
Interaction of Clarithromycin
Clarithromycin inhibits a liver enzyme, CYP3A4, which is involved in the metabolism of most common drugs. Therefore taking Clarithromycin with most other drugs could lead to unexpected increase or decrease in their plasma levels.
Some of these drugs interactions include
- HMG-CoA reductase inhibitors e.g. Simvastatin can lead to rhbdomyolysis and increased risk of myopathy
- colchicine: causes fatal colchicine toxicity especially in people with chronic kidney disease
- calcium channel blockers e.g verapamil may lead to kidney failure and risk of low blood pressure and lactic acidosis
- QT prolonging drugs like Domperidone, pimozide, terfenadine causes increased risks of cardiac arrhythmia and ventricular tachycardia and fibrillation
Other drugs include
- Carbamazepine, cabergoline
- Ergot alkaloids
- some HIV drugs like Saquinavir
- quinidine, chloroquine
Side Effects of Clarithromycin
- Gastrointestinal upsets
- Altered mouth taste
- Allergic reactions like rashes and anaphylaxis
- Abdominal pain
- Elevated BUN
- Steves-Johnson Syndrome
Contraindications of Clarithromycin
- Hypersensitivity to macrolide antibiotic drugs
- Pregnancy and lactation except in the absence of alternative therapy.
- Avoid co-administration with drugs with known risk of QT prolongation
- Use with caution in co-administration with benzodiazepines
- Decrease the dose of statins when co-administered with Clarithromycin
- May increase morbidity among coronary heart disease patients
- Use with caution in patients with liver and kidney impairments
- Discontinue medication immediately if signs and symptoms of hepatitis occur i.e jaundice, loss of appetite, pruitus, tender abdomen or dark urine.
Jennifer E. Onwudiegwu (B.Pharm)