CLARITHROMYCIN

Clarithromycin

Chemistry 6-O-methylerythromycin

Pharmacological category

Macrolide antibiotic

Pharmacology

Clarithromycin exerts its antibacterial effect by binding to 50s ribosome subunit of susceptible organisms and inhibiting protein synthesis

Microbiology

It is active invitro against a variety of aerobic and anaerobic gram positive and gram negative organisms as well as most mycobacterium avium complex organisms

Gram positive aerobes: staphylococcus aureus, streptococcus pneumonia, streptococcus pyogenes

Gram negative aerobes: haemophilus influenza, Moraxella [Branhamella catarrhalis]

Other aerobes: mycoplasma pneumonia

[Mycobacteriae: mycobacterium avium complex consisting of :mycobacterium avium and mycobacterium intracellulare]

Pharmacokinetics

Clarithromycin is rapidly absorbed from the gastrointestinal tract after oral administration. The absolute bioavailability of 250mg clarithromycin tablet was approximately 50%. Food slightly delays both the onset of clarithromycin absorption and formation of he antimicrobially active metabolite, 14-OH-clarithromycin, but does not affect the extent of bioavailability . therefore clarithromycin tablets may be given without regards to meals

Indications and uses

Clarithromycin is indicated in the treatment of upper and lower respiratory tract infections, pharyngitis, tonsillitis due to streptococcus pyogenes , acute maxillary sinusitis ,cute bacterial exacerbation of chronic bronchitis , pneumonia, uncomplicated skin and skin structure infections.

Contraindications

Clarithromycin is contraindicated in patients with known hypersensitivity to clarithromycin, erythromycin or any of the macrolide antibiotics

Side effects/adverse reactions

Diarrheas, nausea, abnormal taste, dyspepsia, abdominal pain/discomfort, and headache.

Precautions and warnings

General

 In presence of severe renal impairment, with or without coexisting hepatic impairment, decreased dosage or prolonged dosing intervals may be appropriate. clarithromycin should not be used in pregnant women except in clinical circumstances where no alternative therapy is appropriate. Pseudomembranous colitis has been reported with nearly all antibacterial agents including macrolides, and may range in severity from mild to severe.

Pediatric use

Safety and effectiveness of clarithromycin in children under 6 months have not been established

Drug interactions

Clarithromycin use in patients who are receiving theophylline may be associated with an increase in serum theophylline concentrations. Clarithromycin may increase carbamazepine concentrations. Active metabolite of terfenadine was three times higher when co-administered with clarithromycin. Concomitant administration of clarithromycin and digoxin has been reported to result in elevated digoxin levels

Use in pregnancy and lactation

Clarithromycin should be used in pregnancy only if potential benefits justifies the potential risk to the fetus. The FDA classifies it at pregnancy category C

It is not known whether clarithromycin is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when clarithromycin is administered to a nursing woman.

Dosage and administration

Upper respiratory tract infections 250-500mg q12h for 10-14 days.

Lower respiratory tract infections 250mg q12h for 7- 14 days

uncomplicated skin and skin structure infections 250mg q12h 7-14 days

Overdose symptoms antidote

Studies on overdose not available

Storage

store below 30°c.

Keep out of reach of children