CLARITHROMYCIN - A REVIEW OF ITS EFFICACY IN THE TREATMENT OF RESPIRATORY-TRACT INFECTIONS IN IMMUNOCOMPETENT PATIENTS

Clarithromycin is a broad spectrum macrolide antibacterial agent activ e in vitro and effective in vivo against the major pathogens responsib le for respiratory tract infections in immunocompetent patients. It is highly active in vitro against pathogens causing atypical pneumonia ( Chlamydia pneumoniae, Mycoplasma pneumoniae and Legionella spp.) and h as similar activity to other macrolides against Staphylococcus aureus, Streptococcus pyogenes, Moraxella catarrhalis and Streptococcus pneum oniae. Haemophilus influenzae is susceptible or intermediately suscept ible to clarithromycin alone, but activity is enhanced when the parent drug and metabolite are combined in vitro. Absorption of clarithromyc in is unaffected by food. More than half of an oral dose is systemical ly available as the parent drug and the active 14-hydroxy metabolite. Pharmacokinetics are nonlinear with plasma concentrations increasing i n more than proportion To the dosage. First-puss metabolism results in the rapid appearance of the active metabolite 14-hydroxy-clarithromyc in in plasma. Clarithromycin and its active metabolite true found in g reater concentrations in the tissues and fluids of the respiratory tra ct than in plasma. Dosage adjustments are required for patients with s evere renal failure, but not for elderly patients or those with hepati c impairment Drug interactions related to the cytochrome P450 system m ay occur with clarithromycin use. In addition to the standard immediat e-release formulation for administration twice daily, a modified-relea se formulation of clarithromycin is now available for use once daily. In dosages of 500 to 1000 mg/day for 5 to 14 days, clarithromycin was as effective in the treatment of community-acquired upper and lower re spiratory tract infections in hospital and community settings as beta- lactam agents (with or without a beta-lactamase inhibitor), cephalospo rins and most other macrolides. Clarithromycin was similar in efficacy to azithromycin in comparative studies and is as effective us anti be tter tolerated than erythromycin. Adverse events are primarily gastroi ntestinal in nature, but result in fewer withdrawals from therapy than are seen with erythromycin. Clarithromycin provides similar clinical and bacteriological efficacy to that seen with beta-lactam agents, cep halosporins cmd other macrolides. It offers a cost-saving alternative to intravenous erythromycin use in US hospitals and is available in bo th once-daily and twice-daily formulations. The spectrum of activity o f clarithromycin against common and emerging respiratory tract pathoge ns may make it suitable for use in the community as empirical therapy of respiratory tract infections in both children and adults.