Clarithromycin is one of the newer macrolide which possess better pharmacokinteic and antimicrobial profiles unlike older compounds like erythromycin. Clarithromycin exhibits even bactericidal activity against

Some of the pathogens and even Post Antibiotic Effect (PAE) which is not seen with others. It has Good activity against;

It is very active against agents causing atypical pneumonia like C.pneumoniae, M.pneumoniae and markedly active against L.pneumophiliae.

Similar effects are also observed against S.aureus, S.pyogenes and all strains of S.pneumoniae and M.catarrhalis and with GOOD against gram positive anaerobes. With reference to H.influenzae clarithromycin has twice the activity of erythromycin ( c.f. Azithromycin has increased activity against gram negative organisms particularly H.influenzae, Enterobactericae, and unlike Erythromycin & Clarithromycin it has activity against Salmonellae, Sigellae and E.coli).

Clarithromycin has very good activity against agents causing opportunistic infections  in AIDS patients  viz.,  MAC infection, Toxoplasmosis, Cryptosporidiosis. Clarithromycin is one of the second line drug  in M.leprae ( along with minocycline). Recent studies have shown that clarithromycin  is an effective agent against M.chelonae which causes disseminated cutaneous lesion and along with Omeprazole (Better Lansoprazole) clarithromycin  is effective in eradication of H.pylori  in patients with peptic ulcer. Very recent investigations revealed the high efficacy of clarithromycin against B.burgedorferi causing Lyme disease.

It is also effective against Toxoplasmosis, and Cryptosporidiosis (c.f Spiramycin).

None of the existing Macrolides are effective against MRSA and Enterococci. Both clarithromycin and its 14 OH metabolite exhibit synergistic activity and PAE (post antibiotic effect) and are bactericidal to H.influenzae, S.pneumoniae, M.catarrhalis, S.pyogenes, S.agalectica. Clinical experience had shown that Clarithromycin improves immune function via its modulatory effects on cytokine production normalizes and/or improves viscoelastic properties of mucus and sputum and reduces sputum volume in normal individuals too.