Spectrum of bacterial susceptibility
Aerobic Gram-positive bacteria

Staphylococcus aureus
Streptococcus pneumoniae
Streptococcus pyogenesAerobic Gram-negative bacteria

Haemophilus parainfluenzae 
Haemophilus influenzae
Moraxella catarrhalisHelicobacter

Helicobacter pyloriMycobacteria
Mycobacterium avium complex consisting of:

Mycobacterium avium avium
Mycobacterium intracellulareOther bacteria

Chlamydia pneumoniae
Mycoplasma pneumoniaeSafety and effectiveness of clarithromycin in treating clinical infections due to the following bacteria have not been established in adequate and well-controlled clinical trials:Aerobic Gram-positive bacteria

Streptococcus agalactiae
Streptococcus (Groups C, F, G)
Viridans group streptococciAerobic Gram-negative bacteria

Bordetella pertussis
Legionella pneumophila
Pasteurella multocidaAnaerobic Gram-positive bacteria

Clostridium perfringens
Peptococcus Niger
Cutibacterium acnesAnaerobic Gram-negative bacteria

Prevotella melaninogenica (formerly Bacteroides melaninogenicus)

Contraindications
Clarithromycin should not be taken by people who are allergic to other macrolides or inactive ingredients in the tablets, including microcrystalline cellulose, croscarmelose sodium, magnesium stearate, and povidone
Clarithromycin should not be used by people with a history of cholestatic jaundice and/or liver dysfunction associated with prior clarithromycin use. Clarithromycin should not be used in the setting of hypokalaemia (low blood potassium)
Use of clarithromycin with the following medications: cisapride, pimozide, astemizole, terfenadine, ergotamine, ticagrelor, ranolazine or dihydroergotamine is not recommended. It should not be used with colchicine in people with kidney or liver impairment. Concomitant use with cholesterol medications such as lovastatin or simvastatin. Hypersensitivity to clarithromycin or any component of the product, erythromycin, or any macrolide antibiotics. QT prolongation or ventricular cardiac arrhythmias, including torsade de pointes. Side effects
The most common side effects are gastrointestinal: diarrhea (3%), nausea (3%), abdominal pain (3%), and vomiting (6%). It also can cause headaches, insomnia, and abnormal liver function tests. Allergic reactions include rashes and anaphylaxis.
FDA Drug Safety Communication.