Clarithromycin is a macrolide antibiotic that belongs to the same class as erythromycin but with improved pharmacokinetics and tolerability. It is widely prescribed in both primary care and hospital settings to treat respiratory tract infections, skin infections, and certain gastrointestinal infections, including Helicobacter pylori eradication when combined with other agents. Clarithromycin exerts its antibacterial effect by binding to the 50S ribosomal subunit of susceptible bacteria, thereby inhibiting protein synthesis and halting bacterial growth. It is considered bacteriostatic, though bactericidal activity may occur at higher concentrations against some organisms.
Clarithromycin is available in immediate-release tablets, extended-release tablets, oral suspensions, and injectable forms. Its broad activity against Gram-positive organisms, atypical pathogens such as Mycoplasma and Chlamydophila, and certain Gram-negative bacteria has made it a valuable agent for respiratory and skin infections. Moreover, its role in combination regimens for H. pylori has made it a cornerstone of gastroenterology protocols worldwide.
The drug was first approved in the early 1990s and has since become part of standard treatment algorithms. It is generally well tolerated but is known to have significant drug–drug interaction potential due to inhibition of cytochrome P450 3A4 (CYP3A4). This requires caution in patients taking other medicines metabolised by this pathway. Resistance patterns have also become a major consideration; clarithromycin resistance in H. pylori and some respiratory pathogens limits effectiveness in certain regions, making local susceptibility data important when selecting therapy.
Compared with erythromycin, clarithromycin has better gastrointestinal tolerability and a longer half-life, allowing for twice-daily dosing in most cases. Extended-release formulations further improve convenience for chronic use. The drug is considered safe for many adults and children, but prescribers must consider age, comorbidities, and potential interactions when using it.
Clarithromycin remains an essential antibiotic, but like all antimicrobials, it must be used judiciously to reduce the spread of resistance. Stewardship programmes emphasise its use only when clearly indicated and encourage alternatives where resistance prevalence is high.
Patients must be advised to complete the full course, even if symptoms improve early, to prevent resistance and recurrence. For H. pylori, adherence is crucial to successful eradication and to avoid promoting resistant strains.
Most side effects resolve upon discontinuation, but patients should be instructed to seek urgent medical advice if they develop jaundice, palpitations, syncope, or severe diarrhoea.
Patients should provide their clinician with full medical and medication histories before starting therapy. Monitoring of liver function and ECG may be warranted in at-risk patients.
Given the extensive interaction profile, clinicians should perform a thorough review of all prescribed and non-prescribed medicines before initiating clarithromycin therapy.
Overdose: Symptoms may include severe gastrointestinal upset, altered mental status, and cardiac arrhythmias. Supportive care, including monitoring of electrolytes and ECG, is recommended in hospital settings. There is no specific antidote.
Accidental double dose: May cause nausea, abdominal discomfort, or headache. Patients should monitor symptoms and contact a healthcare provider if concerned.
Missed dose: Take as soon as remembered unless it is near the time for the next dose. Do not double up. Maintaining consistent blood levels is important for antibiotic effectiveness.
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