Klacid (Clarithromycin)

Clarithromycin is indicated for several bacterial infections affecting the respiratory and skin systems.

• Community‑acquired bacterial pneumonia: reduces bacterial load and improves clinical outcomes.
• Acute bacterial sinusitis: alleviates sinus inflammation caused by susceptible organisms.
• Acute exacerbations of chronic bronchitis: helps restore lung function and reduces symptoms.
• Skin and soft‑tissue infections: eradicates susceptible Gram‑positive and some Gram‑negative bacteria.
• Helicobacter pylori eradication (in combination therapy): contributes to ulcer healing and infection clearance.

• Clarithromycin inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, blocking translocation of the peptidyl‑tRNA. This action prevents the elongation of the nascent peptide chain, leading to bacteriostatic effects against susceptible organisms and, at higher concentrations, bactericidal activity.

Clarithromycin may cause a range of adverse reactions, most of which are mild and reversible.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Diarrhea: watery stools often occurring early in therapy.
• Abdominal pain: cramping or discomfort in the stomach area.
• Taste disturbance: altered or metallic taste perception.
• Headache: transient mild to moderate headache.
• Vomiting: occasional episodes, especially with high doses.

Serious or Rare Side Effects

• Severe allergic reactions: anaphylaxis or angioedema requiring immediate medical attention.
• QT interval prolongation: may lead to cardiac arrhythmias.
• Clostridioides difficile‑associated diarrhea: severe colitis risk.
• Hepatotoxicity: elevated liver enzymes or jaundice.
• Stevens‑Johnson syndrome/toxic epidermal necrolysis: life‑threatening skin reactions.
• Cardiac arrhythmias: irregular heart rhythms beyond QT prolongation.

Before prescribing clarithromycin, clinicians should evaluate patient-specific factors and monitor for potential complications.

• Assess liver function: adjust use in hepatic impairment.
• Monitor cardiac QT interval: avoid in patients with known prolongation or concurrent QT‑prolonging drugs.
• Use caution in renal impairment: dose may need adjustment.
• Avoid in known macrolide hypersensitivity: discontinue if allergic reaction occurs.
• Review concomitant medications: consider interactions that may alter drug levels.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Clarithromycin interacts with several medicines; some combinations should be avoided while others require careful monitoring.

Major Interactions (Avoid)

• Cisapride: risk of serious cardiac arrhythmias.
• Pimozide: can cause QT prolongation and torsades de pointes.
• Ergot alkaloids (e.g., ergotamine): may precipitate ergotism.
• Certain antiarrhythmics (e.g., quinidine): increased plasma concentrations.

Moderate Interactions (Monitor Closely)

• Statins (simvastatin, lovastatin): elevated risk of myopathy.
• Warfarin: possible increase in anticoagulant effect.
• Oral hypoglycemics (e.g., sulfonylureas): enhanced hypoglycemia.
• Digoxin: higher serum levels may occur.
• Colchicine: dose reduction may be needed to avoid toxicity.