Klacid Sr (Clarithromycin)

Clarithromycin is used to treat bacterial infections affecting the respiratory, sinus, skin and gastrointestinal systems.

• Community‑acquired pneumonia: eradicates susceptible organisms and improves respiratory function.
• Acute bacterial sinusitis: reduces sinus inflammation and clears infection.
• Skin and soft‑tissue infections: resolves cellulitis, erysipelas and other bacterial skin conditions.
• Helicobacter pylori eradication (in combination therapy): contributes to bacterial clearance as part of triple‑therapy regimens.
• Mycobacterial infections: used in selected cases of atypical mycobacterial disease.

• Clarithromycin binds to the 50S subunit of bacterial ribosomes, blocking the translocation step of protein synthesis. This inhibition prevents elongation of the peptide chain, halting bacterial growth and leading to a bacteriostatic effect against susceptible Gram‑positive, Gram‑negative and atypical organisms.

Clarithromycin may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Nausea: mild to moderate stomach upset.
• Diarrhea: loose stools, sometimes watery.
• Abdominal pain: cramping or discomfort.
• Taste disturbance: altered or metallic taste.
• Headache: mild to moderate intensity.
• Vomiting: occasional episodes.

Serious or Rare Side Effects

• Severe allergic reactions (anaphylaxis): rash, swelling, difficulty breathing.
• QT interval prolongation: risk of cardiac arrhythmias.
• Hepatic dysfunction: elevated liver enzymes or jaundice.
• Clostridioides difficile‑associated diarrhea: severe colitis.
• Stevens‑Johnson syndrome/toxic epidermal necrolysis: extensive skin blistering.
• Cardiac arrhythmias: ventricular tachycardia or fibrillation.

When prescribing clarithromycin, clinicians should consider several precautionary measures to ensure safe use.

• Assess renal and hepatic function: adjust therapy if impairment is present.
• Monitor for QT prolongation: avoid in patients with known cardiac conduction disorders.
• Review concomitant medications: avoid drugs that may cause dangerous interactions.
• Check for hypersensitivity: discontinue if allergic reaction occurs.
• Use in pregnancy only if benefits outweigh risks: consult obstetric guidance.
• Store at ambient temperature: keep in the original pack, protect from moisture and direct sunlight.

Clarithromycin interacts with several medicines; understanding the level of interaction guides clinical decisions.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole): may increase clarithromycin levels.
• Drugs that prolong QT interval (e.g., cisapride, pimozide): risk of serious arrhythmias.
• Ergot alkaloids (e.g., ergotamine): can cause ergot toxicity.

Moderate Interactions (Monitor Closely)

• Statins metabolized by CYP3A4 (e.g., simvastatin, lovastatin): monitor for myopathy.
• Warfarin: may enhance anticoagulant effect, check INR.
• Theophylline and carbamazepine: may reduce their plasma concentrations.