Klacid (Clarithromycin)

Klacid (clarithromycin) is a macrolide antibiotic used to treat bacterial infections in several organ systems.

• Community‑acquired pneumonia: eradicates the causative bacteria and improves respiratory function.
• Acute bacterial sinusitis: reduces sinus inflammation by eliminating the infecting organisms.
• Acute exacerbations of chronic bronchitis: shortens symptom duration and helps prevent further lung damage.
• Skin and soft‑tissue infections: clears bacterial pathogens from dermal and subdermal tissues.
• Helicobacter pylori eradication (in combination therapy): contributes to successful bacterial clearance when used with other agents.

• Clarithromycin binds to the 50S subunit of bacterial ribosomes, inhibiting the translocation step of protein synthesis. This blockade prevents elongation of the nascent peptide chain, producing a bacteriostatic effect against susceptible Gram‑positive, Gram‑negative and atypical organisms. By disrupting essential protein production, the drug limits bacterial growth and facilitates immune‑mediated clearance.

Clarithromycin may cause a range of adverse reactions, varying in frequency and severity.

Common Side Effects

• Nausea: mild to moderate stomach upset.
• Diarrhea: loose, watery stools.
• Abdominal pain: cramping or discomfort in the abdomen.
• Taste disturbance: altered or metallic taste sensation.

Serious or Rare Side Effects

• Hepatotoxicity: signs of liver injury such as jaundice or elevated enzymes.
• QT prolongation: cardiac rhythm changes that may lead to arrhythmia.
• Severe allergic reactions: rash, itching, swelling, or anaphylaxis.

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

• Assess liver function: avoid use in patients with severe hepatic impairment.
• Review cardiac history: caution in individuals with known QT prolongation or electrolyte disturbances.
• Monitor for drug‑induced diarrhea: discontinue if severe or persistent.
• Evaluate concomitant medications: avoid combinations that may increase clarithromycin levels.
• Pregnancy and lactation: use only if the potential benefit outweighs the risk; consult obstetric guidance.
• Store at ambient temperature: keep below 25 °C, in the original packaging, protected from moisture and light.

Clarithromycin interacts with several medicines through metabolic pathways and transporter inhibition.

Major Interactions (Avoid)

• Simvastatin: increased risk of myopathy; avoid co‑administration.
• Pimozide: elevated plasma levels may cause serious cardiac effects.
• Ergot alkaloids: risk of severe vasospasm; contraindicated.

Moderate Interactions (Monitor Closely)

• Warfarin: may enhance anticoagulant effect; monitor INR.
• Theophylline: possible increase in serum concentration; observe for toxicity.
• Carbamazepine: reduced carbamazepine levels; adjust dosage if needed.