Klacid (Clarithromycin)

Clarithromycin is indicated for several bacterial infections affecting the respiratory tract, sinuses, skin and gastrointestinal system.

• Community‑acquired pneumonia: eliminates causative bacteria and improves clinical symptoms.
• Acute bacterial sinusitis: reduces infection and relieves sinus congestion.
• Acute exacerbations of chronic bronchitis: shortens illness duration and improves airflow.
• Skin and soft‑tissue infections: eradicates susceptible organisms and promotes healing.
• Helicobacter pylori eradication (in combination therapy): contributes to bacterial clearance and ulcer healing.

• Clarithromycin binds to the 50S subunit of bacterial ribosomes, inhibiting the translocation step of protein synthesis. This action blocks the elongation of peptide chains, resulting in a bacteriostatic effect against susceptible Gram‑positive and some Gram‑negative organisms.

Clarithromycin may cause a range of adverse reactions, which are generally categorized by frequency and severity.

Common Side Effects

• Nausea: mild to moderate upset stomach.
• Diarrhea: loose stools, sometimes watery.
• Abdominal pain: cramping or discomfort.
• Taste disturbance: altered or metallic taste.
• Headache: mild to moderate.
• Rash: mild skin redness or itching.

Serious or Rare Side Effects

• Anaphylaxis: severe allergic reaction with airway compromise.
• Hepatic dysfunction: elevated liver enzymes or hepatitis.
• QT interval prolongation: risk of cardiac arrhythmia.
• Clostridioides difficile‑associated diarrhea: severe colitis.
• Eosinophilic pneumonia: respiratory distress with eosinophil infiltration.
• Stevens‑Johnson syndrome: severe skin and mucosal reaction.

When prescribing clarithromycin, clinicians should consider several precautionary measures to minimize risks.

• Assess renal and hepatic function: adjust therapy if significant impairment is present.
• Review patient medication list: avoid concomitant use with drugs that prolong the QT interval.
• Monitor for allergic reactions: discontinue if signs of hypersensitivity appear.
• Use with caution in patients with cardiac arrhythmias: evaluate baseline ECG.
• Avoid use during known macrolide resistance: consider susceptibility testing.
• Store at ambient temperature: keep in original container, protect from moisture and heat.

Clarithromycin interacts with a variety of medicines; the significance of the interaction determines the management approach.

Major Interactions (Avoid)

• Cisapride: risk of serious cardiac arrhythmias; co‑administration is contraindicated.
• Pimozide: may cause QT prolongation and ventricular arrhythmia; avoid combination.
• Ergot alkaloids: risk of severe vasospasm; avoid.
• Theophylline: increased serum levels leading to toxicity; avoid.
• Statins metabolized by CYP3A4 (e.g., simvastatin, lovastatin): risk of rhabdomyolysis; avoid.

Moderate Interactions (Monitor Closely)

• Carbamazepine: may reduce clarithromycin levels; monitor efficacy.
• Warfarin: may increase INR; monitor coagulation parameters.
• Oral contraceptives: may reduce effectiveness; advise additional contraception.
• Antacids containing aluminum or magnesium: may decrease absorption; separate dosing by at least 2 hours.
• Digoxin: possible increased serum concentrations; monitor levels.