Klacid Sr (Clarithromycin)

Clarithromycin is a macrolide antibiotic used to treat bacterial infections in the respiratory, sinus and skin pathways.

• Community‑acquired pneumonia: reduces bacterial load and improves clinical symptoms in adult patients.
• Acute bacterial sinusitis: alleviates sinus inflammation and clears infection.
• Skin and soft‑tissue infections: eradicates susceptible Gram‑positive and some Gram‑negative organisms.
• Helicobacter pylori eradication: used in combination regimens to achieve bacterial clearance and prevent ulcer recurrence.

• Clarithromycin binds to the 50S subunit of bacterial ribosomes, inhibiting translocation of the peptidyl‑tRNA. This blocks protein synthesis, leading to a bacteriostatic effect against susceptible organisms and, at higher concentrations, a bactericidal effect. The drug’s activity is concentration‑dependent and targets a broad range of Gram‑positive, some Gram‑negative and atypical bacteria.

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

Common Side Effects

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

Serious or Rare Side Effects

• Clostridioides difficile‑associated diarrhea: severe colitis requiring medical attention.
• QT interval prolongation: risk of cardiac arrhythmias.
• Hepatotoxicity: elevated liver enzymes or hepatitis.
• Severe allergic reactions: anaphylaxis, rash, or angioedema.
• Cardiac arrhythmias: especially in patients with pre‑existing heart disease.
• Liver failure: rare but potentially life‑threatening.

Before prescribing clarithromycin, clinicians should evaluate patient‑specific factors and monitor for adverse events.

• Assess renal function: dose adjustment may be needed in renal impairment.
• Monitor liver enzymes: avoid use in patients with active hepatic disease.
• Review concomitant QT‑prolonging drugs: increased risk of arrhythmia.
• Use with caution in patients with cardiac disease: monitor ECG if indicated.
• Avoid in individuals with known hypersensitivity to macrolides.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Clarithromycin interacts with several medications; awareness of interaction severity guides clinical decisions.

Major Interactions (Avoid)

• Co‑administration with other QT‑prolonging agents (e.g., erythromycin, cisapride) may cause serious arrhythmias.
• Strong CYP3A4 substrates (e.g., simvastatin, lovastatin) can lead to toxic levels.
• Antacids containing aluminum or magnesium: reduce clarithromycin absorption.

Moderate Interactions (Monitor Closely)

• Warfarin: may increase INR and bleeding risk.
• Carbamazepine: may decrease clarithromycin plasma concentrations.
• Oral contraceptives: reduced efficacy, consider alternative contraception.