Clarithromycin

Oral Antibiotics

Drug class: Macrolide Antibiotics

Clarithromycin (KLACID)（中文：克拉霉素）

Common Strengths

• Tablets: 250 mg, 500 mg
• Extended-release tablets: 500 mg
• Oral suspension: 125 mg/5 mL, 250 mg/5 mL
• Injection: 500 mg

Drug Trade Names

Klacid

Drug Usage

The macrolides have an antibacterial spectrum similar but not identical to penicillin; they are thus an alternative in penicillin-allergic patients.

Clarithromycin is prescribed for:

• Respiratory tract infections (e.g. pneumonia, bronchitis)
• Skin infections
• Ear infections (otitis media)
• Stomach ulcers caused by Helicobacter pylori
• Mycobacterium avium complex (MAC) infections in immunocompromised patients

Mechanism of Action

Clarithromycin works by inhibiting bacterial protein synthesis. It binds to the 50S subunit of the bacterial ribosome, specifically to the 23S rRNA, thereby blocking peptide bond formation and inhibiting bacterial growth.

Route of Administration

Clarithromycin can be administered orally in tablet or liquid form and intravenously

Dosages

• Normal Adults:
  • Typically, 250 mg to 500 mg every 12 hours for 7 to 14 days.
• Diabetic Kidney Disease:
  • Adjustments may be necessary based on renal function.
  • For patients with an eGFR <30 mL/min, the dosage may need to be reduced or extended due to decreased clearance.

Side Effects

Frequency	Adverse reactions
Common Side Effects	Nausea
	Diarrhea
	Stomach pain
	Unpleasant taste in the mouth
Serious Side Effects	Liver problems (e.g. jaundice)
	QT prolongation leading to serious heart rhythm issues
	Severe allergic reaction

Pharmacokinetics

• Clarithromycin is well absorbed after oral administration.
• Peak Concentrations: Peak serum concentrations are typically reached within 2 to 3 hours after oral administration. It achieves higher concentrations in tissue compared to plasma.
• Hepatic Metabolism: Clarithromycin is primarily metabolized by cytochrome P450 (CYP) 3A isoenzymes.
• Half-Life: The elimination half-life of clarithromycin ranges from approximately 3.3 to 4.9 hours, allowing for convenient twice-daily dosing.
• The onset of action typically occurs within a few hours after administration, with effects lasting up to 12 hours for regular forms and up to 24 hours for extended-release formulations.

Drug Precautions

Pregnancy

Avoid, particularly in the first trimester, unless the potential benefit outweighs the risk.

Breastfeeding

Caution is advised as it may pass into breast milk; benefits should be weighed against risks.

Children and Elderly

Safety in children under six months has not been established. Elderly patients may require dosage adjustments due to increased risk of side effects.

Drug Monitoring Items

Liver function tests, renal function tests, and monitoring for QT prolongation are recommended.

Drug Interactions

• Statins: Co-administration with clarithromycin can lead to increased plasma concentrations of these statins, raising the risk of myopathy and rhabdomyolysis. It is advised to suspend these statins during clarithromycin treatment.
• Colchicine: Concomitant use can significantly increase colchicine levels, especially in patients with renal or hepatic impairment, leading to toxicity. This combination is contraindicated.
• Ergot Alkaloids: Drugs like ergotamine and dihydroergotamine may cause severe vasospasm and ischemia when taken with clarithromycin, making their co-administration contraindicated.
• Benzodiazepines: Clarithromycin can enhance the sedative effects of benzodiazepines such as midazolam and triazolam, potentially leading increased sedation and respiratory depression.
• Anticoagulants: There is an increased risk of bleeding when clarithromycin is taken with apixaban, dabigatran, and warfarin.
• Phosphodiesterase Inhibitors: Medications like sildenafil, tadalafil, and vardenafil may have elevated levels when taken with clarithromycin, necessitating dosage adjustments to avoid side effects.
• Pimozide: The combination can lead to serious heart rhythm abnormalities; thus it is contraindicated.

FAQ

How Should I Take the Tablet?

Take with or without food as directed; swallow extended-release tablets whole crushing or chewing.

What Should I Avoid while Taking?

Avoid alcohol and medications that prolong QT interval unless directed by a healthcare provider.

What Happens If I Miss a Dose?

Take it as soon as you remember unless it is almost time for your dose; do not double up on doses.