What Is Clarithromycin?
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Clarithromycin - Uses, Dosage, Side Effects, Warmings, and Interactions

Published on Jan 20, 2023 and last reviewed on Mar 13, 2023   -  5 min read


Clarithromycin is an antibiotic used to treat bacterial infections. Read below to learn more about its uses, dosage, side effects, drug warnings, and precautions.


Clarithromycin is most commonly used to treat and prevent many bacterial infections affecting the skin and respiratory system. The drug may also be prescribed in combination with anti-ulcer drugs to treat stomach ulcers. Clarithromycin is a broad-spectrum antibiotic available only with a doctor's prescription.

Drug Group:

Clarithromycin is a macrolide antibiotic that is useful in treating respiratory, skin, soft tissue, sexually transmitted, H. pylori, and atypical mycobacterial infections. The other antibiotics in the class of macrolides include Erythromycin, Roxithromycin, and Azithromycin. These drugs work by preventing the growth of bacteria.

What Is Clarithromycin Used For?

Clarithromycin is prescribed to treat mild-to-moderate bacterial infections such as pneumonia and infections of the ears, sinuses, skin, and throat. The macrolide may be used to treat and prevent disseminated Mycobacterial infections that often affect people with human immunodeficiency virus (HIV). Clarithromycin can be used in combination with other anti-ulcer medications, such as Vonoprazan and Amoxicillin, to eliminate H.pylori when treating patients with an active history of peptic ulcer disease. The antibiotic may be prescribed for treating pertussis and prophylaxis for bacterial endocarditis.

How Does Clarithromycin Work?

Clarithromycin may be bacteriostatic or bactericidal, depending on the organism and the drug concentration. The drug penetrates the bacterial cell wall and inhibits bacterial protein synthesis by binding to the bacterial ribosomal subunit. This prevents the peptidyl transferase activity and interferes with amino acid translocation during the protein assembling process. Clarithromycin also inhibits the hepatic microsomal CYP3A4 enzyme and P-glycoprotein.

What Is Its Onset of Action?

Absorption of Clarithromycin is rapid and reaches peak concentration within two hours of oral administration. The presence of food may slightly delay the absorption of the drug. The half-life of Clarithromycin is five to seven hours. The antibiotic is distributed widely into the body tissues except for the central nervous system. The bioavailability of Clarithromycin is 50 %. 500 mg of Clarithromycin usually stays in the body for about eight to twelve hours. 40 % of the oral dose of Clarithromycin is excreted unchanged by the kidneys, and the bile excretes the remaining.


No habit-forming tendencies have been reported in people after taking Clarithromycin.

Expiry Date:

The medicine should not be taken after it expires. The expiry date will be printed on the medicine pack.

What Is the Dosage of Clarithromycin?


How to Use Clarithromycin?

Clarithromycin is available in the form of tablets, an extended-release tablet, and an oral suspension to be taken by mouth. These can be taken with or without food every 8 to 12 hours for 7 to 14 days. Clarithromycin should be taken at around the same time every day. Always shake the suspension well before using the medication. Taking a complete Clarithromycin prescription is recommended to ensure the infection is completely treated.

Missed Dose:

If a dose of Clarithromycin is missed, take it soon after it is remembered. Do not take two tablets together as it may cause adverse effects. Skip the forgotten dose and continue from the next dose.

What Are the Drug Warnings and Precautions to Be Taken When Taking Clarithromycin?

Clarithromycin comes with several warnings that include

  • Allergy - Clarithromycin should not be taken if the patient has ever had an allergic reaction to the drug, as it may cause severe allergic reactions that could be fatal.

  • Pregnancy and Breastfeeding - Clarithromycin is a category C pregnancy drug and can cause adverse effects to the fetus when taken during pregnancy. The antibiotic passes into the breast milk and may cause side effects like upset stomach and drowsiness in the baby.

  • Kidney Problems - Patients with severe renal failure may require dose adjustments and should be monitored by measuring their antibiotic serum levels.

  • Children - Clarithromycin should not be given to children younger than six months as it may cause adverse effects.

  • Elderly - The use of Clarithromycin in people over 60 years of age can cause aggravated side effects.

  • Liver Disease - Clarithromycin can cause acute liver injury with jaundice and should not be given to patients with liver problems.

  • Heart Disease - Clarithromycin may increase the risk of cardiac and cerebrovascular events as it may cause the heart rhythm problem QT prolongation. There is an increased risk of myocardial infarction, arrhythmia, and cardiac mortality.

What Are the Side Effects of Clarithromycin?

Clarithromycin may cause side effects such as

  • Diarrhea.

  • Nausea.

  • Vomiting.

  • Stomach pain.

  • Heartburn.

  • Change in taste.

  • Headache.

Some of the serious side effects may include

  • Chest pain.

  • Rash.

  • Swelling of the face, throat, tongue, lips, hands, and feet.

  • Double vision.

  • Fast, pounding, or irregular heartbeat.

  • Hearing loss.

  • Yellowing of the eyes or skin.

  • Blood or mucus in the stool.

  • Dizziness.

  • Trouble breathing.

  • Drowsiness.

  • Mood changes.

What Are the Interactions of Clarithromycin?

Several drugs may interact with Clarithromycin and increase the risk of serious side effects.

Drug Interaction:

  • Amiodarone.

  • Disopyramide.

  • Dofetilide.

  • Pimozide.

  • Procainamide.

  • Quinidine.

  • Sotalol.

  • Efavirenz.

  • Nevirapine.

  • Posaconazole.

  • Saquinavir.

  • Colchicine.

  • Digoxin.

  • Ergotamine.

  • Tamsulosin.

  • Pimozide.

  • Ketoconazole.

  • Benzodiazepines such as Triazolam and Midazolam.

  • Warfarin.

  • Theophylline.

Interaction with Diseases:

  • Colitis - Antibacterial therapy alters the colon's normal flora, leading to the overgrowth of C. difficile and causing clostridium difficile-associated diarrhea. Therapy with broad-spectrum antibacterials should be administered cautiously in patients with a history of gastrointestinal diseases such as colitis.

  • QT Prolongation - Clarithromycin should be given with caution to patients with known prolongation of the QT interval or congenital long QT syndrome as it may cause prolonged cardiac repolarization.

  • Renal Dysfunction - Dose adjustments of Clarithromycin may be required in patients with mild to moderate renal impairment.

  • Myasthenia Gravis - The use of Macrolide may exacerbate symptoms of myasthenia gravis or trigger new symptoms of myasthenia syndrome.

Article Resources

Last reviewed at:
13 Mar 2023  -  5 min read




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