Clarithromycin

Clarithromycin, sold under the brand name Biaxin among others, is an antibiotic used to treat various bacterial infections. This includes strep throat, pneumonia, skin infections, H. pylori infection, and Lyme disease.

Clarithromycin was developed in 1980 and approved for medical use in 1990. It is on the World Health Organization's List of Essential Medicines. Clarithromycin is available as a generic medication.

Medical uses

Antibiotic

Clarithromycin is primarily used to treat a number of bacterial infections including pneumonia, Helicobacter pylori, and as an alternative to penicillin in strep throat. The American Academy of Sleep Medicine's 2021 clinical practice guidelines conditionally suggested its use, especially for those who don't respond to other therapies.

Contraindications

Clarithromycin should not be taken by people who are allergic to other macrolides or inactive ingredients in the tablets, including microcrystalline cellulose, sodium croscarmellose, magnesium stearate, and povidone
Clarithromycin should not be used by people with a history of cholestatic jaundice and/or liver dysfunction associated with prior clarithromycin use.

Cardiac

In February 2018, the US Food and Drug Administration (FDA) issued a safety communication warning with respect to an increased risk for heart problems or death with the use of clarithromycin, and has recommended that alternative antibiotics be considered in those with heart disease.

Clarithromycin can lead to a prolonged QT interval. In patients with long QT syndrome, cardiac disease, or patients taking other QT-prolonging medications, this can increase risk for life-threatening arrhythmias.

In one trial, the use of short-term clarithromycin treatment was correlated with an increased incidence of deaths classified as sudden cardiac deaths in stable coronary heart disease patients not using statins.

Liver and kidney

Clarithromycin has been known to cause jaundice, cirrhosis, and kidney problems, including kidney failure. Some case reports suspect it of causing liver disease.

Central nervous system

Common adverse effects of clarithromycin in the central nervous system include dizziness, headaches. Rarely, it can cause ototoxicity, delirium and mania.

Infection

A risk of oral candidiasis and vaginal candidiasis, due to the elimination of the yeast's natural bacterial competitors by the antibiotic, has also been noted.

Pregnancy and breastfeeding

Clarithromycin should not be used in pregnant women except in situations where no alternative therapy is appropriate.

Interactions

Clarithromycin inhibits a liver enzyme, CYP3A4, involved in the metabolism of many other commonly prescribed drugs. Taking clarithromycin with other medications that are metabolized by CYP3A4 may lead to unexpected increases or decreases in drug levels.

A few of the common interactions are listed below.

Colchicine

Clarithromycin has been observed to have a dangerous interaction with colchicine as the result of inhibition of CYP3A4 metabolism and P-glycoprotein transport. Combining these two drugs may lead to fatal colchicine toxicity, particularly in people with chronic kidney disease.

Calcium channel blockers

Concurrent therapy with calcium channel blocker may increase risk of low blood pressure, kidney failure, and death, compared to pairing calcium channel blockers with azithromycin, a drug similar to clarithromycin but without CYP3A4 inhibition. Administration of clarithromycin in combination with verapamil have been observed to cause low blood pressure, low heart rate, and lactic acidosis.

HIV medications

Depending on the combination of medications, clarithromycin therapy could be contraindicated, require changing doses of some medications, or be acceptable without dose adjustments. For example, clarithromycin may lead to decreased zidovudine concentrations.

Pharmacology

Mechanism of action

Clarithromycin prevents bacteria from multiplying by acting as a protein synthesis inhibitor. It binds to 23S rRNA, a component of the 50S subunit of the bacterial ribosome, thus inhibiting the translation of peptides.

In addition to its antibiotic activity, clarithromycin has been found to act as a negative allosteric modulator of the GABA<sub>A</sub> receptor. In relation to this action, it may have wakefulness-promoting effects in people with hypersomnia.

History

Clarithromycin was invented by researchers at the Japanese drug company Taisho Pharmaceutical in 1980.

Society and culture

thumb|150px|A pack of clarithromycin tablets manufactured by [[Taisho Pharmaceutical]]

Available forms

Clarithromycin is available as a generic medication.