Clarithromycin (6-O-methyl erythromycin) is an antibiotic useful for the treatment of a number of bacterial infections. It is a macrolide antibiotic used particularly for respiratory infections (pharyngitis, tonsillitis, sinusitis, acute exacerbation of chronic obstructive pulmonary disease, pneumonia ), skin infections and Lyme disease. In addition, it is used to treat Helicobacter pylori, a cause of gastritis.
It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.
§Medical uses
Clarithromycin is primarily used to treat a number of bacterial infections including: pneumonia, Helicobacter pylori and as an alternative to penicillin in strep throat. Other uses include: cat scratch disease and other infections due to bartonella, cryptosporidiosis, as a second line agent in Lyme disease and toxoplasmosis. It may also be used to prevent bacterial endocarditis in those who cannot take penicillin.
§Spectrum of resistance and susceptibility
Clarithromycin covers Gram-positive bacteria and atypical bacteria. It has been effective in treating bacterial infections including tonsillitis, sinusitis, pneumonia, and others. The following represents susceptibility data for a few medically significant microorganisms:
- Haemophilus influenzae: 0.008â†'256 μg/ml
- Streptococcus pneumoniae: 0.001â†'256 μg/ml
- Streptococcus pyogenes: 0.001â†'128 μg/ml
Many Gram-positive microbes quickly develop resistance to clarithromycin after standard courses of treatment, most frequently by acquisition of the erm(B) gene, which confers high-level resistance to all macrolides.
Its antibacterial spectrum is the same as erythromycin, but it is also active against Mycobacterium avium complex MAV, M. leprae, and atypical mycobacteria.
§Side effects
The most common (>1%) side effects are gastrointestinal: diarrhea, nausea, abdominal pain, and vomiting. It also can cause headaches, insomnia, and abnormal liver function tests. Allergic reactions include rashes and anaphylaxis. Less common side effects include extreme irritability, hallucinations (auditory and visual), dizziness/motion sickness, and alteration in senses of smell and taste, including a metallic taste. Dry mouth, panic attacks, and nightmares have also been reported, albeit less frequently.[2]
§Cardiac
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.
§Liver and kidney
Clarithromycin has been known to cause jaundice, cirrhosis, and kidney problems, including renal failure.
§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, due to the elimination of the yeast's natural bacterial competitors by the antibiotic, is also incurred.
§Pregnancy
Clarithromycin has been shown to induce miscarriage in animals, and a recent study found an increased risk of miscarriage in women exposed to it in early pregnancy.
In the CLARICOR 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. Some case reports suspect it of causing liver disease.
§Interactions
Clarithromycin inhibits an important enzyme, CYP3A4, involved in the metabolism of many other commonly prescribed drugs. Taking clarithromycin with these other drugs may lead to unexpected increases or decreases in drug levels.
§Statins
When it is taken with some certain statins (a class of drugs used to reduce blood serum cholesterol levels), the risk of side effects is increased, including muscle aches and rhabdomyolysis.
§Calcium channel blockers
Patients on a calcium channel blocker who were also given clarithromycin have a higher risk of critically low blood pressure, kidney failure, and death, compared to pairing calcium channel blockers with azithromycin, a drug similar to clarithromycin but without CYP3A4 inhibition.
When ergotamine migraine medications are taken with clarithromycin, the risk of acute ergot toxicity is increased, including vasospasm and ischemia of the extremities.
§Carbamazepine
Clarithromycin almost doubles the level of carbamazepine in the body by reducing its clearance, inducing toxic symptoms of carbamazepine, including diplopia and nausea, as well as hyponatremia.
§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.
§Buspirone
It can also cause serotonin syndrome symptoms when taken in conjunction with buspirone.
§Contraindications
Clarithromycin should be used with caution if the patient has liver or kidney disease, certain heart problems, or takes drugs that might cause certain heart problems (e.g., QT prolongation or bradycardia), or an electrolyte imbalance (e.g., low potassium or sodium levels).
§Mechanism of action
Clarithromycin prevents bacteria from growing by interfering with their protein synthesis. It binds to the subunit 50S of the bacterial ribosome, thus inhibiting the translation of peptides.
§Pharmacokinetics
Unlike erythromycin, clarithromycin is acid-stable, so can be taken orally without being protected from gastric acids. It is readily absorbed, and diffused into most tissues and phagocytes. Due to the high concentration in phagocytes, clarithromycin is actively transported to the site of infection. During active phagocytosis, large concentrations of clarithromycin are released; its concentration in the tissues can be over 10 times higher than in plasma. Highest concentrations were found in liver, lung tissue, and stool.
§Metabolism
Clarithromycin has a fairly rapid first-pass metabolism in the liver. Its major metabolites include an inactive metabolite, N-desmethylclarithromycin, and an active metabolite, 14-(R)-hydroxyclarithromycin. Compared to clarithromycin, 14-(R)-hydroxyclarithromycin is less potent against mycobacterial tuberculosis and the Mycobacterium avium complex. Clarithromycin (20%-40%) and its active metabolite (10%-15%) are excreted in urine. Of all the drugs in its class, clarithromycin has the best bioavailability at 50%, which makes it amenable to oral administration. Its elimination half-life is about 3 to 4 hours with 250Â mg administered every 12 h, but increased to 5 to 7 h with 500Â mg administered every 8 to 12 h. With any of these dosing regimens, the steady-state concentration of this metabolite is generally attained within 3 to 4 days.
§History
Clarithromycin was invented by researchers at the Japanese drug company Taisho Pharmaceutical in the 1970s. The product emerged through efforts to develop a version of the antibiotic erythromycin that did not experience acid instability in the digestive tract, causing side effects, such as nausea and stomachache. Taisho filed for patent protection for the drug around 1980 and subsequently introduced a branded version of its drug, called Clarith, to the Japanese market in 1991. In 1985, Taisho partnered with the American company Abbott Laboratories for the international rights, and Abbott also gained FDA approval for Biaxin in October 1991. The drug went generic in Europe in 2004 and in the US in mid-2005.
§Brand names
In Pakistan, it is available under the brand name Rithmo, and is manufactured and marketed by SAMI Pharmaceuticals and used by many pharmaceuticals companies such as CCL Pharmaceuticals. In Bangladesh, it is available as Binoclar by Sandoz, Claricin by the Acme Laboratories Ltd. In the United States, generic clarithromycin is available from Andrx, Genpharm, Ivax, Ranbaxy Laboratories, Roxane, Sandoz, Teva, and Wockhardt. In the Middle East, it is available as Claridar, produced by Dar al Dawa. In India, Acnesol-CL gel, containing 1% clarithromycin, marketed by Systopic, is used to treat acne vulgaris.
Clarithromycin is available under several brand names, for example Binoclar, Biclar, Bioclar, Biaxin, Crixan, Clarihexal, Clacid, Claritt, Clacee, Clarac, Clariwin, Claripen, Clarem, Claridar, Fromilid, Infex, Klaricid, Klacid, Klaram, Klabax, Monoclar, Resclar, Truclar, and Vikrol.
§References
§External links
- "Biaxin XL (labeling)" (pdf). Abbott Laboratories.Â
- US patent 4331803, Watanabe, Y.; Morimoto, S. & Omura, S., "Novel erythromycin compounds", issued 1981-05-19, assigned to Taisho PharmaceuticalÂ
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