indication

An alternative medication for the treatment of acute otitis media caused by H. influenzae, M. catarrhalis, or S. pneumoniae in patients with a history of type I penicillin hypersensitivity. Also for the treatment of pharyngitis and tonsillitis caused by susceptible Streptococcus pyogenes, as well as respiratory tract infections including acute maxillary sinusitis, acute bacterial exacerbations of chronic bronchitis, mild to moderate community-acquired pneuomia, Legionnaires' disease, and pertussis. Other indications include treatment of uncomplicated skin or skin structure infections, helicobacter pylori infection, duodenal ulcer disease, bartonella infections, early Lyme disease, and encephalitis caused by Toxoplasma gondii (in HIV infected patients in conjunction with pyrimethamine). Clarithromycin may also decrease the incidence of cryptosporidiosis, prevent the occurence of α-hemolytic (viridans group) streptococcal endocarditis, as well as serve as a primary prevention for Mycobacterium avium complex (MAC) bacteremia or disseminated infections (in adults, adolescents, and children with advanced HIV infection).

pharmacology

Clarithromycin is a macrolide antibiotic whose spectrum of activity includes many gram-positive (Staphylococcus aureus, S. pneumoniae, and S. pyogenes) and gram-negative aerobic bacteria (Haemophilus influenzae, H. parainfluenzae, and Moraxella catarrhalis), many anaerobic bacteria, some mycobacteria, and some other organisms including Mycoplasma, Ureaplasma, Chlamydia, Toxoplasma, and Borrelia. Other aerobic bacteria that clarithromycin has activity against include C. pneumoniae and M. pneumoniae. Clarithromycin has an in-vitro activity that is similar or greater than that of erythromycin against erythromycin-susceptible organisms. Clarithromycin is usually bacteriostatic, but may be bactericidal depending on the organism and the drug concentration.

mechanism of action

Clarithromycin is first metabolized to 14-OH clarithromycin, which is active and works synergistically with its parent compound. Like other macrolides, it then penetrates bacteria cell wall and reversibly binds to domain V of the 23S ribosomal RNA of the 50S subunit of the bacterial ribosome, blocking translocation of aminoacyl transfer-RNA and polypeptide synthesis. Clarithromycin also inhibits the hepatic microsomal CYP3A4 isoenzyme and P-glycoprotein, an energy-dependent drug efflux pump.

toxicity

Symptoms of toxicity include diarrhea, nausea, abnormal taste, dyspepsia, and abdominal discomfort. Transient hearing loss with high doses has been observed. Pseudomembraneous colitis has been reported with clarithromycin use. Allergic reactions ranging from urticaria and mild skin eruptions to rare cases of anaphylaxis and Stevens-Johnson syndrome have also occurred. Rare cases of severe hepatic dysfunctions also have been reported. Hepatic failure is usually reversible, but fatalities have been reported. Clarithromycin may also cause tooth decolouration which may be removed by dental cleaning. Fetal abnormalities, such as cardiovascular defects, cleft palate and fetal growth retardation, have been observed in animals. Clarithromycin may cause QT prolongation.

biotransformation

Hepatic - predominantly metabolized by CYP3A4 resulting in numerous drug interactions.

absorption

Clarithromycin is well-absorbed, acid stable and may be taken with food.

half life

3-4 hours

route of elimination

After a 250 mg tablet every 12 hours, approximately 20% of the dose is excreted in the urine as clarithromycin, while after a 500 mg tablet every 12 hours, the urinary excretion of clarithromycin is somewhat greater, approximately 30%.

drug interactions

Acenocoumarol: The macrolide, clarithromycin, may increase the anticoagulant effect of acenocoumarol.

Alprazolam: The macrolide, clarithromycin, may increase the effect of the benzodiazepine, alprazolam.

Aminophylline: Clarithromycin may increase the effect amd toxicity of aminophylline.

Amiodarone: Increased risk of cardiotoxicity and arrhythmias

Anisindione: The macrolide, clarithromycin, may increase the anticoagulant effect of anisindione.

Aprepitant: The CYP3A4 inhibitor, clarithromycin, may increase the effect and toxicity of aprepitant.

Artemether: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Astemizole: Increased risk of cardiotoxicity and arrhythmias

Atazanavir: Atazanavir may increase serum level of clarithromycin.

Atorvastatin: The macrolide, clarithromycin, may increase the toxicity of the statin, atorvastatin.

Bretylium: Increased risk of cardiotoxicity and arrhythmias

Bromazepam: Clarithromycin, a strong CYP3A4 inhibitor, may increase the serum concentration of bromazepam by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of bromazepam if clarithromycin is initiated, discontinued or dose changed. Dosage adjustments may be required.

Buspirone: Clarithromycin may increase the effect and toxicity of buspirone.

Carbamazepine: Clarithromycin may decrease the metabolism of carbamazepine. Monitor for changes in the therapeutic or adverse effects of carbamazepine if clarithromycin is initiated, discontinued or dose changed.

Cerivastatin: The macrolide, clarithromycin, may increase the toxicity of the statin, cerivastatin.

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Citalopram: Possible serotoninergic syndrome with this combination

Colchicine: Severe colchicine toxicity can occur

Cyclosporine: The macrolide, clarithromycin, may increase the effect of cyclosporine.

Dantrolene: Clarithromycin may increase the serum concentration of dantrolene by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of dantrolene if clarithromycin is initiated, discontinued or dose changed.

Darifenacin: This potent CYP3A4 inhibitor slows darifenacin/solifenacin metabolism

Darunavir: Increased levels of clarithromycin

Diazepam: The macrolide, clarithromycin, may increase the effect of the benzodiazepine, diazepam.

Dicumarol: The macrolide, clarithromycin, may increase the anticoagulant effect of dicumarol.

Digoxin: The macrolide, clarithromycin, may increase the effect of digoxin in 10% of patients.

Dihydroergotamine: Risk of ergotism and severe ischemia with this association

Disopyramide: Increased risk of cardiotoxicity and arrhythmias

Dofetilide: Increased risk of cardiotoxicity and arrhythmias

Dyphylline: Increases the effect and toxicity of theophylline

Efavirenz: Efavirenz decreases levels of clarithromycin

Eletriptan: The macrolide, clarithromycin, may increase the effect and toxicity of eletriptan.

Eplerenone: The macrolide, clarithromycin, may increase the effect and toxicity of eplerenone.

Ergotamine: Risk of ergotism and severe ischemia with this association

Erlotinib: This CYP3A4 inhibitor increases levels/toxicity of erlotinib

Everolimus: The macrolide, clarithromycin, may increase the serum concentration and toxicity of everolimus.

Fluoxetine: Possible serotoninergic syndrome with this combination

Fosphenytoin: Clarithromycin may increase the therapeutic and adverse effects of fosphenytoin.

Gefitinib: This CYP3A4 inhibitor increases levels/toxicity of gefitinib

Imatinib: The macrolide, clarithromycin, may increase the serum concentration of imatinib.

Indinavir: Indinavir may decrease the effectiveness of clarithromycin by decreasing the formatin of the active metabolite, 14-hydroxy-clarithromycin. Clarithromycin may increase the serum concentration of indinavir. Indinavir may increase the serum concentration of clarithromycin. Consider alternate therapy or monitor the efficacy and adverse effects of both agents more closely during concomitant therapy.

Itraconazole: The macrolide, clarithromycin, may increase the effect and toxicity of itraconazole.

Lovastatin: The macrolide, clarithromycin, may increase the toxicity of the statin, lovastatin.

Methylprednisolone: The macrolide, clarithromycin, may increase the effect of corticosteroid, methylprednisolone.

Methysergide: Risk of ergotism and severe ischemia with this association

Midazolam: The macrolide, clarithromycin, may increase the effect of the benzodiazepine, midazolam.

Oxtriphylline: Clarithromycin may increase the effect and toxicity of oxtriphylline.

Phenytoin: Clarithromycin may increase the therapeutic and adverse effects of phenytoin.

Pimozide: Increased risk of cardiotoxicity and arrhythmias

Quetiapine: The macrolide, clarithromycin, may increase the effect and toxicity of quetiapine.

Quinidine: Increased risk of cardiotoxicity and arrhythmias

Quinidine barbiturate: Increased risk of cardiotoxicity and arrhythmias

Quinupristin: This combination presents an increased risk of toxicity

Ranolazine: Clarithromycin, a strong CYP3A4 inhibitor, may increase the serum level of ranolazine. Concomitant therapy is contraindicated.

Repaglinide: Clarithromycin may increase the effect of repaglinide.

Rifabutin: The rifamycin, rifabutin, may decrease the effect of the macrolide, clarithromycin.

Rifampin: The rifamycin, rifampin, may decrease the effect of the macrolide, clarithromycin.

Sertraline: Possible serotoninergic syndrome with this combination

Sildenafil: Increases the effect and toxicity of sildenafil

Simvastatin: The macrolide, clarithromycin, may increase the toxicity of the statin, simvastatin.

Sirolimus: The macrolide, clarithromycin, may increase the serum concentration of sirolimus.

Solifenacin: This potent CYP3A4 inhibitor slows darifenacin/solifenacin metabolism

Sotalol: Increased risk of cardiotoxicity and arrhythmias

Sunitinib: Possible increase in sunitinib levels

Tacrolimus: Additive QTc-prolongation may occur increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution. The macrolide antibiotic, Clarithromycin, may also increase the blood concentration of Tacrolimus.

Tadalafil: Clarithromycin may reduce the metabolism of Tadalafil. Concomitant therapy should be avoided if possible due to high risk of Tadalafil toxicity.

Tamoxifen: Clarithromycin may increase the serum concentration of Tamoxifen by decreasing its metabolism. Monitor for increased adverse/toxic effects of Tamoxifen.

Tamsulosin: Clarithromycin, a CYP3A4 inhibitor, may decrease the metabolism and clearance of Tamsulosin, a CYP3A4 substrate. Monitor for changes in therapeutic/adverse effects of Tamsulosin if Clarithromycin is initiated, discontinued, or dose changed.

Telithromycin: Co-administration may result in altered plasma concentrations of Clarithromycin and/or Telithromycin. Consider alternate therapy or monitor the therapeutic/adverse effects of both agents.

Temsirolimus: Clarithromycin may inhibit the metabolism and clearance of Temsirolimus. Concomitant therapy should be avoided.

Teniposide: The strong CYP3A4 inhibitor, Clarithromycin, may decrease the metabolism and clearance of Teniposide, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Teniposide if Clarithromycin is initiated, discontinued or dose changed.

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Theophylline: Clarithromycin may increase the therapeutic and adverse effects of theophylline.

Thiothixene: May cause additive QTc-prolonging effects. Increased risk of ventricular arrhythmias. Consider alternate therapy. Thorough risk:benefit assessment is required prior to co-administration.

Tiagabine: The strong CYP3A4 inhibitor, Clarithromycin, may decrease the metabolism and clearance of Tiagabine, a CYP3A4 substrate. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Tiagabine if Clarithromycin is initiated, discontinued or dose changed.

Tipranavir: The concentrations of Tipranavir and Clarithromycin increase during concomitant therapy. Dose adjustments are required for patients with renal impairment.

Tolterodine: Clarithromycin may decrease the metabolism and clearance of Tolterodine. Adjust Tolterodine dose and monitor for efficacy and toxicity.

Topotecan: The p-glycoprotein inhibitor, Clarithromycin, may increase the bioavailability of oral Topotecan. A clinically significant effect is also expected with IV Topotecan. Concomitant therapy should be avoided.

Toremifene: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Consider alternate therapy. A thorough risk:benefit assessment is required prior to co-administration.

Tramadol: Clarithromycin may increase Tramadol toxicity by decreasing Tramadol metabolism and clearance.

Trazodone: The CYP3A4 inhibitor, Clarithromycin, may increase Trazodone efficacy/toxicity by decreasing Trazodone metabolism and clearance. Consider alternate therapy or monitor for changes in Trazodone efficacy/toxicity if Clarithromycin is initiated, discontinued or dose changed.

Triazolam: The macrolide, clarithromycin, may increase the effect of the benzodiazepine, triazolam.

Trimipramine: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Clarithromycin, a strong CYP3A4 inhibitor, may also decrease the metabolism and clearance of Trimipramine, a CYP3A4 substrate. Concomitant therapy should be used with caution.

Valproic Acid: The macrolide antibiotic, Erythromycin, may increase the serum concentratin of Valproic acid. Consider alternate therapy or monitor for changes in Valproic acid therapeutic and adverse effects if Clarithromycin is initiated, discontinued or dose changed.

Vardenafil: Clarithromycin, a strong CYP3A4 inhibitor, may reduce the metabolism and clearance of Vardenafil. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of Vardenafil.

Venlafaxine: Clarithromycin, a CYP3A4 inhibitor, may decrease the metabolism and clearance of Venlafaxine, a CYP3A4 substrate. Monitor for changes in therapeutic/adverse effects of Venlafaxine if Clarithromycin is initiated, discontinued, or dose changed.

Verapamil: Clarithromycin, a strong CYP3A4 inhibitor, may increase the serum concentration of Veramapil, a CYP3A4 substrate, by decreasing its metabolism and clearance. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Verapamil if Clarithromycin is initiated, discontinued or dose changed.

Vilazodone: CYP3A4 Inhibitors (Strong) may increase the serum concentration of Vilazodone. imit maximum adult vilazodone dose to 20 mg/day in patients receiving strong CYP3A4 inhibitors.

Vinblastine: Clarithromycin, a CYP3A4 and p-glycoprotein inhibitor, may increase the Vinblastine serum concentration and distribution in certain cells. Consider alternate therapy to avoid Vinblastine toxicity. Monitor for changes in the therapeutic/adverse effects of Vinblastine if Clarithromycin is initiated, discontinued or dose changed.

Vincristine: Clarithromycin, a CYP3A4 and p-glycoprotein inhibitor, may increase the Vincristine serum concentration and distribution in certain cells. Consider alternate therapy to avoid Vincristine toxicity. Monitor for changes in the therapeutic and adverse effects of Vincristine if Clarithromycin is initiated, discontinued or dose changed.

Vinorelbine: Clarithromycin, a CYP3A4 and p-glycoprotein inhibitor, may increase the Vinorelbine serum concentration and distribution in certain cells. Consider alternate therapy to avoid Vinorelbine toxicity. Monitor for changes in the therapeutic and adverse effects of Vinorelbine if Clarithromycin is initiated, discontinued or dose changed.

Voriconazole: Additive QTc prolongation may occur. Voriconazole, a strong CYP3A4 inhibitor, may increase the serum concentration of clarithromycin by decreasing its metabolism. Clarithromycin may increase the serum concentration of voriconazole by decreasing its metabolism. Consider alternate therapy or monitor for QTc prolongation and changes in the therapeutic and adverse effects of both agents if concomitant therapy is initiated, discontinued or dose changed.

Vorinostat: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Warfarin: The macrolide, clarithromycin, may increase the anticoagulant effect of warfarin.

Zidovudine: Clarithromycin may decrease the serum concentration of zidovudine. Increased myelosuppression in mice has been observed. Consider staggering doses during concomitant therapy and closely monitor response to zidovudine therapy.

Ziprasidone: Additive QTc-prolonging effects may increase the risk of severe arrhythmias. Concomitant therapy is contraindicated.

Zolpidem: Clarithromycin, a strong CYP3A4 inhibitor, may increase the serum concentration of zolpidem by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zolpidem if clarithromycin is initiated, discontinued or dose changed.

Zonisamide: Clarithromcyin, a strong CYP3A4 inhibitor, may increase the serum concentration of zonisamide by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zonisamide if clarithromycin is initiated, discontinued or dose changed.

Zopiclone: Clarithromycin, a strong CYP3A4 inhibitor, may increase the serum concentration of zopiclone by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zopiclone if clarithromycin is initiated, discontinued or dose changed.

Zuclopenthixol: Additive QTc prolongation may occur. Consider alternate therapy or use caution and monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).