Clarithromycin is a semi-synthetic macrolide antimicrobial for oral use. Chemically, it is 6- 0 ‑ methylerythromycin. The molecular formula is C 38 H 69 NO 13 , and the molecular weight is 747.96. The structural formula is: Clarithromycin is a white to off-white crystalline powder. It is soluble in acetone, slightly soluble in methanol, ethanol, and acetonitrile, and practically insoluble in water. Clarithromycin tablets, USP are intended for oral administration and contain 250 mg or 500 mg of clarithromycin, USP. In addition, each clarithromycin tablet contains the following inactive ingredients: croscarmellose sodium, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80, povidone, talc, and titanium dioxide. chemicalstructure

Clarithromycin is a macrolide antimicrobial indicated for mild to moderate infections caused by designated, susceptible bacteria in the following: Acute Bacterial Exacerbation of Chronic Bronchitis in Adults Acute Maxillary Sinusitis Community-Acquired Pneumonia Pharyngitis/Tonsillitis Uncomplicated Skin and Skin Structure Infections Acute Otitis Media in Pediatric Patients Treatment and Prophylaxis of Disseminated Mycobacterial Infections Helicobacter pylori Infection and Duodenal Ulcer Disease in Adults Limitations of Use To reduce the development of drug-resistant bacteria and maintain the effectiveness of clarithromycin tablets and other antibacterial drugs, clarithromycin tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria

Acute Bacterial Exacerbation of Chronic Bronchitis Clarithromycin tablets are indicated in adults for the treatment of mild to moderate infections caused by susceptible isolates due to Haemophilus influenzae , Haemophilus parainfluenzae , Moraxella catarrhalis , or Streptococcus pneumoniae

Acute Maxillary Sinusitis Clarithromycin tablets are indicated for the treatment of mild to moderate infections caused by susceptible isolates due to Haemophilus influenzae , Moraxella catarrhalis , or Streptococcus pneumoniae

Community-Acquired Pneumonia Clarithromycin tablets are indicated for the treatment of mild to moderate infections caused by susceptible isolates due to: Haemophilus influenzae (in adults) Mycoplasma pneumoniae, Streptococcus pneumoniae, Chlamydophila pneumoniae (in adults and pediatric patients) 1.4 Pharyngitis/Tonsillitis Clarithromycin tablets are indicated for the treatment of mild to moderate infections caused by susceptible isolates due to Streptococcus pyogenes as an alternative in individuals who cannot use first line therapy

Uncomplicated Skin and Skin Structure Infections Clarithromycin tablets are indicated for the treatment of mild to moderate infections caused by susceptible isolates due to Staphylococcus aureus , or S treptococcus pyogenes

Acute Otitis Media Clarithromycin tablets are indicated in pediatric patients for the treatment of mild to moderate infections caused by susceptible isolates due to Haemophilus influenzae , Moraxella catarrhalis , or Streptococcus pneumoniae

Treatment and Prophylaxis of Disseminated Mycobacterial Infections Clarithromycin tablets are indicated for the treatment of mild to moderate infections caused by susceptible isolates due to Mycobacterium avium or Myc obacterium intracellulare in patients with advanced HIV infection

Helicobacter pylori Infection and Duodenal Ulcer Disease Clarithromycin tablets are given in combination with other drugs in adults as described below to eradicate H. pylori . The eradication of H. pylori has been demonstrated to reduce the risk of duodenal ulcer recurrence . Clarithromycin tablets in combination with amoxicillin and PREVACID (lansoprazole) or PRILOSEC (omeprazole) delayed-release capsules, as triple therapy, are indicated for the treatment of patients with H. pylori infection and duodenal ulcer disease (active or five-year history of duodenal ulcer) to eradicate H. pylori . Clarithromycin tablets in combination with PRILOSEC (omeprazole) capsules are indicated for the treatment of patients with an active duodenal ulcer associated with H. pylori infection. Regimens which contain clarithromycin tablets as the single antibacterial agent are more likely to be associated with the development of clarithromycin resistance among patients who fail therapy. Clarithromycin-containing regimens should not be used in patients with known or suspected clarithromycin resistant isolates because the efficacy of treatment is reduced in this setting

Limitations of Use There is resistance to macrolides in certain bacterial infections caused by Streptococcus pneumoniae and Staphylococcus aureus . Susceptibility testing should be performed when clinically indicated

Usage To reduce the development of drug-resistant bacteria and maintain the effectiveness of clarithromycin and other antibacterial drugs, clarithromycin tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Clarithromycin tablets, USP (white, oval shaped, film-coated tablets) 250 mg: debossed GG C6 on one side and plain on the reverse side 500 mg: debossed GG C9 on one side and plain on the reverse side Tablets: 250 mg and 500 mg

Adults : clarithromycin tablets 250 mg or 500 mg every 12 hours for 7 to 14 days H. pylori eradication (in combination with lansoprazole/amoxicillin, omeprazole/amoxicillin, or omeprazole): clarithromycin tablets 500 mg every 8 or 12 hours for 10 to 14 days. See full prescribing information (FPI) for additional information. Pediatric Patients : clarithromycin 15 mg/kg/day divided every 12 hours for 10 days Mycobacterial Infections : clarithromycin tablets 500 mg every 12 hours; clarithromycin tablets 7.5 mg/kg up to 500 mg every 12 hours in pediatric patients Reduce dose in moderate renal impairment with concomitant atazanavir or ritonavir-containing regimens and in severe renal impairment 2.1 Important Administration Instructions Clarithromycin tablets may be given with or without food

Adult Dosage The recommended dosages of clarithromycin tablets for the treatment of mild to moderate infections in adults are listed in Table 1 . Table 1. Adult Dosage Guidelines Infection Clarithromycin Tablets Dosage (every 12 hours) Duration (days) Acute bacterial exacerbation of chronic bronchitis 250 to 500 mg 7 † -14 Acute maxillary sinusitis 500 mg 14 Community-acquired pneumonia 250 mg 7 ǂ -14 Pharyngitis/Tonsillitis 250 mg 10 Uncomplicated skin and skin structure infections 250 mg 7-14 Treatment and prophylaxis of disseminated Mycobacterium avium disease 500 mg § - H.pylori eradication to reduce the risk of duodenal ulcer recurrence with amoxicillin and omeprazole or lansoprazole 500 mg 10-14 H.pylori eradication to reduce the risk of duodenal ulcer recurrence with omeprazole 500 mg every 8 hours 14 * For M. catarrhalis and S. pneumoniae use 250 mg. For H. influenzae and H. parainfluenzae , use 500 mg. † For H parainfluenzae , the duration of therapy is 7 days. ǂ For H. influenzae , the duration of therapy is 7 days. § Clarithromycin therapy should continue if clinical response is observed. Clarithromycin can be discontinued when the patient is considered at low risk of disseminated infection

Combination Dosing Regimens for H. pylori Infection Triple therapy: clarithromycin/lansoprazole/amoxicillin The recommended adult dosage is 500 mg clarithromycin tablets, 30 mg lansoprazole, and 1 gram amoxicillin, all given every 12 hours for 10 or 14 days . Triple therapy: clarithromycin/omeprazole/amoxicillin The recommended adult dosage is 500 mg clarithromycin tablets, 20 mg omeprazole, and 1 gram amoxicillin; all given every 12 hours for 10 days. In patients with an ulcer present at the time of initiation of therapy, an additional 18 days of omeprazole 20 mg once daily is recommended for ulcer healing and symptom relief . Dual therapy: clarithromycin/omeprazole The recommended adult dosage is 500 mg clarithromycin tablets given every 8 hours and 40 mg omeprazole given once every morning for 14 days. An additional 14 days of omeprazole 20 mg once daily is recommended for ulcer healing and symptom relief

Pediatric Dosage The recommended daily dosage is 15 mg/kg/day divided every 12 hours for 10 days (up to the adult dose). Refer to dosage regimens for mycobacterial infections in pediatric patients for additional dosage information

Dosage Regimens for Mycobacterial Infections For the treatment of disseminated infection due to Mycobacterium avium complex (MAC), clarithromycin tablets are recommended as the primary agents. Clarithromycin tablets should be used in combination with other antimycobacterial drugs (e.g. ethambutol) that have shown in vitro activity against MAC or clinical benefit in MAC treatment . Adult Patients For treatment and prophylaxis of mycobacterial infections in adults, the recommended dose of clarithromycin tablets is 500 mg every 12 hours. Pediatric Patients For treatment and prophylaxis of mycobacterial infections in pediatric patients, the recommended dose is 7.5 mg/kg every 12 hours up to 500 mg every 12 hours. . Clarithromycin tablets therapy should continue if clinical response is observed. Clarithromycin tablets can be discontinued when the patient is considered at low risk of disseminated infection

Dosage Adjustment in Patients with Renal Impairment See Table 2 for dosage adjustment in patients with moderate or severe renal impairment with or without concomitant atazanavir or ritonavir-containing regimens . Table 2. Clarithromycin Tablets Dosage Adjustments in Patients with Renal Impairment Recommended Clarithromycin Tablets Dosage Reduction Patients with severe renal impairment (CL cr of <30 mL/min) Reduce the dosage of clarithromycin tablets by 50% Patients with moderate renal impairment (CL cr of 30 to 60 mL/min) taking concomitant atazanavir or ritonavir-containing regimens Reduce the dosage of clarithromycin tablets by 50% Patients with severe renal impairment (CL cr of <30 mL/min) taking concomitant atazanavir or ritonavir-containing regimens Reduce the dosage of clarithromycin tablets by 75% 2.7 Dosage Adjustment Due to Drug Interactions Decrease the dose of clarithromycin tablets by 50 % when co-administered with atazanavir . Dosage adjustments for other drugs when co-administered with clarithromycin tablets may be recommended due to drug interactions .

Severe Acute Hypersensitivity Reactions : Discontinue clarithromycin tablets if occurs QT Prolongation : Avoid clarithromycin tablets in patients with known QT prolongation or receiving drugs known to prolong the QT interval, ventricular arrhythmia ( torsades de pointes ), hypokalemia/hypomagnesemia, significant bradycardia, or taking Class IA or III antiarrhythmics Hepatotoxicity : Discontinue if signs and symptoms of hepatitis occur Serious adverse reactions can occur due to drug interactions of clarithromycin tablets with colchicine, some lipid-lowering agents, some calcium channel blockers, and other drugs Risk of all-cause mortality one year or more after the end of treatment in patients with coronary artery disease. Balance this potential risk with the treatment benefits when prescribing clarithromycin tablets in these patients Clostridium difficile associated diarrhea (CDAD) : Evaluate if diarrhea occurs Embryo-Fetal Toxicity : Based on animal findings, clarithromycin tablets is not recommended for use in pregnant women except in clinical circumstances where no alternative therapy is appropriate Exacerbation of myasthenia gravis has been reported in patients receiving clarithromycin tablets therapy 5.1 Severe Acute Hypersensitivity Reactions In the event of severe acute hypersensitivity reactions, such as anaphylaxis, Stevens-Johnson Syndrome, toxic epidermal necrolysis, drug rash with eosinophilia and systemic symptoms (DRESS), Henoch-Schonlein purpura, and acute generalized exanthematous pustulosis, discontinue clarithromycin tablets therapy immediately and institute appropriate treatment

QT Prolongation Clarithromycin tablets have been associated with prolongation of the QT interval and infrequent cases of arrhythmia. Cases of torsades de pointes have been spontaneously reported during postmarketing surveillance in patients receiving clarithromycin tablets. Fatalities have been reported. Avoid clarithromycin tablets in the following patients: patients with known prolongation of the QT interval, ventricular cardiac arrhythmia, including torsades de pointes patients receiving drugs known to prolong the QT interval • patients with ongoing proarrhythmic conditions such as uncorrected hypokalemia or hypomagnesemia,clinically significant bradycardia and in patients receiving Class IA (e.g., quinidine, procainamide,disopyramide) or Class III (e.g., dofetilide, amiodarone, sotalol) antiarrhythmic agents. Elderly patients may be more susceptible to drug-associated effects on the QT interval

Hepatotoxicity Hepatic dysfunction, including increased liver enzymes, and hepatocellular and/or cholestatic hepatitis, with or without jaundice, has been reported with clarithromycin. This hepatic dysfunction may be severe and is usually reversible. In some instances, hepatic failure with fatal outcome has been reported and generally has been associated with serious underlying diseases and/or concomitant medications. Symptoms of hepatitis can include anorexia, jaundice, dark urine, pruritus, or tender abdomen. Discontinue clarithromycin tablets immediately if signs and symptoms of hepatitis occur

Serious Adverse Reactions Due to Concomitant Use with Other Drugs Drugs metabolized by CYP3A4: Serious adverse reactions have been reported in patients taking clarithromycin tablets concomitantly with CYP3A4 substrates. These include colchicine toxicity with colchicine; markedly increased transaminases with lomitapide; rhabdomyolysis with simvastatin, lovastatin, and atorvastatin; hypoglycemia and cardiac arrhythmias (e.g., torsades de pointes) with disopyramide; and hypotension and acute kidney injury with calcium channel blockers metabolized by CYP3A4 (e.g., verapamil, amlodipine, diltiazem, nifedipine). Most reports of acute kidney injury with calcium channel blockers metabolized by CYP3A4 involved elderly patients 65 years of age or older. Use clarithromycin tablets with caution when administered concurrently with medications that induce the cytochrome CYP3A4 enzyme. The use of clarithromycin with lomitapide, simvastatin, lovastatin, ergotamine, or dihydroergotamine is contraindicated . Colchicine: Life-threatening and fatal drug interactions have been reported in patients treated with clarithromycin and colchicine. Clarithromycin is a strong CYP3A4 inhibitor and this interaction may occur while using both drugs at their recommended doses. If co-administration of clarithromycin tablets and colchicine is necessary in patients with normal renal and hepatic function, reduce the dose of colchicine. Monitor patients for clinical symptoms of colchicine toxicity. Concomitant administration of clarithromycin tablets and colchicine is contraindicated in patients with renal or hepatic impairment . Lomitapide: Concomitant use of clarithromycin with lomitapide is contraindicated . Lomitapide is metabolized by CYP3A4, and concomitant treatment with clarithromycin increases the plasma concentration of lomitapide, which increases the risk of elevation in transaminases . If treatment with clarithromycin cannot be avoided, therapy with lomitapide must be suspended during the course of treatment. HMG-CoA Reductase Inhibitors (statins): Concomitant use of clarithromycin tablets with lovastatin or simvastatin is contraindicated as these statins are extensively metabolized by CYP3A4, and concomitant treatment with clarithromycin increases their plasma concentration, which increases the risk of myopathy, including rhabdomyolysis. Cases of rhabdomyolysis have been reported in patients taking clarithromycin concomitantly with these statins. If treatment with clarithromycin tablets cannot be avoided, therapy with lovastatin or simvastatin must be suspended during the course of treatment. Exercise caution when prescribing clarithromycin tablets with atorvastatin or pravastatin. In situations where the concomitant use of clarithromycin tablets with atorvastatin or pravastatin cannot be avoided, atorvastatin dose should not exceed 20 mg daily and pravastatin dose should not exceed 40 mg daily. Use of a statin that is not dependent on CYP3A metabolism (e.g. fluvastatin) can be considered. It is recommended to prescribe the lowest registered dose if concomitant use cannot be avoided. Oral Hypoglycemic Agents/Insulin: The concomitant use of clarithromycin tablets and oral hypoglycemic agents and/or insulin can result in significant hypoglycemia. With certain hypoglycemic drugs such as nateglinide, pioglitazone, repaglinide and rosiglitazone, inhibition of CYP3A enzyme by clarithromycin may be involved and could cause hypoglycemia when used concomitantly. Careful monitoring of glucose is recommended . Quetiapine: Use quetiapine and clarithromycin concomitantly with caution. Co-administration could result in increased quetiapine exposure and quetiapine related toxicities such as somnolence, orthostatic hypotension, altered state of consciousness, neuroleptic malignant syndrome, and QT prolongation. Refer to quetiapine prescribing information for recommendations on dose reduction if co-administered with CYP3A4 inhibitors such as clarithromycin . Oral Anticoagulants: There is a risk of serious hemorrhage and significant elevations in INR and prothrombin time when clarithromycin is co-administered with warfarin. Monitor INR and prothrombin times frequently while patients are receiving clarithromycin tablets and oral anticoagulants concurrently . Benzodiazepines: Increased sedation and prolongation of sedation have been reported with concomitant administration of clarithromycin and triazolobenzodiazepines, such as triazolam and midazolam

All-Cause Mortality in Patients With Coronary Artery Disease 1 to 10 Years After Clarithromycin Exposure In one clinical trial evaluating treatment with clarithromycin on outcomes in patients with coronary artery disease, an increase in risk of all-cause mortality one year or more after the end of treatment was observed in patients randomized to receive clarithromycin. 1 Clarithromycin for treatment of coronary artery disease is not an approved indication. The cause of the increased risk has not been established. Other epidemiologic studies evaluating this risk have shown variable results . Consider balancing this potential risk with the treatment benefits when prescribing Clarithromycin in patients who have suspected or confirmed coronary artery disease

Clostridium difficile Associated Diarrhea Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including clarithromycin tablets, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile . C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibacterial use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents. If CDAD is suspected or confirmed, ongoing antibacterial use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibacterial treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated

Embryo-Fetal Toxicity Based on findings from animal studies, Clarithromycin is not recommended for use in pregnant women except in clinical circumstances where no alternative therapy is appropriate. If clarithromycin tablets are used during pregnancy, or if pregnancy occurs while the patient is taking this drug, the patient should be apprised of the potential hazard to the fetus. Clarithromycin demonstrated adverse effects on pregnancy outcome and/or embryo fetal development, including fetal malformations, in pregnant animals administered oral clarithromycin

Exacerbation of Myasthenia Gravis Exacerbation of symptoms of myasthenia gravis and new onset of symptoms of myasthenic syndrome has been reported in patients receiving clarithromycin tablets therapy

Development of Drug Resistant Bacteria Prescribing clarithromycin tablets in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

Co-administration of clarithromycin tablets is known to inhibit CYP3A, and a drug primarily metabolized by CYP3A may be associated with elevations in drug concentrations that could increase or prolong both therapeutic and adverse effects of the concomitant drug. Clarithromycin tablets should be used with caution in patients receiving treatment with other drugs known to be CYP3A enzyme substrates, especially if the CYP3A substrate has a narrow safety margin (e.g., carbamazepine) and/or the substrate is extensively metabolized by this enzyme. Adjust dosage when appropriate and monitor serum concentrations of drugs primarily metabolized by CYP3A closely in patients concurrently receiving clarithromycin. Table 8. Clinically Significant Drug Interactions with Clarithromycin Tablets Drugs That Are Affected By Clarithromycin Tablets Drug(s) with Pharmacokinetics Affected by Clarithromycin Tablets Recommendation Comments Antiarrhythmics: Disopyramide Quinidine Dofetilide Amiodarone Sotalol Procainamide Not Recommended Disopyramide, Quinidine: There have been postmarketing reports of torsades de pointes occurring with concurrent use of clarithromycin and quinidine or disopyramide. Electrocardiograms should be monitored for QTc prolongation during coadministration of clarithromycin with these drugs . Serum concentrations of these medications should also be monitored. There have been spontaneous or published reports of CYP3A based interactions of clarithromycin with disopyramide and quinidine. There have been postmarketing reports of hypoglycemia with the concomitant administration of clarithromycin and disopyramide. Therefore, blood glucose levels should be monitored during concomitant administration of clarithromycin and disopyramide. Digoxin Use With Caution Digoxin: Digoxin is a substrate for P-glycoprotein (Pgp) and clarithromycin is known to inhibit Pgp. When clarithromycin and digoxin are co‑administered, inhibition of Pgp by clarithromycin may lead to increased exposure of digoxin. Elevated digoxin serum concentrations in patients receiving clarithromycin and digoxin concomitantly have been reported in postmarketing surveillance. Some patients have shown clinical signs consistent with digoxin toxicity, including potentially fatal arrhythmias. Monitoring of serum digoxin concentrations should be considered, especially for patients with digoxin concentrations in the upper therapeutic range. Oral Anticoagulants: Warfarin Use With Caution Oral anticoagulants: Spontaneous reports in the postmarketing period suggest that concomitant administration of clarithromycin and oral anticoagulants may potentiate the effects of the oral anticoagulants. Prothrombin times should be carefully monitored while patients are receiving clarithromycin and oral anticoagulants simultaneously . Antiepileptics: Carbamazepine Use With Caution Carbamazepine: Concomitant administration of single doses of clarithromycin and carbamazepine has been shown to result in increased plasma concentrations of carbamazepine. Blood level monitoring of carbamazepine may be considered. Increased serum concentrations of carbamazepine were observed in clinical trials with clarithromycin. There have been spontaneous or published reports of CYP3A based interactions of clarithromycin with carbamazepine. Antifungals: Itraconazole Use With Caution Itraconazole: Both clarithromycin and itraconazole are substrates and inhibitors of CYP3A, potentially leading to a bi-directional drug interaction when administered concomitantly . Clarithromycin may increase the plasma concentrations of itraconazole. Patients taking itraconazole and clarithromycin concomitantly should be monitored closely for signs or symptoms of increased or prolonged adverse reactions. Fluconazole No Dose Adjustment Fluconazole: Anti-Gout Agents: Colchicine (in patients with renal or hepatic impairment) Contraindicated Colchicine: Colchicine is a substrate for both CYP3A and the efflux transporter, P-glycoprotein (Pgp). Clarithromycin and other macrolides are known to inhibit CYP3A and Pgp. The dose of colchicine should be reduced when co-administered with clarithromycin in patients with normal renal and hepatic function . Colchicine (in patients with normal renal and hepatic function) Use With Caution Antipsychotics: Pimozide Contraindicated Pimozide: Quetiapine Lurasidone Quetiapine: Quetiapine is a substrate for CYP3A4, which is inhibited by clarithromycin. Co‑administration with clarithromycin could result in increased quetiapine exposure and possible quetiapine related toxicities. There have been postmarketing reports of somnolence, orthostatic hypotension, altered state of consciousness, neuroleptic malignant syndrome, and QT prolongation during concomitant administration. Refer to quetiapine prescribing information for recommendations on dose reduction if co‑administered with CYP3A4 inhibitors such as clarithromycin. Lurasidone: Antispasmodics: Tolterodine (patients deficient in CYP2D6 activity) Use With Caution Tolterodine: The primary route of metabolism for tolterodine is via CYP2D6. However, in a subset of the population devoid of CYP2D6, the identified pathway of metabolism is via CYP3A. In this population subset, inhibition of CYP3A results in significantly higher serum concentrations of tolterodine. Tolterodine 1 mg twice daily is recommended in patients deficient in CYP2D6 activity (poor metabolizers) when co-administered with clarithromycin. Antivirals: Atazanavir Use With Caution Atazanavir: Both clarithromycin and atazanavir are substrates and inhibitors of CYP3A, and there is evidence of a bi-directional drug interaction . Saquinavir (in patients with decreased renal function) Saquinavir: Both clarithromycin and saquinavir are substrates and inhibitors of CYP3A and there is evidence of a bi-directional drug interaction . Ritonavir Etravirine Ritonavir, Etravirine: . Maraviroc Maraviroc: Clarithromycin may result in increases in maraviroc exposures by inhibition of CYP3A metabolism. See maraviroc prescribing information for dose recommendation when given with strong CYP3A inhibitors such as clarithromycin. Boceprevir (in patients with normal renal function) Didanosine No Dose Adjustment Boceprevir: Both clarithromycin and boceprevir are substrates and inhibitors of CYP3A, potentially leading to a bi-directional drug interaction when co‑administered. No dose adjustments are necessary for patients with normal renal function . Zidovudine Zidovudine: Simultaneous oral administration of clarithromycin immediate-release tablets and zidovudine to HIV-infected adult patients may result in decreased steady-state zidovudine concentrations. Administration of clarithromycin and zidovudine should be separated by at least two hours . The impact of co-administration of clarithromycin extended-release tablets or granules and zidovudine has not been evaluated. Calcium Channel Blockers: Verapamil Use With Caution Verapamil: Hypotension, bradyarrhythmias, and lactic acidosis have been observed in patients receiving concurrent verapamil, . Amlodipine Diltiazem Amlodipine, Diltiazem: Nifedipine Nifedipine: Nifedipine is a substrate for CYP3A. Clarithromycin and other macrolides are known to inhibit CYP3A. There is potential of CYP3A‑mediated interaction between nifedipine and clarithromycin. Hypotension and peripheral edema were observed when clarithromycin was taken concomitantly with nifedipine . Ergot Alkaloids: Ergotamine Dihydroergotamine Contraindicated Ergotamine, Dihydroergotamine: Postmarketing reports indicate that coadministration of clarithromycin with ergotamine or dihydroergotamine has been associated with acute ergot toxicity characterized by vasospasm and ischemia of the extremities and other tissues including the central nervous system . Gastroprokinetic Agents: Cisapride Contraindicated Cisapride: Lipid-lowering agents: Lomitapide Lovastatin Simvastatin Contraindicated Lomitapide, Lovastatin, Simvastatin: Clarithromycin may increase the exposure of these drugs by inhibition of CYP3A metabolism, thereby increasing the risk of toxicities from these drugs Atorvastatin, Pravastatin, Fluvastatin: Atorvastatin Pravastatin Use With Caution Fluvastatin No Dose Adjustment Hypoglycemic Agents: Nateglinide Pioglitazone Repaglinide Rosiglitazone Use With Caution Nateglinide, Pioglitazone, Repaglinide, Rosiglitazone: Insulin Insulin: Immunosuppressants: Cyclosporine Use With Caution Cyclosporine: There have been spontaneous or published reports of CYP3A based interactions of clarithromycin with cyclosporine. Tacrolimus Tacrolimus: There have been spontaneous or published reports of CYP3A based interactions of clarithromycin with tacrolimus. Phosphodiesterase inhibitors: Sildenafil Tadalafil Vardenafil Use With Caution Sildenafil, Tadalafil, Vardenafil: Each of these phosphodiesterase inhibitors is primarily metabolized by CYP3A, and CYP3A will be inhibited by concomitant administration of clarithromycin. Co-administration of clarithromycin with sildenafil, tadalafil, or vardenafil will result in increased exposure of these phosphodiesterase inhibitors. Co-administration of these phosphodiesterase inhibitors with clarithromycin is not recommended. Increased systemic exposure of these drugs may occur with clarithromycin; reduction of dosage for phosphodiesterase inhibitors should be considered . Proton Pump Inhibitors: Omeprazole No Dose Adjustment Omeprazole: The mean 24-hour gastric pH value was 5.2 when omeprazole was administered alone and 5.7 when coadministered with clarithromycin as a result of increased omeprazole exposures . Xanthine Derivatives: Theophylline Use With Caution Theophylline: Clarithromycin use in patients who are receiving theophylline may be associated with an increase of serum theophylline concentrations . Monitoring of serum theophylline concentrations should be considered for patients receiving high doses of theophylline or with baseline concentrations in the upper therapeutic range. Triazolobenzodiazepines and Other Related Benzodiazepines: Midazolam Use With Caution Midazolam: When oral midazolam is co‑administered with clarithromycin, dose adjustments may be necessary and possible prolongation and intensity of effect should be anticipated . Alprazolam Triazolam Triazolam, Alprazolam: Caution and appropriate dose adjustments should be considered when triazolam or alprazolam is co-administered with clarithromycin. There have been postmarketing reports of drug interactions and central nervous system (CNS) effects (e.g., somnolence and confusion) with the concomitant use of clarithromycin and triazolam. Monitoring the patient for increased CNS pharmacological effects is suggested. In postmarketing experience, erythromycin has been reported to decrease the clearance of triazolam and midazolam, and thus, may increase the pharmacologic effect of these benzodiazepines. Temazepam Nitrazepam Lorazepam No Dose Adjustment Temazepam, Nitrazepam, Lorazepam: For benzodiazepines which are not metabolized by CYP3A (e.g., temazepam, nitrazepam, lorazepam), a clinically important interaction with clarithromycin is unlikely. Cytochrome P450 Inducers: Rifabutin Use With Caution Rifabutin: Concomitant administration of rifabutin and clarithromycin resulted in an increase in rifabutin, and decrease in clarithromycin serum levels together with an increased risk of uveitis . Other Drugs Metabolized by CYP3A: Alfentanil Bromocriptine Cilostazol Methylprednisolone Vinblastine Phenobarbital St. John’s Wort Use With Caution There have been spontaneous or published reports of CYP3A based interactions of clarithromycin with alfentanil, methylprednisolone, cilostazol, bromocriptine, vinblastine, phenobarbital, and St. John’s Wort. Other Drugs Metabolized by CYP450 Isoforms Other than CYP3A: Hexobarbital Phenytoin Valproate Use With Caution There have been postmarketing reports of interactions of clarithromycin with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate. Drugs that Affect Clarithromycin Tablets Drug(s) that Affect the Pharmacokinetics of Clarithromycin Tablets Recommendation Comments Antifungals: Itraconazole Use With Caution Itraconazole: Itraconazole may increase the plasma concentrations of clarithromycin. Patients taking itraconazole and clarithromycin concomitantly should be monitored closely for signs or symptoms of increased or prolonged adverse reactions . Antivirals: Atazanavir Use With Caution Atazanavir: When clarithromycin is co-administered with atazanavir, the dose of clarithromycin should be decreased by 50% . Since concentrations of 14-OH clarithromycin are significantly reduced when clarithromycin is co‑administered with atazanavir, alternative antibacterial therapy should be considered for indications other than infections due to Mycobacterium avium complex. Doses of clarithromycin greater than 1000 mg per day should not be co-administered with protease inhibitors. Ritonavir (in patients with decreased renal function) Ritonavir: Since concentrations of 14-OH clarithromycin are significantly reduced when clarithromycin is co-administered with ritonavir, alternative antibacterial therapy should be considered for indications other than infections due to Mycobacterium avium . Doses of clarithromycin greater than 1000 mg per day should not be co-administered with protease inhibitors. Saquinavir (in patients with decreased renal function) Saquinavir: When saquinavir is co-administered with ritonavir, consideration should be given to the potential effects of ritonavir on clarithromycin (refer to ritonavir above) . Etravirine Etravirine: Clarithromycin exposure was decreased by etravirine; however, concentrations of the active metabolite, 14-OH-clarithromycin, were increased. Because 14-OH-clarithromycin has reduced activity against Mycobacterium avium complex (MAC), overall activity against this pathogen may be altered; therefore alternatives to clarithromycin should be considered for the treatment of MAC. Saquinavir (in patients with normal renal function) Ritonavir (in patients with normal renal function) No Dose Adjustment Proton Pump Inhibitors: Omeprazole Use With Caution Omeprazole: Clarithromycin concentrations in the gastric tissue and mucus were also increased by concomitant administration of omeprazole . Miscellaneous Cytochrome P450 Inducers: Efavirenz Nevirapine Rifampicin Rifabutin Rifapentine Use With Caution Inducers of CYP3A enzymes, such as efavirenz, nevirapine, rifampicin, rifabutin, and rifapentine will increase the metabolism of clarithromycin, thus decreasing plasma concentrations of clarithromycin, while increasing those of 14-OH-clarithromycin. Since the microbiological activities of clarithromycin and 14-OH-clarithromycin are different for different bacteria, the intended therapeutic effect could be impaired during concomitant administration of clarithromycin and enzyme inducers. Alternative antibacterial treatment should be considered when treating patients receiving inducers of CYP3A. There have been spontaneous or published reports of CYP3A based interactions of clarithromycin with rifabutin . Co-administration of clarithromycin tablets can alter the concentrations of other drugs. The potential for drug-drug interactions must be considered prior to and during therapy. ( 4 , 5.2 , 5.4 , 7 )