Calcium Interactions

7 DRUG INTERACTIONS The drug interaction of calcium acetate is characterized by the potential of calcium to bind to drugs with anionic functions (e.g., carboxyl, and hydroxyl groups). Calcium acetate may decrease the bioavailability of tetracyclines or fluoroquinolones via this mechanism. There are no empirical data on avoiding drug interactions between calcium acetate and most concomitant drugs. When administering an oral medication with calcium acetate where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy, administer the drug one hour before or three hours after calcium acetate. Monitor blood levels of the concomitant drugs that have a narrow therapeutic range. Patients taking anti-arrhythmic medications for the control of arrhythmias and anti-seizure medications for the control of seizure disorders were excluded from the clinical trials with all forms of calcium acetate. Calcium acetate may decrease the bioavailability of tetracyclines or fluoroquinolones. ( 7 ) When clinically significant drug interactions are expected, administer the drug at least one hour before or at least three hours after calcium acetate or consider monitoring blood levels of the drug. ( 7 ) 7.1 Ciprofloxacin In a study of 15 healthy subjects, a co-administered single dose of 4 calcium acetate tablets, approximately 2.7g, decreased the bioavailability of ciprofloxacin by approximately 50%.

7 DRUG INTERACTIONS See full prescribing information for details regarding concomitant use of atorvastatin calcium with other drugs or grapefruit juice that increase the risk of myopathy and rhabdomyolysis ( 2.5 , 7.1 ). Rifampin: May reduce atorvastatin plasma concentrations. Administer simultaneously with atorvastatin calcium ( 7.2 ). Oral Contraceptives: May increase plasma levels of norethindrone and ethinyl estradiol; consider this effect when selecting an oral contraceptive (7.3 ). Digoxin: May increase digoxin plasma levels; monitor patients appropriately ( 7.3 ). 7.1 Drug Interactions that may Increase the Risk of Myopathy and Rhabdomyolysis with Atorvastatin Calcium Atorvastatin is a substrate of CYP3A4 and transporters (e.g., OATP1B1/1B3, P-gp, or BCRP). Atorvastatin plasma levels can be significantly increased with concomitant administration of inhibitors of CYP3A4 and transporters. Table 2 includes a list of drugs that may increase exposure to atorvastatin and may increase the risk of myopathy and rhabdomyolysis when used concomitantly and instructions for preventing or managing them [see Warnings and Precautions (5.1) and Clinical Pharmacology (12.3) ]. Table 2: Drug Interactions that may Increase the Risk of Myopathy and Rhabdomyolysis with Atorvastatin Cyclosporine or Gemfibrozil Clinical Impact: Atorvastatin plasma levels were significantly increased with concomitant administration of atorvastatin and cyclosporine, an inhibitor of CYP3A4 and OATP1B1 [see Clinical Pharmacology (12.3) ]. Gemfibrozil may cause myopathy when given alone. The risk of myopathy and rhabdomyolysis is increased with concomitant use of cyclosporine or gemfibrozil with atorvastatin. Intervention: Concomitant use of cyclosporine or gemfibrozil with atorvastatin is not recommended. Anti-Viral Medications Clinical Impact: Atorvastatin plasma levels were significantly increased with concomitant administration of atorvastatin with many anti-viral medications, which are inhibitors of CYP3A4 and/or transporters (e.g., BCRP, OATP1B1/1B3, P-gp, MRP2, and/or OAT2) [see Clinical Pharmacology (12.3) ]. Cases of myopathy and rhabdomyolysis have been reported with concomitant use of ledipasvir plus sofosbuvir with atorvastatin. Intervention: Concomitant use of tipranavir plus ritonavir or glecaprevir plus pibrentasvir with atorvastatin is not recommended. In patients taking lopinavir plus ritonavir, or simeprevir, consider the risk/benefit of concomitant use with atorvastatin. In patients taking saquinavir plus ritonavir, darunavir plus ritonavir, fosamprenavir, fosamprenavir plus ritonavir, elbasvir plus grazoprevir or letermovir, do not exceed atorvastatin 20 mg. In patients taking nelfinavir, do not exceed atorvastatin 40 mg [see Dosage and Administration (2.5) ]. Consider the risk/benefit of concomitant use of ledipasvir plus sofosbuvir with atorvastatin. Monitor all patients for signs and symptoms of myopathy particularly during initiation of therapy and during upward dose titration of either drug. Examples: Tipranavir plus ritonavir, glecaprevir plus pibrentasvir, lopinavir plus ritonavir, simeprevir, saquinavir plus ritonavir, darunavir plus ritonavir, fosamprenavir, fosamprenavir plus ritonavir, elbasvir plus grazoprevir, letermovir, nelfinavir, and ledipasvir plus sofosbuvir. Select Azole Antifungals or Macrolide Antibiotics Clinical Impact: Atorvastatin plasma levels were significantly increased with concomitant administration of atorvastatin with select azole antifungals or macrolide antibiotics, due to inhibition of CYP3A4 and/or transporters [see Clinical Pharmacology (12.3) ]. Intervention: In patients taking clarithromycin or itraconazole, do not exceed atorvastatin 20 mg [see Dosage and Administration (2.5) ]. Consider the risk/benefit of concomitant use of other azole antifungals or macrolide antibiotics with atorvastatin. Monitor all patients for signs and symptoms of myopathy particularly during initiation of therapy and during upward dose titration of either drug. Examples: Erythromycin, clarithromycin, itraconazole, ketoconazole, posaconazole, and voriconazole. Niacin Clinical Impact: Cases of myopathy and rhabdomyolysis have been observed with concomitant use of lipid modifying dosages of niacin ( > 1 gram/day niacin) with atorvastatin. Intervention: Consider if the benefit of using lipid modifying dosages of niacin concomitantly with atorvastatin outweighs the increased risk of myopathy and rhabdomyolysis. If concomitant use is decided, monitor patients for signs and symptoms of myopathy particularly during initiation of therapy and during upward dose titration of either drug. Fibrates (other than Gemfibrozil) Clinical Impact: Fibrates may cause myopathy when given alone. The risk of myopathy and rhabdomyolysis is increased with concomitant use of fibrates with atorvastatin. Intervention: Consider if the benefit of using fibrates concomitantly with atorvastatin outweighs the increased risk of myopathy and rhabdomyolysis. If concomitant use is decided, monitor patients for signs and symptoms of myopathy particularly during initiation of therapy and during upward dose titration of either drug. Colchicine Clinical Impact: Cases of myopathy and rhabdomyolysis have been reported with concomitant use of colchicine with atorvastatin. Intervention: Consider the risk/benefit of concomitant use of colchicine with atorvastatin. If concomitant use is decided, monitor patients for signs and symptoms of myopathy particularly during initiation of therapy and during upward dose titration of either drug. Grapefruit Juice Clinical Impact: Grapefruit juice consumption, especially excessive consumption, more than 1.2 liters/daily, can raise the plasma levels of atorvastatin and may increase the risk of myopathy and rhabdomyolysis. Intervention: Avoid intake of large quantities of grapefruit juice, more than 1.2 liters daily, when taking atorvastatin. 7.2 Drug Interactions that may Decrease Exposure to Atorvastatin Calcium Table 3 presents drug interactions that may decrease exposure to atorvastatin and instructions for preventing or managing them. Table 3: Drug Interactions that may Decrease Exposure to Atorvastatin Rifampin Clinical Impact: Concomitant administration of atorvastatin with rifampin, an inducer of cytochrome P450 3A4 and inhibitor of OATP1B1, can lead to variable reductions in plasma concentrations of atorvastatin. Due to the dual interaction mechanism of rifampin, delayed administration of atorvastatin after administration of rifampin has been associated with a significant reduction in atorvastatin plasma concentrations. Intervention: Administer atorvastatin and rifampin simultaneously. 7.3 Atorvastatin Calcium Effects on Other Drugs Table 4 presents Atorvastatin’s effect on other drugs and instructions for preventing or managing them. Table 4: Atorvastatin Effects on Other Drugs Oral Contraceptives Clinical Impact: Co-administration of atorvastatin and an oral contraceptive increased plasma concentrations of norethindrone and ethinyl estradiol [see Clinical Pharmacology (12.3) ]. Intervention: Consider this when selecting an oral contraceptive for patients taking atorvastatin. Digoxin Clinical Impact: When multiple doses of atorvastatin and digoxin were co-administered, steady state plasma digoxin concentrations increased [see Clinical Pharmacology (12.3) ]. Intervention: Monitor patients taking digoxin appropriately.

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7 DRUG INTERACTIONS Drugs that Affect Electrolyte and/or Fluid Balance : Avoid concomitant use. If concomitant use cannot be avoided, closely monitor electrolyte concentrations and fluid balance. ( 7.1 ) Lithium : Avoid concomitant use. If concomitant use is unavoidable monitor serum lithium concentrations more frequently. ( 7.2 ) Digoxin : Consider reducing the volume or rate of Ringer’s Injection due to the increased risk of digoxin toxicity with calcium-containing solutions. ( 7.3 ) 7.1 Drugs that Affect Electrolyte and/or Fluid Balance Hyperkalemia Administration of Ringer’s Injection to patients concomitantly treated or recently treated with drugs that are associated with hyperkalemia increases the risk of severe and potentially fatal hyperkalemia, especially in the presence of other hyperkalemia risk factors . Avoid use of Ringer’s Injection in patients receiving drugs that are associated with hyperkalemia (e.g., potassium-sparing diuretics, ACE inhibitors, angiotensin II receptor antagonists, or calcineurin inhibitors). If concomitant use cannot be avoided, closely monitor serum potassium concentrations during concomitant use [see Warnings and Precautions (5.4) ]. Hyponatremia Administration of Ringer’s Injection to patients treated concomitantly with drugs associated with hyponatremia may increase the risk of developing hyponatremia. These drugs include diuretics and those that cause SIADH (e.g., arginine vasopressin analogs, certain antiepileptic, psychotropic, or cytotoxic drugs). Avoid use of Ringer’s Injection in patients receiving such drugs. If use cannot be avoided, closely monitor serum sodium concentrations during concomitant use [see Warnings and Precautions (5.5) ] . Hypercalcemia Avoid the use of Ringer’s Injection in patients treated with thiazide diuretics or vitamin D because these drugs can increase the risk of hypercalcemia. If use cannot be avoided, closely monitor serum calcium concentrations during concomitant use [see Warnings and Precautions (5.6) ]. Hypernatremia and Fluid Retention Administration of Ringer’s Injection to patients treated concomitantly with drugs associated with sodium and fluid retention (e.g., corticosteroids or corticotropin) may increase the risk of hypernatremia and volume overload. Avoid use of Ringer’s Injection in patients receiving such drugs. If use cannot be avoided, closely monitor serum electrolytes, fluid balance, and acid-base balance during concomitant use. 7.2 Lithium Renal sodium and lithium clearance may be increased during concomitant use of Ringer’s Injection and lithium and may result in decreased lithium concentrations. Avoid use of Ringer’s Injection in patients receiving lithium. If use cannot be avoided, increase the frequency of monitoring of serum lithium concentrations during concomitant use. 7.3 Digoxin Administration of calcium via use of Ringer’s Injection may increase digoxin’s effects and lead to digoxin toxicity including serious or fatal cardiac arrhythmias. In digoxin-treated patients, consider reducing the volume and/or rate of Ringer’s Injection administration .