Levofloxacin (Page 8 of 17)

7 DRUG INTERACTIONS

7.1 Chelation Agents: Antacids, Sucralfate, Metal Cations, Multivitamins


While the chelation by divalent cations is less marked than with other fluoroquinolones, concurrent administration of levofloxacin tablets with antacids containing magnesium, or aluminum, as well as sucralfate, metal cations such as iron, and multivitamin preparations with zinc may interfere with the gastrointestinal absorption of levofloxacin, resulting in systemic levels considerably lower than desired. Tablets with antacids containing magnesium, aluminum, as well as sucralfate, metal cations such as iron, and multivitamin preparations with zinc or didanosine may substantially interfere with the gastrointestinal absorption of levofloxacin, resulting in systemic levels considerably lower than desired. These agents should be taken at least two hours before or two hours after oral levofloxacin administration.

7.2 Warfarin

No significant effect of levofloxacin on the peak plasma concentrations, AUC, and other disposition parameters for R- and S- warfarin was detected in a clinical study involving healthy volunteers. Similarly, no apparent effect of warfarin on levofloxacin absorption and disposition was observed. However, there have been reports during the postmarketing experience in patients that levofloxacin enhances the effects of warfarin. Elevations of the prothrombin time in the setting of concurrent warfarin and levofloxacin use have been associated with episodes of bleeding. Prothrombin time, International Normalized Ratio (INR), or other suitable anticoagulation tests should be closely monitored if levofloxacin is administered concomitantly with warfarin. Patients should also be monitored for evidence of bleeding [see Adverse Reactions ( 6.3) ; Patient Counseling Information ( 17) ].

7.3 Antidiabetic Agents


Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with fluoroquinolones and an antidiabetic agent. Therefore, careful monitoring of blood glucose is recommended when these agents are co-administered [see Warnings and Precautions ( 5.13); Adverse Reactions ( 6.2) and Patient Counseling Information ( 17)].

7.4 Non-Steroidal Anti-Inflammatory Drugs


The concomitant administration of a non-steroidal anti-inflammatory drug with a fluoroquinolone, including levofloxacin, may increase the risk of CNS stimulation and convulsive seizures [see Warnings and Precautions ( 5.4)].

7.5 Theophylline

No significant effect of levofloxacin on the plasma concentrations, AUC, and other disposition parameters for theophylline was detected in a clinical study involving healthy volunteers. Similarly, no apparent effect of theophylline on levofloxacin absorption and disposition was observed. However, concomitant administration of other fluoroquinolones with theophylline has resulted in prolonged elimination half-life, elevated serum theophylline levels, and a subsequent increase in the risk of theophylline-related adverse reactions in the patient population. Therefore, theophylline levels should be closely monitored and appropriate dosage adjustments made when levofloxacin is co-administered. Adverse reactions, including seizures, may occur with or without an elevation in serum theophylline levels [see Warnings and Precautions ( 5.4)].

7.6 Cyclosporine


No significant effect of levofloxacin on the peak plasma concentrations, AUC, and other disposition parameters for cyclosporine was detected in a clinical study involving healthy volunteers. However, elevated serum levels of cyclosporine have been reported in the patient population when co-administered with some other fluoroquinolones. Levofloxacin C max and k e were slightly lower while T max and t ½ were slightly longer in the presence of cyclosporine than those observed in other studies without concomitant medication. The differences, however, are not considered to be clinically significant. Therefore, no dosage adjustment is required for levofloxacin or cyclosporine when administered concomitantly.

7.7 Digoxin


No significant effect of levofloxacin on the peak plasma concentrations, AUC, and other disposition parameters for digoxin was detected in a clinical study involving healthy volunteers. Levofloxacin absorption and disposition kinetics were similar in the presence or absence of digoxin. Therefore, no dosage adjustment for levofloxacin or digoxin is required when administered concomitantly.

7.8 Probenecid and Cimetidine


No significant effect of probenecid or cimetidine on the C max of levofloxacin was observed in a clinical study involving healthy volunteers. The AUC and t ½ of levofloxacin were higher while CL/F and CL R were lower during concomitant treatment of levofloxacin with probenecid or cimetidine compared to levofloxacin alone. However, these changes do not warrant dosage adjustment for levofloxacin when probenecid or cimetidine is co-administered.

7.9 Interactions with Laboratory or Diagnostic Testing


Some fluoroquinolones, including levofloxacin, may produce false-positive urine screening results for opiates using commercially available immunoassay kits. Confirmation of positive opiate screens by more specific methods may be necessary.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Risk Summary

Published information from case reports, case control studies and observational studies on levofloxacin administered during pregnancy have not identified any drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes.

In animal reproduction studies, oral administration of levofloxacin to pregnant rats and rabbits during organogenesis at doses up to 9.4 times and 1.1 times the maximum recommended human dose (MRHD), respectively, did not result in teratogenicity. Fetal toxicity was seen in the rat study, but was absent at doses up to 1.2 times the maximum recommended human dose ( see Data).

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Data

Animal Data

Levofloxacin was not teratogenic in an embryofetal development study in rats treated during organogenesis with oral doses as high as 810 mg/kg/day which corresponds to 9.4 times the MRHD (based upon doses normalized for total body surface area). The oral dose of 810 mg/kg/day (high dose) to rats caused decreased fetal body weight and increased fetal mortality that was not seen at the next lower dose (mid-dose, 90 mg/kg/day, equivalent to 1.2 times the MRHD (based upon doses normalized for total body surface area).

Maternal toxicity was limited to lower weight gain in the mid and high dose groups. No teratogenicity was observed in an embryofetal development study in rabbits dosed orally during organogenesis with doses as high as 50 mg/kg/day, which corresponds to 1.1 times the MRHD (based upon doses normalized for total body surface area). Maternal toxicity at that dose consisted of lower weight gain and decreased food consumption relative to controls and abortion in four of sixteen dams.

8.2 Lactation

Risk Summary

Published literature reports that levofloxacin is present in human milk following intravenous and oral administration ( see Data). There is no information regarding effects of levofloxacin on milk production or the breastfed infant. Because of the potential risks of serious adverse reactions, in breastfed infants, a lactating woman may consider pumping and discarding breast milk during treatment with levofloxacin and an additional two days (five half-lives) after the last dose. Alternatively, advise a lactating woman that breastfeeding is not recommended during treatment with levofloxacin and for an additional two days (five half-lives) after the last dose [ see Use in Specific Populations ( 8.4) and Clinical Pharmacology ( 12.3) ].

Data

A published literature reports that peak levofloxacin human milk concentration was 8.2 mg/L at 5 hours after dosing in a woman who received 500 mg of intravenous, followed by oral, levofloxacin daily. For an infant fed exclusively with human milk (approximately 900 ml/day), an estimated maximum daily dose of levofloxacin through breastfeeding is 5 mg (i.e., approximately 1% of maternal daily dose). The above data come from a single case and may not be generalizable to the general population of lactating women.

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