Levofloxacin

7 DRUG INTERACTIONS Interacting Drug Interaction Multivalent cation-containing products including antacids, metal cations or didanosine Absorption of levofloxacin is decreased when the tablets are taken within 2 hours of these products. ( 2.4 , 7.1 ) Warfarin Effect may be enhanced. Monitor prothrombin time, INR and watch for bleeding ( 7.2 ) Antidiabetic agents Carefully monitor blood glucose ( 5.13 , 7.3 ) 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 ) and 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.

Levofloxacin tablets are indicated in adults (18 years and older) for infections including nosocomial and community-acquired pneumonia, "acute bacterial sinusitis," "acute bacterial exacerbation of chronic bronchitis," complicated and uncomplicated skin and skin structure infections, "chronic bacterial prostatitis," complicated and uncomplicated urinary tract infections, "acute pyelonephritis," and "inhalational anthrax, post-exposure." The label directs that it be reserved for infections with no alternative treatment when benefits outweigh risks.

2 DOSAGE AND ADMINISTRATION Days 1 through 3: Instill one to two drops in the affected eye(s) every 30 minutes to 2 hours while awake and approximately 4 and 6 hours after retiring. Day 4 through treatment completion: Instill one to two drops in the affected eye(s) every 1 to 4 hours while awake. Days 1 through 3: Instill one to two drops in the affected eye(s) every 30 minutes to 2 hours while awake and approximately 4 and 6 hours after retiring. Day 4 through treatment completion: Instill one to two drops in the affected eye(s) every 1 to 4 hours while awake. (2)

The label states "the most common adverse drug reactions (greater than or equal to 3%) are nausea, headache, diarrhea, insomnia, constipation, and dizziness." Less common but serious reactions include tendon rupture, peripheral neuropathy, seizures and other CNS effects, psychiatric reactions (anxiety, confusion, hallucinations), hypoglycemia (especially with concomitant oral antidiabetic agents), and hypersensitivity reactions including anaphylaxis and severe skin reactions such as Stevens-Johnson syndrome.