Tizanidine
In a pharmacokinetic study, systemic exposure of tizanidine (4 mg single dose) was significantly increased (Cmax 7-fold, AUC 10-fold) when the drug was given concomitantly with ciprofloxacin (500 mg bid for 3 days). The hypotensive and sedative effects of tizanidine were also potentiated. Concomitant administration of tizanidine and ciprofloxacin is contraindicated (see CONTRAINDICATIONS).
Theophylline
As with some other quinolones, concurrent administration of ciprofloxacin with theophylline may lead to elevated serum concentrations of theophylline and prolongation of its elimination half-life. This may result in increased risk of theophylline-related adverse reactions. (See WARNINGS.) If concomitant use cannot be avoided, serum levels of theophylline should be monitored and dosage adjustments made as appropriate.
Other Xanthine Derivatives
Some quinolones, including ciprofloxacin, have also been shown to interfere with the metabolism of caffeine. This may lead to reduced clearance of caffeine and a prolongation of its serum half-life. On concurrent administration of ciprofloxacin and caffeine or pentoxifylline containing products, elevated serum concentrations of these xanthine derivatives were reported.
Chelation Complex Foundation
Concurrent administration of a quinolone, including ciprofloxacin, with multivalent cation-containing products such as magnesium/aluminum antacids, polymeric phosphate binders (for example, sevelamer, lanthanum carbonate), sucralfate, didanosine chewable/buffered tablets or pediatric powder, other highly buffered drugs, or products containing calcium, iron, or zinc may substantially decrease its absorption, resulting in serum and urine levels considerably lower than desired. (See DOSAGE AND ADMINISTRATIONfor concurrent administration of these agents with ciprofloxacin.)
Histamine H2-receptor antagonists appear to have no significant effect on the bioavailability of ciprofloxacin.
Omeprazole
Concomitant administration of a single tablet dose of 500 mg ciprofloxacin and once-daily administration of 20 mg omeprazole pretreatment for 4 days resulted in a 16% reduction of mean Cmax and mean AUC of ciprofloxacin.
Phenytoin
Altered serum levels of phenytoin (increased and decreased) have been reported in patients receiving concomitant ciprofloxacin.
Glyburide
The concomitant administration of ciprofloxacin with the sulfonylurea glyburide has, on rare occasions, resulted in severe hypoglycemia.
Metronidazole
The serum concentrations of ciprofloxacin and metronidazole were not altered when these two drugs were given concomitantly.
Cyclosporine
Some quinolones, including ciprofloxacin, have been associated with transient elevations in serum creatinine in patients receiving cyclosporine concomitantly.
Oral Anti-coagulants
Simultaneous administration of ciprofloxacin with an oral anticoagulant may augment the effect of the anticoagulant. The risk may vary with the underlying infections, age and general status of the patient so that the contribution of ciprofloxacin to the increase in INR (international normalized ratio) is difficult to assess. Prothromin time and INR should be monitored frequently during and shortly after co-administration of ciprofloxacin with an oral anticoagulant (for example, warfarin).
Probenecid
Probenecid interferes with renal tubular secretion of ciprofloxacin and produces an increase in the level of ciprofloxacin in the serum. This should be considered if patients are receiving both drugs concomitantly.
Methotrexate
Renal tubular transport of methotrexate may be inhibited by concomitant administration of ciprofloxacin potentially leading to increased plasma levels of methotrexate. This might increase the risk of methotrexate associated toxic reactions. Therefore, patients under methotrexate therapy should be carefully monitored when concomitant ciprofloxacin therapy is indicated.
Metoclopramide
Metoclopramide significantly accelerates the absorption of oral ciprofloxacin resulting in shorter time to reach maximum plasma concentrations. No significant effect was observed on the bioavailability of ciprofloxacin.
Duloxetine
In clinical studies it was demonstrated that concomitant use of duloxetine with strong inhibitors of the CYP450 1A2 isozyme such as fluvoxamine, may result in a 5-fold increase in mean AUC and a 2.5-fold increase in mean Cmax of duloxetine. Although no clinical data are available on a possible interaction with ciprofloxacin, similar effects can be expected upon concomitant administration.
NSAIDs
Non-steroidal anti-inflammatory drugs (but not acetyl salicylic acid) in combination of very high doses of quinolones have been shown to provoke convulsions in pre-clinical studies.
Ropinirole
In a study conducted in 12 patients with Parkinson’s disease who were administered 6 mg ropinirole once daily with 500 mg ciprofloxacin twice-daily, the mean Cmax and mean AUC of ropinirole were increase by 60% and 84%, respectively. Monitoring for ropinirole-related side effects and appropriate dose adjustment of ropinirole is recommended during and shortly after co-administration with ciprofloxacin (see WARNINGS , Cytochrome P450).
Lidocaine
In a study conducted in 9 healthy volunteers, concomitant use of 1.5 mg/kg IV lidocaine with 500 mg ciprofloxacin twice daily, resulted in an increase of lidocaine Cmax and AUC by 12% and 26%, respectively. Although lidocaine treatment was well tolerated at this elevated exposure, a possible interaction with ciprofloxacin and an increase in side effects related to lidocaine may occur upon concomitant administration.
Clozapine
Following concomitant administration of 250 mg ciprofloxacin with 304 mg clozapine for 7 days, serum concentrations of clozapine and N-desmethylclozapine were increased by 29% and 31%, respectively. Careful monitoring of clozapine associated adverse effects and appropriate adjustment of clozapine dosage during and shortly after co-administration with ciprofloxacin are advised (see WARNINGS ).
Sildenafil
Following concomitant administration of a single oral dose of 50 mg sildenafil with 500 mg ciprofloxacin to healthy subjects, the mean Cmax and mean AUC of sildenafil were both increased approximately two-fold. Therefore, sildenafil should be used with caution when co-administered with ciprofloxacin.
Class IA or III Antiarrhythmics
Precaution should be taken when using ciprofloxacin concomitantly with class IA or III antiarrhythmics as ciprofloxacin may have an additive effect on the QT interval (see WARNINGS AND PRECAUTIONS, Geriatric Use).