Fluoroquinolone drug interactions

Factors directly related to the drug selection include an inappropriate selection of drug, dosage, or route of administration. Malabsorption of a drug product because of GI disease (e.g., short-bowel syndrome) or a drug interaction (e.g., complexation of fluoroquinolones with multivalent cations resulting in reduced absorption) may lead to potentially subtherapeu-tic serum concentrations. 

All quinolones interact with multivalent cations, forming chelation complexes resulting in reduced absorption. Major offenders are antacids vitamins containing calcium and iron can also be problematic. All fluoroquinolones interact with warfarin, didanosine (ddi), and phenytoin, resulting in decreased absorption or metabolism. Ciprofloxacin and other second-generation drugs interact with theophylline by decreasing its clearance, which leads to theophylline toxicity. 

Polk RE. Drug-drug interactions with ciprofloxacin and other fluoroquinolones. Am J Med 1989 87(suppl 5A) 76S-81S. 

Fish DN. Fluoroquinolone adverse effects and drug interactions. Pharmacotherapy 2001 21(10 Pt 2) S253-72. 

Marchbanks CR. Drug-drug interactions with fluoroquinolones. Pharmacotherapy 1993 13(2 Pt 2) S23-8. 

Warfarin The exact warfarin-quinolone drug interaction is unknown. Reduction of intestinal flora responsible for vitamin K production by antibiotics is probable, as are deaeased metabolism and clearance of warfarin due to CYP450 inhibition by the quinolones. Multivalent cations such as aluminum, magnesium, calcium, iron, zinc, and multivitamins with minerals may chelate with fluoroquinolones and decease the oral absorption if administered concurrently. 

Many drug interactions—toxicity is increased by erythromycin, cimetidine, and fluoroquinolones. 

ADRAC. Fluoroquinolone antibiotics interactions with warfarin. Aust Adverse Drug React... 

Pharmacokinetic interaction between fluoroquinolones and other drugs 98MI5. 

Discuss the uses, general drug action, contraindications, precautions, interactions, and adverse reactions of the fluoroquinolones and aminoglycosides. 

Absorption of antimicrobial agents such as fluoroquinolones and tetracyclines that can be bound by divalent and trivalent cations potentially could be compromised by administration with EN formulas containing these cations. The fluoroquinolones (e.g., levofloxacin and ciprofloxacin) have been best studied in this regard, and results of studies are not consistent. Mechanisms for an interaction between fluoroquinolones and EN formulas other than chelation by cations have been postulated.40 Some institutions hold tube feedings for 30 to 60 minutes or more before and after enteral dosages of fluoroquinolones. Because ciprofloxacin absorption has been shown to be decreased with jejunal administration, this drug probably should not be given by jejunal tube.41... 

Kang, J., Wang, L., Chen, X.L., Higgle, D.J. and Rampe, D. (2001) Interactions of a series of fluoroquinolone antibacterial drugs with the human cardiac K+ channel HERG. Molecular Pharmacology, 29, 122-126. 

Drugs that may affect amiodarone include hydantoins, cholestyramine, fluoroquinolones, rifamycins, ritonavir, and cimetidine. Drugs that may be affected by amiodarone include anticoagulants, beta-blockers, calcium channel blockers, cyclosporine, dextromethorphan, digoxin, disopyramide, fentanyl, flecainide, hydantoins, lidocaine, methotrexate, procainamide, quinidine, and theophylline. Drug/Lab test interactions Amiodarone alters the results of thyroid function tests, causing an increase in serum T4 and serum reverse T3 levels and a decline in... 

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