Chapter 127. Treatment and Prophylaxis of Bacterial Infections (Part 12) Drug Interactions Antimicrobial drugs are a common cause of drug-drug interactions. Table 127-8 lists the most common and best-documented interactions of antibacterial agents with other drugs and characterizes the clinical relevance of these interactions. Coadministration of drugs paired in the tables does not necessarily result in clinically important adverse consequences. Recognition of the potential for an interaction before the administration of an antibacterial agent is crucial to the rational use of these drugs, since adverse consequences can often be prevented if the interaction is anticipated. Table 127-8 is intended only to heighten awareness of the potential for an interaction. Additional sources should be consulted to identify appropriate options. For further discussion of drug interactions, see Chap. 5. Table 127-8 Interactions of Antibacterial Agents with Other Drugs Antibiotic Interacts with Potential Consequence (Clinical Significance a ) Theophylline Theophylline toxicity (1) Erythromycin/clarithromycin/ telithromycin Carbamazepine CNS depression (1) Digoxin Digoxin toxicity (2) Triazolam/mida zolam CNS depression (2) Ergotamine Ergotism (1) Warfarin Bleeding (2) Cyclosporine/ta crolimus Nephrotoxicit y (1) Cisapride Cardiac arrhythmias (1) Statins b Rhabdomyoly sis (2) Valproate Valproate toxicity (2) Vincristine/vinb lastine Excess neurotoxicity (2) Quinupristin/dalfopristin Similar to erythromycin c Fluoroquinolones Theophylline Theophylline toxicity (2) d Antacids/sucralf ate/iron Subtherapeuti c antibiotic levels (1) Tetracycline Antacids/sucralf ate/iron Subtherapeuti c antibiotic levels (1) Phenytoin Phenytoin toxicity (2) Trimethoprim- sulfamethoxazole Oral hypoglycemics Hypoglycemi a (2) Warfarin Bleeding (1) Digoxin Digoxin toxicity (2) Metronidazole Ethanol Disulfiram- like reactions (2) Fluorouracil Bone marrow suppression (1) Warfarin Bleeding (2) Rifampin Warfarin Clot formation (1) Oral contraceptives Pregnancy (1) Cyclosporine/ta crolimus Rejection (1) HIV- 1 protease inhibitors Increased viral load, resistance (1) Nonnucleoside reverse-transcriptase inhibitors Increased viral load, resistance (1) Glucocorticoids Loss of steroid effect (1) Methadone Narcotic withdrawal symptoms (1) Digoxin Subtherapeuti c digoxin levels (1) Itraconazole Subtherapeuti c itraconazole levels (1) Phenytoin Loss of seizure control (1) Statins Hypercholeste rolemia (1) Diltiazem Subtherapeuti c diltiazem levels (1) Verapamil Subtherapeuti c verapamil levels (1) a 1 = a well- documented interaction with clinically important consequences; 2 = an interaction of uncertain frequency but of potential clinical importance. b Lovastatin and simvastatin are most affected; pravastatin and atorvastatin are less prone to clinically important effects. c The macrolide antibiotics and quinupristin/dalfopristin inhibit the same human metabolic enzyme, CYP3A4, and similar interactions are anticipated. d Ciprofloxacin only. Levofloxacin and moxifloxacin do not inhibit theophylline metabolism. Note : New interactions are commonly reported after marketing. Consult the most recent prescribing information for updates. Abbreviation: CNS, central nervous system. . Chapter 127. Treatment and Prophylaxis of Bacterial Infections (Part 12) Drug Interactions Antimicrobial drugs are a common cause of drug-drug interactions. Table 127- 8 lists. lists the most common and best-documented interactions of antibacterial agents with other drugs and characterizes the clinical relevance of these interactions. Coadministration of drugs paired in. Recognition of the potential for an interaction before the administration of an antibacterial agent is crucial to the rational use of these drugs, since adverse consequences can often be prevented