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Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Side Effects


Single-Dose Studies

During clinical trials, approximately 9% of patients treated with a single dose of 400 mg of enoxacin for uncomplicated urethral or endocervical gonorrhea reported adverse events.

The most frequently reported events in single-dose trials, without regard to drug relationship, were nausea and vomiting (2%). Events that occurred in less than 1% of patients are listed below.

CENTRAL NERVOUS SYSTEM:  headache, dizziness, somnolence; GASTROINTESTINAL: abdominal pain; GYNECOLOGIC: vaginal moniliasis; SKIN/HYPERSENSITIVITY: rash; LABORATORY ABNORMALITIES: increased AST (SGOT), decreased hemoglobin, decreased hematocrit, eosinophilia, leukocytosis, leukopenia, thrombocytosis, increased urinary protein, increased alkaline phosphatase, increased ALT (SGPT), increased bilirubin, hyperkalemia.

Multiple-Dose Studies

The incidence of adverse events reported by patients in multiple-dose clinical trials, without regard to drug relationship, was 23%. The incidence of drug-related adverse reactions in multiple-dose clinical trials was 16%. Among patients receiving multiple-dose therapy, enoxacin was discontinued because of an adverse event in 3.8% of patients.

The following events were considered likely to be drug-related in patients receiving multiple doses of enoxacin in clinical trials: nausea and/or vomiting 6%, dizziness 2%, headache 1%, abdominal pain 1%, diarrhea 1%, dyspepsia 1%.

The most frequently reported events in all multiple-dose clinical trials, without regard to drug relationship, were as follows: nausea and/or vomiting 8%, dizziness and/or vertigo 3%, headache 2%, diarrhea 2%, abdominal pain 2%, insomnia 1%, dyspepsia 1%, rash 1%, nervousness and/or anxiety 1%, unusual taste 1%, pruritus 1%.

Additional events that occurred in less than 1% of patients but >0.1% of patients are listed below.

BODY AS A WHOLE:  asthenia, fatigue, fever, malaise, back pain, chest pain, edema, chills; GASTROINTESTINAL: flatulence, constipation, dry mouth/throat, stomatitis, anorexia, gastritis, bloody stools; CENTRAL NERVOUS SYSTEM: somnolence, tremor, convulsions, paresthesia, confusion, agitation, depression, syncope, myoclonus, depersonalization, hypertonia; SKIN/HYPERSENSITIVITY: photosensitivity reaction, urticaria, hyperhidrosis, mycotic infection, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome; SPECIAL SENSES: tinnitus, conjunctivitis, visual disturbances including amblyopia; MUSCULOSKELETAL: myalgia, arthralgia; CARDIOVASCULAR: palpitations, tachycardia, vasodilation; RESPIRATORY: dyspnea, cough, epistaxis; HEMIC AND LYMPHATIC: purpura; UROGENITAL: vaginal moniliasis, vaginitis, urinary incontinence, renal failure.

The following adverse events occurred in less than 0.1% of patients in multiple-dose clinical trials but were considered significant: pseudomembranous colitis, hyperkinesia, amnesia, ataxia, hypotonia, psychosis, emotional lability, hallucination, schizophrenic reaction.

LABORATORY CHANGES: The following laboratory abnormalities appeared in ≥1.0% of patients receiving multiple doses of enoxacin: elevated AST (SGOT), elevated ALT (SGPT). It is not known whether these abnormalities were caused by the drug or the underlying conditions.

Worldwide Post-Marketing Experience

The most frequent spontaneously-reported adverse events in the worldwide post-marketing experience with multiple- and single-dose enoxacin use have been rashes, seizures/convulsions, and photosensitivity reactions; however, there is no evidence that the incidences of these events were larger than those observed in the clinical trials population.

Quinolone-class adverse reactions:   Although not reported in completed clinical studies with enoxacin, a variety of adverse events have been reported with other quinolones.

Clinical adverse events include:  erythema nodosum, hepatic necrosis, possible exacerbation of myasthenia gravis, nystagmus, intestinal perforation, hyperpigmentation, interstitial nephritis, polyuria, urinary retention, renal calculi, cardiopulmonary arrest, cerebral thrombosis, and laryngeal or pulmonary edema.

Laboratory adverse events include:  agranulocytosis, elevation of serum triglycerides and/or serum cholesterol, prolongation of the prothrombin time, candiduria, and crystalluria.


Read the Penetrex (enoxacin) Side Effects Center for a complete guide to possible side effects


Bismuth:   Bismuth subsalicylate, given concomitantly with enoxacin or 60 minutes following enoxacin administration, decreased enoxacin bioavailability by approximately 25%. Thus, concomitant administration of enoxacin and bismuth subsalicylate should be avoided.

Caffeine:   Enoxacin is a potent inhibitor of the cytochrome P-450 isozymes responsible for the metabolism of methylxanthines. In a multiple-dose study, enoxacin caused a dose-related increase in the mean elimination half-life of caffeine, thereby decreasing the clearance of caffeine by up to 80% and leading to a five-fold increase in the AUC and the half-life of caffeine. Trough plasma enoxacin levels were also 20% higher when caffeine and enoxacin were administered concomitantly. Caffeine-related adverse effects have occurred in patients consuming caffeine while on therapy with enoxacin. (See WARNINGS.)

Cyclosporine:   Elevated serum levels of cyclosporine have been reported with concomitant use of cyclosporine with other members of the quinolone class.

Digoxin:   Enoxacin may raise serum digoxin levels in some individuals. If signs and symptoms suggestive of digoxin toxicity occur when enoxacin and digoxin are given concomitantly, physicians are advised to obtain serum digoxin levels and adjust digoxin doses appropriately.

Non-steroidal anti-inflammatory agents:   Seizures have been reported in patients taking enoxacin concomitantly with the nonsteroidal anti-inflammatory drug fenbufen. Animal studies also suggest an increased potential for seizures when these two drugs are given concomitantly. Fenbufen is not approved in the United States at this time.

Sucralfate and antacids:   Quinolones form chelates with metal cations. Therefore, administration of quinolones with antacids containing calcium, magnesium, or aluminum; with sucralfate; with divalent or trivalent cations such as iron; or with multivitamins containing zinc may substantially interfere with drug absorption and result in insufficient plasma and tissue quinolone concentrations. Antacids containing aluminum hydroxide and magnesium hydroxide reduce the oral absorption of enoxacin by 75%. The oral bioavailability of enoxacin is reduced by 60% with coadministration of ranitidine. These agents should not be taken for 8 hours before or for 2 hours after enoxacin administration.

Theophylline:   Enoxacin is a potent inhibitor of the cytochrome P-450 isozymes responsible for the metabolism of methylxanthines. Enoxacin interferes with the metabolism of theophylline resulting in a 42% to 74% dose-related decrease in theophylline clearance and a subsequent 260% to 350% increase in serum theophylline levels. Theophylline-related adverse effects have occurred in patients when theophylline and enoxacin were coadministered. (See WARNINGS.)

Warfarin:   Quinolones, including enoxacin, decrease the clearance of R-warfarin, the less active isomer of racemic warfarin. Enoxacin does not affect the clearance of the active S-isomer, and changes in clotting time have not been observed when enoxacin and warfarin were coadministered. Nevertheless, the prothrombin time or other suitable coagulation test should be monitored when warfarin or its derivatives and enoxacin are given concomitantly.

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 12/8/2004

Side Effects

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