Does Floxin (ofloxacin) cause side effects?

Floxin (ofloxacin) is a fluoroquinolone antibiotic used to treat bacterial infections that cause bronchitis, pneumonia, chlamydia, gonorrhea, skin infections, urinary tract infections (UTIs), and prostate infections.

Floxin stops the multiplication of bacteria by inhibiting the reproduction and repair of their genetic material (DNA). The brand name Floxin is discontinued. 

Common side effects of Floxin include

Serious side effects of Floxin include

Drug interactions of Floxin include theophylline because Floxin reduces the elimination of theophylline, elevating blood levels of theophylline.

  • Floxin can enhance the action of the anticoagulant warfarin and increase the risk of bleeding.
  • Both high and low blood sugar levels have been reported, especially in patients with diabetes who were also receiving insulin or other medications used to lower the blood sugar.
  • Sucralfate, iron, multivitamins containing zinc, didanosine, and antacids containing calcium, magnesium, or aluminum should not be taken within two hours before or after taking Floxin.

There are no adequate and well-controlled studies of Floxin in pregnant women. Floxin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Floxin is secreted in breast milk and can cause adverse events in the infant. Floxin should be avoided in breastfeeding mothers, as safe use has not been established.

What are the important side effects of Floxin (ofloxacin)?

The most common side effects of ofloxacin include:

Allergic reactions have been described, such as hives and anaphylaxis (shock).

Other important side effects include symptoms of nervous system stimulation, such as:

Ofloxacin may cause low or high blood sugar levels especially in people with diabetes who are taking insulin or oral hypoglycemic drugs.

Patients taking ofloxacin can develop skin sensitivity (photsensitivity) to direct sunlight and should avoid exposure to sunlight or use sun protection and sunscreens.

Ofloxacin as well as other antibiotics in the fluoroquinolone class of antibiotics, has been associated with tendinitis and even rupture of tendons, particularly the Achilles tendon. Some physicians recommend that patients discontinue vigorous exercise while they are taking fluoroquinolone antibiotics.

Ofloxacin should be used with caution in patients with central nervous system diseases such as seizures because rare seizures have been reported in patients receiving this medication.

Ofloxacin should be avoided in children and adolescents under 18 years of age, as safe use in these patients have not been established.

Many antibiotics, including ofloxacin, can alter the normal bacteria in the colon and encourage overgrowth of a bacterium responsible for the development of inflammation of the colon (Clostridium difficile, pseudomembranous colitis). Pseudomembranous colitis can cause fever, abdominal pain, diarrhea, and sometimes even shock.

Ofloxacin should not be used in patients with myasthenia gravis because it can increase muscle weakness.

Floxin (ofloxacin) side effects list for healthcare professionals

The following is a compilation of the data for ofloxacin based on clinical experience with both the oral and intravenous formulations. The incidence of drug-related adverse reactions in patients during Phase 2 and 3 clinical trials was 11%. Among patients receiving multiple-dose therapy, 4% discontinued ofloxacin due to adverse experiences.

In clinical trials, the following events were considered likely to be drug-related in patients receiving multiple doses of ofloxacin:

  • nausea 3%,
  • insomnia 3%,
  • headache 1%,
  • dizziness 1%,
  • diarrhea 1%,
  • vomiting 1%,
  • rash 1%,
  • pruritus 1%,
  • external genital pruritus in women 1%,
  • vaginitis 1%,
  • dysgeusia 1%.

In clinical trials, the most frequently reported adverse events, regardless of relationship to drug, were:

  • nausea 10%,
  • headache 9%,
  • insomnia 7%,
  • external genital pruritus in women 6%,
  • dizziness 5%,
  • vaginitis 5%,
  • diarrhea 4%,
  • vomiting 4%.

In clinical trials, the following events, regardless of relationship to drug, occurred in 1 to 3% of patients:

Additional events, occurring in clinical trials at a rate of less than 1%, regardless of relationship to drug, were:

Body as a whole: asthenia, chills, malaise, extremity pain, pain, epistaxis

Cardiovascular System: cardiac arrest, edema, hypertension, hypotension, palpitations, vasodilation

Gastrointestinal System: Dyspepsia

Genital/Reproductive System: burning, irritation, pain and rash of the female genitalia; dysmenorrhea; menorrhagia; metrorrhagia

Musculoskeletal System: arthralgia, myalgia

Nervous System: seizures, anxiety, cognitive change, depression, dream abnormality, euphoria, hallucinations, paresthesia, syncope, vertigo, tremor, confusion

Nutritional/Metabolic: thirst, weight loss

Respiratory System: respiratory arrest, cough, rhinorrhea

Skin/Hypersensitivity: angioedema, diaphoresis, urticaria, vasculitis

Special Senses: decreased hearing acuity, tinnitus, photophobia

Urinary System: dysuria, urinary frequency, urinary retention

The following laboratory abnormalities appeared in ≥ 1.0% of patients receiving multiple doses of ofloxacin. It is not known whether these abnormalities were caused by the drug or the underlying conditions being treated.

Hematopoietic: anemia, leukopenia, leukocytosis, neutropenia, neutrophilia, increased band forms, lymphocytopenia, eosinophilia, lymphocytosis, thrombocytopenia, thrombocytosis, elevated ESR

Hepatic: elevated: alkaline phosphatase, AST (SGOT), ALT (SGPT) Serum chemistry: hyperglycemia, hypoglycemia, elevated creatinine, elevated BUN Urinary: glucosuria, proteinuria, alkalinuria, hyposthenuria, hematuria, pyuria

Post-Marketing Adverse Events

Additional adverse events, regardless of relationship to drug, reported from worldwide marketing experience with quinolones, including ofloxacin:


Cardiovascular System: cerebral thrombosis, pulmonary edema, tachycardia, hypotension/shock, syncope, torsades de pointes

Endocrine/Metabolic: hyper-or hypoglycemia, especially in diabetic patients on insulin or oral hypoglycemic agents.

Gastrointestinal System: hepatic dysfunction including: hepatic necrosis, jaundice (cholestatic or hepatocellular), hepatitis; intestinal perforation; hepatic failure (including fatal cases); pseudomembranous colitis (the onset of pseudomembranous colitis symptoms may occur during or after antimicrobial treatment), GI hemorrhage; hiccough, painful oral mucosa, pyrosis.

Genital/Reproductive System: vaginal candidiasis

Hematopoietic: anemia, including hemolytic and aplastic; hemorrhage, pancytopenia, agranulocytosis, leukopenia, reversible bone marrow depression, thrombocytopenia, thrombotic thrombocytopenic purpura, petechiae, ecchymosis/bruising.

Musculoskeletal: tendinitis/rupture; weakness; rhabdomyolysis.

Nervous System: nightmares; suicidal thoughts or acts, disorientation, psychotic reactions, paranoia; phobia, agitation, restlessness, aggressiveness/hostility, manic reaction, emotional lability; peripheral neuropathy, ataxia, incoordination; exacerbation of: myasthenia gravis and extrapyramidal disorders; dysphasia, lightheadedness.

Respiratory System: dyspnea, bronchospasm, allergic pneumonitis, stridor.

Skin/Hypersensitivity: anaphylactic (-toid) reactions/shock; purpura, serum sickness, erythema multiforme/Stevens-Johnson Syndrome, erythema nodosum, exfoliative dermatitis, hyperpigmentation, toxic epidermal necrolysis, conjunctivitis, photosensitivity/phototoxicity reaction, vesiculobullous eruption.

Special Senses: diplopia, nystagmus, blurred vision, disturbances of: taste, smell, hearing and equilibrium, usually reversible following discontinuation

Urinary System: anuria, polyuria, renal calculi, renal failure, interstitial nephritis, hematuria.


Hematopoietic: prolongation of prothrombin time

Serum chemistry: acidosis, elevation of: serum triglycerides, serum cholesterol, serum potassium, liver function tests including: GGTP, LDH, bilirubin

Urinary: albuminuria, candiduria

In clinical trials using multiple-dose therapy, ophthalmologic abnormalities, including cataracts and multiple punctate lenticular opacities, have been noted in patients undergoing treatment with other quinolones. The relationship of the drugs to these events is not presently established.

Crystalluria and cylindruria have been reported with other quinolones.

What drugs interact with Floxin (ofloxacin)?

Antacids, Sucralfate, Metal Cations, Multivitamins

Quinolones form chelates with alkaline earth and transition metal cations. 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 or with Videx (didanosine) may substantially interfere with the absorption of quinolones resulting in systemic levels considerably lower than desired.

These agents should not be taken within the two-hour period before or within the two-hour period after ofloxacin administration.


Interactions between ofloxacin and caffeine have not been detected.


Cimetidine has demonstrated interference with the elimination of some quinolones. This interference has resulted in significant increases in half-life and AUC of some quinolones. The potential for interaction between ofloxacin and cimetidine has not been studied.


Elevated serum levels of cyclosporine have been reported with concomitant use of cyclosporine with some other quinolones. The potential for interaction between ofloxacin and cyclosporine has not been studied.

Drugs metabolized by Cytochrome P450 enzymes

Most quinolone antimicrobial drugs inhibit cytochrome P450 enzyme activity. This may result in a prolonged half-life for some drugs that are also metabolized by this system (e.g., cyclosporine, theophylline/methylxanthines, warfarin) when co-administered with quinolones. The extent of this inhibition varies among different quinolones. 

Non-steroidal anti-inflammatory drugs

The concomitant administration of a non-steroidal anti-inflammatory drug with a quinolone, including ofloxacin, may increase the risk of CNS stimulation and convulsive seizures.


The concomitant use of probenecid with certain other quinolones has been reported to affect renal tubular secretion. The effect of probenecid on the elimination of ofloxacin has not been studied.


Steady-state theophylline levels may increase when ofloxacin and theophylline are administered concurrently. As with other quinolones, concomitant administration of ofloxacin may prolong the half-life of theophylline, elevate serum theophylline levels, and increase the risk of theophylline-related adverse reactions.

Theophylline levels should be closely monitored and theophylline dosage adjustments made, if appropriate, when ofloxacin is co-administered. Adverse reactions (including seizures) may occur with or without an elevation in the serum theophylline level.


Some quinolones have been reported to enhance the effects of the oral anticoagulant warfarin or its derivatives. Therefore, if a quinolone antimicrobial is administered concomitantly with warfarin or its derivatives, the prothrombin time or other suitable coagulation test should be closely monitored.

Antidiabetic Agents (e.g., insulin, glyburide/glibenclamide)

Since disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concurrently with quinolones and an antidiabetic agent, careful monitoring of blood glucose is recommended when these agents are used concomitantly.

Interaction with Laboratory or Diagnostic Testing

Some quinolones, including ofloxacin, 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.


Floxin (ofloxacin) is a fluoroquinolone antibiotic used to treat bacterial infections that cause bronchitis, pneumonia, chlamydia, gonorrhea, skin infections, urinary tract infections (UTIs), and prostate infections. Common side effects of Floxin include nausea, vomiting, diarrhea, insomnia, headache, dizziness, itching, vaginitis in women, allergic reactions such as hives and anaphylaxis (shock), and symptoms of nervous system stimulation (such as anxiety, euphoria, and hallucinations). There are no adequate and well-controlled studies of Floxin in pregnant women. Floxin is secreted in breast milk and can cause adverse events in the infant.

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Medically Reviewed on 8/14/2020
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Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.