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Flavoxate Side Effects

The most commonly reported side effects of flavoxate include peripheral swelling, anaemia, and fibromyalgia, based on 707 FDA adverse event reports from 2004 to 2025. 13.0% of reports found the drug to be ineffective.

Flavoxate side effects

Percentages show how often each reaction appears relative to total reports for flavoxate.

1
Peripheral Swelling19.2%136
2
Anaemia17.5%124
3
Fibromyalgia16.5%117
4
Blood Cholesterol Increased16.4%116
5
Infection16.3%115
6
Liver Function Test Abnormal16.1%114
7
Herpes Zoster16.1%114
8
Leukopenia16.1%114
9
Synovitis16.0%113
10
Arthritis15.8%112
11
Joint Swelling15.4%109
12
Soft Tissue Disorder14.0%99
13
Drug Ineffective13.0%92
14
Pneumonia Viral12.7%90
15
Arthralgia12.2%86

These are voluntary reports and do not establish that flavoxate caused these reactions.

Report severity

90.5%Serious640 reports
42.7%Hospitalizations302 reports
9.6%Fatal68 reports

Seriousness is determined by the reporter, not by OpenClaim.

Flavoxate drug interactions

Other drugs that appear in adverse event reports alongside flavoxate. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Adalimumab17.7%125
2
Abatacept16.1%114
3
Tocilizumab15.8%112
4
Tofacitinib15.8%112
5
Methotrexate15.6%110
6
Leflunomide15.6%110
7
Etanercept15.3%108
8
Infliximab14.9%105
9
Hydroxychloroquine-sulfate14.9%105
10
Rituximab7.4%52
11
Mycophenolate4.7%33
12
Diclofenac3.5%25
13
Metoprolol3.3%23
14
Acetaminophen3.0%21
15
Prednisone2.8%20

Taken alongside

1
Acetaminophen33.1%234
2
Furosemide28.7%203
3
Levothyroxine-sodium22.8%161
4
Lorazepam22.6%160
5
Pantoprazole-sodium21.1%149
6
Diphenhydramine19.8%140
7
Trimethoprim19.7%139
8
Loperamide-hydrochloride18.7%132
9
Morphine-sulfate18.2%129
10
Estradiol17.8%126
11
Hydromorphone-hydrochloride17.8%126
12
Triamcinolone17.3%122
13
Cyclosporine16.8%119
14
Orphenadrine16.4%116
15
Darifenacin-hydrobromide16.1%114

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports flavoxate side effects

65.3% of flavoxate adverse event reports involve female patients and 28.1% involve male patients. The largest age group is elderly at 60%. These figures reflect who reports side effects, not underlying risk.

Sex

Female65.3%
Male28.1%
Unknown6.5%

Age group

< 21.0%
2–110.2%
12–170.2%
18–6439.1%
65+59.5%

What is flavoxate used for

Conditions and purposes for which patients were taking flavoxate when the adverse event was reported.

Abdominal PainAcute TonsillitisBenign Prostatic HyperplasiaBladder DisorderBladder ObstructionBladder PainBladder SpasmBladder DisorderBladder PainBladder SpasmCholinergic SyndromeColitisCystitisCystitis InterstitialCystitis

Showing 15 of 56 indications

Flavoxate brand names and reporting trend

Quarterly reports (20042025)

20052010201520202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking flavoxate with another medication?

Ask OpenClaim about your specific drug combination. Get a sourced report using FDA data, drug labels, and medical literature.