Urex Side Effects

Generic name: methenamine

Note: This document contains side effect information about methenamine. Some of the dosage forms listed on this page may not apply to the brand name Urex.

Some side effects of Urex may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to methenamine: oral suspension, oral tablet

If you experience any of the following serious side effects, stop taking methenamine (the active ingredient contained in Urex) and seek emergency medical attention or contact your doctor immediately:

• an allergic reaction (shortness of breath; closing of the throat; swelling of the lips, face, or tongue; or hives;

• lower back or side pain;

• blood in urine; or

• increasingly painful or difficult urination.

Other, less serious side effects may be more likely to occur. Continue to take methenamine and talk to your doctor if you experience

• nausea or upset stomach;

• decreased appetite; or

• skin rash.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

For Healthcare Professionals

Applies to methenamine: compounding powder, oral suspension, oral tablet

General

Methenamine (the active ingredient contained in Urex) is generally well tolerated. Minor side effects have been reported in less than 3.5% of patients.

Dermatologic

Dermatologic side effects have included rash and pruritus.

Gastrointestinal

Gastrointestinal side effects have included nausea, vomiting, diarrhea, anorexia, and abdominal cramping.

Genitourinary

Genitourinary side effects have included dysuria, hematuria, and urinary frequency. High doses have been associated with albuminuria, gross hematuria, bladder wall irritation, and painful/frequent micturition.

Hepatic

Methenamine (the active ingredient contained in Urex) is contraindicated in patients with severe liver disease due to the risk of systemic acidosis.

Hepatic side effects have rarely included transient elevations of AST (SGOT) and ALT (SGPT).

Hypersensitivity

Hypersensitivity reactions have included rashes in 1% to 4% of patients.

Respiratory

Respiratory system side effects may occur in patients with a poor gag reflex or a swallow disorder. Methenamine oral suspension has a vegetable base, and should be used with caution in elderly patients and in those with swallow disorders to prevent lipid pneumonia. Long-term therapy with methenamine (the active ingredient contained in Urex) suspension has been associated with lipoid pneumonitis in elderly patients.

Ocular

Ocular side effects have included rare cases of anterior uveitis.

Renal

Renal side effects have been more likely and more severe in patients with mild to moderate renal insufficiency. Methenamine (the active ingredient contained in Urex) is contraindicated in patients with severe renal insufficiency.

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