Applies to methenamine: oral tablet.
Serious side effects of Methenamine
Along with its needed effects, methenamine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking methenamine:
Less common
- Skin rash
Rare
- Blood in urine
- lower back pain
- pain or burning while urinating
Other side effects of Methenamine
Some side effects of methenamine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Less common
- Nausea and vomiting
For Healthcare Professionals
Applies to methenamine: compounding powder, oral suspension, oral tablet.
General
This drug was generally well tolerated. Minor side effects have been reported in less than 3.5% of patients and were reversible when the drug was stopped.[Ref]
Dermatologic
Uncommon (0.1% to 1%): Rash, pruritus
Frequency not reported: Generalized skin rash[Ref]
Gastrointestinal
Uncommon (0.1% to 1%): Gastric irritation
Frequency not reported: Nausea, vomiting, upset stomach, stomatitis, gastrointestinal disturbances, diarrhea, abdominal cramping[Ref]
Genitourinary
High doses have been associated with albuminuria, gross hematuria, bladder irritation, and painful/frequent micturition.[Ref]
Uncommon (0.1% to 1%): Bladder irritation
Frequency not reported: Dysuria, hematuria, urinary frequency, albuminuria[Ref]
Hepatic
Frequency not reported: Elevated AST, elevated ALT[Ref]
Hypersensitivity
Frequency not reported: Hypersensitivity reactions[Ref]
Metabolic
Frequency not reported: Anorexia
Ocular
Frequency not reported: Anterior uveitis[Ref]
