Methenamine

Methenamine

What is Methenamine?

Methenamine may also be used for purposes not listed in this medication guide.

Methenamine side effects

If necessary, get emergency medical helpSigns of an allergic reaction: hives; difficult breathing; Swelling of your face, lips, tongue, or throat.

Methenamine can cause serious side effects. Call your doctor immediately if you have:

• increased urination;

• painful urination;

• blood in your urine; or

• Swelling, shortness of breath.

Common side effects of methenamine can include:

• painful urination;

• nausea, vomiting; or

• Rash, itching.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You can report side effects to FDA at 1-800-FDA-1088.

Warnings

Use only as directed. Tell your doctor if you are taking other medicines or have any other medical conditions or allergies.

Before you take this medicine

You should not use methenamine if you are allergic to it or if you have:

• kidney disease;

• severe liver disease; or

• if you are dehydrated.

Ask a doctor or pharmacist whether it is safe to use methenamine if you have ever had liver problems.

If you are pregnant, ask a doctor before using this medicine.

Don't breastfeed.

How should I take methenamine?

Use exactly as directed on the label or as prescribed by your doctor.

Methenamine works best when your urine has a low pH and is acidic. You can measure your pH at home using urine test strips purchased at the pharmacy. Your doctor may occasionally test your urine to make sure an infection has cleared.

Learn about the foods you should eat or avoid to keep your urine acidic. Your doctor may also prescribe other medicines for you. Drink plenty of fluids.

Follow your doctor's dietary and medication instructions closely.

Continue taking this medicine even if your symptoms improve quickly. Skipping doses could cause your infection to become resistant to medication. Methenamine does not treat viral infections (flu or cold).

This medicine may affect the results of certain medical tests. Tell any doctor who treats you that you are taking methenamine.

Do not use methenamine to treat any condition that has not been evaluated by your doctor.

Do not share this medicine with anyone else, even if they have the same symptoms as you.

Store at room temperature, protected from moisture, heat and light. Keep the bottle tightly closed when not in use.

What happens if I miss a dose?

Take the medicine as soon as possible, but skip the missed dose if it is almost time for the next dose. Do not take two doses at the same time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help hotline at 1-800-222-1222.

What should I avoid while taking methenamine?

Avoid taking additional methenamine as this could cause side effects such as bladder irritation, pain, increased urination and blood in the urine.

What other drugs affect methenamine?

Other medicines can affect methenamine, especially a sulfonamide. Tell your doctor about all other medicines you are taking. This includes prescription and over-the-counter medications, vitamins and herbal products.

More information

Remember to keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medicine only for the prescribed indication.