Generic Name: methenamine (meth-EN-a-meen)
Brand Name: Examples include Hiprex and Urex
Methenamine is used for:
Preventing urinary tract infections.
Methenamine is a urinary antiseptic. It works by concentrating in the urine as formaldehyde, which kills bacteria in the urine.
Do NOT use methenamine if:
- you are allergic to any ingredient in methenamine
- you have kidney problems
- you are taking a sulfonamide (eg, sulfamethizole)
Contact your doctor or health care provider right away if any of these apply to you.
Before using methenamine:
Some medical conditions may interact with methenamine. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:
- if you are pregnant, planning to become pregnant, or are breast-feeding
- if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
- if you have allergies to medicines, foods, or other substances
- if you have diarrhea, a stomach infection, liver or kidney problems, or gout, or you are severely dehydrated
Some MEDICINES MAY INTERACT with methenamine. Tell your health care provider if you are taking any other medicines, especially any of the following:
- Sulfonamides (eg, sulfamethizole) because they may decrease methenamine's effectiveness
This may not be a complete list of all interactions that may occur. Ask your health care provider if methenamine may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.
How to use methenamine:
Use methenamine as directed by your doctor. Check the label on the medicine for exact dosing instructions.
- Take methenamine by mouth with or without food. If stomach upset occurs, take with food to reduce stomach irritation.
- Before you begin using an antacid, check with your doctor or pharmacist.
- If you miss a dose of methenamine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.
Ask your health care provider any questions you may have about how to use methenamine.
Important safety information:
- It is important that your urine be acidic while you are taking methenamine. Check with your doctor to see if you should eat or avoid certain foods to keep your urine acidic.
- Methenamine may interfere with certain lab tests. Be sure your doctor and lab personnel know you are taking methenamine.
- Lab tests, including urine pH, may be performed while you use methenamine. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
- PREGNANCY and BREAST-FEEDING: It is not known if methenamine can cause harm to the fetus. If you become pregnant, contact your doctor. You will need to discuss the benefits and risks of using methenamine while you are pregnant. Methenamine is found in breast milk. If you are or will be breast-feeding while you use methenamine, check with your doctor. Discuss any possible risks to your baby.
Possible side effects of methenamine:
All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:
Seek medical attention right away if any of these SEVERE side effects occur:
Nausea; upset stomach.
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blood in the urine.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.
If OVERDOSE is suspected:
Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately.Proper storage of methenamine:
Store methenamine at room temperature, between 59 and 86 degrees F (15 and 30 degrees C). Store away from heat, moisture, and light. Do not store in the bathroom. Keep methenamine out of the reach of children and away from pets.
- If you have any questions about methenamine, please talk with your doctor, pharmacist, or other health care provider.
- Methenamine is to be used only by the patient for whom it is prescribed. Do not share it with other people.
- If your symptoms do not improve or if they become worse, check with your doctor.
- Check with your pharmacist about how to dispose of unused medicine.
This information should not be used to decide whether or not to take methenamine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about methenamine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to methenamine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using methenamine.
Disclaimer: This information should not be used to decide whether or not to take this medicine or any other medicine. Only your health care provider has the knowledge and training to decide which medicines are right for you. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from your health care provider. You must talk with your healthcare provider for complete information about the risks and benefits of using this medicine.