Urex (Oral)

Methenamine is part of a group of medicines known as anti-infectives. It is used to help prevent and treat infections in the urinary tract. You can only get methenamine with a prescription from your doctor.

If your symptoms do not get better in a few days, or if they get worse, contact your doctor.

In deciding to use a medicine, you and your doctor will consider the risks of taking the medicine versus the benefits it may provide. For this medicine, the following points should be taken into account:

Allergies

Inform your doctor if you have ever had any unusual or allergic reactions to this medicine or any other medicines. Also, let your healthcare professional know if you have any other allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, carefully read the label or package ingredients.

Pediatric

There is no specific information comparing the use of methenamine in children to its use in other age groups, but this medicine is not expected to cause different side effects or issues in children compared to adults.

Geriatric

Many medicines have not been specifically studied in older adults. Therefore, it may not be clear if they work the same way as in younger adults or if they cause different side effects or problems in older adults. There is no specific information comparing the use of methenamine in the elderly to its use in other age groups.

Breast Feeding

There are no adequate studies to determine the risk to infants when using this medication during breastfeeding. Consider the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Some medicines should never be used together, while in other cases, two different medicines may be used together despite the possibility of an interaction. In such cases, your doctor may want to adjust the dose or take other precautions. When taking this medicine, it is especially important for your healthcare professional to know if you are taking any of the medicines listed below. The following interactions have been chosen based on their potential importance and are not necessarily a complete list.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to prescribe this medication or change some of the other medicines you take.

• Acetazolamide
• Mafenide
• Silver Sulfadiazine
• Sulfabenzamide
• Sulfacetamide
• Sulfacytine
• Sulfadiazine
• Sulfamerazine
• Sulfamethazine
• Sulfamethoxazole
• Sulfanilamide
• Sulfapyridine
• Sulfasalazine
• Sulfathiazole
• Sulfisoxazole
• Zonisamide

Interactions with Food/Tobacco/Alcohol

Some medicines should not be used at or around the time of eating food or certain types of food because interactions may happen. Using alcohol or tobacco with certain medicines may also lead to interactions. The following interactions have been chosen based on their potential importance and are not necessarily a complete list.

Other Medical Problems

Having other medical problems may affect the use of this medicine. Make sure to tell your doctor if you have any other medical issues, especially:

• Dehydration (severe) or
• Kidney disease (severe)—Patients with severe kidney disease who take methenamine may experience increased side effects that affect the kidneys.

• Liver disease (severe)—Patients with severe liver disease who take methenamine may experience increased symptoms of their liver disease.

Along with its needed effects, a medicine 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:

Less common

• Skin rash

Rare

• Blood in urine
• lower back pain
• pain or burning while urinating

Some side effects 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

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

In the U.S.

• Hiprex
• Mandelamine
• Urex

In Canada

• Urasal

Available Dosage Forms:

• Tablet

Therapeutic Class: Antiseptic

Before you start taking this medicine, check your urine with phenaphthazine paper or another test to see if it is acid. Your urine must be acidic (pH 5.5 or below) for this medicine to work properly. If you have any questions about this, check with your health care professional.

The following changes in your diet may help make your urine more acid; however, check with your doctor first if you are on a special diet (for example, for diabetes). Avoid most fruits (especially citrus fruits and juices), milk and other dairy products, and other foods that make the urine less acid. Also, avoid antacids unless otherwise directed by your doctor. Eating more protein and foods such as cranberries (especially cranberry juice with vitamin C added), plums, or prunes may also help. If your urine is still not acid enough, check with your doctor.

If this medicine causes nausea or upset stomach, it may be taken after meals and at bedtime.

For patients taking the dry granule form of this medicine:

• Dissolve the contents of each packet in 2 to 4 ounces of cold water immediately before taking. Stir well. Be sure to drink all the liquid to get the full dose of medicine.

For patients taking the oral liquid form of this medicine:

• Use a specially marked measuring spoon or other device to measure each dose accurately. The average household teaspoon may not hold the right amount of liquid.

For patients taking the enteric-coated tablet form of this medicine:

• Swallow tablets whole. Do not break, crush, or take if chipped.

To help clear up your infection completely, keep taking this medicine for the full time of treatment, even if you begin to feel better after a few days. Do not miss any doses.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

• For the treatment of urinary tract infections: For oral dosage form (methenamine hippurate tablets): Adults and children 12 years of age and over—1 gram two times a day. Take in the morning and the evening. Children up to 6 years of age—Use and dose must be determined by your doctor. Children 6 to 12 years of age—500 milligrams (mg) to 1 gram two times a day. Take in the morning and the evening. For oral dosage form (methenamine mandelate enteric-coated tablets, regular tablets, solution, and suspension): Adults and children 12 years of age and over—1 gram four times a day. Take after meals and at bedtime. Children up to 6 years of age—Dose is based on body weight. The usual dose is 18.3 mg per kilogram (kg) (8.3 mg per pound) of body weight four times a day. Take after meals and at bedtime. Children 6 to 12 years of age—500 mg four times a day. Take after meals and at bedtime.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.