Methenamine (Systemic)

Brand Names : Hiprex, Mandelamine, Urex, Hip-Rex

Before Using This Medicine

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For methenamine, the following should be considered:

Allergies - Tell your doctor if you have ever had any unusual or allergic reaction to methenamine. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy - Methenamine has not been studied in either humans or animals. However, individual case reports on the use of methenamine during pregnancy have not shown that this medicine causes birth defects or other problems in humans.

Breast-feeding - Methenamine passes into the breast milk. However, methenamine has not been reported to cause problems in nursing babies.

Children - Although there is no special information comparing use of methenamine in children with use in other age groups, this medicine is not expected to cause different side effects or problems in children than it does in adults.

Older adults - Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing use of methenamine in the elderly with use in other age groups.

Other medicines - Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking methenamine, it is especially important that your health care professional knows if you are taking any of the following:

• Sulfamethizole (use of methenamine with this medicine may damage your kidneys)
• Thiazide diuretics (water pills) or
• Urinary alkalizers (medicine that makes the urine less acid, such as acetazolamide [e.g., Diamox], calcium- and/or magnesium-containing antacids, dichlorphenamide [e.g., Daranide], methazolamide [e.g., Neptazane], potassium or sodium citrate and/or citric acid, sodium bicarbonate [baking soda]) - Use of methenamine with any of these medicines may decrease the effectiveness of methenamine

Other medical problems - The presence of other medical problems may affect the use of methenamine. Make sure you tell your doctor if you have any other medical problems, especially:

• Dehydration (severe) or
• Kidney disease (severe) - Patients with severe kidney disease who take methenamine may have an increase in side effects that affect the kidneys

• Liver disease (severe) - Patients with severe liver disease who take methenamine may have an increase in symptoms of their liver disease