Methenamine (Systemic)

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

Proper Use of This Medicine

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 methenamine 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 methenamine. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets or teaspoonfuls of solution or suspension that you take depends on the strength of 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 - To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store the dry granule or tablet form of this medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Keep the oral liquid form of this medicine from freezing.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.