Home  >  Health Resources  >  Health Encyclopedia

Methenamine; Sodium Acid Phosphate

Methenamine Mandelate, Sodium Phosphate, Monobasic Oral tablet

What is this medicine?

METHENAMINE; SODIUM ACID PHOSPHATE (meth EN a meen; SOE dee um AS id FOS fate) is used to reduce the bacteria in the urine, which can help relieve discomfort caused by infection of the urinary tract or help prevent urinary tract infections. This medicine is not an antibiotic. It will not cure a urinary tract infection.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:

  • dehydration

  • heart disease

  • high blood pressure

  • high levels of phosphate in the blood

  • high levels of sodium in the blood

  • history of pancreatitis

  • kidney disease

  • liver disease

  • parathyroid disease

  • sodium (salt) restricted diet

  • an unusual or allergic reaction to methenamine; sodium acid phosphate, other medicines, foods, dyes, or preservatives

  • pregnant or trying to get pregnant

  • breast-feeding

How should I use this medicine?

Take this medicine by mouth with a full glass of water. Follow the directions on the prescription label. Take your medicine at regular intervals. Do not take your medicine more often than directed. Take all of your medicine as directed even if you think you are better. Do not skip doses or stop your medicine early.

Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.

Overdosage: If you think you've taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medicine?

  • acetazolamide

  • antacids

  • aspirin

  • choline salicylate

  • certain antibiotics like sulfacetamide and sulfamethoxazole

  • certain medicines for blood pressure like hydrochlorothiazide

  • fludrocortisone

  • hydrocortisone

  • magnesium salicylate

  • methazolamide

  • sodium bicarbonate

  • topiramate

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medicine?

Tell your doctor or healthcare professional if your symptoms do not start to get better or if they get worse.

Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you.

You may need to be on a special diet while taking this medicine. Ask your health care professional how many glasses of water or other fluids to drink each day. Also, ask which foods to include and which to avoid to help keep your urine acidic. Your urine must be acidic for this medicine to work.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:

  • allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue

  • breathing problems

  • bone pain

  • confusion

  • fast, irregular heartbeat

  • pain, tingling or numbness in hands or feet

  • tremors

  • seizures

  • trouble passing urine or change in the amount of urine

  • unusually weak or tired

Side effects that usually do not require medical attention (Report these to your doctor or health care professional if they continue or are bothersome.):

  • diarrhea

  • dizziness

  • headache

  • nausea

  • upset stomach

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medicine?

Keep out of the reach of children.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Throw away any unused medicine after the expiration date. Protect from light.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.