Is methenamine a prescription medication?

Methenamine is a heterocyclic organic compound with the formula (CH2)6N4. This white crystalline compound is highly soluble in water and polar organic solvents. It has a cage-like structure similar to adamantane. It is useful in the synthesis of other chemical compounds, e.g. plastics, pharmaceuticals, rubber additives. It sublimes in a vacuum at 280 °C. The compound was discovered by Aleksandr Butlerov in 1859.


A prescription drug (also prescription medication or prescription medicine) is a licensed medicine that is regulated by legislation to require a medical prescription before it can be obtained.
Methenamine has an FDA labeled indication for the treatment or prevention of recurrent urinary tract infections or urinary tract discomfort.  This medication is considered an antibiotic and works by forming compounds in the body, more specifically in the urine, to suppress bacterial growth and increase urine acidity to help get rid of bacteria causing the UTI.

Methenamine is considered a prescription medication, but at much higher doses than what is contained in OTC products.  For example, methenamine used in a hospital setting or as a prescription medication has a dosage of 1 gram, two to four times daily.  In an OTC product, such as Cystex(containing aspirin, benzocaine, and methenamine), the dosage is equivalent to 162.5 milligrams of methenamine four times a day.  So, the amount of methenamine in over-the-counter products is less than the amount in a prescription from a physician. 
In conclusion, methenamine could be viewed as a prescription medication or an OTC medication.  Large doses (usually 1gram or more) of the medication are considered prescription only, whereas low doses of methenamine (usually 160-170 milligrams) are considered an OTC product and do not require a prescription. Although this medication is an antibiotic used for the treatment of urinary tract infections, an OTC medication containing methenamine will not cure a UTI.  The low dose of methenamine contained in OTC medications is solely used to help prevent the progression of infection until you can see a doctor.


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