Methenamine, also known as hexamethylenetetramine, is a medication primarily used as an antiseptic to treat urinary tract infections. It works by decomposing in acidic urine to release formaldehyde, which has antimicrobial properties. Methenamine is often prescribed in combination with other medications to enhance its efficacy. It is important to note that it should be used with caution in patients with certain conditions, such as liver or kidney issues.