Hiprex (Methenamine Hippurate)

Hiprex is indicated for the prophylactic management of urinary tract infections in patients who experience recurrent episodes.

• Prevention of recurrent uncomplicated urinary tract infections in women.
• Prophylaxis of urinary tract infections in patients with known risk factors such as catheter use.
• Use in individuals with normal acidic urinary pH to ensure drug activation.
• Adjunct to non‑pharmacologic measures (hydration, hygiene) for long‑term infection control.
• May be considered in patients who have completed an acute treatment course and require ongoing protection.

• Methenamine hippurate is a prodrug that is excreted unchanged in the urine. In an acidic urinary environment (pH ≤ 6), it hydrolyzes to release formaldehyde, a potent antimicrobial agent. The generated formaldehyde exerts nonspecific bactericidal activity against a broad range of urinary pathogens, thereby reducing bacterial colonisation and preventing infection recurrence.

Like most medications, Hiprex may cause adverse reactions, most of which are mild and reversible.

Common

• Nausea.
• Dyspepsia.
• Flatulence.
• Headache.

Serious

• Severe allergic reaction (anaphylaxis).
• Hematuria.
• Acute interstitial nephritis.

Before starting Hiprex, several safety considerations should be reviewed.

• Ensure urinary pH is acidic; effectiveness decreases when urine is alkaline.
• Not recommended for patients with known hypersensitivity to methenamine or formaldehyde.
• Use with caution in individuals with renal impairment or reduced kidney function.
• Avoid in patients with severe liver disease that may affect drug metabolism.
• Monitor for signs of allergic reaction during initial therapy.
• Pregnant or breastfeeding women should consult a healthcare professional before use.

Hiprex can interact with other agents that affect urinary pH or renal function.

Avoid

• Alkalinizing agents (e.g., potassium citrate, sodium bicarbonate) that raise urinary pH and reduce drug activation.
• Concurrent use of strong acids that may cause urinary irritation.

Use with caution

• Anticoagulants (warfarin) as formaldehyde may affect clotting parameters.
• Other urinary antiseptics or antibiotics, which could alter the overall antimicrobial effect.
• Diuretics that increase urine output, potentially affecting drug concentration.