Methenamine
Also known as: Hiprex
Administer this medication with food to minimize stomach upset. Your veterinarian may recommend a specific diet or urinary acidifier supplement; it is critical to follow these instructions, as this medication **only works if the urine is acidic**. Ensure your pet has free access to fresh water. Do not give your pet any over-the-counter antacids without consulting your veterinarian.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
How it is given
Possible side effects
- Gastrointestinal upset (nausea, vomiting, diarrhea)
- Dysuria or pollakiuria (due to formaldehyde irritation)
- Hematuria
- Crystalluria (at high doses)
Cautions & contraindications
- Renal insufficiency (can exacerbate systemic acidosis)
- Severe hepatic disease (due to ammonia production)
- Severe dehydration
- Metabolic acidosis
- Concurrent use of sulfonamides
- > **Urine pH must be monitored and maintained below 5.5** for the drug to be effective. > Not effective for upper urinary tract infections (pyelonephritis) or systemic infections. > Use with caution in patients with pre-existing gastrointestinal disease.
Drug interactions
- Sulfonamides: Formaldehyde forms an insoluble precipitate with sulfonamides, increasing the risk of crystalluria and renal damage.
- Urinary alkalinizers (e.g., Potassium citrate, Sodium bicarbonate): Raises urine pH, preventing the conversion of methenamine to its active form (formaldehyde).
- Thiazide diuretics: May increase urine pH and promote diuresis, reducing formaldehyde concentration and contact time in the bladder.
Frequently asked questions
What is Methenamine used for in pets?
Administer this medication with food to minimize stomach upset. Your veterinarian may recommend a specific diet or urinary acidifier supplement; it is critical to follow these instructions, as this medication **only works if the urine is acidic**. Ensure your pet has free access to fresh water. Do not give your pet any over-the-counter antacids without consulting your veterinarian.
Is Methenamine safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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