Vetdrugs 2.0DL-methionine, also called racemethionine, is a sulfur-containing amino-acid preparation used in selected urinary acidification plans. Its clinical purpose is to provide a metabolic acid load when lowering urinary pH is an appropriate treatment goal. Methionine is also a nutritional amino acid, but nutritional replacement and deliberate urinary acidification are separate applications.
Group
Urinary acidifier and amino-acid supplement
Mechanism of Action
Metabolism of methionine’s sulfur-containing groups generates sulfate and an acid load. Renal handling of this load increases acid excretion and can lower urinary pH. A more acidic urine environment alters mineral solubility, including reducing conditions favoring struvite precipitation. The effect depends on the overall diet, acid–base balance and the patient’s ability to metabolize and excrete the acid load.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Urinary acidification | 22.2222222222 mg/kg | PO | Every 12–24 h | 200 mg tablet-label alternative: half a tablet per 4.5 kg once or twice daily with food. |
| Urinary acidification | 55.5555555556 mg/kg | PO | Every 12–24 h | 500 mg tablet-label alternative: half a tablet per 4.5 kg once or twice daily with food. |
| Struvite urine acidification | 100 mg/kg | PO | Every 12 h | Separate veterinary urinary-disease recommendation when diet alone does not achieve the required urine pH; titrate to avoid acidosis. |
| Urinary acidification | 0.2–1 g/animal | PO | Every 8 h | Separate fixed alternative when diet and antimicrobials do not achieve acidification. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Urinary acidification | 44.4444444444 mg/kg | PO | Every 6–8 h | Do not use in: Kittens; Adult-cat 200 mg tablet-label alternative: one tablet per 4.5 kg three or four times daily. |
| Urinary acidification | 111.1111111111 mg/kg | PO | Every 12–24 h | Do not use in: Kittens; Adult-cat 500 mg tablet-label alternative: one tablet per 4.5 kg once or twice daily. |
| Urinary acidification | 1000–1500 mg/animal | PO | Every 24 h | Historical food-mixed alternative; titrate urine pH and monitor CBC/acid-base status. |
| Urinary acidification | 0.2–1 g/animal | PO | Every 24 h | Separate lower fixed-dose alternative; do not combine with acidifying diets without monitoring. |
Cattle
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical methionine administration | Reference only | PO | 20-30 g per animal is listed, but indication and repeat interval are not specified. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical tapered methionine course | Reference only | PO | 22 mg/kg daily for 7 days, then 11 mg/kg daily for 7 days, then 5.5 mg/kg daily for 7 days. The indication is not specified in the dose entry, so this is not assigned as routine urine acidification. | |
| Proposed Senecio-associated hepatic-injury adjunct | 12.5 g/animal | IV | Dilute in 1 L saline/dextrose; limited efficacy information, not a substitute for treating the intoxication and monitoring hepatic function. |
Indications
- Adjunctive urinary acidification in selected dogs or cats with a defined need to lower urine pH.
- Selected support of struvite dissolution or recurrence prevention when acidification is part of a complete stone-specific dietary and medical plan.
Contraindications
- Acidosis
- Severe hepatic or renal damage
- Kittens for the cited tablet products
- Oxalate or urate calculi, pancreatic disease or frank renal failure. Hepatic insufficiency can worsen encephalopathy through mercaptan-like metabolites.
Interactions
- Other acidifying diets or medicines may produce excessive acidification.
- Urine acidification may reduce aminoglycoside/erythromycin efficacy in urinary infection and increase quinidine renal excretion.
Adverse effects
- Gastrointestinal intolerance
- Excessive acidification and metabolic acidosis
- Cats may develop haemolytic anaemia with excessive exposure.
Toxicity
Stop treatment if weakness, acidosis or haemolytic signs appear; assess acid-base balance and CBC.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| V.E.T. DL-Methionine 200 mg tablet V.E.T. Pharmaceuticals | Tablet | 200 mg / tablet | PO |
| V.E.T. DL-Methionine 500 mg tablet V.E.T. Pharmaceuticals | Tablet | 500 mg / tablet | PO |
Monitoring and Administration
Give with food and titrate using urine pH; the cited tablet label aims below pH 6.6. Do not institute chronic acidification without investigating urolith composition and acid-base status.
Store tightly closed, dry and protected from light at 15-30°C.
Recheck suspected struvite dissolution after about a month; inadequate stone reduction warrants reassessment of compliance, infection control and mineral composition. Mature cats receiving 2 g/day have developed Heinz-body haemolysis, methaemoglobinaemia, ataxia and cyanosis; monitor urine pH, acid-base status and CBC when indicated.