Methionine (DL-Methionine)
DL-methionine, also called racemethionine, is used to acidify urine when a full assessment supports that aim.
Group
Urinary acidifier and amino-acid supplement
Mechanism of Action
Sulfur amino-acid metabolism produces an acid load, lowering urinary pH.
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
- Selected urinary acidification
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.