Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.


Chemistry - A sulfur-containing amino acid, methionine occurs as a white, crystalline powder witha characteristic odor. One gram is soluble in about 30 ml of water and it is very slightly soluble inalcohol. 74.6 mg is equivalent to 1 mEq of methionine.

Storage, Stability, Compatibility

Methionine should be stored at room temperature.


Methione has several pharmacologic effects. It is an essential amino acid (l-form)and nutrient, a lipotrope (prevents or corrects fatty liver in choline deficiency), and a urine acidifier.
Two molecules of methionine can be converted to 1 molecule of cysteine. Methionine supplies bothsulfahydryl and methyl groups to the liver for metabolic processes. Choline is formed whenmethionine supplies a methyl group to ethanolamine. After methionine is metabolized, sulfate isexcreted in the urine as sulfuric acid, thereby acidifying it.
Uses, Indications - In small animals, methionine has been used primarily for its urine acidificationeffects in the treatment and prevention of certain types (e.g., struvite) of stone formation and toreduce ammoniacal urine odor. In food animals, it has been used as a nutritional supplement inswine and poultry feed and in the treatment of ketosis in cattle. It also has been touted as a treatmentfor laminitis in horses and cattle (purportedly provides a disulfide bond substrate to maintain thehoof-pedal bone bond), but definitive studies demonstrating its effectiveness for this indication arelacking.
The drug is used in humans to reduce urine ammonia (pH) and odor.


No information is available on the pharmacokinetics of this agent in veterinary species or humans.
Contraindications/Precautions - Methionine (in therapeutic doses) is considered to be contraindicated in patients with renal failure or pancreatic disease. If used in patients with frank hepaticinsufficiency, methionine can cause increased production of mercaptan-like compounds andintensify the symptoms of hepatic dementia or coma. Methionine should not be given to animalswith preexisting acidosis or urate calculi. It is not recommended to be used in kittens.

Adverse Effects, Warnings

At usual doses, gastrointestinal distress can occur; give with food toalleviate this effect and to enhance efficacy. Methionine may cause Heinz-body hemolytic anemia incats. See Overdosage (below) for other potential adverse effects.
Overdosage - Methionine may be toxic to kittens who consume other cats' food in which methionine has been added. When methionine was administered at a dose of 2 grams orally per day tomature cats, anorexia, methemoglobinemia, Heinz body formation (with resultant hemolytic anemia), ataxia and cyanosis were noted. No specific information was located on the treatment of methionineoverdosage.

Drug Interactions

Urine acidification may increase the renal excretion of quinidine.
The aminoglycosides (e.g., gentamicin) and erythromycin are more effective in an alkalinemedium; urine acidification may diminish these drugs effectiveness in treating bacterial urinary tractinfections.