Tryptophan (Nutricalm®) for Dogs and Cats

Overview of Tryptophan for Dogs and Cats

Tryptophan, commonly known as Nutricalm®, is primarily used to decrease aggression and stabilize mood for dogs and cats.

• L-tryptophan is a large neutral amino acid that is an essential dietary constituent for dogs and cats.
• It has been banned for retail in the United States as a dietary additive since the eosinophilia-myalgia (EM) scare of 1989. The later occurred when a batch of contaminated tryptophan was shipped to the US from Japan. Humans who had ingested tryptophan from this batch became ill, complaining of severe incapacitating muscle pain, muscle weakness, peripheral and facial swelling, painful joints, hair loss, skin rashes, and thickening of the skin. Pulmonary symptoms, neurological symptoms, gastrointestinal symptoms (e.g., dysphagia, diarrhea) also occurred.
• L-tryptophan is metabolized along numerous biochemical pathways, one of which involves its conversion to 5-hydroxytryptophan (5HTP), and ultimately serotonin (5-HT).
• In the United States, L-tryptophan has limited availability for human use but 5-HTP, its first metabolite, is supplied as an over-the-counter (OTC) drug. 5-HTP is, in many ways, superior to L-tryptophan. It is very well absorbed when taken by mouth and rapidly crosses into the brain, where it is decarboxylated to serotonin. Increasing brain serotonin stabilizes mood and may reduce impulsivity and aggression i.e. it produces beneficial behavioral changes.
• While some people regard the EM scare as a thing of the past, others think that both tryptophan and 5-HTP may result in similar problems in the future because of contaminants common to both. Meanwhile 5-HTP continues to be used by humans who self-medicate, and is prescribed for the treatment of some animal behavior problems, so far without serious untoward effects. European trials in humans comparing 5-HTP with antidepressant pharmacotherapy have shown no significant difference between the antidepressant effects of either treatment.

Brand Names and Other Names of Trytophan

• L-tryptophan has limited availability for use in humans but is obtainable in combination with other substances for use in animals. 5-HTP is available OTC in US pharmacies and is marketed for use in humans
• Human formulations: Various generic preparations
• Veterinary formulations: Nutricalm® (Rx Vitamins)

Uses of Tryptophan for Dogs and Cats

• Tryptophan and 5-HTP have been used to decrease aggression and impulsivity in dogs and cats. They also have both mood stabilizating and calming effects.
• Tryptophan and 5-HTP have also been used as a primary or adjunctive treatment to palliate obsessive-compulsive disorders.

Precautions and Side Effects

• While generally safe and effective when prescribed by a veterinarian, tryptophan can cause side effects in some animals.
• Tryptophan should not be used in animals with known hypersensitivity or allergy to the drug.
• The most common side effects are vomiting and diarrhea. Unwanted gastrointestinal effects may result from the drug’s known stimulatory effects on propulsive contractions of dogs’ proximal small intestine.
• Tryptophan may interact with other medications. Consult your veterinarian to determine if other drugs your pet is receiving could interact with tryptophan. Such drugs include certain antidepressants and other “behavior modifying drugs,” as the effects may be additive.

How Tryptophan is Supplied

• Tryptophan for animals is available in capsules containing 75mg or 150 mg tryptophan. 5-HTP is available as 50 mg or 100 mg capsules.

Dosing Information of Tryptophan for Dogs and Cats

• Medication should never be administered without first consulting your veterinarian.
• The minimum quantity of tryptophan that is required to maintain nitrogen equilibrium in adult dogs was estimated to be 6.5 mg per pound (13 mg/kg/day), daily and has been set as the daily requirement. In puppies, the requirement is considerably higher, around 41 mg per pound (82 mg/kg). Much of the D-form of tryptophan is inverted to L-tryptophan in mature dogs. Normally, tryptophan is derived from dietary proteins. A behavioral study conducted at Tufts using 10 mg/kg of tryptophan twice daily, fed incorporated into custom diets, showed no obvious side effects while study dogs’ dominant and territorial aggressive behavior was significantly reduced.
• In cats, the dose of L-tryptophan is 7.5 to 10 mg per pound (15 to 20 mg/kg) once to twice daily.
• The dose of 5-HTP used at Tufts University School of Veterinary Medicine for treatment of canine aggression is 1 mg per pound (2 mg/kg) orally twice a day.
• The duration of administration depends on the condition being treated, response to the medication, and the development of any adverse effects. Be certain to complete any prescription from a veterinarian unless specifically directed otherwise.