tryptophan: protein binding::xylitol:...........
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Answer:
Explanation:
Five‐hydroxytryptophan (5‐HTP) is a by‐product of L‐tryptophan, an essential amino acid, and is produced commercially from Griffonia simplicifolia seeds. Tryptophan is converted to 5‐HTP via tryptophan hydroxylase, and 5‐HTP is then converted to serotonin (5‐HT; hydroxytryptamine) by L‐amino decarboxylase.1 Serotonin is a central nervous system neurotransmitter with additional effects on platelet aggregation and stimulatory effects on the smooth muscle of the gastrointestinal tract, respiratory tract, and cardiovascular system. Five‐hydroxytryptophan is available over‐the‐counter in a variety of formulations, and is used to enhance serotonin production, thereby assisting in the treatment of a number of conditions in people, including sleep disorders, anxiety, and obesity.2 The authors are aware of anecdotal reports of the use of 5‐HTP in dogs at low doses (1 mg/kg by mouth every 12 hours) to help manage fear, anxiety, and reactivity. Natrol 5‐HTP Fast Dissolve tablets (Natrol 5‐HTP Fast Dissolve tablets wild berry flavor, Natrol LLC., Chatsworth, CA) are manufactured with an artificial sweetener called xylitol. Xylitol is a 5‐carbon sugar alcohol that has gained popularity in recent years as a sugar substitute in foodstuffs for people with diabetes. It is also popular with dental health professionals for its natural anti‐cariogenic properties and has been used in wound dressings to decrease biofilm efficacy of Pseudomonas aeruginosa and methicillin‐resistant Staphylococcus aureus in dogs.2, 3 Both 5‐HTP and xylitol have been reported to cause toxicosis in dogs, however to the authors’ knowledge, this is the first report of an over‐the‐counter supplement causing simultaneous signs of both toxicities in a dog.
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2. CASE SUMMARY
A 3‐year‐old male, castrated, Dachshund, weighing 8 kg, was presented to the primary care veterinarian following ingestion of 29 tablets of Natrol 5‐HTP Fast Dissolve Tablets. Each tablet contained 100 mg of 5‐HTP and 820 mg of xylitol, corresponding to a dose of 362.5 mg/kg 5‐HTP and 2.973 g/kg of xylitol. The ingestion was witnessed by the owner, and induction of emesis was attempted by administration of hydrogen peroxide in the home (quantity and formulation unknown). Emesis was unsuccessful, and the patient was presented to the primary care veterinarian. Upon arrival, the patient was agitated and tremoring. A full neurologic assessment was not documented, however, bilateral mydriasis was reported. The patient was ambulatory and responsive. Heart rate was 120 beats per minute (bpm), respiratory rate was 60 breaths per minute, and rectal temperature was 37.7°C (100°F) (RI 37.5‐39.2°C; 99.5−102.5°F). Mucous membranes were pink with a capillary refill time (CRT) of <2 seconds. The patient exhibited increased respiratory effort, and harsh bronchovesicular sounds were auscultated bilaterally. Oxygen saturation as measured by pulse oximetry was 95% on room air. An apomorphine tablet (2 mg tablet, 0.25 mg/kg) was administered into the right conjunctival sac. Induction of emesis was unsuccessful. Initial