Thyro tabs for dogs
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Thyro-Tabs for Dogs: Safety, Bioavailability, and Accidental Ingestion
Safety of Thyro-Tabs in Dogs
Levothyroxine Sodium Tolerance in Canines
Thyro-Tabs, a synthetic levothyroxine sodium tablet, has been evaluated for safety in dogs through a comprehensive study. In this study, young, healthy Beagle dogs were administered varying doses of levothyroxine sodium, ranging from 0 to 10 times the labeled starting dose of 0.022 mg/kg/day over a period of 182 days. The results indicated a dose-dependent increase in serum concentrations of total and free thyroxine, along with suppression of the hypothalamic-pituitary-thyroid axis. Despite these changes, clinical signs of thyrotoxicosis such as excitation, tachypnea, and tachycardia were sporadic and showed no clear dose-response relationship. Overall, the findings suggest that doses up to 10 times the labeled starting dose are well tolerated in healthy dogs, with only mild and clinically insignificant side effects1.
Bioavailability of Thyro-Tabs in Dogs
Comparative Pharmacokinetics of Tablet and Liquid Formulations
A study comparing the bioavailability of two L-thyroxine formulations—an investigative liquid and a reference tablet—was conducted in healthy dogs. The trial revealed that the maximum plasma concentration for the tablet formulation (100 µg/kg) was approximately 96.2 nmol/L, reached within 3.77 hours. For the liquid formulation (50 µg/kg), the maximum plasma concentration was 60.1 nmol/L, reached within 3.59 hours. The geometric mean of the relative bioavailability for the liquid/tablet product was 1.1, indicating that both formulations have similar bioavailability. This suggests that either formulation can be effectively used for thyroid hormone replacement in dogs2.
Accidental Ingestion of Thyro-Tabs by Humans
Case of Thyrotoxicosis in a Veterinarian
An interesting case of accidental thyrotoxicosis was reported in a 33-year-old veterinarian with Hashimoto’s thyroiditis. The veterinarian, who was stable on a prescribed levothyroxine dosage, inadvertently ingested levothyroxine "dog tabs" at a dose 10 times higher than her prescribed amount. This led to symptoms of mild anxiety, jitteriness, and insomnia, with significantly elevated serum total T4 and free thyroxine index levels. Upon discontinuation of the dog tabs and resumption of her prescribed medication, her thyroid function normalized. This case underscores the importance of proper medication management and the potential risks of using veterinary medications in humans3.
Conclusion
Thyro-Tabs are a safe and effective option for managing hypothyroidism in dogs, with well-tolerated doses up to 10 times the recommended amount. Both tablet and liquid formulations of L-thyroxine show similar bioavailability, providing flexibility in treatment options. However, caution must be exercised to prevent accidental ingestion by humans, as it can lead to significant health issues.
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Most relevant research papers on this topic
Safety of orally administered, USP‐compliant levothyroxine sodium tablets in dogs
Levothyroxine sodium tablets, up to 10x the labeled starting dose, are well-tolerated in healthy dogs, with dose-dependent increases in thyroxine levels and suppression of the hypothalamic-pituitary-thyroid axis.
RCT
Animal StudyBioavailability of two L-thyroxine formulations after oral administration to healthy dogs.
The relative bioavailability of L-thyroxine after oral administration of tablet or liquid formulation is similar in healthy dogs.
RCTAnimal StudyAccidental thyrotoxicosis caused by inadvertent ingestion of levothyroxine "dog-tabs" by a veterinarian with hypothyroidism.
Inadvertent ingestion of levothyroxine "dog-tabs" by a veterinarian with hypothyroidism can lead to thyrotoxicosis, requiring immediate medical attention.
Case ReportPharmacokinetics of total thyroxine in dogs after administration of an oral solution of levothyroxine sodium.
Oral L-thyroxine supplementation in dogs with hypothyroidism can be safely administered at a dose rate of 20 microg/kg once daily, with a mean bioavailability of 22%.
Non-RCTAnimal StudyHog thyrocalcitonin in the dog: urinary calcium, phosphorus, magnesium and sodium responses.
Hog thyrocalcitonin, at the doses tested, had no direct acute effects on urinary excretion of calcium, phosphorus, magnesium, or sodium in the dog.
Non-RCTAnimal StudyThe effects of thyroxine on hair growth in the dog
Thyroxine, regardless of administration route, increases hair growth rate and the number of hair follicles entering the anagen phase in dogs, with orally administered thyroxine showing the most significant changes in the flank region.
Non-RCTAnimal StudyEffects of deracoxib and aspirin on serum concentrations of thyroxine, 3,5,3'-triiodothyronine, free thyroxine, and thyroid-stimulating hormone in healthy dogs.
Aspirin has substantial suppressive effects on thyroid hormone concentrations in dogs, requiring discontinuation prior to evaluation of thyroid function.
RCTAnimal StudyEffects of deracoxib and aspirin on serum concentrations of thyroxine, 3,5,3'-triiodothyronine, free thyroxine, and thyroid-stimulating hormone in healthy dogs.
Aspirin has substantial suppressive effects on thyroid hormone concentrations in dogs, and should be discontinued prior to evaluation of thyroid function.
RCTInfluence of reserpine on high calcium perfusion of thyro-parathyroid glands in dogs.
Reserpine blocks the release of hypocalcemic factor from thyro-parathyroid glands in dogs when exposed to high calcium concentrations, resulting in a decrease in systemic plasma calcium levels.
Non-RCTAnimal StudyEffects of thyroxine on cortical bone remodeling in adult dogs: a histomorphometric study.
Thyroxine is a potent activator of skeletal remodeling in adult dogs, increasing bone turnover and both formation and resorption under both normal and accelerated conditions.
Non-RCTAnimal Study