New solutions for inappetence
In the next couple of years, you could have new tools available to address inappetence in dogs and cats. The new product, being developed by pet therapeutics company Aratana, is an oral delivery of capromorelin, a small molecule that mimics ghrelin, the naturally occurring hormone that stimulates appetite, increases body weight and increases serum growth hormone levels.
In June 2015, Aratana announced positive top-line data from its pivotal field effectiveness study of capromorelin in dogs, and company representatives say they continue to anticipate approval of the product for dogs in mid-2016. In July 2015, they announced positive results in a pilot field study of capromorelin in cats, and they expect FDA approval in 2018.
Current drugs used (off-label) to stimulate appetite in veterinary patients work like this:
> Diazepam* or oxazepam in cats. Benzodiazepines bind to GABA-A receptors in the parabrachial nucleus and enhance the sensory characteristics of food, such as taste. Because food becomes more palatable, benzodiazepines can produce a voracious increase in food consumption, but these drugs do not directly modulate hunger or satiety.
> Cyproheptadine in cats. An antihistamine with serotonin-receptor-antagonist activity. The lateral hypothalamus releases endogenous opiates which stimulate appetite, but serotonin inhibits their release. So by blocking serotonin, the endogenous opiates can work unencumbered.
> Mirtazapine in cats and dogs. An antidepressant that has presynaptic alpha-2 adrenergic antagonist and postsynaptic serotonin-receptor antagonist activities. In addition to stimulating appetite, it has anti-emetic effects.
> Megestrol acetate in cats and dogs. A synthetic progestin with antiestrogen and glucocorticoid activities.
> Prednisone or prednisolone in dogs and cats. Glucocorticoids stimulate gluconeogenesis and are insulin antagonists. Their corticosteroid-induced euphoria promotes appetite.
*Oral diazepam may cause acute hepatic failure and death in cats. (Center SA, Elston TH, Rowland PH, et al. Fulminant hepatic failure associated with oral administration of diazepam in 11 cats. J Am Vet Med Assoc 1996;209(3):618-625; Park FM. Successful treatment of hepatic failure secondary to diazepam administration in a cat. J Feline Med Surg 2012;14(2):158-160.)