Proin is a prescription liverflavored chewable tablet intended to manage urinary incontinence in dogs and cats by constricting and strengthening the urinary sphincter Proin is a supplemental adrenergic agent which means it mimics adrenaline or epinephrine which are the hormones needed to trigger vasoconstriction the constriction of blood vessels Proin also maintains balanced phenylpropanolamine levels helping to prevent the negative side effects associated with high levels including heightened blood pressure and hyperexciteability Proin is a classified controlled substance in Arkansas Iowa Louisiana and OregonOther products from PetCareRx