Epinephrine therapeutic activity

Many therapeutically active ingredients are administered or applied to the body by means of the aerosol dosage form, including agents such as epinephrine, isoproterenol, antibiotics, antiseptics, steroids, and ergotamine. Oral aerosols have been used for the symptomatic treatment of asthma as well as for the treatment of migraine headaches, whereas topical aerosols find use in numerous dermatological manifestations. 

The metered-dose aerosol inhaler is not only a most convenient system for the delivery of therapeutically active drugs but it has proven to be a life-saving device for many asthmatics. This system has made it possible for millions of asthma sufferers to lead normal lives. The convenience of self-administering a dose of drug accurately and quickly has made the metered-dose aerosol the dosage form of choice for the delivery of drugs to the respiratory system. From epinephrine to albuterol, from triamcinolone to flunisolide, from proteins and peptides to hormones, this dosage form has proven its value. 

Epinephrine has a narrow benefit-to-risk ratio. Along with its therapeutic effects, when administered in recommended doses by any route, it potentially causes transient anxiety, fear, restlessness, palpitations, pallor, tremor, and headache. Although usually perceived as adverse effects, such symptoms indicate that a pharmacologically active dose of the medication has been absorbed. The desirable pharmacologic effects of epinephrine cannot be separated from the undesirable pharmacologic effects [10]. 

MecfianismofAction An antidepressant that inhibits the MAO enzyme system at central nervous system (CNS) storage sites. The reduced MAO activity causes an increased concentration in epinephrine, norepinephrine, serotonin, and dopamine at neuron receptor sites. Therapeutic Effect Produces antidepressant effect. 

Mechanism of Action An MAOI that inhibits the activity of the enzyme monoamine oxidase at CNS storage sites, leading to increased levels of the neurotransmitters epinephrine, norepinephrine, serotonin, and dopamine at neuronal receptor sites. Therapeutic Effect Relieves depression. 

There are major differences in receptor types predominantly expressed in the various vascular beds (Table 9-4). The skin vessels have predominantly receptors and constrict in response to epinephrine and norepinephrine, as do the splanchnic vessels. Vessels in skeletal muscle may constrict or dilate depending on whether a or 13 receptors are activated. The blood vessels of the nasal mucosa express a, receptors, and local vasoconstriction induced by sympathomimetics explains their decongestant action (see Therapeutic Uses of Sympathomimetic Drugs). 

Circulating catecholamines such as epinephrine also result in an intracellular movement of potassium by two mechanisms. They stimulate the /S-receptor, which directly activates the Na" " -K" " -ATPase pump. Secondly, they stimulate glycogenolysis, which raises blood glucose levels, thereby increasing insulin secretion. This dual mechanism is often used therapeutically in patients with hyperkalemia to normalize serum potassium concentrations. 

Other enzymes that catalyze decarboxylation and dehydration reactions require Mg2+. As will be seen, the a-adrenergic receptor, which includes the enzyme adenyl cyclase in association with ATP, utilizes Mg2+ to mediate the increased cardiac activity associated with epinephrine. It is therefore apparent that pharmaceutical products that provide these inorganic ions (i.e., mineral supplements), as well as vitamin preparations, should actually be considered drugs whether they are used therapeutically to treat clinical symptoms of deficiency, or as food supplements for the maintenance of good health. 

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