|Epinephrine is used medicinally as a stimulant in cardiac arrest, as a vasoconstrictor in shock, as a bronchodilator and antispasmodic in bronchial asthma, and to lower intra-ocular pressure in the treatment of glaucoma. Epinephrine plays a central
role in the short-term stress reaction—the physiological response to conditions that threaten the physical integrity of the body. It is secreted by the adrenal medulla. When released into the bloodstream, epinephrine binds to multiple receptors and has numerous effects throughout the body. It increases heart rate and stroke volume, dilates the pupils, and constricts arterioles in the skin and gut while dilating arterioles in leg muscle. It elevates the blood sugar level by increasing hydrolysis of glycogen to glucose in the liver, and at the same time begins the breakdown of lipids in fat cells.
Epinephrine is used as a drug to promote peripheral vascular resistance via alpha-stimulated vasoconstriction in cardiac arrest and other cardiac disrhythmias resulting in diminished or absent cardiac output, such that blood is shunted to the body's core. This beneficial action comes with a significant negative consequence, increased cardiac irritability, which may lead to additional complications immediately following an otherwise successful resuscitation. Alternatives to this treatment include Vasopressin, a powerful diuretic which also promotes peripheral vascular resistance leading to blood shunting via vasoconstriction, but without the attendant increase to myocardial irritability.
Epinephrine is also used as a vasoconstrictor in anaphylaxis and sepsis, and as a bronchodilator for asthma if specific beta-2-adrenergic agonists are unavailable or ineffective. Allergy patients undergoing immunotherapy can get an epinephrine rinse before their allergen extract is administered. Adverse reactions to epinephrine include palpitations, tachycardia, anxiety, headache, tremor, hypertension, and acute pulmonary edema.
Epinephrine is widely used as an additive in local anesthetics to improve the depth and duration of the anesthesia, as well as to reduce bleeding in the operative field. Epinephrine counteracts the anesthetic's localized vasodilator effects in subcutaneous and submucosal vessels, thereby reducing the risk of anesthetic toxicity by decreasing the rate of systemic absorption from the site of injection. Epinephrine is the drug of choice for treating an anaphylactic reaction. Anaphylaxis, the most severe type of allergic reaction, refers to a collection of symptoms affecting multiple systems of the body. The most dangerous symptoms include breathing difficulties and a drop in blood pressure or shock, which are potentially fatal.