Epinephrine, also known as adrenalin or adrenaline, is a medication and hormone. As a medication, it is used to treat a number of conditions, including anaphylaxis, cardiac arrest, and superficial bleeding. Inhaled epinephrine may be used to improve the symptoms of croup. It may also be used for asthma when other treatments are not effective. It is given intravenously, by injection into a muscle, by inhalation, or by injection just under the skin.
Common side effects include shakiness, anxiety, and sweating. A fast heart rate and high blood pressure may occur. Occasionally, it may result in an abnormal heart rhythm. While the safety of its use during pregnancy and breastfeeding is unclear, the benefits to the mother must be taken into account.
Epinephrine is normally produced by both the adrenal glands and certain neurons. It plays an important role in the fight-or-flight response by increasing blood flow to muscles, output of the heart, pupil dilation, and blood sugar. Epinephrine does this by its effects on alpha and beta receptors. It is found in many animals and some one cell organisms.
Jokichi Takamine first isolated epinephrine in 1901. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication. The wholesale cost in the developing world is between US$0.10 and US$0.95 a vial. In the United States, the cost of the most commonly used autoinjector for anaphylaxis was about US$600 for two in 2016, while a generic version was about US$140 for two.
Video Epinephrine (medication)
Medical uses
Epinephrine is used to treat a number of conditions including: cardiac arrest, anaphylaxis, and superficial bleeding. It has been used historically for bronchospasm and hypoglycemia, but newer treatments for these that are selective for ?2 adrenoceptors, such as salbutamol are currently preferred.
Cardiac arrest
While epinephrine is often used to treat cardiac arrest, it has not been shown to improve long-term survival or mental function after recovery. It does, however, improve return of spontaneous circulation.
Anaphylaxis
Epinephrine is the drug of choice for treating anaphylaxis. Different strengths, doses and routes of administration of epinephrine are used.
The commonly used epinephrine autoinjector delivers a 0.3 mg epinephrine injection (0.3 mL, 1:1000) and is indicated in the emergency treatment of allergic reactions including anaphylaxis to stings, contrast agents, medicines or people with a history of anaphylactic reactions to known triggers. A single dose is recommended for people who weigh 30 kg or more, repeated if necessary. A lower strength product is available for children.
Intramuscular injection can be complicated in that the depth of subcutaneous fat varies and may result in subcutaneous injection, or may be injected intravenously in error, or the wrong strength used. Intramuscular injection does give a faster and higher pharmacokinetic profile when compared to subcutaneous injection.
Asthma
Epinephrine is also used as a bronchodilator for asthma if specific ?2 agonists are unavailable or ineffective.
When given by the subcutaneous or intramuscular routes for asthma, an appropriate dose is 0.3 to 0.5 mg.
Because of the high intrinsic efficacy (receptor binding ability) of epinephrine, high concentrations of the drug cause negative side effects when treating asthma. The value of using nebulized epinephrine in acute asthma is unclear.
Croup
Racemic epinephrine has historically been used for the treatment of croup. Regular epinephrine however works equally well. Racemic adrenaline is a 1:1 mixture of the dextrorotatory (D) and levorotatory (L) isomers of adrenaline. The L-form is the active component. Racemic adrenaline works by stimulation of the alpha adrenergic receptors in the airway, with resultant mucosal vasoconstriction and decreased subglottic edema, and by stimulation of the ? adrenergic receptors, with resultant relaxation of the bronchial smooth muscle.
Local anesthetics
Adrenaline is added to injectable forms of a number of local anesthetics, such as bupivacaine and lidocaine, as a vasoconstrictor to slow the absorption and, therefore, prolong the action of the anesthetic agent. Due to epinephrine's vasoconstricting abilities, the use of epinephrine in localized anesthetics also helps to diminish the total blood loss the patient sustains during minor surgical procedures. Some of the adverse effects of local anesthetic use, such as apprehension, tachycardia, and tremor, may be caused by adrenaline. Epinephrine/adrenaline is frequently combined with dental and spinal anesthetics and can cause panic attacks in susceptible patients at a time when they may be unable to move or speak due to twilight anesthesia. Currently the maximum recommended daily dosage for people in a dental setting requiring local anesthesia with a peripheral vasoconstrictor is 10 µg/lb of total body weight.
Adrenaline is mixed with cocaine to form Moffett's solution, used in nasal surgery.
Maps Epinephrine (medication)
Adverse effects
Adverse reactions to adrenaline include palpitations, tachycardia, arrhythmia, anxiety, panic attack, headache, tremor, hypertension, and acute pulmonary edema. The use of epinephrine based eye-drops, commonly used to treat glaucoma, may also lead to buildup of adrenochrome pigments in the conjunctiva, iris, lens, and retina.
Use is contraindicated in people on nonselective ?-blockers, because severe hypertension and even cerebral hemorrhage may result. Although it is commonly believed that administration of adrenaline may cause heart failure by constricting coronary arteries, this is not the case. Coronary arteries have only ?2 receptors, which cause vasodilation in the presence of adrenaline. Even so, administering high-dose adrenaline has not been definitively proven to improve survival or neurologic outcomes in adult victims of cardiac arrest.
Mechanism of action
As a hormone, epinephrine acts on nearly all body tissues. Its actions vary by tissue type and tissue expression of adrenergic receptors. For example, high levels of epinephrine causes smooth muscle relaxation in the airways but causes contraction of the smooth muscle that lines most arterioles.
Epinephrine acts by binding to a variety of adrenergic receptors. Epinephrine is a nonselective agonist of all adrenergic receptors, including the major subtypes ?1, ?2, ?1, ?2, and ?3. Epinephrine's binding to these receptors triggers a number of metabolic changes. Binding to ?-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis in the liver and muscle, and stimulates glycolysis and inhibits insulin-mediated glycogenesis in muscle. ? adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue. Together, these effects lead to increased blood glucose and fatty acids, providing substrates for energy production within cells throughout the body.
Its actions are to increase peripheral resistance via ?1 receptor-dependent vasoconstriction and to increase cardiac output via its binding to ?1 receptors. The goal of reducing peripheral circulation is to increase coronary and cerebral perfusion pressures and therefore increase oxygen exchange at the cellular level. While epinephrine does increase aortic, cerebral, and carotid circulation pressure, it lowers carotid blood flow and end-tidal CO2 or ETCO2 levels. It appears that epinephrine may be improving macrocirculation at the expense of the capillary beds where actual perfusion is taking place.
History
Extracts of the adrenal gland were first obtained by Polish physiologist Napoleon Cybulski in 1895. These extracts, which he called nadnerczyna, contained adrenaline and other catecholamines. American ophthalmologist William H. Bates discovered adrenaline's usage for eye surgeries prior to 20 April 1896. Japanese chemist Jokichi Takamine and his assistant Keizo Uenaka independently discovered adrenaline in 1900. In 1901, Takamine successfully isolated and purified the hormone from the adrenal glands of sheep and oxen. Adrenaline was first synthesized in the laboratory by Friedrich Stolz and Henry Drysdale Dakin, independently, in 1904.
Society and culture
Cost
The wholesale cost of epinephrine in the developing world is between US$0.10 and US$0.95 a vial.
Brand names
Common brand names include:
- Asthmanefrin
- Micronefrin
- Nephron
- VapoNefrin
Delivery forms
Epinephrine is available in an autoinjector delivery system.
There is an epinephrine metered-dose inhaler sold over-the-counter in the United States for the relief of bronchial asthma. It was introduced in 1963 by Armstrong Pharmaceuticals. In 2008, the Food and Drug Administration (FDA) announced that inhalers, which contain chlorofluorocarbons (CFCs), failed to comply with the environmental regulations of the Montreal Protocol and therefore could not be manufactured or sold after December 31, 2011. In April 2013, after completing several years of trials, Armstrong Pharmaceuticals submitted a New Drug Application to the FDA for an hydrofluoroalkane (HFA) version.
A common concentration for epinephrine is a 2.25% epinephrine solution, which contains 2.25g/100mL or 2.25 mg/mL. While a 1% solution is typically used for aerosolization.
- Adults: 0.5-0.75 ml of a 2.25% solution in 2.0 ml normal saline.
- Pediatrics: 0.25-0.75 ml of a 2.25% solution in 2.0 ml normal saline.
References
External links
- U.S. National Library of Medicine: Drug Information Portal - Epinephrine
Source of article : Wikipedia
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