Definitions Sympathetic and parasympathetic divisions typically function in opposition to each other. But this opposition is better termed complementary in nature rather than antagonistic. For an analogy, one may think of the sympathetic division as the accelerator and the parasympathetic division as the brake. Sympathetic The sympathetic division typically functions in actions requiring quick responses. The parasympathetic division functions with actions that do not require immediate reaction. Consider sympathetic as "fight or flight" and parasympathetic as "rest and digest".

Epinephrine (INN) (IPA: [ ˌɛ p ɪˈ n ɛ frən]) or adrenaline (European Pharmacopoeia and BAN) (IPA: [ə ˈ dr ɛ nələn]), sometimes spelled "epinephrin" or "adrenalin" respectively, is a hormone. It is a catecholamine, a sympathomimetic monoamine derived from the amino acids phenylalanine and tyrosine. The Latin roots ad-+renes and the Greek roots epi-+nephros both literally mean "on/to the kidney" (referring to the adrenal gland, which secretes epinephrine). Epinephrine is sometimes shortened to epi in medical jargon. Epinephrine is now also used in EpiPens and Twinjects. EpiPens are long narrow auto- injectors that administer epinephrine, Twinjects are similar but contain two doses of epinephrine. Though both EpiPen and Twinject are trademark names, common usage of the terms are drifting toward the generic context of any epinephrine autoinjector.

Anaphylaxis is a severe and rapid multi-system allergic reaction. The term comes from the Greek words ana (against) and phyllus (protection). Anaphylaxis occurs when a person is exposed to a trigger substance, called an allergen, to which they have already become sensitized. Minute amounts of allergens may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, inhalation, skin contact or injection of an allergen. The most severe type of anaphylaxis— anaphylactic shock —will usually lead to death in minutes if left untreated. Most common presentation is sudden cardiovascular collapse (88% of reported cases of severe anaphylaxis). Anaphylaxis

Anaphylactic shock, the most serious of allergic reactions, is a life-threatening medical emergency because of rapid constriction of the airway, often within minutes of onset. Calling for help immediately is important, as brain and organ damage rapidly occurs if the patient cannot breathe. Anaphylactic shock requires immediate advanced medical care; but other first aid measures include rescue breathing (part of CPR) and administration of epinephrine (adrenaline). Rescue breathing may be hindered by the constricted airways but is essential if the victim stops breathing on their own. If the patient has previously been diagnosed with anaphylaxis, they may be carrying an EpiPen (or similar device) for immediate administration of epinephrine (adrenaline) by a layperson to help keep the airway open. Use of an EpiPen or similar device will only provide temporary and limited relief of symptoms, so emergency medical services must still be contacted. Repetitive administration of epinephrine can cause tachycardia (rapid heartbeat) and occasionally ventricular tachycardia with heart rates potentially reaching 240 beats per minute, which can also be fatal. Extra doses of epinephrine can sometimes cause cardiac arrest. This is why some protocols advise intramuscular injection of only 0.3–0.5mL of a 1:1,000 dilution. The epinephrine will prevent worsening of the airway constriction, stimulate the heart to continue beating, and may be life-saving. Anaphylactic shock

Ephinephrine can be injected directly into the heart to stimulate it after it as stopped beating due to drowning, suffocation, shock, electrocution, and anesthesia. The epinephrine dramatically restores the heart beat. In cases of shock, norepinephrine has been used to restore and maintain sufficient blood pressure and ensure adequate blood flow to vital organs. When local anesthetics are used to reduce or eliminate pain in a specific area, epinephrine is frequently used in conjunction with these agents to constrict the blood vessels at the area and prevent drug diffusion from that area

Biosynthesis of norepinephrine and epinephrine

Metabolism involves two key enzymes: MAO and COMT

The design of a drug to treat asthma Asthma is a chronic disease of the respiratory system in which the airway occasionally constricts, becomes inflamed, and is lined with excessive amounts of mucus, often in response to one or more triggers. These acute episodes may be triggered by such things as exposure to an environmental stimulant (or allergen), cold air, exercise or exertion, or emotional stress. In children, the most common triggers are viral illnesses such as those that cause the common cold.[1] This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing, which respond to bronchodilators. Between episodes, most patients feel fine.The disorder is a chronic or recurring inflammatory condition in which the airway develops increased responsiveness to various stimuli, characterized by bronchial hyper-responsiveness, inflammation, increased mucus production, and intermittent airway obstruction. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and environmental changes.Public attention in the developed world has recently focused on asthma because of its rapidly increasing prevalence, affecting up to one in four urban children.[2]diseaserespiratory systemairwayallergenexercisestress[1]symptomswheezingshortness of breathcoughingbronchodilatorschronicinflammatory airway bronchialinflammationmucusdrugsdeveloped worldprevalence[2]