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Anti Allergic

Anti Allergic
Anti Allergic

Anti Allergic

  • Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of

the immune system to something in the environment that usually causes little or no problem in most people

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  • These diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis
  • Symptoms may include red eyes, an itchy rash, runny nose, shortness of breath, or swelling

ALLERGENS

  • Common allergens include pollen and certain food. Metals and other substances may also cause problems. Food, insect stings, and medications are common causes of severe reactions.
  • Their development is due to both genetic and environmental factors
  • The underlying mechanism

involves immunoglobulin E antibodies (IgE), part of the body’s immune system, binding to an allergen and then to a receptor on mast cells or basophils where it triggers the release of inflammatory chemicals such as histamine

  • Histamine is involved in

the inflammatory response and has a central role as a mediator of pruritus.

  • As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues.
  • Histamine increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues.
  • In general, there is no cure for allergies, but there are several types of medications available both over-the-counter and prescription -to help ease and treat annoying symptoms like congestion and runny nose.
  • These allergy drugs

include antihistamines, decongestants, corticosteroids

Histamine

  • Histamine is involved in

the inflammatory response and has a central role as a mediator of pruritus.

  • As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues.
  • Histamine increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues

Storage and release

  • Most histamine in the body is generated in granules in mast cells and in white blood cells (leukocytes)

called basophils and eosinophils.

  • Mast cells are especially numerous at sites of potential injury — the nose,

mouth, and feet, internal body surfaces,

and blood vessels.
  • The most important pathophysiologic mechanism of mast cell and basophil histamine release is immunologic.
  • These cells, if sensitized

by IgE antibodies attached to

their membranes, degranulate when exposed to the appropriate antigen.

  • Histamine release occurs when allergens bind to mast-cell-bound IgE antibodies
Type Location Function
Histamine CNS CNS: sleep-wake
H1receptor cycle (promotes
wakefulness),
Histamine Located on parietal Primarily involved in
H2receptor cells and vascular vasodilation and
smooth muscle cells stimulation of gastric
acid secretion.
Modulates
gastrointestinal function.
Histamine Found on central ????????????????????
H3receptor nervous system and to a
lesser extent peripheral
nervous system tissue

Roles in the body

  • Vasodilation and a fall in blood pressure
  • Effects on nasal mucous membrane
  • Increased vascular permeability causes fluid to escape from capillaries into the tissues, which

leads to the classic symptoms of an

allergic reaction: a runny nose and

watery eyes.

  • Sleep-wake regulation

Histamine neurons increase wakefulness and prevent sleep.

Gastric acid release

Protective effects

Erection and sexual function

  • Libido loss and erectile failure can occur during treatment with histamine H2 receptor antagonists such

as cimetidine, ranitidine, and risperidone

H1 antagonist

  • H1 antagonists, also called H1 blockers, are a class of medications that block the action of histamine at the H1 receptor, helping relieve allergic reactions
  • Histamine, acting on H1-receptors,

produces pruritus, vasodilation, hypotension,

  • flushing, headache, tachycardia, bronchoconstriction, increase in vascular permeability and potentiation of pain

Clinical use of H1-antihistamines

  • Allergic rhinitis
  • Allergic conjunctivitis
  • Allergic dermatological conditions (contact dermatitis)
  • Rhinorrhea (Runny nose)
  • Urticaria

Pharmacist Edson                                                                                                                                                                                                    21

Angioedema

Diarrhea

  • Pruritus (atopic dermatitis, insect bites)
  • Anaphylactic or anaphylactoid reactions—adjunct only
  • Nausea and vomiting
  • Sedation (first-generation H1-antihistamines)

Pharmacist Edson

First-generation antihistamines

include

diphenhydramine

chlorpheniramine

Adverse drug reactions

The most common adverse effect is sedation;

  • This is due to their relative lack of selectivity for the H1-receptor and their ability to cross the blood-brain barrier.

second-generation H1-antihistamines

  • The newer, second-generation H1-antihistamines are far more selective for peripheral histamine H1-receptors and have a better tolerability profile compared to the first-generation agents.
  • The most common adverse effects noted for second-generation agents include drowsiness, fatigue, headache, nausea and dry mouth.

Examples

 

Ketotifen

Cetirizine

Loratadine

Third-generation

  • are intended to have increased efficacy with fewer adverse drug reactions
  • desloratadine & fexofenadine are third generation drugs

H2 antagonist

  • H2 antagonists, also called H2 blockers, are a class of medications that block the action of histamine at the histamine H2 receptors of the parietal cells in the stomach
  • This decreases the production of stomach acid.
  • H2 antagonists can be used in the treatment

of dyspepsia, but have been surpassed by the more effective proton pump inhibitors. They are also used to treat peptic ulcer disease and gastroesophageal reflux disease.

Class members

cimetidine

ranitidine

famotidine

nizatidine

Decongestants

  • Decongestants relieve congestion and are often prescribed along with antihistamines for allergies. They can come in nasal spray, eye drop, liquid, or pill form.
  • Some examples of decongestants that are available over-the-counter include:

pseudoephedrine , phenylephrine

and oxymetazoline nasal sprays, and some eye drops

How Do Decongestants Work?

  • During an allergic reaction, tissues in your nose may swell in response to contact with the allergen. That swelling produces fluid and mucous
  • Blood vessels in the eyes can also swell, causing redness. Decongestants work by shrinking swollen nasal tissues and blood vessels, relieving the symptoms of nasal swelling, congestion, mucus secretion, and redness.

What Are the Side Effects of

Decongestants?

  • Decongestants may raise blood pressure, so they typically are not recommended for people who have blood pressure problems or glaucoma.
  • They may also cause insomnia or irritability and restrict urinary flow.

Steroids

  • Steroids, known medically as corticosteroids, can reduce inflammation associated with allergies.
  • They prevent and treat nasal stuffiness,sneezing, and itchy, runny nose due to seasonal or year-round allergies. They can also decrease inflammation and swelling from other types of allergic reactions.

Some steroids include:

Prescription nasal

steroids:beclomethasone , fluticasone and mometasone

  • Over-the-counter nasal

steroids: budesonide, triamcinolone

  • Inhaled steroids :beclomethasone , fluticasone , mometasone

Eye drops: dexamethasone

Oral steroids: prednisone

What Are the Side Effects of

Steroids

Weight gain

Fluid retention

High blood pressure

 

Anaphylaxis

  • Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death.
  • It typically causes more than one of the following: an itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness, and low blood pressure. These symptoms typically come on over minutes to hours.
  • Common causes include insect bites and stings, foods, and medications
  • The primary treatment of anaphylaxis

is epinephrine injection into a muscle, intravenous fluids, and positioning the person flat

  • Other measures, such as antihistamines and steroids, are complementary

Drugs Used in Anaphylaxis

 

Epinephrine (Adrenaline)

The first step in the management of anaphylaxis is the administration of epinephrine and restoring blood pressure.

  • It should be given immediately by deep intramuscular (IM) or subcutaneous injection to produce vasoconstriction and
  • It is important to keep the air way open.
  • A further treatment follows, including intravenous (IV) hydrocortisone and antihistamine.
  • If the patient has asthma-like symptoms, aminophylline 5 mg/kg is given by slow IV injection.
  • The patient on recovery is maintained with oral antihistamine therapy.

Mode of Action of Epinephrine

  • Acts on the adrenergic nerves (alpha receptors and beta receptors) of the sympathetic system.
  • Alpha receptors are mainly postsynaptic and are found on smooth muscle and beta receptors are mainly presynaptic and are located at peripheral adrenergic nerve terminals.

Dosage

In cardiac arrest: By central IV injection every 5 minutes during the resuscitation efforts, 5-10ml (0.5-1 mg) of 1 in 10,000 (1mg/10ml) solution

Therapeutic Uses

  • Epinephrine is used in the treatment of severe anaphylactic reaction and severe angioedema
  • It relaxes the bronchial muscles and may be injected subcutane-ously to relieve bronchospasm in an acute attack of bronchial asthma
  • Different dilutions of epinephrine solution are used for different routes of administration
  • For the treatment of anaphylaxis, use the treatment regime as shown in the table below
  • The dose may be repeated every 10 minutes as necessary based on blood pressure and pulse records until the patient improves

Caution

Epinephrine should be used with caution in patients with hyperthyroidism, diabetes mellitus and elderly patients

Adverse Effects

Headache is quite common

  • Side effects such as hypertension, tremor, anxiety, sweating, nausea, vomiting, weakness, tachycardia, arrhythmia, dizziness and pulmonary oedema have been reported

Injections may be an irritant but decrease CNS stimulation and hypoten-sion

Mechanism Of Action

  • Epinephrine acts on both alpha and beta-adrenergic receptors.
  • Through its action on alpha-adrenergic receptors, epinephrine lessens the vasodilation and decrease vascular permeability.
  • Through its action on beta-adrenergic receptors, epinephrine causes smooth muscle relaxation and helps alleviate

bronchospasm, wheezing and dyspnea that may occur during anaphylaxis.