Introduction to Histamine and Antihistamine Role of histamine, Synthesis, Storage, release of histamine Mechanism of action of histamine Anti histamine, Therapeutic uses, Adverse effects Presented by Shaik Sabeena Department of Pharmacology

1. RIPER
AUTONOMOUS
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NBA (UG)
SIRO- DSIR
Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721
A Seminar as a part of curricular requirement
for Ist Year M.Pharm, Ist
Semester.
Shaik Sabeena (20L81S0112)
M pharm ( Department of Pharmacology)
A. Sudheer Kumar, M.Pharm
Associate Professor, Department of Pharmacology
HISTAMINE AND ANTIHISTAMINE

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NAAC &
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Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 2
CONTENTS
Introduction
Role of histamine
Synthesis, Storage, release of histamine
Mechanism of action of histamine
Anti histamine
Therapeutic uses
Adverse effects
Reference

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AUTONOMOUS
NAAC &
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Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 3
Chemical messenger that mediates a wide range of cellular responses,
including allergic and inflammatory reactions, gastric acid secretion, and
neurotransmission in parts of the brain
Plays an important role in gastric acid secretion as well as acting as a
neurotrasmitor.
HISTAMINE
Introduction:
Histos:tissue
Histamine:tissue amine

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K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 4
 Histamine is present mostly with in storage granules of mast cells.
 Tissues rich in histamine are skin, gastric and intestinal mucosa, lungs liver
and placenta.
 Non mast cells of histamine occurs in brain, epidermis and gastric mucosa
growing regions.
Occurs as a component of venoms and in secretions from insect strings.
Location of Histamine

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K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 5
Synthesis of Histamines :
Histamine is an amine formed by the decarboxylation of the
amino acid histidine by histidine decarboxylase

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K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 6
Immunologic Release:
immunological stimulus.
↓
 In mast cells, if sensitized by surface IgE antibodies, degranulate
when exposed specific antigen.
 Degranulation is involved in the immediate (type I) allergic
reaction.
Histamine: Storage and Release

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K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 8
Mechanism of action of Histamine

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K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 9
 Itching, Urticaria
 Flushing
 Hypotension
 Tachycardia
 Bronchospasm
 Angioedema
 Wakefullness
 Increased acidity (Gastric acid secretion)
Adverse Effects of Histamine Release

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Antihistamines
classification:
H1-blockers
First generation agents Second-generation agent
Diphenhydramine Cetirizine
Promethazine Levocetirizine
Cinnarizine Azelastine
Cyclizine Loratadine
Hydroxyzine Fexofenadine
Triprolidine Rupatadine

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• widely used
• effective
• inexpensive
• penetrate the CNS
• cause sedation
• Produces side effect
First Generation Drugs

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 Allergic rhinitis and common cold
 Allergic dermatitis, itching, Urticaria
 Allergic conjunctivitis
 Motion sickness
 Morning sickness
 Vertigo
 Appetite stimulant
Therapeutic Uses

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Absorption:
• Oral, parenteral routes
Distribution:
• Throughout body.. Enter Brain Newer compounds penetrate
poorly
Metabolism:
• Metabolized by Liver
Excretion:
• Excreted in Urine
Pharmacokinetics

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 Specific for H1 receptors.
 Do not penetrate the blood-brain barrier.
 Show less CNS toxicity than the first-generation
drugs.

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 Block the actions of histamine at all H2 receptors.
 Chief clinical use is to inhibit gastric acid secretion.
 Effective against nocturnal acid secretion.
 Competitively blocking the binding of histamine to H2 receptors.
Drugs: Cimetidine, Ranitidine, Famotidine, Nizatidine.
Histamine H2-Receptor Blockers

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 Act selectively on H2 receptors in the stomach, blood
vessels, and other sites.
 No effect on H1 receptors.
 Competitive antagonists of histamine.
 Fully reversible.
 Completely inhibit gastric acid secretion induced
by histamine or gastrin.
Mechanism Of Action

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 Peptic ulcers
 Acute stress ulcers
 Gastro-esophageal reflux disease
Therapeutic Uses:

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Cimetidine:
Given orally, distribute widely throughout the body. Excreted mainly in the urine.
Ranitidine:
Five- to ten-fold more potent. Longer acting.
Minimal side effects.
Famotidine:
Similar to ranitidine
20 to 50 times more potent than cimetidine.
Nizatidine:
Similar to ranitidine in its pharmacologic action and potency.
Eliminated by the kidney.
Pharmacokinetics

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• Reduced gastric acid production
• Headache
• Dizziness
• Diarrhea
• Muscular pain
Adverse Effects

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Raghavendra Institute of Pharmaceutical Education and Research - Autonomous
K.R.Palli Cross, Chiyyedu, Anantapuramu, A. P- 515721 20
• H3-selective ligands may be of value in sleep disorders, obesity,
and cognitive and psychiatric disorders.
• Tiprolisant, an inverse H3-receptor agonist, has been shown to reduce
sleep cycles in mutant mice and in humans with narcolepsy.
• Not clinically important.
• Other drugs
Clobenpropit
Histamine H3-Receptor Blockers

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• Chronic inflammatory conditions such as asthma.
• No selective H4 ligand is available for use in humans.
• Useful in pruritus.
• Not yet clinically important
• Drug: Thioperamide
Histamine H4-Receptor Blockers

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• Basic and Clinical Pharmacology 11th Edition Katzung.
• Lippincott's Illustrated Reviews Pharmacology 4th Edition.
• Tara V Shanbhag.
References

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