HISTAMINE AND ANTIHISTAMINE

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. A Seminar as a part of curricular requirement for Ist Year M.Pharm, Ist Semester. Presented By Shaik Sabeena (20L81S0112) M pharm ( Department of Pharmacology) Under the guidance of A. Sudheer Kumar, M.Pharm Associate Professor, Department of Pharmacology HISTAMINE AND ANTIHISTAMINE

2. CONTENTS Introduction Role of histamine Synthesis, Storage, release of histamine Mechanism of action of histamine Anti histamine Therapeutic uses Adverse effects Reference

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

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

5. Synthesis of Histamines : Histamine is an amine formed by the decarboxylation of the amino acid histidine by histidine decarboxylase

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

7. Mechanism of action of Histamine

8. Itching, Urticaria Flushing Hypotension Tachycardia Bronchospasm Angioedema Wakefullness Increased acidity (Gastric acid secretion ) Adverse Effects of Histamine Release

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

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

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

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

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

14. 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, F a motidine, Nizatidine. Histamine H2-Receptor Blockers

15. 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

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

17. Cimet i dine : 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

18. Reduced gastric acid production Headache Dizziness Diarrhea Muscular pain Adverse Effects

19. 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

20. 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

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

22. THANK YOU