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Questions and Answers
What is the main function of histamine in the body?
What is the main function of histamine in the body?
Inflammation, immediate allergic reaction, neurotransmitter, neuromodulator
Which receptor type leads to vasoconstriction in the cardiovascular system when activated by serotonin?
Which receptor type leads to vasoconstriction in the cardiovascular system when activated by serotonin?
Serotonin is formed from amino acids 'L-tryptophan' by hydroxylation, followed by decarboxylation, and is metabolized to '5-hydroxyindoleacetic acid (5-HIAA)' by ________ and ________.
Serotonin is formed from amino acids 'L-tryptophan' by hydroxylation, followed by decarboxylation, and is metabolized to '5-hydroxyindoleacetic acid (5-HIAA)' by ________ and ________.
monoamine oxidase, aldehyde dehydrogenase
Histamine agonists can be used for the treatment of allergy symptoms.
Histamine agonists can be used for the treatment of allergy symptoms.
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What is the primary use of Dexfenfluramine?
What is the primary use of Dexfenfluramine?
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Which receptors does Cyproheptadine act on?
Which receptors does Cyproheptadine act on?
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Methysergide is primarily used for the treatment of postoperative ________.
Methysergide is primarily used for the treatment of postoperative ________.
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Ergotamine is contraindicated in liver disease.
Ergotamine is contraindicated in liver disease.
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Match the ergot alkaloid with its use:
Match the ergot alkaloid with its use:
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Study Notes
Autacoids
- Definition: Local hormones, heterogeneous substances with different structures and diverse pharmacological actions.
Histamine
- Chemistry: Formed from amino acid "Histidine" by decarboxylation, stored in mast cells and basophils.
- Functions:
- Inflammation
- Immediate allergic reaction
- Neurotransmitter and neuromodulator
- Release:
- Immunologic reaction (Allergy)
- Mechanical injury
- Inflammation
- Chemical release (e.g., morphine, trimethaphan, succinylcholine)
- Toxins (e.g., snake venom)
Histamine Receptors
- H1: Endothelium, smooth muscles, brain, and skin
- H2: Gastric mucosa, cardiac muscle, brain, and endothelium
- H3: Presynaptic neurons
- H4: Leukocytes, bone marrow, and blood
- Intracellular receptor mechanism:
- H1: Increase IP3 and DAG, nitric oxide release, and vasodilatation
- H2: Increase cAMP, calcium, and gastric HCl and pepsin
- H3: Decrease cAMP, decrease transmitter release
- H4: Decrease cAMP, chemotactic effect on eosinophils and mast cells
Histamine Agonists and Antagonists
- Agonists:
- H3: Treatment of obesity, antipsychotics
- H4: Allergic rhinorrhea
- Antagonists:
- Physiologic antagonists: Adrenaline
- Histamine release inhibitors: Cromolyn, Nedocromil
- Adrenal steroids: Inhibit antigen-antibody reaction
- Pharmacologic competitive antagonists:
- H1: Doxylamine, Diphenhydramine, Loratidine
- H2: Burimamide
- H3: Clobenpropit, Tiprolisant
- H4: Diphenhydramine, Cetrizine, Loratidine
Antihistaminics (H1 Receptor Blockers)
- Classification:
- First generation: Sedating, lipophilic, and penetrate CNS
- Second generation: Less sedating, less lipophilic, and less CNS penetration
- Pharmacodynamics:
- Reversible competitive blockers at H1 receptors
- Block effects of histamine: Vasodilatation, hypotension, increased capillary permeability
- Sedation, antiemetic, and antiparkinsonian effects
- Pharmacokinetics:
- Lipid soluble, metabolized by liver microsomal enzymes, and excreted through renal and milk
- Therapeutic uses:
- Allergic reactions
- Nausea and vomiting of pregnancy
- Motion sickness prophylaxis
- Sedative-hypnotic
- Adverse effects:
- Sedation, dizziness, CNS depression, dry mouth, constipation, and urine retention
Serotonin (5-HT)
- Chemistry: Formed from amino acid "L-tryptophan" by hydroxylation and decarboxylation
- Functions:
- Neurotransmitter
- Gastrointestinal tract:
- Contraction of smooth muscles
- Stimulates ACh release
- Cardiovascular system:
- Vasoconstriction
- Platelet aggregation
- Reflex bradycardia
Serotonin Receptors
- 5-HT1A and 5-HT1B: CNS
- 5-HT2: CNS, platelets, and smooth muscles
- 5-HT3: CNS, peripheral nerves, and vagal afferent
- 5-HT4: GIT (ENS)
Serotonin Agonists and Antagonists
- Agonists:
- 5-HT1A: Buspirone, Triptans
- 5-HT2: Appetite suppressant
- 5-HT4: Prokinetic
- Antagonists:
- 5-HT2: Cyproheptadine, Methysergide
- 5-HT3: Ondansetron, Granisetron
Ergot Alkaloids
- Chemistry: Derivatives of "Lysergic acid"
- Classification:
- Natural alkaloids
- Semisynthetic derivatives
- Pharmacokinetics:
- Ergotamine: Poor oral absorption, delayed onset, and prolonged duration
- Ergometrine: Complete oral absorption, short duration, and no CNS distribution
- Pharmacodynamics:
- Ergotamine:
- Alpha-1 adrenoceptor: Partial agonist
- 5-HT2: Partial agonist
- Oxytocic effect
- Stimulates CIC and CTZ
- Ergotoxine:
- Alpha-1 adrenoceptor blocker
- Inhibits VMC
- Oxytocic effect
- Stimulates CIC and CTZ
- Ergotamine:
Ergot Alkaloids (continued)
- Uses:
- Ergotamine: Acute attack of migraine
- Ergotoxine: Senile cerebral insufficiency, peripheral vascular disease
- Ergometrine: Postpartum hemorrhage, subinvolution of uterus
- Methylergometrine: Treatment of postpartum hemorrhage
- Adverse effects:
- Ergotamine: Cold extremities, tingling, numbness, gangrene, hypertension, and nausea
- Contraindications:
- Ergotamine: Coronary heart disease, peripheral vascular disease, hypertension, pregnancy, liver disease, and renal disease
Migraine Headache
- Definition: Paroxysmal, unilateral headache
- Clinical picture:
- Aura: Visual, sensory, and motor manifestations
- Headache: Vasodilatation of cerebral blood vessels, unilateral, throbbing, and lasts for several hours
- Prophylaxis:
- Avoid precipitating factors
- Serotonin antagonists
- Propranolol
- Amitriptyline
- Flunarizine
- Treatment:
- Mild attack: Analgesics, antiemetics
- Severe attack: Ergotamine or Dihydroergotamine + Caffeine, Sumatriptan, or Triptans
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Description
This quiz covers autacoids, including antihistaminics, H2 antagonists, serotonin agonists and antagonists, and ergot alkaloids, their therapeutic uses, and adverse effects.
