9 Questions
Ergot alkaloids are derivatives of ______.
Lysergic acid
Which of the following are adverse effects of Ergotamine? (Select all that apply)
Cold extremities
Ergometrine has no CNS distribution. (True/False)
True
What is the primary use of Methylergometrine?
Treatment of postpartum hemorrhage
What is the main function of histamine in the body?
Inflammation, immediate allergic reaction, neurotransmitter, neuromodulator
Which receptors are involved in the actions of histamine?
H1
Histamine agonists are used in the treatment of allergic rhinorrhea.
False
Histamine antagonists that inhibit degranulation of mast cells are known as ____________.
histamine release inhibitors
Match the following serotonin receptors with their effects:
5-HT1A and 5-HT1B = CNS actions related to mood, behavior, sleep, and anxiety 5-HT2 = Vasoconstriction, platelet aggregation, and contraction in various systems 5-HT3 = Regulates emesis, pain perception, and the chemoreceptor reflex 5-HT4 = Enhances gastrointestinal motility and has a prokinetic effect
Study Notes
Autacoids
Definition and Classification
- Autacoids: local hormones with heterogenous structures and diverse pharmacological actions
- Classified into:
- Amines: histamine, serotonin
- Ergot alkaloids
- Vasoactive peptides: angiotensin II, vasopressin, endothelin, natriuretic peptides, substance P, neurotensin
- Fatty acid derivatives: eicosanoids, platelet-activating factor (PAF)
Histamine
Chemistry and Functions
- Amine formed from amino acid histidine
- Functions:
- Inflammation
- Immediate allergic reaction
- Neurotransmitter
- Neuromodulator
Release of Histamine
- Release mechanisms:
- Immunologic reaction (allergy)
- Mechanical injury
- Inflammation
- Chemical stimulation (drugs, toxins)
Histamine Receptors
- Four types of receptors:
- H1: endothelium, smooth muscles, brain, skin
- H2: gastric mucosa, cardiac muscle, brain
- H3: presynaptic neurons
- H4: leukocytes, bone marrow
Actions of Histamine
- Vasoactive effects:
- H1: vasodilation, hypotension, increased capillary permeability
- H2: positive chronotropic and inotropic effects
- H3: decreased transmitter release
- H4: chemotactic effect
Antihistamines
- Types:
- Physiologic antagonists (adrenaline)
- Histamine release inhibitors (mast cell stabilizers)
- Adrenal steroids (inhibit antigen-antibody reaction)
- Pharmacologic competitive antagonists (H1, H2, H3, H4 receptors)
Antihistaminics (H1 Receptor Blockers)
First Generation
- Examples: diphenhydramine, chlorpheniramine, promethazine
- Characteristics:
- Lipid soluble
- Metabolized by liver microsomal enzymes
- Renal excretion
- Short duration (4-6 hours)
- Sedation
Second Generation
- Examples: fexofenadine, loratidine, cetirizine
- Characteristics:
- Less lipid soluble
- Metabolized by hepatic microsomal enzymes (CYP3A4)
- Longer duration (12-24 hours)
- No sedation
Pharmacodynamics
- Reversible competitive blockade of H1 receptors
- Effects:
- Relief of allergic symptoms
- Sedation
- Antiemetic and antinausea
- Antiparkinsonian
Therapeutic Uses
- Allergic reactions
- Nausea and vomiting of pregnancy
- Motion sickness prophylaxis
- Sedative-hypnotic
Adverse Effects
- Sedation
- Dizziness
- CNS depression
- Excitation
- Dry mouth
- Constipation
- Urine retention
- Teratogenic
Serotonin (5-HT)
Chemistry and Functions
- Formed from amino acid L-tryptophan
- Functions:
- Neurotransmitter
- Neuromodulator
- Potent stimulant for pain and itching
- Gastrointestinal tract contraction
Receptors
- Five types of receptors:
- 5-HT1A and 5-HT1B: CNS
- 5-HT2: CNS, platelets, peripheral blood vessels
- 5-HT3: CNS, peripheral nerves
- 5-HT4: GIT (enteric nervous system)
Agonists and Antagonists
- Agonists:
- Buspirone (5-HT1A)
- Triptans (5-HT1D)
- Itopride (5-HT4)
- Antagonists:
- Cyproheptadine (5-HT2, H1, muscarinic)
- Methysergide (5-HT2)
Adverse Effects and Contraindications
- Agonists:
- Tingling, dizziness, neck pain, chest pain
- Contraindicated in angina, hypertension, peripheral vascular disease, pregnancy
- Antagonists:
- Drowsiness, dry mouth, retroperitoneal and pleural fibrosis
Ergot Alkaloids
Chemistry and Classification
- Derivatives of lysergic acid
- Classification:
- Natural alkaloids
- Semisynthetic derivatives
Pharmacokinetics
- Poor oral absorption
- Caffeine increases absorption
- Delayed onset and prolonged duration
Pharmacodynamics
- Partial agonist at alpha-1 adrenoceptor and 5-HT2 receptors
- Stimulates oxytocic effect, cardiac inhibitory center, and chemoreceptor trigger zone
Uses
- Acute attack of migraine
- Postpartum hemorrhage
- Subinvolution of uterus
- Variant (Prinzmetal) angina
Adverse Effects and Contraindications
- Cold extremities, tingling, numbness, gangrene, hypertension, nausea, and vomiting
- Contraindicated in coronary heart disease, peripheral vascular disease, hypertension, pregnancy, liver disease, and renal disease
Migraine Headache
Definition and Clinical Picture
- Paroxysmal unilateral headache
- Preceded by aura
- Characterized by unilateral throbbing headache, nausea, and pallor
Prophylaxis
- Avoidance of precipitating factors
- Serotonin antagonists
- Propranolol
- Amitriptyline
- Flunarizine
Treatment
- Mild attack: analgesics, antiemetics
- Severe attack: ergotamine or dihydroergotamine with caffeine, sumatriptan
This quiz covers autacoids, antihistaminics, and serotonin agonists and antagonists, including their therapeutic uses and adverse effects.
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