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Pharmacology > Autacoid and Autacoid Antagonists > Flashcards

Autacoid and Autacoid Antagonists Flashcards

1
Q

Histamine receptors location and MOA

A

All are G-protein linked and have constitutive activity

H1: endothelium, smooth muscle cells and nerve endings (Gq linked)

H2: gastric mucosa, cardiac muscle cells and some immune cells (Gs linked)

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2
Q

Histamine synthesis and storage

A

Found in granules of mast cells and basophils and can be released due to certain stimuli

Mast cells - found in tissues where there is potential for tissue injury, pressure points, feet, mouth, bifurcations, blood vessels, internal body cavities.

Histamine can also be stored and released from the enterocromaffin-like-cell of the fundus of the stomach.

Formed by decarboxylation of the amino acid L-histidine, a reaction catalyzed by histidine decarboxylase. Once formed, histamine is stored or rapidly inactivated.

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3
Q

Effects of histamine on CVS

A

Vasodilation:
H1: endothelial cell stimulation leads to formation of NO
H2: located on vascular smooth muscle and vasodilation is mediated by cAMP

Heart:
H2 effect
Increased contractility and heart rate

Increased capillary permeability:
H1 action on blood vessels: histamine induced edema due to the separation of endothelial cells –> permits transudation of fluid into perivascular tissue –> responsible for urticaria (hives)

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4
Q

Histamine effects on extravascular smooth muscle, CNS and secretory tissue

A

Contraction of GI Tract smooth muscle (H1)

Bronchoconstriction (H1)

CNS: Stimulant of sensory nerve ending –> mediates pain and itching (H1)

Stimulates gastric acid secretion (H2)

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5
Q

Uses of histamine

A

Pulmonary function testing –> histamine aerosol is sometimes used as provocative test for nonspecific bronchial hyperactivity (like methacholine)

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6
Q

Physiological antagonist of histamine

A

Epinephrine

Opposite action of smooth muscle and acts on different receptors

DOC for anaphylaxis

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7
Q

Histamine release inhibitors and use

A

Cromolyn
Nedocromil

Reduce immunologic mast cell degranulation

b2 agonists - capable of reducing histamine release

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8
Q

H1 receptor antagonists 1st gen (7)

A 
Chlorpheniramine 
Cyclizine 
Diphenhydramine 
Dimenhydrinate 
Hydroxyzine 
Meclizine 
Promethazine
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9
Q

H1 receptor antagonists 2nd gen

A

Fexofenadine
Loratadine
Cetirizine

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10
Q

H1 receptor antagonists 1st gen vs 2nd gen

A

1st gen - have sedative effects and are more likely to enter CNS and have anti-muscarinic effects

2nd gen - less sedating because they are less liposoluble. Substates for P-glycoprotein (limits brain penetration)

H1 antagonists are actually inverse

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11
Q

Uses of H1 receptor antagonists

A

Allergic conditions:
DOC for allergic rhinitis and urticaria

Motion sickness and nausea: First gen block central H1 and M1 receptors. Second gen are ineffective

Somnifacients - First gen used in treatment of insomnia

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12
Q

H1 receptor antagonists AE

A

Sedation - less common with 2nd gen

Dry mouth - due to anticholinergic effects

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13
Q

H2 receptor antagonists and MOA

A

Cimetidine
Ranitidine
Famotidine
Nizatidine

Inhibitors of gastric acid secretion from parietal cells by competitively blocking H2 receptors

Gastrin can stimulate parietal cells to secrete gastric acid in two ways:

1) Directly
2) Stimulate enterocromaffin cells which release histamine which binds to H2 receptors on parietal cells –> main action of gastrin

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14
Q

H2 receptor antagonists uses

A

Peptic ulcers
Acute stress ulcers
GERD

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15
Q

H2 receptor antagonists AE and PK

A

Extremely safe drugs

Headache, dizziness, diarrhea, muscular pain, constipation

Confusion, hallucinations and agitation may occur when given IV (esp in patients in ICU who are elderly or who have renal or hepatic dysfunction)

AE more common with cimetidine

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16
Q

Why are H2 receptor antagonists AE more common with cimetidine?

A

1) Inhibits cytochrome P450 and can slow metabolism of several drugs
2) Binds androgen receptor and has anti-androgenic effects: gynecomastia and reduced sperm count in men and galactorrhea in women

17
Q

Serotonin MOA

A

Formed from the amino acid L-tryptophan by hydroxylation of the indole ring
followed by decarboxylation of the amino acid.

Serotonin is stored or is rapidly inactivated, usually by oxidation catalyzed by MAO.

7 families of 5-HT subtypes: 6 are GPCRs

5-HT3: only monamine NT receptor that functions as a ligand gated ion channel

18
Q

Sumatriptan MOA and uses

A

5-HT1d/1b receptor agonist

First line therapy for acute severe migraine attacks

MOA: Migranes involve trigeminal nerve. At nerve terminal, CGRP (calcitonin gene-related peptide) is released –> binds to receptor on blood vessels and causes vasospasms

5HT1dR on nerve terminal inhibits release of CGRP

5HT1bR on blood vessels mediates vasoconstriction

19
Q

Sumatriptan contraindications

A

Patients with CAD or angina –> may cause coronary vasospasms

20
Q

Cisapride MOA and use

A

5-HT4 receptor agonists use

Prokinetic agent

Prolongs QT interval –> serious cardiac effects therefore no longer generally available in US

21
Q

Cyrproheptadine MOA and uses

A

5-HT2 receptor antagonist + potent H1 antagonist

Uses:

  • allergic rhinitis
  • vasomotor rhinitis
  • management of serotonin syndrome
22
Q

Ondansetron MOA and uses

A

5-HT3 receptor antagonist –> ligand gated receptor

Anti-emetic –> used for severe N/V that occurs due to cancer chemotherapy

23
Q

Ergot alkaloids

A 
Ergotamine 
Dihydroergotamine 
Bromocriptine 
Cabergoline 
Ergonovine 
Methylergonovine

Effects include:
Agonist, partial agonist, antagonist at a-adrenoceptor and 5-HT receptors

Agonist or partial agonists at CNS dopamine receptors

24
Q

Ergot alkaloids used to treat migraines

A

Ergotamine

Dihydroergotamine

25
Q

Ergot alkaloids used to treat hyperprolactinemia

A

Bromocriptine
Cabergoline

Reduce high levels of prolactin due to pituitary tumors

26
Q

Drugs used to treat postpartum hemorrhage

A

Oxytocin - preferred agent

If it is ineffective: can use ergot alkaloids IM
Ergonovine
Methylergonovine

27
Q

Ergonovine uses

A

IM for postpartum hemorrhage

IV for diagnosis of variant angina (it provokes coronary artery vasospasm)

28
Q

Ergot alkaloids AE and contraindications

A

Causes vasospasm

Contraindications:
Pregnancy: may cause fatal distress and miscarriage

Peripheral vascular disease, CAS, hypertension, and impaired hepatic or renal function

Should not be used with other drugs that can cause vasoconstriction

29
Q

Difference between COX1 and COX2

A

COX1 is found in most cells as a constitutive enzyme –> produces prostaglandins involved in normal homeostasis

COX2 is found mainly on inflammatory cells and is induced by inflammatory stimuli

30
Q

Eicosanoids MOA

A

Act in autocrine and paracrine fashion

Activate GPCRs

Contractile effects: mediated by Ca2+

Relaxing effects: mediated by cAMP

31
Q

Misoprostol MOA and uses

A

PGE1 analog

Prevention of peptic ulcers in patients taking high doses of NSAIDs

To ripen cervix at or near term

Management of postpartum hemorrhage

Abortion - used in combination with antiprogestin mifepristone or methotrexate

32
Q

Dinoprostone MOA and uses

A

PGE2

To ripen cervix at or near term

Abortion

33
Q

Alprostadil MOA and uses

A

PGE1

To maintain potency of ductus arteriosus in infants with transposition of the great vessels until surgical correction can be undertaken

For impotence

34
Q

Epoprostenol MOA and uses

A

PGI2

Used in severe pulmonary hypertension

To prevent platelet aggregation in dialysis machines

35
Q

Latanoprost MOA and uses

A

PGFa derivative

Used for glaucoma

36
Q

Inhibitors of 5-lipoxygenase

A

Zileuton

37
Q

Antagosis of LTD4 receptors

A

Zafirlukast

Montelukast

38
Q

Glucocorticoids MOA

A

Inhibit PLA2 –> block release of arachidonic acid

Inhibit synthesis of COX2

Pharmacology (20 decks)

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