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Pharmacology & Medical Chemistry II > Exam 2: Lecture X, Histamines > Flashcards

Exam 2: Lecture X, Histamines Flashcards

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1
Q

Histamine and serotonin are synthesized from…..

A

amino acids

also antacids

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2
Q

Histamine made from…

A

histidine

stored in high conc in mast cells

Important in pathophysiological reactions (inflammation)
Released in response to IGE-mediated (immediate) allergy

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3
Q

Histamine in mast cells….

A

bound form is biologically inactive, stored in granules in mast/basophils

stimuli can trigger release

mast cells numbers at sites of potential tissue injury

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4
Q

Non-mast cell Histamine….

A

found in several tissues and brain

function as NT in brain…sleep + arousal, thermal/body weight regulation, neuroendocrine control and cardiovascular regulation

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5
Q

Ergot Alkaloids Toxicity Brain

A

Hallucinations resembling psychosis are common with the LSD

Methysergide is occasionally used as a “recreational drug” (an LSD substitute)

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6
Q

Ergot Alkaloids Toxicity Uterus

A

Powerful contractions may be produced during pregnancy
Uterus is progressively more sensitive to ergot alkaloids
Abortions are rare, however better to avoid ergot alkaloids
Avoid migraine treatment with ergot alkaloids during pregnancy

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7
Q

Ergot Alkaloids Toxicity Blood Vessels

A

Strong and prolonged vasoconstriction

An overdose may cause severe ischemia and gangrene

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8
Q

Release of Histamine (immunologic)

A

Immunologic response the important mechanism of mast cell/basophil histamine release

Cells sensitized by IgE attached antibodies degranulate explosively exposed to antigen

Degranulation leads to the release of histamine,ATP, and other stored mediators

Histamine released by this mechanism is a mediator in immediate (type I) allergic reaction

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9
Q

Chemical and Mechanical Release of Histamine

A

Drugs (morphineand tubocurarine) can displace bound histamine from the cells

Loss of granules from the mast cell also releases histamine

Chemical/Mechanical mast cell injury causes degranulation and histamine release

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10
Q

Histamine Effects

A

Flushing
Hypotension
Tachycardia
Bronchoconstriction

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11
Q

H1

A

Tissue:Smooth muscles, endothelium, brain

Signal Transduction:Gq; ↑IP3, DAG

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12
Q

H2

A

Tissue:Stomach, heart, mast cells, brain

Signal Transduction:Gs; ↑cAMP

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13
Q

H3

A

Tissue:Nerve endings, CNS, plexuses

Signal Transduction:Gi; ↓cAMP

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14
Q

H4

A

Tissue:Eosinophils, neutrophils, CD4 T-cells

Signal Transduction:Gi; ↓cAMP

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15
Q

H1 effects

A

Important in processes caused by IgE-mediated allergic responses
Typical responses – bronchoconstriction, and vasodilation
Vasodilation occurs due to release of NO
Capillary endothelium permeability increases with edema formation

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16
Q

H2 effects

A

Mediates gastric acid secretion by parietal cells
Cardiac stimulant effect.
By a negative feedback reduces histamine release from mast cells

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17
Q

H3 effects

A

Operates in presynaptic neurons in the CNS

Modulation of histamine neurotransmission in the CNS

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18
Q

H4 effects:

A

Operates in chronic inflammatory conditions

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19
Q

H1 antagonists:

A

Histamine solo = no therapeutic application

Histamine aerosol used as provocative test of bronchial hyperactivity

drug that block histamine effect = v important

Competitive antagonists at the H1 receptor in the periphery

Do not affect the release of histamine from storage sites

H1 antagonists resemble muscarinic antagonists and alpha-adrenergic blockers

H1 antagonists are pharmacological antagonists at muscarinic receptors and alpha-receptors

H1 antagonists may block serotonin receptors

H1 antagonists are characterized by extensive liver metabolism

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20
Q

1st vs 2nd Gen H1 antagonists

A

1st = strong sedative effects
more likely to block autonomic receptors

2nd = less sedating
h1 blockers less distributed into CNS

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21
Q

H1 antagonist Typical Effects

A 
Sedation
Antinausea and antiemetic effect
Antiparkinsonism effects
Anticholinoceptors effects
Antiadrenoreceptor effects
Antiserotonin effects
Local anesthesia
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22
Q

1st gen antihistamines

A

Ethanolamines: Carbinoxamine (Clistin), Diphenhydramine (Benadryl)

Piperazine derivatives: Hydroxyzine (Atarax), Meclizine (Bonine)

Alkylamines: Brompheniramine (Dimetane), Chlorpheniramine (Chlor-Trimeton )

Phenothiazine derivatives: Promethazine (Phenergan)

Miscellaneous agents: Cyproheptadine (Periactin)

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23
Q

2nd gen antihistamines

A

Piperidine: Fexofenadine (Allegra)

Miscellaneous agents: Loratadine (Claritin), Cetirizine (Zyrtec)

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24
Q

Diphenhydramine (Benadryl)

A

Treatment of Allergic reactions:
H1 receptors blockers are used for allergic conditions
Hay fever, urticaria, drug-sensitivity rashes, insect bite and stings
Agents are not effective in asthma.

CNS effects: Sedation, motion sickness, nausea, and vomiting

Anesthetic effect: Many H1 blockers are potent local anesthetics

25
Q

Diphenhydramine (Benadryl) Toxicity

A

Toxicity: Common
Highly sedative (diphenhydramine and promethazine)
Antimuscarinic effect: Dry mouth and blurred vision
Alpha-blocking effect: Orthostatic hypotension

Less common toxicity:
Excitation and convulsion in children
Allergic responses (topical application of H1 antagonists)

26
Q

H2 antagonists

A

Selectively block H2 receptors

Structurally do not resemble H1 blockers

No effect upon H1 receptors, 5-HT receptors, or α-receptors

Active orally

Relatively non-toxic

Possible to use in large doses (single dose for 12-24 hours)

27
Q

H2 antagonists Clinical Uses

A

Reduction of gastric acid secretion

Acid-peptic disease - especially duodenal ulcer

Effective in healing and preventing recurrences in gastric peptic ulcer

Effective in acid hypersecretion, GI bleedings, and diarrhea

Acute ulcer is treated with 2 doses/day

Accelerate healing

Prevent recurrences

Recurrence can often be prevented with 1 single bedtime dose
Very useful agents!

28
Q

H2 prototype antagonist

A

Cimetidine (Tagamet)

Relatively selective and have no effect upon H1 receptors

Relatively non-toxic - can be given in large doses

Main application in acid-peptic disease - especially duodenal ulcer

Accelerates healing and prevents recurrences

Recurrences may be prevented by a single bedtime dose

Also effective in healing and preventing severe gastric peptic ulcers

Very helpful in controlling acid hypersecretion

Very helpful in treatment of GI bleeding and diarrhea

May be used to treat gastroesophageal efflux disease (GERD)

29
Q

Cimetidine (Tagamet) Toxicity

A

Relatively non-toxic

Potent inhibitor of hepatic enzymes

May reduces hepatic blood flow

Antiandrogen effect in many patients

(Newer H2 blockers do not have endocrine effects)

** Alcohol: Very serious drug interaction may occur

30
Q

Serotonin Syndorme

A

skeletal muscle contraction precipitated when MAO inhibitors are given together with SSRI antidepressants. Two mechanisms are discussed – hyperthermia caused by muscle contraction, or by the effect of drugs upon the CNS

31
Q

Serotonin is produced from amino acid….

A

tryptophan

potent pain stimulant

32
Q

Ondansetron (Zofran, Zuplenz)

A

5-HT3 blocker

Prevention of nausea and vomiting caused by chemotherapy and radiotherapy

33
Q

Cyproheptadine (Periactin)

A

5-HT2 blocker and H1 blocker

Treatment of allergy symptoms – sneezing, watery eyes, and itching

34
Q

Ketanserin ( Sufrexal )

A

5-HT2 and alpha adrenoreceptor blocker

An antihypertensive agent, and a scientific tool to study 5-HT2 receptors

35
Q

Dexfenfluramine (Redux)

A

serotonin uptake inhibitor
Inhibits the reuptake carrier for 5-HT
Characterized by a pronounced and effective appetite-reducing effect

Toxicity:
Related to serious cardiac disease in patients – was withdrawn (2010)

36
Q

Sumatriptan (Imitrex)

A

5-HT1d and 5-HT1B agonist.
Effective in the treatment of acute migraine and cluster headaches
Available for oral, nasal, and parenteral administration

37
Q

5-HT3 Distribution

A

CNS sensory system. Chemoreceptors, vomiting center,

and enteric system

38
Q

5-HT2 Distribution

A

CNS excitation system, smooth muscles, gut, bronchi,

uterus, vessels, and platelets

39
Q

5-HT1d Distribution

A

Brain

40
Q

5-HT6,7 Mechanism

A

Gs, increase cAMP

41
Q

5-HT2 Mechnism

A

Gq, increase IP3/DAG

42
Q

All other 5-HT receptors mechanism….

A

Gi, decrease cAMP

43
Q

5-HT3 Mechanism

A

Gated channels, resembles Ach at nicotinic channels

44
Q

Ergot Alkaloids

A

Ergot alkaloids are complex molecules

Produced by a fungus in wet or spoiled grain

Fungus also synthetize histamine, Ach, and tyramine

Were responsible for the epidemics of “St. Anthony’s Fire”

These epidemics were frequent during the Middle Ages

45
Q

Ergot Alkaloids Receptors

A

Partial agonists at alpha-adrenoreceptors and 5-HT receptors

Some ergot alkaloids are strong agonists at dopamine receptors

46
Q

Ergot Alkaloids Classification base on….

A

organ or tissue involved

47
Q

Bromocriptine (Parlodel, Barlolin, Brocriptin, and Butin )

A

for Parkinsonism

extremely effective in reducing the high levels of prolactin from pituitary tumors

associated with regression of the tumor, in some cases

48
Q

Ergotamine used to treat….

A

acute migraine

49
Q

Methysergide (Deseril) used for…..

A

migraine prophylaxis….not frequently prescribed

50
Q

Ergot Alkaloid effect on blood vessel

A

OD can cause ischemia and gangrene

Strong/prolonged a receptor mediated vasoconstriction

51
Q

Migraine treatment

A

Ergot derivatives are highly specific for migraine pain
Preferred by clinicians and patients

Ergotaminetartrate for oral, sublingual, rectal, and inhaler use

Often combined withcaffeine

Vasoconstriction is long-lasting and cumulative

Patient: careful with the oral preparation (10 mg per week)

Ergotaminetartrate may be given intravenously or intramuscularly

52
Q

Ergot Alkaloid effect on Brain

A

Hallucinations – more prominent with naturally occurring substances and LSD

Hallucinations – less prominent with therapeutic agents

53
Q

Ergot Alkaloid effect on Uterus

A

Powerful contraction near term

Early in pregnancy high doses may cause abortion or miscarriage

Useful contraction after placenta delivery (postpartum bleeding)

Postpartum contractions reduce blood loss

  • **Ergonovine (Ergotrate)
  • *** Ergotamine
54
Q

Preferred agent for control of postpartum hemorrhage…..

A

Oxytocin

55
Q

Ergonovine use….

A

only for control for postpartum uterine bleeding

should never be given before delivery

56
Q

Vasoselective Ergot

A

Ergotamine

used: Migraine/cluster headache

Duration: 12–24 h
Toxicity:Prolonged vasospasm causing angina, gangrene; uterine spasm

57
Q

Uteroselective Ergot

A

Ergonovine

Used: postpartum bleeding/migraine headache

Duration: 2-4 h
Toxicity:Prolonged vasospasm causing angina, gangrene; uterine spasm

58
Q

CNS selective Ergot

A

LSD
uses: none
Duration: hours
Toxicity: prolonged psychotic state/flashbacks

Pharmacology & Medical Chemistry II (43 decks)

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