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PHARM3 > Histamine-final > Flashcards

Histamine-final Flashcards

1
Q

Where is histamine located?

A

Mainly in mast cells… they have high affinity IgE binding sites on their plasma membranes

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2
Q

Where is the highest concentration of histamine found?

A

In the lung, skin, nasal and GI mucosa

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3
Q

How is histamine formed?

A

by decarboxylation of the amino acid histidine then stored in granules

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4
Q

What are ways that histamine can be released?

A

trauma, allergies (antibodies), anaphylaxis, cold, bacterial toxins, bee sting venoms, drugs

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5
Q

What are the 2 types of histamine release from mast cells?

A

Cytolytic and noncytolytic

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6
Q

What happens in cytolytic release?

A

The plasma membrane is damaged.
Not energy dependent, No calcium is required
Leakage of cytoplasmic contents

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7
Q

What induces cytolytic release?

A

phenothiazines and narcotic analgesics

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8
Q

What happens in noncytolytic release?

A

no damage to mast cell
Requires energy (ATP) and calcium, and occurs by exocytotic release from granules.
IgE antibodies binding to antigen

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9
Q

what are some other substances and drugs that stimulate histamine release from mast cells without prior sensitization?

A

—Mast cell degranulation protein (from bee venom),
—Radiocontrast media
—d-tubocurare, succinylcholine, morphine, codeine, doxorubicin, protamine
—Vancomycin (red man syndrome)

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10
Q

What are s/s of red man syndrome?

A

flushing, pruritus, chest pain, muscle spasm and hypotension during vancomycin infusion

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11
Q

How can you prevent redman?

A

Pretreatment with intravenous antihistamines

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12
Q

What drugs block the release of histamine from mast cells?

A

Cromolyn and Nedocromil

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13
Q

How do Cromolyn and Nedocromil block the release?

A

Stabilizes mast cells: prevents noncytolytic degranulation.

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14
Q

What are uses of these drugs? When is the only time they are effective?

A

Decreases symptoms of allergic rhinitis.
Prophylactic use to block asthmatic reactions but not useful in managing acute asthmatic attack.
—Effective only if used before a challenge. **

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15
Q

What are the 4 types of histamine receptors?

A

—H1 receptors – phospholipase C mechanism (respiratory and allergic reactions)
—H2 receptors – adenylyl cyclase mechanism parietal cell acid secretion
—H3 receptors – on neurons and inhibit the release of histamine (feedback inhibition)
—H4 receptors – proinflammatory activity

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16
Q

What is the role of histamine in allergy and anaphylaxis?

A
  • stimulate secretions
  • constriction of smooth muscle
  • stimulates sensory nerve endings (itching/pain)
  • dilation of smooth muscle in blood vessels
  • stimulates heart rate and contractility
  • releases catecholamines from the adrenal gland
  • dilation and increased permeability of capillaries
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17
Q

What is the triple response of lewis?

A

1) RED LINE/SPOT - Dilates arterioles producing where injected. (within seconds, maximal 1 min)
2) FLARE - Histamine stimulates nerve endings, which lead to dilatation of arterioles 1-2 cm distant from the injection. A greater area of redness is the third response.
3) WHEAL - Increase in capillary permeability due to local edema

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18
Q

What are the principle targets in hypersensitivity rxn?

A

Mast cells and basophils

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19
Q

What does an allergic response consist of?

A

An antigen producing the formation of IgE antibodies which bind to high affinity receptors specific for these IgE antibodies and activate tyrosine kinase.
This leads to an increase in intracellular calcium which triggers exocytosis of the contents of secretory granules in the mast cells.

20
Q

What are the main differences in allergic rxn and anaphylaxis?

A

—Location of the sites from which mediators are released

—The rates of release of the mediators.

21
Q

What are s/s of a hypersensitivity rxn?

A

Intense warmth, skin reddens, marked effect on palms, hands, face, scalp and ears; hives, nausea, ↓ BP & ↑ HR, bronchospasm and constriction.

22
Q

How does true anaphylaxis need to be tx?

A

Epi

23
Q

When is histamine phosphate used?

A

—Assess nasal and bronchial reactivity.

—Positive control injection: For allergy skin testing.

24
Q

What needs to be d/c before using histamine phosphate testing?

A

antihistamines, tricyclic antidepressants, corticosteroids, benzodiazepines.

25
Q

What are the first generation histamine H1 receptor blockers?

A

triprolidine, diphenhydramine, promethazine, hydroxyzine, chlorpheniramine

26
Q

What are the second generation drugs?

A

loratadine (Claritin, OTC), desloratadine (Clarinex), azelastine (Astelin) , cetirizine (Zyrtec,OTC) fexofenadine (Allegra, OTC)

27
Q

What side effects do second generation drugs lack?

A

Less CNS toxicity or side effects since they do notcross the blood brain barrier or are excluded by p-glycoprotein

28
Q

What is the MOA of H1 blockers?

A

antagonize all actions of histamine except those mediated solely by H2 receptors.
Mainly block the effects histamine on ↑ capillary permeability, edema formation and itching.

29
Q

What do H1 blockers have less of an effect on?

A

bronchoconstriction & vasodilation which are caused predominantly by prostaglandins and leukotrienes

30
Q

Do FDA approved antihistamines prolong the QT interval?

A

NO … terfenadine does when taken with drugs that inhibit the CYP3A4 enzyme… this was removed from the market

31
Q

What are the major differences between first and second generation H1 blockers?

A 
1st generation 
—Anticholinergic
—CNS sedation
—Short acting
2nd generation
—No anticholinergic
—No CNS sedation
—Longer acting
32
Q

When are H1 blockers the DOC?

A

1) allergic rhinitis: itching and edema and prophylactic treatment when a drug known to release histamine must be given.
2) allergic conjunctivitis

33
Q

What is allergic conjunctivitis?

A

Common form of allergic ocular disease, usually associated with rhinitis - itching, hyperemia, tearing, mucus & lid edema.

34
Q

What are side effects of all products?

A

burning/redness/itching of the eyes. In general for all products avoid wearing contact lenses if eyes are red and remove contacts prior to using product

35
Q

What are other therapeutic uses of antihistamines?

A 
Prevention of the Symptoms of Motion sickness:
Prevention of Nausea and Vomiting 
Sleep meds
Antiparkinsonism effects
Local anesthetic actions
36
Q

What is used for motion sickness and when?

A

—Promethazine is the most effective of antihistamines used. Others - diphenhydramine, cyclizine, meclizine
—Action probably relates to anticholinergic effects.
Administered 1 hr before the anticipated motion.

37
Q

What is used for prevention of N/V?

A

—Phenothiazine class: promethazine, timeprazine.

Blockade of dopamine D2 receptors.

38
Q

What drugs are used for sleep meds?

A

—OTC treatment of hyposomnia; diphenhydramine
(Nytol, Benadryl, Tylenol PM, Nytol, Sominex, Tylenol Simply Sleep) & doxylamine (Aldex AN, Nighttime Sleep Aid and Unisom) are FDA approved. [Doxepin(Silenor) ® FDA approved]

39
Q

What is the tolerance for antihistamines when using for sleep?

A

limit to 10 consecutive nights

40
Q

What antihistamine can be used for antiparkinsonism effects?

A

Antimuscarinic actions - Diphenhydramine.

41
Q

What are the 2 uses for local anesthetic actions?

A

—Sunburn preparations – promethazine

—Magic Mouthwash: Formulated from prescription. Used to treat oral ulcers, infections, inflammation, pain

42
Q

What are the ADRs of H1 blockers?

A

Sedation
—Most frequent side effect -1st generation antihistamines
—Other CNS effects - fatigue, dizziness, blurred vision.
CNS sedation correlates with H1 receptor binding in brain
Anticholinergic effects
—Dry mouth and nasal passages, constipation, blurred vision, and urinary retention.
2nd generation antihistamines-
Paradoxical excitation can occur in children.

43
Q

What H1 blockers can cause CNS probs?

A

mainly 1st generation H1 blockers

Combining CNS H1 antagonists with other sedating medications may be dangerous.

44
Q

What are the H1 antagonist drug interactions?

A

potentiate all other CNS depressants

45
Q

What pt population can H1 antagonist poisoning occur in? what are the acute effects?

A 
young children.
These acute effects include:
—initial excitement
—ataxia and convulsions
—coma and cardiorespiratory collapse.

PHARM3 (16 decks)

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