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Pharm Block 2 > Histamine and Serotonin > Flashcards

Histamine and Serotonin Flashcards

1
Q

What is Red Man Syndrome?

A

Caused by vancomycin (last resort antibiotic, used to treat gram+ bacteria), following a RAPID IV infusion.

Causes rashes on face, neck and upper torso AND hypotension

Due to mast cell degranulation, not an allergy to vancomycin

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2
Q

What is the mechanism for cromolyn sodium? Route of admin?

A

Stabilizes mast cell membrane to prevent mast cell degranulation and release of histamine.

Anti inflammatory agent used in asthma.

Inhaled; can also be oral, nasal, ophthalmic

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3
Q

Therapeutic use for cromolyn sodium? Side effects?

A

Chronic control of asthma
Prophylaxis of bronchospasms (allergen or exercise induced)
NOT A RESUE MEDICINE

Safe drug/few side effects

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4
Q

When would you use oral, nasal or ophthalmic formulations of cromolyn sodium?

A

Oral: systemic mastocytosis (sig increases in mast cell numbers in skin and internal organs)
Nasal: for allergies
Ophthalmic: for conjunctivitis

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5
Q

How many types of histamine receptors are there? What kind of receptors are they?

A

4; H1-H4

GPCRs

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6
Q

What does histamine do, generally speaking? Include resistance vessels, capillary permeability and BP

A

Dilates resistance vessels
Increase capillary permeability
Decrease BP
* In some vascular beds, histamine constricts VEINS and contributes to edema formation (increased permeability)

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7
Q

Where does histamine act on besides resistance vessels and large vessels?

A

Post capillary venules (endothelial cells)
Heart
Bronchioles
Intestinal smooth muscle
Exocrine glands/GI Secretory tissue (parietal cell)
Peripheral nerve endings
Neuroendocrine effects

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8
Q

H1 receptor blockers are considered ______ (agonist, antagonist, etc)

A

Inverse agonists because they reduce constitutive activity at the receptor and compete with histamine (reversible competitive antagonists with receptors in periphery and brain)

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9
Q

Effects of H1 antagonists are:

A

Reduce symptoms of allergic responses/inflammation

  • Inhibition of vascular permeability
  • Suppress itching/hypersensitivity
  • NO EFFECT ON BP OR BRONCHOCONSTRICTION
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10
Q

What are CNS effects of first generation H1 antagonists?

A

CNS depression - sedation, slowed reaction times, decreased alertness

*Can see CNS stimulation in children with overdose

Some first generation histamine antagonists prevent motion sickness via CNS anti-cholinergic effects

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11
Q

Peripheral and central anticholinergic effects of H1 antagonists?

A

Atropine-like effects (like blocking of muscarinic receptors; mydriasis, increase HR, etc)

  • dry mucus membranes
  • urinary retention
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12
Q

Local anesthetic effect of H1 antagonists?

A

Block nerve conduction with some first generation drugs

PROMETHAZINE

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13
Q

Route of H1 antagonists? When is their peak concentration?

A

Oral administration, rapid absorption
Topical (skin and ophthalmic)
Nasal
Peak concentration 1-2 hours

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14
Q

Which generation of H1 antagonists is less likely to enter the brain?

A

Second generation

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15
Q

How are 2nd generation histamine antagonists metabolized?

A

Heavily by liver; P450 (CYP3A4/CYP2D6)

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16
Q

Minor and less common side effects of H2 antagonists?

A

Diarrhea, headaches, drowsiness

CNS: confusion, delirium, slurred speech with IV use or eldery

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17
Q

Long term use of cimetidine side effects?

A

Decreases testosterone binding
Inhibits CYP that prolongs half life of other drugs
Inhibits CYP enzyme that hydroxylates estradiol -> gynecomastia, reduced sperm count, impotence

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18
Q

Therapeutic uses of H2 antagonists?

A

Treat UNCOMPLICATED GERD - MAJOR USE
Promote healing of gastric/duodenal ulcers
Prevent occurrence of stress ulcers
Heal gastric injury caused by NSAIDs and peptic ulcers secondary to Helicobacter pylori

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19
Q

What is the ranking of potency among H2 antagonists?

A

Famotidine > Ranitidine > Cimetidine

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20
Q

Major side effect of H1 antagonists? Mechanism?

A

Sedation with first generation H1 antagonists; TWO REASONS: (1) inhibition of CENTRAL cholinergic and (2) histaminergic pathways that stimulate arousal/wakefulness

21
Q

Besides sedation, what are other side effects of H1 antagonists?

A
  • GI: loss of appetite, nausea, vomiting (RARELY increases appetite/weight gain via H1 CENTRAL effect to decrease appetite)
  • Anti-muscarinic side effects (FIRST GEN ONLY) like dry mouth, dryness of respiratory passages, urinary retention
22
Q

Where is serotonin located/distributed?

A

Enterochromaffin-like cells, partially in neurons of GI tract 90% - SLOW TURNOVER/RELEASE
Platelets 8% - NO SYNTHESIS
CNS (midbrain raphe nuclei) 2% - FAST TURNOVER/RELEASE, LESS THAN 4 HOURS

23
Q

How many serotonin receptor subtypes are there? What kind of receptors?

A

At least 13

GPCRs

24
Q

What are the serotonin receptor subtypes we learned and each function?

A

5-HT 1(A-E): inhibition of adenylate cyclase
5-HT 2(A-C): phosphoinositide hydrolysis
5-HT 3: ligand gated CATION channel
5-HT4-7: activation of adenylate cyclase/unknown
Autoreceptors 1A and 1D: decrease serotonin release. 1A is somatodendritic and 1D is presynaptic

*5-HT 1A also opens K+ channels

25
Q

Describe melatonin receptors:

A

M1 and M2 subtypes

Associated with Gi - inactive adenylate cyclase

26
Q

Why would someone want to use Loratadine over the other histamine blockers?

A

No cardiac toxicity has been associated with Loratadine

27
Q

What is the difference between H1 and H2 receptors?

A

H1 is found on endothelial cells

H2 is found on VSM cells

28
Q

What happens if a smooth muscle cell has H1 receptors?

A

Contraction

29
Q

How does histamine effect peripheral nerve endings and neuroendocrine effects?

A

Peripheral nerve endings: H1 pain and itching

Neuroendocrine: H1 increase arousal and decrease appetite

30
Q

What effects does histamine have on the GI system?

A

H1: Intestinal smooth muscle contraction
H2: Gastric acid secretion via parietal

31
Q

What effects does histamine have on bronchioles?

A

H1: contraction
H2: relaxation (minor)

32
Q

What effect does histamine have on vessels (resistance vs large)

A

Large vessels: predominated by H1 receptors on SMOOTH muscle (which usually has H2 receptors); histamine acts on H1 receptor on large vessels -> vasoconstriction*

Resistance vessels: Has H1 and H2 receptors in EC and VSM; H1 receptors on EC -> increase calcium -> more NO -> acts on H2 receptors on VSM -> dilation

*Blood pressure not effected by large vessels, ONLY RESISTANCE vessels

33
Q

What effect does histamine have on the heart?

A

Acts via H2 receptors to increase contractility and electrical conduction

THIS IS THE ODD ONE; usually H1 => contraction

34
Q

Anti-cholingeric effects such as _______ are seen with first generation histamine antagonists. True or false?

A

Dry mouth, dryness of respiratory passages, urine retention

TRUE; only seen with first generation antihistamines

35
Q

Allergies are treated with which histamine antagonists?

A

First generation H1 antagonists:
- Diphenhydramine (benadryl, MOST sedation of 1st gens)
- Chlorpheniramine (Most potent, less sedation)
Second Generation H1 antagonists:
ALL of them; cetirizine has MOST sedative effect of 2nd gens

36
Q

Which histamine antagonists are used for motion sickness?

A

Those with anti-cholinergic effects:
DDCP (MINUS C)
- Diphenhydramine, dimenhydrinate, promethazine

37
Q

Non prescription sleeping pills are also which drug?

A

Diphenhydramine (benadryl)

38
Q

What drug is used for early stage Parkinsons?

A

Diphenhydramine (benadryl)

39
Q

What drug is used for vestibular disturbances?

A

Dimenhydrinate

40
Q

What drug is used for chemo-induced nausea and vomiting?

A

Promethazine

41
Q

What are the H2 antagonists?

A

FCR

Famotidine, Cimetidine, Ranitidine

42
Q

Explain how histamine can treat GERD

A

Histamine release from mast cells and ECL cells, stimulated by the vagus nerve and gastrin

Histamine (along with gastrin and Ach) promote acid secretion by parietal cells via H2 receptors

Increase adenyl cyclase, increase cAMP, increase PKA, increase H+ secretion

43
Q

Both H1 and H2 are true antagonists; true or false?

A

False; both act as inverse agonists

44
Q

H2 antagonists reduce _____ and _____ in order to treat ulcers/GERD

A

Gastric acid volume

H+ volume

45
Q

H2 antagonists inhibit ______ and ______; one of which is a major determinant in healing ulcers

A

Basal/fasting gastric acid secretion

Nocturnal gastric acid secretion (MAJOR DETERMINANT)

46
Q

If your patient is on multiple drugs, why is it important to make sure the patient is taking H2 antagonists at the right time?

A

Any drug that inhibits gastric acid secretion can change bioavailability of other drugs

47
Q

What is Zollinger-Ellison Syndrome? How is it treated?

A

Non-beta cell tumor of pancreas -> overproduction of gastrin

H2 antagonists (cimetidine) were used BUT now PPI are preferred.

48
Q

What is Omalizumab and how does it work?

A

Prevents mast cell degranulation

  • Monoclonal IgG antibody who’s Fab region binds to IgE Fc region
  • Decreases the amount of antigen specific IgE antibody that sensitizes mast cells
  • Forms Omalizumab-IgE complex that has no affinity for FcRI
49
Q

How is omalizumab administered? Any adverse effects?

A

SubQ

  • Injection site reaction
  • Anaphylaxis after first dose and in some cases >1 year after initiation of regular treatment

Pharm Block 2 (7 decks)

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