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Pharm Exam 5 > Antihistamines > Flashcards

Antihistamines Flashcards

1
Q

H1 receptors

  • tissue expression?
  • post-receptor mechanism?
A
  • smooth muscle, endothleium, brain, sensory neurons in skin, immune cells
  • G_q–> +IP3 –> DAG
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2
Q

H2 receptors

  • tissue expression?
  • post-receptor mechanism?
A
  • gastric mucosa, cardiac muscle, mast cells, brain vasculature
  • G_s –> inc cAMP
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3
Q

H3 receptors

  • tissue expression?
  • post-receptor mechanism?
A
  • pre-synaptic autoreceptors and heteroreceptors: brain, myenteric plexus and other neurons
  • G_i –> dec cAMP
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4
Q

H4 receptors

  • tissue expression?
  • post-receptor mechanism?
A
  • eosinophils, neutrophils, CD4 T-cells

- G_i –> dec cAMP

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5
Q

H1 inhibitors are used to?

A

tx:

  • allergic rxns
  • motion sickness
  • nausea
  • vomiting
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6
Q

H2 inhibitors are used for?

A

tx:

-inh acid secretion from parietal cells (GERD & ulcers)

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7
Q

What do H3 inhibitors tx?

A

-NO approved Tx’s

but H3=allergic rhinitis, Alzheimers, ADHD, epilepsy, narcolepsy, neuropathic pain, obesity

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8
Q

What do H4 inhibitors tx?

A

NO approved tx’s

-but H4=allergic rhinitis, atopic dermatitis, asthma, and other chronic inflammatory & autoimmune disorders

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9
Q

Histamine in the nervous system:

  • His neurons found where?
  • His release?
  • what effect does histamine have via PNS and CNS receptors?
A
  • histaminergic neuron cell bodies found in part of hypothalamus and go to all parts of the brain
  • release is circadian pattern =inc at night and dec at day (regulates wakefulness and appetite/satiety)
  • mediates itch
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10
Q

Histamine effects on the vasculature? WHich receptor?

A

1) H1 and H2 mediated dilation of small blood vessel
- dec TPR – dec systemic BP (reflex tachycardia)
- inc vascular permeability - H1 receptors

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11
Q

Histamine effects on the lungs? Which receptor?

A

H1 in lungs =elevated secretion of airway fluid and electrolytes + BRONCHOCONSTRICTION

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12
Q

Histamine effects on the heart? Which receptor?

A

H2 activation = +pacemaker rate and contractility (more calcium in cells)

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13
Q

Histaime effect on the immune system?

A
  • part of response against foreign stuff
  • facilitates accumulation of immune cells at site of infection or damage
  • -> inc vascular permeability
  • ->Immune cell adhesion (inc P-selectin expression)
  • -> Chemotaxis of eosinophils and neutrophils
  • -> Inc release of inflammatory cytokines
  • -> Inc antigen presentation of APC cells
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14
Q

Describe process and role of histamine in an allergic reaction:

A

1) APC cell expresses allergen to Naive T-cell on MHC class II
2) Naive T-cells acquire the characteristics of TH2 helper cells
3) IL4 and IL3 secreted + other interactions == B-cells secrete allergen specific IgE
4) IgE cross links antigen on mast cell=degranulation of histmine and other stuff ===> airways and smooth muscle vasoconstriction + BV vasodilation + mucous production

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15
Q

Symptoms of histamine release?

A
  • wheal (bumps) & flare (redness)
  • pruritus
  • nasal conjunctival discharge
  • mucous production
  • angioedema
  • systemic anaphylaxis
  • brochoconstriction
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16
Q

Molecular cascade of mast cell histmaine release:

A

1) Allergen binding to IgE bound FCERI membrane protein
- -> activates tyrosine kinases Lyn and Syk
2) Lyn and Syk phos membrane protein LAT
3) Activated LAT –> helps with PLCy activation –> (–> IP3
- -> DAG) inc intracellular calcium and PKC activation
4a) ==> degranulation of preformed Histamine + activation of transcription factors that inc the synthesis of cytokines
4b) ==> MAPK cascade activated –> ++ expression of eicosanoids and cytokines

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17
Q

MOA for histamine release from mast cells? triggers for each?

A

1) Cytolytic histamine release
- membrane damage
- high levels (more than therapeutic) phenothiazines, H1 antagonists, opioids
- mechanical damage
2) Noncytolytic histamine release
- immune response from prior sensitization
- non-immune respone from basic polypeptides ex) neuropep substance P (wasp venom) and protamine –> response not through FCERI receptor
- morphine, codine, antibiotic release of histamine
- unexpected anaphylactoid reactions

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18
Q

Anaphylaxis is what and effects on body?

A
  • severe alelrgic rxn
  • hypotension - vasodilation
  • myocardial depression
  • dysrhythmias
  • utricaria (hives)
  • angioedema
  • bronchospasm
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19
Q

Anaphylaxis is partially relieved by inhibiting which receptors?

A
  • partially via H1 and H2

only partial bc leukotrienes, prostaglandins and cytokines are also involved

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20
Q

What is an anaphylactoid response?

A

cant clinically distinguish from anaphylaxis but this IS NOT CAUSED BY IMMUNE RESPONSE

21
Q

diseases that inc histamine levels:

A

1) myelogenous leukemia
- inc in basophils
- high levels of histamine = chronic pruritus
2) gastric carcinoid tumors secrete histamine
- =episodes of vasodilation
3) systemic mast cell diseases
- leukemia –> pruritus, flushing, diarrhea, GERD, anaphylactoid response

22
Q

3 classes of anti-histamines

A

1) physiological antagonists
- reverse physiological effects of histamine ex) epinephrine
2) release inhibitors
- prophylactic treatment
ex) cromolym & nedocromil
- monoclonal IgE antibody ex) Omalizumab
3) Receptor antagonists
- drugs competitively block receptors (H1-allergy, H2-gastic acid secretion, H3/H4 nothing clinically yet)

23
Q

1st gen vs 2nd gen H1-antihistaimnes

A
  • first = effective H1 block but many side effects bc cross BBB - can inh M, alpha1, serotonin, and D2 receptors
  • 2nd=non-sedating bc no BBB penetration
24
Q

Effects of 1st gen H1 antihistamines-

A

1) dec production of H1 mediated pro-inflammatory cytokines + chemotaxis of immune cells
2) inh vascular permeability and vasodilation (dec edema and wheals)
3) reduce flare and itch
4) cross BBB = sedation, dec alertness & memory
5) antiemetic - reduce motion sickness via CNS cholinergic receptor inhibition

25
Q

Main uses of first gen antihistaimnes:

A
  • alleric rhinitis
  • allergic conjunctivitis
  • urticaria

Other: nasuea/vomit, motion sickness, sedative, sleep aid, parkinsons, acute extrapyramidal symptoms, cough, common cold (drying effect)

26
Q

H1 anti-histamine specific molecular MOA?

A

INVERSE AGONISTS - so they BIND TO THE transmembrane protein and stabilize the inactive form

27
Q

Chlorpheniramine

  • type?
  • sedation effect?
  • anti-M effect?
  • antiemetic/motion-sickness
  • primary tx?
A
  • 1st gen H1 inh
  • moderate sedation
  • moderate anti-M
  • NO antiemetic/antimotion
  • tx- allergic rhinitis and other allergies
28
Q

Diphenhydramine

  • type?
  • sedation effect?
  • anti-M effect?
  • antiemetic/motion-sickness
  • other effects?
  • primary tx?
A
  • 1st gen H1 inh
  • significant sedation, anti-M, anti-motion actions
  • tx allergic rhinitis, conjunctivitis, utricaria, cough and motion sickness
  • tx extrapyramidal reactions from anti-psychotic drugs
  • tx parenterally for acute dystonic reactions to antiphsycotics
  • local anesthetic effect via Na channel blockade
29
Q

1st gen H1 anti-histamines?

A
  • chlorpheniramine
  • diphenhydramine
  • pyrilamine
  • hydroxyzine
  • meclizine
  • promethazine
  • cyproheptadine
30
Q

Pyrilamine

  • type?
  • sedation effect?
  • anti-M effect?
  • antiemetic/motion-sickness
A
  • 1st gen H1 inh
  • low to mod sedation
  • little anti M
  • no antimotion
31
Q

Hydroxyzine

  • type?
  • sedation effect?
  • anti-M effect?
  • primary tx?
A
  • 1st gen H1 inh
  • much sedation
  • much anti-M
  • tx- antiemetic, sedative, mild anxiolytic, and for skin allergies
32
Q

Meclizine

  • type?
  • sedation effect?
  • anti-M effect?
  • antiemetic/motion-sickness
  • primary tx?
A
  • 1st gen H1 inh
  • much sedation but less than hydroxyzine
  • minimal anti-M
  • tx=motion sickness and vertigo
33
Q

Patient with benign prostatic hyperplasia with trouble urinating can give?

A

-meclizine bc minimal anti-M effects = no urinary retention

34
Q

Promethazine

  • type?
  • sedation effect?
  • anti-M effect?
  • antiemetic/motion-sickness
  • other effets?
A
  • 1st gen H1 inh
  • marked anti-M, antiemetic, and antimotion sickness
  • significant sedation
  • alpha1 block = hypotension
  • local anasthetic effect via Na channel block
  • CAN BLOCK D2** (=not good in PD patient on D2 agonists)
35
Q

Cyproheptadine

  • type?
  • sedation effect?
  • anti-M effect?
  • antiemetic/motion-sickness
  • tx?
A
  • 1st gen H1 inh
  • low-mod sedative and anti-M
  • anti-serotonin
  • inc weight and appetite (bc of serotonin receptor block)
  • tx - serotonin syndrome
36
Q

Chlorpromazine

  • used for?
  • blocks what receptors?
A
  • antipsychotic agent

- blcok D2 and H1 (sedation)

37
Q

Adverse effects of 1st gen H1 blockers:

A

1) CNS H1 receptors
- dec alertness, cognition, memory…
- impairment w/ or w/out sedation
2) Muscarinic receptors
- inc dry mouth, urinary retention, and sinus tachycardia. mydriasis, constipation
3) Serotonin receptors
- inc appetitite; inc WG
4) alpha1 receptors
- inc dizziness; inc postural hypotension
4) CNS depression
5) glaucoma & prostate hypertrophy due to anticholinergic effects
6) crosses placenta
7) Gi upset

38
Q

Which H1 blockers have strong effects on D2?

A
  • Promethazine

and Chlorpromazine? an antipsychotic

39
Q

Do not use H1 blockers with what other drugs?

A
  • other depressants - alcohol, hypnotics/sedatives opioids, neuroleptics
  • MAOIs = prolonged and intensified anticholinergic effects
  • additive anticholinergic effects with other anticholinergics
  • diphenhdramine OD is common
  • max dose 300mg/day
40
Q

2nd generation H1 blockers - the drugs?

  • MOA?
  • feature?
A
  • fexofenadine
  • loratadine
  • desloratadine
  • citirizine
  • non-competitive binding to H1 receptor
  • not lipophillic = no BBB crossing = no sedation
41
Q

MOA of Citirizine? side effect?

A
  • 2nd gen block of H1 receptors
  • reduce mast cell degranulation

potential drowsiness (not worse than 1st gen H1 blocekrs

42
Q

Metabolism of 1st gen vs 2nd gen H1 blocekrs?

A
  • 1st are all highly metabolized in liver

- 2nd varies by drug + age + liver + renal function

43
Q

1st gen vs 2nd gen MOA comparison?

A

1st = INVERSE AGONISTS - so the BIND TO THE transmembrane protein and stabilize the inactive form

2nd=non-competitive binding to H1 receptor

44
Q

1st gen vs 2nd gen

-Drug interactions comparison?

A

1st gen many

2nd gen low risk of any interactions

45
Q

Cromolyn and Nedocromil

  • MOA?
  • administration?
  • tx/prophyalxis for?
A
  • stabilize mast cell + inh degranulation of histamine (via inh of Cl channel membranes)
  • nasal spray or eye drops
  • allergic rhinitis and conjunctivitis
  • helps with antigen and exercise induced astma
46
Q

Omalizumab

  • what kind of drug? MOA?
  • tx for?
A
  • recomb humanized monoclonal antibody that binds to IgE
  • tx for chronic utricaria & asthma

(-very expensive)

47
Q
  • Which tricyclic antidepressant has antihistamine activity?
  • which receptors?
  • Tx for?
A
  • Doxepin
  • H1 and H2 block
  • chronic utricaria
48
Q

Ketotifen

  • MOA/
  • tx for?
A
  • H1 block + mast cell and basophil stabilization

- chronic utricaria + conjunctivitis-available as ophthalmic solution

49
Q

Doxepin

  • what kind of drug?
  • MOA?
  • tx?
A
  • tricyclic antidepressant
  • Block H1 and H2
  • chronic utricaria

Pharm Exam 5 (10 decks)

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