Antihistamines - H1 antagonists

Question 1

H1 activation

Answer 1

is coupled to the Gq protein

• mediates allergic inflammation
  (“Q” dandelion”)

-increases nasal and bronchial mucus production
(“Dripping nose sap”)

-histamine increases vascular receptor permeability
(“Dripping vascular sap”)

-histamine causes constriction of bronchial smooth muscle
(“Constricted lung branch”)

-histamine functions as a neurotransmitter

• regulates sleep and arousal
  (“Brain tree”)

Question 2

H2 activation

Answer 2

coupled to Gs protein
(“Honeypot with 2”S””)

-mediates gastric acid secretion
(“Golden gastric honey”)

Question 3

Name 1st Generation Anti-Histamine drugs

Answer 3

Diphenhydramine
Dimenhydrinate
(“Dragonfly fairy”)

Chlorphenamine
(“Color fairy”)

Hydroxyzine
Meclizine
Promethazine
(“fairy cuiSINE”)

Question 4

H1 antagonists can treat …

Answer 4

-are 1st line therapy for type-1 allergic reaction􏰀 hives, allergic rhinitis
(“Fairy dust and dander”)

-treat vestibular nausea or motion sickness lipophilic􏰀 → enter CNS􏰀 → act on vestibular system and brainstem
(“Seasick fairy sailors”)

treat extrapyramidal side effects caused by antipsychotics (acute dystonia)
(“Falling “extra parking cone”)

• antimuscarinic effects re-establish dopaminergic- cholinergic balance

Question 5

H1 Antagonists Side Effects

Answer 5

-can cause drowsiness

• lipophilic􏰀 → cross BBB → 􏰀central effects
  (“Sleeping under brain tree”)

-antagonize peripheral and central muscarinic receptors

• pupillary dilation
• dry mouth
• urinary retention
• constipation
• exacerbation of glaucoma
• delirium
  ​(“Anti-muscarinic tea party”)

1st generation H1 blockers antagonize serotonin receptors in the CNS
(“Cut smiley face cake”)

• stimulate appetite and weight gain anti-serotonergic effects
  (“Stuffed fairy”)

-1st generation H1 blockers antagonize alpha-1 receptors􏰀 dizziness and hypotension

(“Extinguished single alpha candle”)
(“Fainted fairy”)

-cause cognitive impairment in the elderly (central antihistamine and antimuscarinic effects)
(“Delirious elderly man”)

​

Question 6

Name 2nd Generation H1 Antagonists

Answer 6

Fexofenadine
Loratidine
Cetirizine

(“Fox, satyr, and rat”)

Question 7

difference between 1st and 2nd Generation H1 antagonists

Answer 7

2nd generation H1 blockers are less lipophilic →􏰀do not cross BBB→ 􏰀less sedating

• also less antimuscarinic, antiserotonergic, or anti- alpha

(“Fox, satyr, and rat stand outside the brain tree”)