Antihistamines- Khan

based off the study guide

What are cellular storage sites of histamine?

• mast cells- MAINLY

• basophils

• non-mast cells in GI and neurons in CNS

Histamine receptors are what type of receptor?

GCPRs

Of the 4 different histamine receptors identified, which is important for antihistamines?

H1

How does histamine effect vascular smooth muscle?

causes erythema

How does histamine effect endothelial cells?

causes edema (contraction that releases plasma/fluid)

How does histamine effect bronchial smooth muscle?

bronchoconstriction

How does histamine effect the CNS?

H1 receptor and histamine deal with wakefulness, satiety, and hunger

How does histamine effect the Peripheral Nerve?

causes pain, itch

What is the MOA of histamine? Is it an antagonist or agonist? How does it shift the equilibirum?

Histamine is an AGONIST for active conformation

• Histamine shifts the equilibrium towards active state

What is the MOA of antihistamine? Is it an antagonist or agonist? How does it shift the equilibrium?

Antihistamine is an INVERSE AGONIST for the inactive conformation

• Antihistamine shifts the equilibrium towards the inactive state

Histamine would move the equilibrium to what direction?

a. towards A

b. towards B

c. both

d. neither

A

Diphenhydramine would move the equilibrium to what direction?

a. towards A

b. towards B

c. both

d. neither

B (ALL antihistamines will move equilibrium towards inactive state!)

What are the properties of 1st generation antihistamines?

• Is it hydro/lipophilic?

• What type of effects are produced?

• What do these block?

• lipophilic (can enter CNS easy)

• strong SEDATIVE effects

• Blocks:

  • vestibular afferent to vomiting center

  • cholinergic receptors

What ANS is blocked by 1st generation H1 antihistamines? (sympathetic or parasympathetic)

PARASYMPATHETIC

A drug with this functional group would be what kind of antihistamine?

a. tricyclic antihistamine

b. piperazine

c. ethanolamine ethers

d. alkyl amines

c

A drug with this functional group would be what kind of antihistamine?

a. tricyclic antihistamine

b. piperazine

c. ethanolamine ethers

d. alkyl amines

d

A drug with this functional group would be what kind of antihistamine?

a. tricyclic antihistamine

b. piperazine

c. ethanolamine ethers

d. alkyl amines

a

A drug with this functional group would be what kind of antihistamine?

a. tricyclic antihistamine

b. piperazine

c. ethanolamine ethers

d. alkyl amines

b

What generation of antihistamines is ONLY used for allergy symptoms?

a. 1st gen

b. 2nd gen

c. 3rd gen

b

What are the names of all the 2nd generation antihistamines?

• Cetirizine (Zyrtec)

• Levocetirizine (Xyzal)

• Loratadine—>Desloratadine

• Fexofenadine (Allegra)

______________________ is a metabolite of Terfenadine.

Fexofenadine

Desloratadine is metabolized from loratadine using what 2 CYP enzymes?

CYP3A4 and CYP2D6

_________________ is a metabolite of Hydroxyzine.

Cetirizine

What is anaphylaxis? What is it treated with?

severe allergic reaction and treated with epinephrine

Compared to 1st generation antihistamines, 2nd gen do not have what side effects?

NO CNS or ANTICHOLINGERIC

Compared to other 1st generation antihistamines, diphenhydramine or benadryl also can be used for…

cough