Allergies and Anaphylaxis

Question 1

Histamine

Answer 1

Dilates vessels, increases permeability (decrease BP)
Bronchoconstriction via Smooth muscle
High levels in skin, lungs, GI. synthesized in mast and basophils
IgE Abs are generated following exposure to specific allergens
On re-exposure, may induce a very rapid release from secretory granules and lead to anaphylaxis

Question 2

Physiologic and Pharmacologic Effects

Answer 2

Histamine acts on H1 for allergies or H2 for gastric acid secretion
H1: vasodilation/hypotension, prominent in face and upper body, increased capillary permeability which can lead to edema. Bronchoconstriction and other effects like itching.
Mild allergy: Histamine on H1R. Respond to anti-histamine
Severe: Histamine involved with other, primary mediators: leukotrienes, prostaglandins and tryptase. Epinephrine FIRST then anti-histamines

Question 3

1st Gen Antihistamines

Answer 3

1st and 2nd generations. First is more sedating.

Question 4

Diphenhydramine

Answer 4

Benadryl
IND: Motion sickness, Premed for chemo. Allergies, antitussives, anaphylaxis
MOA: Antihistamine 
BOX: NONE
CONTRA: 
ADRs: Anticholinergic effects
M/E: NONE

Question 5

Hydroxyzine HCl and Pamoate

Answer 5

IND: urticaria, pruritis, anxiety
MOA: H1/5HT2
BOX: NONE
CONTRA: Pregnancy and QT prolongation 
ADRs: Anticholinergic 
M/E: NONE

Oral caps and oral tabs = which one is which?

Question 6

Cyproheptadine

Answer 6

Peri-Actin
IND: Last line allergies. Mostly for off label: Serotonin syndrome, decreased appetite, mast cell activation disorder
MOA: H1 Antagonist 1st gen
BOX: NONE
CONTRA: Conditions worsened by strong anticholinergic effects (glaucoma, urine retention)
ADRs: Drowsy
M/E: NONE

Question 7

Antihistamines 2nd Gen

Answer 7

KNOW ALL 5
IND: Mild allergy, adjunct in anaphylaxis, motion sickness/N/V, insomnia, cold remedies
MOA: H1RA however, poorly cross blood brain barrier = less sedation. Have a low binding affinity with CNS histamine receptors. Mostly lack anticholinergic effects
BOX: NONE
CONTRA: NONE
ADRs: Headache
Cetirizine
M/E: NONE

Zzzzzyrtec = drowsy adr

Question 8

Anaphylaxis Treatment

Answer 8

NO CONTRA, GIVE EPINEPHRINE IMMEDIATELY
Establish airway if required (immediate intubation) otherwise may need a cricothyrotomy

Bronchospasm: Albuterol
Hypotension: Isotonic fluids, normal saline 1-2L bolus rapidly
Adjunctive therapies: Diphenhydramine, Famotidine, Methylprednisolone

Refractory Anaphylaxis: Epinephrine drip. Additional vasopressors if required. Glucagon if required to reverse the effect of Beta blockers and allow Epi to work

Question 9

Epinephrine

Answer 9

IND: Anaphylaxis, hypotension, ACLS
MOA: Alpha1 Agonist. Causes vasoconstriction. Beta1 agonism = increases CO. Beta2 agonism = counteract bronchoconstriction
BOX: NONE
ROUTE: DO NOT IV push in anaphylaxis. 
Adult/Kids over 25 Kg: 0.3mg IM.
Kids 13-25Kg: 0.15mg IM
Kids 7.5 - 13Kg: Vial/needle/syringe 0.1mg IM. Or .15 if that is the only thing available
 Adult ACLS: 1mg IV push every 3-5.
CONTRA: 
ADRs: Tachycardia, elevated BP
M/E: NONE

Question 10

Gen 2 Antihistamines

Answer 10

Cetirizine - Zyrtec
Loratadine - Claritin
Levocetirizine 
Fexofenadine
Desloratadine