Pharm: L16: Antihistamines Flashcards Preview

Pharm Winter 2013 Midterm 2 > Pharm: L16: Antihistamines > Flashcards

Flashcards in Pharm: L16: Antihistamines Deck (19)
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1
Q
  1. How is Histamine Released?
A
  1. IgE Receptors stimulated –> PLP A2 turned on –> Increased Platelet Factor, Leukotrienes, Kinins –> Mast Cell Degranulation –> Histamine Release
2
Q

H1 Histamine Receptor

  1. Used in what?
A
  1. Allergic response; Sm Muscle, Endothelium (turns on NO and causes Vasodilation); Brain (wakefulness and appetite control); Acts thru Gq
3
Q

H2 Histamine Receptors

  1. What G-Protein?
  2. Secretes what?
A
  1. Gs (increased cAMP)
  2. Gastric ACID SECRETION

(found in heart, brain and mast cells)

4
Q

H3/H4 Receptors

  1. Linked to what G protein
  2. H3?
  3. H4?
A
  1. Gi (decrease cAMP)
  2. Presynaptic in Brain; Inhibits release of NT and can promote sleep
  3. on Leukocytes, Eosinophils, and Neutrophils…can stimulate Chemotaxis in Inflammation and Allergic Reactions.
5
Q
  1. Histamine NT: in CNS (what receptors)?

2. Regulation of Gastric ACID? (what receptor)

A
  1. H1 and H3 RECEPTORS

2. H2 RECEPTOR

6
Q

Effects of Histamine

  1. Cardiovascular: What receptor increases production of NO from endothelium?
    a. At higher concentrations?
  2. Smooth Muscle: BRONCHOSPASM: what receptor?
  3. GI?
A
  1. H1
    a. H2 is activated –> Direct Vasodilation
  2. H1: Problem in ASTHMATICS
  3. Increased GASTRIC ACID SECRETION (H2)
7
Q

Effects of Histamine

  1. TRIPLE RESPONSE?
A
  1. Localized Red Spot in a few seconds (due to vasodilation)

Followed by BRIGHTER FLUSH (FLARE) (Due to Axon Reflexes)

then WHEAL Appears in 2-3 minutes (Increased Capillary Permeability)

8
Q

Effects of Antihistamines

  1. What do they Inhibit?
A
  1. Smooth Muscle response (NOT BRONCHOSPASM); Inhibit VASODILATION due to H1 stimulation; Inhibit Flare, itch, and Wheal, salivary and lacrimal gland secretion
    * COUNTER MOTION SICKNESS (ANTICHOLINERGIC)
9
Q

First Gen Antihistamines

  1. What about them?
A
  1. Enter Brain. VERY SEDATING
10
Q

First Gen H1 Anatagonists

  1. What 2 are SEDATING ONLY?
  2. 2 for Motion Sickness?
  3. What is an Antiemetic and also used for Motion Sickness?
A
  1. Benadryl/Tylenol PM and VISTARIL
  2. Benadryl and DRAMAMINE
  3. PHENERGAN (also VERY SEDATING)
11
Q

Second Gen H1 Antagonists

  1. What about them
A
  1. Don’t enter Brain well. (PERIPHERY mainly). NOT ANTICHOLINERGIC. NON-SEDATING. FEWER SIDE EFFECTS

Dont help with Motion Sickness

*CYP450

12
Q

What 2 Second gen H1 Antagonists are EXCRETED DIRECTLY by the KIDNEY?

A

ZYRTEC and ZYXAL

13
Q

What drug might INHIBIT RELEASE of HISTAMINE from MAST CELLS?

A

ZYRTEC!

14
Q

Clinical Applications

  1. Best used for what?
A

Allergic Rhinitis, Seasonal Itching/Conjunctivits, Itching and Hives

*Motion Sickness (PROPHYLACTIC…usually VERY SEDATING AS WELL (so 1st Gen for this)

Sedation: safe for occasional use (1st gen…long-term TOLERANCE can develop.. DRY up secretions (1st gen))

15
Q

First Gen Side Effects?

A

SEDATION! (worse if used with CNS depressants. ANTICHOLINERGIC (DRY MOUTH))

16
Q

Side Effects on ALL?

A

GI: Nausea, Anorexia, Increased appetite and weight gain. Maybe Teratogenic.

Allergic Reactions (Topical)

Decrease Seizure Threshold (TCAs, Phenothiazines)

17
Q

Interactions

  1. 1st Gen
  2. 2nd Gen
A
  1. CNS Depressants

2. Erythromycin, Ketoconazole, Grapefruit Juice, Cimetidine (Inhibit their Metabolism)

18
Q

Overdose

  1. 1st Gen
  2. 2nd Gen
A
  1. Like ATROPINE POISONING; Sedation

2. Cardiac Arrhythmias occurred w/older drugs but not newer ones. Sinus Tachycardia w/newer drugs

19
Q

Topical Drugs

  1. AZELASTINE
  2. KETOTIFEN and EPINASTINE
A
  1. decrease Histamine Release AND BLOCKS RECEPTORS (H1 Blocker)
  2. EYE drops for allergies in the eye