Antihistamines

Question 1

Histamines

Answer 1

Neuromodulators
Neurotransmitters
Gastric Acid stimulators
Allergy & Inflammatory mediators 
Involved in WBC immune functions & chemotaxis

Question 2

What cells create histamine?

Answer 2

Mast cells (tissue) - skin, intestinal & bronchial mucosa
Basophils - from the blood into the tissue

Question 3

Index of histamine production

Answer 3

Metabolite concentration in urine

Question 4

Possible mechanisms of histamine release

Answer 4

Directly facilitate Ca2+ entry
GPCR leads to increased cAMP
Secretagogues

Question 5

Symptoms of Histamine release

Answer 5

1) Hypotension
2) Flushing
3) Anaphylactoid rxn

Question 6

H1 antagonists - 1st generation

Answer 6

1) CNS & peripheral distribution
2) Hepatic metabolism
3) Renal excretion
4) Half life: 4-8 hrs

Question 7

H1 antagonists - 2nd generation

Answer 7

1) Peripheral distribution - less BBB penetration
2) Hepatic CYP3A4, 2D6
3) Excretion unchanged
4) Duration of effects 24 hrs

Question 8

Antihistamines are inverse agonists

Answer 8

Reduce constitutive activity of the receptor & compete with histamine

Question 9

Therapeutic uses of Anti-H

Monotherapy

Answer 9

1) Conjunctivitis
2) Motion sickness
3) Seasonal rhinitis
4) Sedation (hang-over effect)
5) Vertigo

Question 10

Motion sickness

Answer 10

Diphenhydramine

Promethazine

Question 11

Therapeutic uses of Anti-H

Adjunctive use

Answer 11

1) Allergic drug rxn: gluco + epi
2) Anaphylaxis/angioedema: epi
3) Atopic/contact dermatitis: topical gluc
4) Serum sickness: antihistamine for urticaria/edema (fever & arthralgia are not responsive)

Question 12

Promethazine: AE

Answer 12

Parenteral use can cause severe tissue injury such as gangrene

Question 13

Anti-H: AE

Answer 13

1) Abdominal pain
2) Anaphylaxis
3) Dry mouth
4) Drug fever
5) Pharyngitis
6) Photosensitivity
7) Wheezing

Question 14

Anti-H 1st generation: AE

Answer 14

CNS:
Dizziness
Fatigue
Somnolence

Question 15

Anti-H 1st generation: anticholinergic

Answer 15

1) Blurred vision
2) Constipation
3) Dry mouth
4) Dry Respiratory passages
5) Urinary retention

Question 16

1st generation Anti-H Precautions

Answer 16

1) Acute asthma
2) Young children
3) Elderly

Question 17

Children: Anti-H

Answer 17

2nd generation for > 2 yo

Question 18

Anti-H: Drug interactions

Answer 18

1) Anticholinergic AE drugs
2) CYP2D6 or CYP3A4
3) Depressants
4) P-glycoproteins

Question 19

H2 receptor Antagonists

Answer 19

“tidines”

1) Cimetidine
2) Famotidine
3) Nizatidine
4) Ranitidine

Question 20

H2 uses

Answer 20

1) Acid indigestion
2) GERD
3) Heartburn
4) Ulcer (duodenal & gastric)
- Multidrug against H. pylori

Question 21

Cimetidine: AE

Answer 21

Drug interactions - CYP inhibition

Question 22

H2 MOA

Answer 22

Inverse Agonists

Question 23

H2 reduce

Answer 23

Gastric acid secretion and are used to treat acid peptic disease (proton pump inhibitors are better)

Question 24

First generation agents are more likely to block

Answer 24

Muscarinic & alpha-adrenergic receptors