Histamine and Antihistamines

Question 1

What is a major effect of H2 receptor activation in the body that H1 receptor activation does not include? Also what S/E is related to H2 activation that can be harmful?

Answer 1

inc. gastric acid secretion > GI ulcers

Question 2

What is a major use for Meclizine?

Answer 2

highly effective in motion sickness

Question 3

Name some 1st generation antihistamines.

Answer 3

diphenhydramine, promethazine, chlorpheniramine, meclizine

Question 4

Name some 2nd generation antihistamines?

Answer 4

cetirizine, loratadine, fexofenadine

Question 5

Name some uses of antihistamines. (name 4)

Answer 5

• allergic reactions: hay fever, rhinitis, urticaria
• motion sickness, vertigo
• nausea and vomiting with pregnancy
• preoperative sedation
• OTC: sleep aids and cold medications
• acute EPS

Question 6

What are some S/E of antihistamines?

Answer 6

extensions of M block and sedation (additive with other CNS depressants)

Question 7

What second messenger system does H1 activation go through in order to create bronchiolar smooth muscle contraction?

Answer 7

IP3 DAG pathway

Question 8

How does H1 activation affect the heart?

Answer 8

dec. AV nodal conduction

Question 9

H2 activation of the heart affects the heart in what way?

Answer 9

inc. SA nodal rate, positive inotropism and automaticity