GIT Lec 4 Pt 3 - Anti H1 And M Receptor Agents

Question 1

What are examples of H1-agonists?

Answer 1

1. Promethazine.
2. Diphenhydramine.
3. Cyclizine.
4. Meclizine.
5. Cinnarizine.

Question 2

What are the indications of H1-agonists?

Answer 2

They are indicated for the following reasons of emesis:
1. motion sickness
2. Ménière’s disease
3. Pregnancy
4. Uremia
5. Post-operation

Question 3

What are the drug-specific characteristics of H1-antagonists?

Answer 3

1. Promethazine has atropine like effects
2. Diphenhydramine has anti-emetic, anti-histamine and sedative properties
3. Cyclizine and meclizine have potent anti-emetic effects
4. Cinnarizine has calcium channel blocking effects alongside its anti-emetic effect

Question 4

What are the MOA and indications of Cinnarizine?

Answer 4

1. It suppresses labyrinthine activity by inhibiting the passage of calcium ions from the endolymph to the vestibular sensory cells.
2. It increases blood flow to the vestibular nucleus by inhibiting vasoconstrictors. This is useful in treating patients with vertigo alongside prophylaxis for motion sickness.
3. It is taken as 25mg or 75mg tablets

Question 5

What are some examples of muscaranic receptor blockers?

Answer 5

1. Atropine
2. Scopolamine (0.2-0.4mg)
3. Dicyclomine (10-20mg)
4. Trihexyphenidyl
5. Benztropine

Question 6

What are the indications of M-receptor blockers?

Answer 6

They can be used for:
1. Prophylaxis for motion sickness; should be taken half an hour before travel
2. Treat vomiting that occurs due to peripherally acting agents like copper sulphate