Question

1) Describe the pharmacological effects of H1-receptor antagonists.

2) Describe the pharmacological effects of H2-receptor antagonists.

3) Describe the metabolism and elimination of H1-receptor antagonists.-

4) Describe the metabolism and elimination of H2-receptor antagonists

Answer 1

Answer 1:

H1 receptor antagonist inhibits the effects of histamine by binding on H1 recptors present at smooth muscles, nerve endings and glandular cells thereby preventing histamine to bind and elicit it's reactions. By doing this H1 receptor antagonist prevents nausea, vomiting, allergic reactions, rhinitis, etc. Example: Cetrizine, Cyclizine.

Answer 2:

H2 receptor antagonist competes with histamine when binding on H2 receptors present on gastric parietal cells and thus prevents secretion of hydrochloric acid from parietal cells and thus is useful in treating acidity, heart burn and ulcers. Examples: Ranitidine, Cimetidine

Answer 3:

H1 receptor antagonists are absorbed from the gastrointestinal tract and are metabolized in liver by cytochrome P-450 system. Some are even metabolized by hepatic CYP-2D6, miner CYP-1A2,2C9,2C19 systems. The metabolites are excreted via renal system.

Answer 4:

H2 receptor antagonist are metabolized in the liver by the cytochrome P450 system and are excreted by renal system.