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USES OF ANTIHISTAMINES

USES OF ANTIHISTAMINES

Anticholinergic

Scopolamine is the drug of choice to prevent motion sickness. It blocks afferent impulses from vestibular apparatus to the vomiting centre by its anticholinergic action. Its sedative effect also contributes to its antiemetic effect. Scopolamine is not effective for other types of vomiting.

ANTIHISTAMINES (H-1 BLOCKERS)

h-1 blockers are mainly useful for the prevention of motion sickness. They are also effective in morning sickness, postoperative and other types of vomiting. Dimenhdyrinate, diphenhydramine, doxylamine, promethazine, cyclizine, and meclizine are some of the h-1 blockers that are antiemetic properties. Their antiemetic effect is due to sedative and central anticholinergic actions. Cyclizine and meclizine have less sedative effect. Meclizine has longer duration of action.

5-HT3-RECEPTOR ANTAGONIST

Ondasetron is the prototype drug. Other drug are granisetron, dolasetron, and palonosetron. Their antiemetic effect is mainly due to the blockade of 5-HT3 receptors on vagal afferents in the gut. In addition they also block 5-HT 3 receptors in the CTZ and solitary tract nucleus(STN).

Ondansetron and other 5-HT3 antagonist control vomiting by blocking enetogenic impulses in the gut and their central relay.

PHARMACOKINETICS

5-HT 3 antagonist are well absorbed after oral administration –ondansetron undergoes extensive first pass metabolism. The metabolites are excreted in urine and facecs. These agents are also available for intravenous administration. Ondansetron can also be administred intramuscularly. Granisetron is more potent and longer acting than ondasetron. Transdermal patch of granisetron is available for prevention of cancer chemotherapy induced vomiting. Palonosetron has the longest duration of action among the 5-HT3 antagonist.

USES OF ANTIHISTAMINES

  1. 5-HT 3 antagonist re the most effective agent for prevention and treatment of anti-cancer drug induced nausea and vomiting.
  2. They are also effective in hyperemesis of pregnancy postoperative and postradiation vomiting but they are ineffective against motion sickness.

ADVERSE EFFECTS

5-HT3 antagonist are well tolerated. They may cause headache , dizziness and diarrhoea.

THATS ALL ABOUT USES OF ANTIHISTAMINES.HOPE YOU ALL FIND THIS TOPIC USEFUL.

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