Antiemetics
They are the drugs that is effective against vomiting and nausea
They are typically used to treat
Motion sickness
The side effects of opioid analgesics and chemotherapy
directed against cancer
And postoperative emesis
Main classes of antiemetics
Dopamine D2 antagonists
Metoclopramide
Domperidone
Metopimazine
5 HT3 receptor antagonists
Granisetron
Ondansetron
Dolasetron
Tropisetron
Antihistamines
Diphenhydramine
Dimenhydrinate
Meclizine
Cyclizine
(1)
Dopamine D2 receptor antagonists
(1)
Metoclopramide
Mode of action
is a potent dopamine D2 receptor antagonist used for its antiemetic and prokinetic properties
Thus it is primarily used to treat nausea and vomiting, and to facilitate gastric emptying in patients with gastric stasis
The anti-emetic action of metoclopramide is due to its antagonist activity at D2 receptors in the CTZ
At higher doses, 5-HT3 antagonist activity may also contribute to the anti-emetic effect
The prokinetic activity of metoclopramide is mediated by mascarinic activity, D2 receptor antagonist activity
The prokinetic itself may also contribute to the anti-emetic effect
Clinical uses
(1)
Antiemetic use
considered ineffective in post-operative nausea and vomiting
and ineffective for motion sickness
also used by itself or in combination with paracetamol for the relief of migraine
as in
(2)
Prokinetic use
Metoclopramide
increases peristalsis
increases tone and amplitude of gastric contractions
relaxes the
so
it is useful in the treamtent of gastric stasis e.g. after gastric surgery
also used in
(3)
Other indications
By inhibiting the action of prolactin inhibiting hormone (i.e. dopamine), metoclopramide has sometimes been used to stimulate lactation
Contraindications
It should be used with caution in
Parkinson's disease since, as a dopamine antagonist, it may worsen symptoms
Obstruction, perforation, or hemorrhage of the stomach or small bowel
Not given in the first trimester of pregnancy
Metoclopramide hydrochloride is not recommended for patients under 18 years of age
Adverse effects
restlessness, drowsiness, dizziness, and headache
Extrapyramidal side effects as parkinsonism like symptoms
Dose
The usual dose is 10 milligrams 30 minutes before each meal and at bedtime
Trade names
(2)
Domperidone
Mode of action
Related to that of metoclopramide
Uses
(1)
Antiemetic use
used in the treatment of nausea and vomiting
It is useful in patients with
(2)
Lactation
Domperidone, by acting as an anti-dopaminergic, results in increased prolactin secretion, and thus promotes lactation
Adverse effects
no extrapyramidal side effects as it does not cross BBB
Dose
The usual dose is 10 milligrams 30 minutes before each meal and at bedtime
Trade names
(2)
5 HT3 receptor antagonists
(1)
Granisetron
Mode of action
Granisetron is a serotonin5-HT3 receptor antagonist used to treat nausea and vomiting following chemotherapy
It does not have much effect on vomiting due to motion sickness
Clinical uses
chemotherapy induced nausea and vomiting
Post-operative and post-radiation nausea and vomiting
Adverse effects
Headache, dizziness, and constipations are the most commonly reported side effects associated with its use
Dose
Given intravenously about 30 minutes before beginning therapy
Trade names
(2)
Ondansetron
Mode of action
Clinical uses
Adverse effects
As Granisetron
Dose
The drug is administered 1–3 times daily, depending on the severity of nausea and/or vomiting
The normal dose for adults and children over the age of 12, is 8 mg initially, followed by a second dose of 8 mg, eight hours later. The drug is then administered once every 12 hours, usually not for more than 2-3 days
Trade names
(3)
Dolasetron
Mode of action
Clinical uses
Adverse effects
Dose
As Granisetron
(4)
Tropisetron
Mode of action
Clinical uses
Adverse effects
Dose
As Granisetron
Trade names