It is an ethanolamine H1-receptor antagonist.
Mechanism of action:
Dimenhydrinate is thought to inhibit acetylcholine. It inhibits vestibular stimulation. (Vestibular and reticular systems stimulates nausea and vomiting in motion sickness.)
Therapeutic uses:
It is used to treat motion sickness. It is also used in Meniere’s disease and some of the other vestibular disturbances. It has been used in the allergic conditions also.
Administration and Dosage:
It can be administered orally, IM or IV. In motion sickness 50 mg of the drug is taken 30 minutes before motion. For vomiting 50-100 mg is taken 4-6 times in 24 hours.
Pharmacokinetics:
Its duration of action is 2.5-6 hours. It is widely distributed in the body cavities. It can cross the placenta. It is metabolized in liver and excreted through urine.
Adverse effects:
It may cause drowsiness, headache, dryness of the mouth and respiratory passages.
Sunday, April 3, 2011
Metocloprmamide
It is a substituted benzamide and is D2-receptor antagonist.
Mechanism of action:
It acts by blocking dopamine D2-receptor in the chemoreceptor trigger zone in the brain. It also causes increased action of the acetylcholine at muscarinic nerve endings in stomach resulting in more peristalsis and emptying of the upper part of the stomach.
Therapeutic uses:
It is primarily used in nausea and vomiting. It is also used in emptying of the stomach.
Administration and dosage:
It can be administered orally, IM or IV in the dose of 10 mg three times a day.
Adverse effects:
It causes antidopaminergic side effects i.e. twisting of the neck towards one side due to muscle spasm, diarrhea, sedation and extra pyramidal symptoms that are the main adverse effects of dopamine receptor blockers characterized by symptoms very similar to Parkinson’s disease and include tremor.
Mechanism of action:
It acts by blocking dopamine D2-receptor in the chemoreceptor trigger zone in the brain. It also causes increased action of the acetylcholine at muscarinic nerve endings in stomach resulting in more peristalsis and emptying of the upper part of the stomach.
Therapeutic uses:
It is primarily used in nausea and vomiting. It is also used in emptying of the stomach.
Administration and dosage:
It can be administered orally, IM or IV in the dose of 10 mg three times a day.
Adverse effects:
It causes antidopaminergic side effects i.e. twisting of the neck towards one side due to muscle spasm, diarrhea, sedation and extra pyramidal symptoms that are the main adverse effects of dopamine receptor blockers characterized by symptoms very similar to Parkinson’s disease and include tremor.
Classification of anti-emetic agents
1. Classification according to action:
a. Dopamine D2-receptor antagonists:
Metoclopromide, Domperidone, Phenothiazines (e.g. chlorpromazine, thioridazine)
b. Sedative-hypnotics:
Barbiturates, Benzodiazepines.
c. Anti-histamines:
Promethazine, Cyclizine, Dimenhydrinate, Diphenhydramine.
d. 5-HT3 (serotonin) receptor antagonists:
Ondansetron, Tropisetron, Granisetron.
e. Anti-cholinergic:
Scopolamine
f. Demulcents:
Gum acacia, Gum tragacanth.
g. Miscellaneous:
Aprepitant, Diphenidol hydrochloride
2. Classification according to specific causes:
a. Motion sickness:
Anti-cholinergic drugs, Anti-histamines
b. Nausea and vomiting due to other causes:
i. Vomiting by cytotoxic drugs:
Phenothiazines, metoclopramide, serotonin antagonists
ii. Vomiting induced by pregnancy:
Anti-histamines, Vit. B6 alongwith anti-histamine such as meclizine
iii. Vertigo:
Cyclizine, Phenothiazine, Cinnarizine
a. Dopamine D2-receptor antagonists:
Metoclopromide, Domperidone, Phenothiazines (e.g. chlorpromazine, thioridazine)
b. Sedative-hypnotics:
Barbiturates, Benzodiazepines.
c. Anti-histamines:
Promethazine, Cyclizine, Dimenhydrinate, Diphenhydramine.
d. 5-HT3 (serotonin) receptor antagonists:
Ondansetron, Tropisetron, Granisetron.
e. Anti-cholinergic:
Scopolamine
f. Demulcents:
Gum acacia, Gum tragacanth.
g. Miscellaneous:
Aprepitant, Diphenidol hydrochloride
2. Classification according to specific causes:
a. Motion sickness:
Anti-cholinergic drugs, Anti-histamines
b. Nausea and vomiting due to other causes:
i. Vomiting by cytotoxic drugs:
Phenothiazines, metoclopramide, serotonin antagonists
ii. Vomiting induced by pregnancy:
Anti-histamines, Vit. B6 alongwith anti-histamine such as meclizine
iii. Vertigo:
Cyclizine, Phenothiazine, Cinnarizine
Vomiting
It is the forcible throwing of contents of stomach up through mouth as a result of involuntary spasms of the muscles of the stomach. It is also called emesis.
The chemoreceptor trigger zone as well as vomiting center of the medulla oblongata is involved in the emesis.
Following illustration is helpful in this context.
Causes of vomiting:
Vomiting may have from one of the following causes:
1. Motion sickness
2. Intestinal obstruction
3. Disease or disorder of the inner ear
4. Some kind of injury to the head
5. Appendicitis
6. Adverse effects or direct effects of certain drugs
7. Pregnancy
8. Renal failure
After effects of vomiting:
In severe cases vomiting may result in dehydration, malnutrition, or rupturing of the esophageal wall.
Therapeutic strategies:
Its treatment is directly towards the cause or origin of vomiting. It is beneficial to drink a lot of clear water or any other fluids so that the chances of dehydration will not be there.
On the other hand, medicines can also be used.
The chemoreceptor trigger zone as well as vomiting center of the medulla oblongata is involved in the emesis.
Following illustration is helpful in this context.
Vomiting may have from one of the following causes:
1. Motion sickness
2. Intestinal obstruction
3. Disease or disorder of the inner ear
4. Some kind of injury to the head
5. Appendicitis
6. Adverse effects or direct effects of certain drugs
7. Pregnancy
8. Renal failure
After effects of vomiting:
In severe cases vomiting may result in dehydration, malnutrition, or rupturing of the esophageal wall.
Therapeutic strategies:
Its treatment is directly towards the cause or origin of vomiting. It is beneficial to drink a lot of clear water or any other fluids so that the chances of dehydration will not be there.
On the other hand, medicines can also be used.
Nausea
It is the disturbance of the stomach which accompanies the feeling to vomit.
Nausea directly is caused from irritation of the nerve endings present in the stomach or duodenum, which stimulates nausea and vomiting control centers present in the brain.
Causes of nausea:
The most common causes of nausea are
1. Indigestion:
The nausea caused by indigestion is due to eating too rapidly or emotional stress.
2. Motion sickness:
This is caused by the disturbance in the balance organs of the inner ear i.e. semicircular canals of the ear. The messages for disturbance go to the lower brain.
3. Pregnancy:
Nausea directly is caused from irritation of the nerve endings present in the stomach or duodenum, which stimulates nausea and vomiting control centers present in the brain.
Causes of nausea:
The most common causes of nausea are
1. Indigestion:
The nausea caused by indigestion is due to eating too rapidly or emotional stress.
2. Motion sickness:
This is caused by the disturbance in the balance organs of the inner ear i.e. semicircular canals of the ear. The messages for disturbance go to the lower brain.
3. Pregnancy:
Saturday, April 2, 2011
Streptokinase
It is an extracellular protein.
Production:
It is obtained from cultured medium of group C-β hemolytic streptococci.
Mechanism of action:
It causes the conversion of plasminogen to plasmin. It causes the degradation of fibrinogen.
It also results in the breakdown of factor V and VII.
Pharmacokinetics:
Its half life is half an hour. It is administered within 4 hours of myocardial infarction and is infused for 1 hour.
Therapeutic uses:
It is used for reopening of occluded shunts, arterial and deep vein thrombosis and acute myocardial infarction (in addition with aspirin this effect is increased).
Dosage:
Its loading intravenous dose is 2, 50,000 units. Then it will be given as a continuous infusion of 100,000 units per hour for 24-72 hours.
Adverse effects:
It may cause hemorrhage. In severe cases of hemorrhage, aminocaproic acid can be given as an antidote.
Hypersensitivity reactions can also be developed such as rashes, fever and anaphylaxis. Antibodies developed due to streptococcal infection in some peoples may neutralize fibrinolytic properties of streptokinase. These antistreptococcal antibodies may cause fever, allergy and treatment ineffectiveness. In that case of treatment ineffectiveness more amount of streptokinase is to be administered.
Fever and shivering have also been observed in 1-4% of patients.
Production:
It is obtained from cultured medium of group C-β hemolytic streptococci.
Mechanism of action:
It causes the conversion of plasminogen to plasmin. It causes the degradation of fibrinogen.
It also results in the breakdown of factor V and VII.
Pharmacokinetics:
Its half life is half an hour. It is administered within 4 hours of myocardial infarction and is infused for 1 hour.
Therapeutic uses:
It is used for reopening of occluded shunts, arterial and deep vein thrombosis and acute myocardial infarction (in addition with aspirin this effect is increased).
Dosage:
Its loading intravenous dose is 2, 50,000 units. Then it will be given as a continuous infusion of 100,000 units per hour for 24-72 hours.
Adverse effects:
It may cause hemorrhage. In severe cases of hemorrhage, aminocaproic acid can be given as an antidote.
Hypersensitivity reactions can also be developed such as rashes, fever and anaphylaxis. Antibodies developed due to streptococcal infection in some peoples may neutralize fibrinolytic properties of streptokinase. These antistreptococcal antibodies may cause fever, allergy and treatment ineffectiveness. In that case of treatment ineffectiveness more amount of streptokinase is to be administered.
Fever and shivering have also been observed in 1-4% of patients.
Alteplase
It is a single chain recombinant tissue plasminogen activator.
Production:
Initially, produced from cultured melanoma cells taken from humans and now it is obtained with recombination technology.
Mechanism of action:
It is fibrin selective or clot selective.
It gets bind more strongly to plasminogen, which is bound to fibrin in thrombus or hemostatic plug, causing its activation.
Due to fibrin selectivity its low dosage has very less effect on other proteins.
Therapeutic uses:
It is effective in large type of pulmonary embolism. It is also used for myocardial infarction and acute ischemic stroke. Therapy must be started within 3 hours of stroke symptoms.
It has better ability to dissolve chronic type of clots.
Pharmacokinetics:
Its half life is 5 minutes.
Dosage:
It is administered as 100 mg dose in which 10 mg is given quickly by IV injection and the remaining is given in 90 minutes (1mg/minute).
Adverse effects:
It may cause hemorrhage.
Production:
Initially, produced from cultured melanoma cells taken from humans and now it is obtained with recombination technology.
Mechanism of action:
It is fibrin selective or clot selective.
It gets bind more strongly to plasminogen, which is bound to fibrin in thrombus or hemostatic plug, causing its activation.
Due to fibrin selectivity its low dosage has very less effect on other proteins.
Therapeutic uses:
It is effective in large type of pulmonary embolism. It is also used for myocardial infarction and acute ischemic stroke. Therapy must be started within 3 hours of stroke symptoms.
It has better ability to dissolve chronic type of clots.
Pharmacokinetics:
Its half life is 5 minutes.
Dosage:
It is administered as 100 mg dose in which 10 mg is given quickly by IV injection and the remaining is given in 90 minutes (1mg/minute).
Adverse effects:
It may cause hemorrhage.
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