Anti-emetics, Anti-spamodics, Anti-diarrhea, Laxatives And Prokines Flashcards by abigail Oguttu

What is vomitting?

Nausea and vomiting are protective reflexes that rid the stomach and intestine of toxic substances and prevent further ingestion.

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What autonomic complex process are associated with nausea and vomiting?

Pallor
Sweating
Bradycardia
Profuse salivary secretions

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What part of the brain is responsible for vomiting?

Caused by the central coordination by cells in

- The dorsolateral reticular formation in the floor of the 4th ventricle.

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Name the 3 physiological steps in vomiting:

Nausea
Retching
Emesis

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Explain phase 1 of the physiological steps in vomiting:

Nausea:

Unpleasant sensation
Awareness of an urge to vomit

Accompanied by:

Cold sweat
Pallor
Salivation
Disinterest in surroundings
Loss of gastric tone
Duodenal contractions
Reflux of intestinal contents in stomach.

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Explain phase 2 of the physiological steps in vomiting:

Retching
- Laboured, spasmodic rhythmic contractions of respiratory muscles.
> Diaphragm, Chest wall, Abdominal wall muscles.
- No expulsion of gastric content.
- Normally generates pressure gradient leading to vomiting.

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Explain phase 3 of the physiological steps in vomiting:

Vomiting (Emesis).
- Forceful expulsion of gastric content from the mouth.

Caused by

powerful sustained contraction of abdominal muscle.
Descent of diaphragm.
Opening of gastric cardia.

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What are 4 mechanisms of vomiting?

Stimulation of the higher cortical areas
- Due to sensory (smell, pain, sight) input, memory, fear anticipation.
Radiation sickness: Stimulates receptors in stomach and small intestines.
- Radiation, chemotherapy, surgery.
Labyrinth impulse triggers
- Due to motion sickness, surgery etc.
Stimulation of chemoreceptor trigger zones.
- Opiods, anaesthetics, chemotherapy, uremia, bacterial toxins.

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Name a few causes of vomiting:

Radiation sickness
Chemotherapy
Drug induced: estrogens
Metabolic causes: Uraemia, keto-acidosis
Centrally acting emetics: morphine, apo-morphine
Stimulation of higher centers: Psyche, smell etc.
Labyrinth impulses: motion sickness,

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What is the vomiting center and where is it found?

Responsible for central coordination of vomitting act.

Group of cells in dorsolateral reticular formation in the floor of the 4th ventricle.
It is in close tube cardiovascular and respiratory centers .

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What are the major efferent pathways involved in the vomiting process?

Phrenic nerve
Visceral efferent of vagus to stomach and Oesophagus
Spinal nerves to abdominal muscles.

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What neuronal receptors are found in the vomit center in the brain?

AchM
- H1
- 5HT2

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What is the chemoreceptor trigger zone.

This is a group of neurons in the brain found in the:
- Postrema of the 4th ventricle.

Stimulation of the chemoreceptor trigger zone activates the vomiting center. 
Sensitive to stimuli I.e. 
  - Radiation. 
  - Uraemia.
  - Bacterial toxins.
  - Opiods.

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What neuroreceptors are found in the chemoreceptor trigger zone

D2
NK1 (Neurokinin)
5HT3

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What is the vestibular system?

These are intracerebral projections leading straight to the vomitting center:

There is vestibular stimulation via the cerebellum
Main mechanism: Vestibular projections to the CTZ

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What neuroreceptors are found in the vestibular system?

AchM

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What are the major efferent pathways seen in the peripheral pathways?

Phrenic nerve
Visceral efferent of Vagus nerve to stomach and oesophagus
Spinal nerves to abdominal muscles

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Practice: Name the Neuroreceptors and Neural pathway involved when the following input leads to vomiting:
-Input: Labryinth disorders and motion sickness.

Input :- Motion and labyrinth disorders
- Neuroreceptors in the brain stimulated :- AchM and H1
- Neuronal pathway :- Vestibular system.
- Projections from vestibular nuclei stimulate the vomiting center.

Note main mechanism:

Uses Vestibular projections to the CTZ which stim. the vomiting center.
Vomitting center is activated
Leading to nausea and vomiting

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Practice: Name the Neuroreceptors and Neural pathway involved when the following input leads to vomiting:
-Input: Drugs, Metabolic products, Bacterial toxins

Input : Drugs, bacterial toxins, metabolic products.
- Neuroreceptors in the stimulated : NK1, D2 (central), 5HT3.
- Neuronal pathway :- Chemoreceptor trigger zone.
- Projections from vestibular nuclei stimulate the vomiting center.

Note main mechanism:

Uses Vestibular projections to the CTZ which stim. the vomiting center.
Vomitting center is activated
Leading to nausea and vomiting

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There are 8 groups of anti-emetic drugs, what are they?

Antihistamines.
Anticholinergic drugs.
Serotonin antagonist
Dopamine antagonist
Neurokinin antagonist
Corticosteroids
Cannabinoids
Benzodiazepines

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Name 4 anti-histamine drugs that one can admit for nausea and vomiting:

Promethazine
Cyclizine
Betahistine
Cinnarizine

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What cause of nausea and vomiting are anti-histamines most effect against fighting?

Motion sickness and labyrinth disorders

- Acts on vestibular efferents and within brain stem

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What limitations are there to using this drug?

Modest efficacy.
Dose related adverse effects.
Antimuscarinic drugs.

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What is betahistine used for?

Used in vertigo

Hearing loss associated with Ménière’s disease

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What is Cinnarizine and where is UGIT used?

Anti histamine and calcium antagonist. | Treatment of vertigo Nd motion sickness

Name the 3 types of dopamine antagonists:

Phenothiazines Benzamines Butyrophenones

Give a few facts about phenothiazines

Most common anti-emetics. - Prochlorperazine Act on CTZ in small doses and vomit center in high doses. Helpful in treating hiccups (chlorpromazine)

Which drugs are the least effective in testing motion sickness?

Phenothiazines

What are the side effects of phenothiazines?

Extra- pyramidal S/E, Hypotension and restlessness

Give an example of a benzamine:

Metoclopramide. | - Maxolon

How does Metoclopramide work?

Promotes gastric emptying due to 5HT4 receptor (serotonin) stim.

When is Metaclopramide ineffective?

Ménière’s disease Motion sickness and vertigo Labyrinth disorder

What are the adverse effects of metaclopramide?

- Extra-pyramidal symptoms - Diarrhea - Sedation

Where are 5HT3 receptor antagonists usually used?

Chemotherapy- induced emesis. | Post operative nausea and vomiting: Alongside anti-histamines

Give a few examples of 5HT3 antagonists (end on setron):

Ondansetron. Ganisetron. Palonsetron. Dolasetron.

Why are serotonin antagonists so effective?

5HT3 Antagonists have action at both periphery and central sites. Peripheral: - Block 5HT3 visceral vagal afferent fibers Central sites - block 5HT3 in CTZ

What are some adverse effects of using 5HT3 receptor antagonists?

Headaches are most common | Constipation.

Name 4 5HT3 receptor antagonist drugs:

Ondansetron Granisetron Palonsetron Dolasetron

What are Benzodiazepines?

These are anti-emetics with a relatively low potency

Name 3 side effects of benzodiazepines:

Sedative. Anxiolytic drug. Amnesic.

To enhance the effect of the drug, which drug class is administered alongside a 5HT3 receptor antagonist

Corticosteroids Examples include: - Dexamethazone - Methylprednisolone.

Give an example of a Neurokinin antagonist drug:

Aprepitant (Emend) - A new class drug targeting the N1 receptors in the brain - Blocks substance P in the CTZ vomit center.

Name 2 indications of Neurokinin (Aprepitant):

Prevention of chemotherapy induced nausea and vomiting | Prevention of postoperative nausea and vomiting.

Name 3 adverse effects of Neurokinin antagonist Aprepitant:

Extensive metabolism of CYP34A Constipation and fatigue Shorten the half life of warfarin

Name 2 corticosteroids that can be used as anti-emetics

Dexamethasone | Methylprednisolone

Which 2 drug groups can corticosteroids-steroids be co-administered with, for an additive effect?

5HT3 antagonists | N1 antagonists

When would corticosteroids-steroids be used an anti-emetic?

Cytotoxic drugs

Name 2 cannibinoid anti-emetics:

Nabilone | Dronabinol

When are canniboids useful?

Useful in nausea and vomiting in cytotoxic therapy.

What is the mechanism of action for cannabinoids?

Block descending pathway in cortical areas.

What side effects are associated with cannabinoids?

``` Hallucinations Dysphoria Sedation Vertigo Disorientation. ```

What reaction is expected to be observed in the GIT, when muscarinic receptors are stimulated?

Increase GI motility | Increase in secretions.

Name the receptor subtype as well as, It’s parasympathetic and sympathetic effect on: 1. Stomach motility and tone: 2. Stomach sphincters: 3. Stomach secretion:

1. Motility and tone: Parasympathetic: M2= M3 ~ Increase in contraction. Sympathetic: Beta 2 ~Decrease in dilation 2. Sphincters Parasympathetic: M3>M2 ~ Increase in relaxation Sympathetic: Alpha 1 ~ Contraction 3. Secretion: Parasympathetic: M3>M2 ~ Increase in stimulation Sympathetic: Alpha 2 ~ Inhibition.

Name the receptor subtype as well as, It’s parasympathetic and sympathetic effect on: 1. Intestinal motility and tone: 2. Intestinal sphincters: 3. Intestinal secretion:

Name the receptor subtype as well as, It’s parasympathetic and sympathetic effect on: 1. The gallbladder and bile ducts

Parasympathetic: M ~ Increase in Contraction Sympathetic: Beta 2 ~ Relaxation

Name 4 drugs that are classified as an anti-muscarinic anti-emetic:

Mebeverine. Hyoscine butylbromide. Dicyclomide. Propantheline.

What is Dicyclomide commonly used for?

Relief of biliary, intestinal and genitourinary spasms | - Associated with respiratory collapse.

What is anti-emetic, propantheline, typically used for?

Peptic ulcer disease | - Associated with inhibition of sweating.

What is the anti-emetic, Hyoscine butyl-bromide, typically used for?

Anti-spasmodic

What is the anti-emetic, Mebeverine typically used for?

Selective spasmolytic on GI | Most effective on sphincter of Oddi

What is the mechanism of diarrhea:

1. Increase in osmotic load in intestine= retention of water in the lumen. 2. Excessive secretion of electrolytes and water. 3. Disrupted intestinal motility = Rapid transit and dec. fluid absorption. 4. Exudation of protein and fluid from the mucosa.

What is the treatment goal of anti-diarrheal agents?

Anti-infective agents. Restore electrolyte imbalance and prevent dehydration. Use of spasmolytics

Anti-diarrheal agents fall into 1 of 4 categories depending on their mechanism of action . What are these categories?

Anti-motility. Modify fluid and electrolyte transport. Absorbent. Probiotics.

Name 3 anti-motility agents

Loperamide Diohenoxylate Codeine

Name 3 adverse effects of anti-motility drugs:

Constipation Drowsiness Abdominal cramps

Where should anti-motilities be avoided?

Avoid in patients with suspected inflammatory diarrhea | - Toxic mega colon in patients with C. difficile

What is Bismuth Subsalicylate?

Anti-diarrheal agent | - Modifies fluid and electrolyte transport

Where is Bismusth subsalicylate indicated?

-Travellers diarrhea

Side effects of Bismuth Subsalicylate?

- Black discoloration of mucous membranes

What are 4 kinds of absorbents?

Bile acid sequestrats Kaolin and pectin Methylcellulose Aluminum hydroxide

What is the mechanism of action for absorbents?

Absorb intestinal toxins or micro-organisms | Coat/protect intestinal mucosa

Hat is the mechanism of action for probiotics?

Contain a variety of bacteria strains that help in - Antibiotic related diarrhea - Acute diarrhea - Infectious diarrhea

What are laxatives? | What are 4 types of laxatives

Supplements that accelerate transit time through intestines. Types include: - Dietry fiber and supplements (Bulk laxatives) - Stool wetting and emollients laxative - Osmotic active laxative - Irritant laxative

Name 2 risks of chronic laxative use:

- Habit forming. | - Electrolyte imbalance if use chronically

What is the mechanism of action of dietary fibre laxatives?

Unfermented fibre attracts water and increases stool bulk. - Forms a gel that retains water. - And distends intestine which increases peristalsis.

What are the contra-indications of dietary supplement laxatives?

Megacolon. | Megarectum.

Name 3 types of osmotic agents that are working laxatives

1. Saline laxatives 2. Electrolyte solution laxatives 3. Non-digestible sugars - Lactulose. - Cannot be hydrolyzed by intestinal enzymes. - Degraded into lactic acid, formic and acetic acid. - Increase osmotic pressure. - Increase lumen, increase fluid, increase diarrhea.

What stool emollient leads to anal leakage?

Mineral oils