Anti-Emetics Flashcards
What are the 3 stages of Emesis?
- Feelings of nausea
- Retching
- Vomiting
What is an Emetic?
It’s an agent that causes vomitting
What is Emesis?
It’s a physical event of forceful evacuation of gastric content through the mouth.
It’s a protective mechanism in response to something harmful being digested or can occur in motion sickness and vestibular disorders.
True or false…
The vomiting reflex is regulated by the CNS in the midbrain
FALSE!!!
The vomiting reflex is regulated by the CNS (MEDULLA)
It’s controlled and centralized within the brain stem in a neural network on the dorsal surface of the medulla.
What are the 3 main imputs to the dorsal vagal complex which cause nausia and vomitting.
- The chemoreceptor trigger zone (in the dorsal vagal complex) - Endogenous substances/ toxins/ drugs
- The Vagal Pathway - sensory imput, stimuli from pharynx, stimuli from GI tract
- The Vestibular Pathway - Disorientated motion
Which part of the vomiting centre is effected by :
Disorientated motion
Vestibular Pathway
For example travel sickness
Which part of the vomiting centre is effected by:
Sensory imput (smell, pain, sight, tough)
Vagal Pathway
Which part of the vomiting centre is effected by:
Toxins/ Drugs and Endogenous substances?
The chomoreceptor trigger zone
Main sight of action for anti emetic drugs
What part of the vomiting centre is the main site of action for antiemetic drugs?
The Chemoreceptor Trigger Zone
Name some of the types of Endogenous mediators (neurotransmitters) for Emesis that attach to specific receptors .
(these receptors are targets from anti emetic drugs as it prevents the neurotransmitters from binding and causing emesis)
- seretonin (5HT3 receptor)
- ACh (M receptor)
- Dopamine (D2 receptor)
- Substance P (NK1 receptor)
- Histamine (H1 receptor)
- Enkephalin (delta recetor)
Name some of the receptors that are targets for anti-emetics.
Anti-emetics bind to the receptors preventing neurotransmitters from binding and causing emesis.
- Histamine receptors_ H1
- Seretonin in 5HT3 receptors
- Muscarinic: M
- Dopamine D2
- Substance P/Neurokinin: Nk receptors
Where is the location of most of the neurotransmitter receptors envolved in emesis?
THE VOMITING CENTRE (M , H1, 5HT3 , NK1 receptors)
There are also other zones where other receptors are:
- Chemoreceptor Triggering zone (5HT3, NK1, D2)
- Vestibular Pathway (M, H1)
- Vagal Pathway (5HT3)
Name some H1 receptor antagonists and what they’re used for
CYCLAZINE - Motion Sickness
CINNARIZINE - Motion Sickness & Vestibular diseases
PROMETHAZINE - Severe morning sickness
SE- drousiness and sedation (zzzzz for sleepiness)
Which of the following is NOT associated with emesis?
- The sympathetic pathway
- The chemoreceptor trigger zone (CTZ)
- The vestibular pathway
- The vagal pathway
The sympathetic pathway
What is the drug ‘Promethazine’ used for?
It’s used for severe morning sickness. It’s a H1 receptor antagonist.
(P is for Pregnancy)
What is the H3 receptor agonist drug
BETAHISTINE HYDROCLORIDE
used for?
It’s used as an antivertigo drug.
Activated the H receptors on blood vessles and inner ear causing vasodilation and permiability.
SE - GI disturbances, Rash, Pruritis, Headache
True of false:
D2 receptor antagonist drugs have weak anti-sickness properties
FALSE:
They have powerful anti-emetic properties
Phenophiazines - morning sickness
Metoclopramide
Doperidone (Motilium)
Quite a lot of SEs
What is the drug of choice for chemo sickness and post op sickness?
ONDANSETRON (5HT3 Antagonist)
Name some 5HT3 Receptor antagonist drugs for nausia:
ONDANSETRON - drug of choice for chemo + post op
GRANISETRON
POLONOSTERON
TROISETRON
What category do these drugs fall under?
- APREPITANT
- FOSAPREPITANT
- CASOPITANT
- MAROPITANT
They are NK1 Receptor Antagonists
Aprepitant is a substance P antagonist used for chemo and post op n/v.
What NK1 Receptor Antagonist is a Substance P antagoinst
APREPITANT (P is for substance P)
What is the ‘non selective antagonist’ drug which is the drug of choice for motion sickness?
HYCOSINE SCOPOLAMINE
is it a non-selective antagonist and is the drug of choice for motion sickness. Given orally / TD patch.
SE: Dry mouth, blurred vision, less sedative that anti-histamines (H1 antagonists)
What class of Drug are histamine antagonists?
H1 Antagonists:
Cyclasine,
Cinnarizine,
Promethazine.
(zzzzzs for sleepiness)
What class of anti-emetics does ‘MARINOL’ fall under?
Cannabinoids
What corticosteroid can be used to treat vomiting?
DEXAMETHASONE
- Used in vomitting caused by chemotherapy
- Mechanism not fully known
- Used in combo with D2 or 5HT3 antagonists (causes improved action)
May also increase apatite
When would you be able to give a therapeutic EMETIC?
- If someone had ingested a poisonous substance
- Drug overdose
- Alcohol Intoxication
NOT:
- Unconscious Patients
- Kerosine Poisoning
- CNS Stimulant/morphine overdose
- Ingestion of Corrosive substances
Name some therapeutic Emetics:
- Syrup of Ipecac (ipecacanta) - oral works in 15 mins
- Apomorphine - IM/SC works in 10/15 mins
- Activated Charcoal -MOST COMMONLY USED
What is the most commonly used Emetic?
Activated Charcoal
