PH3113 - Pain and Analgesia 1 Flashcards
Where is 89% of the total body content of 5-HT found?
Enterochromaffin cells in the intestine
Where is 10% of the total body content of 5-HT found?
Platelets
- take up 5-HT from the plasma
Where is 1% of the total body content of 5-HT found?
Central nervous system
- very important role
How can the turnover of 5-HT be measured?
5-HIAA levels in the urine
- 5-hydroxyindoleactic acid
Give examples of stimuli that can induce nausea and vomiting
Emesis can be stimulated by
- gastric irritation and peritonitis
- gets rid of the irritant
- reflex to remove something toxic
- inner ear dysfunction
- motion sickness
- pregnancy
- drugs
- digitalis
- cancer chemotherapeutics
- general anaesthetics
- radiotherapy
Which areas of the brain are involved in nausea and vomiting?
Cerebellum - controls balance
- motion sickness
Nucleus Tractus Solitarius (NTS)
- irritants
Chemoreceptive Trigger Zone (CTZ)
part of the blood brain barrier that is a bit leaky as it is detecting what is happening in the blood.
- drugs/chemicals in the blood
Higher centres
- cortex
- thalamus
- psychological influences
Vomiting centre
- medulla
- pontile reticular formation
- controls the complex series of events which precede vomiting
Which receptors are involved in nausea and vomiting?
Muscarinic
- M1 and others
Dopamine
- D2
Histamine
- H1
Serotonin
- 5HT3
Neurokinin
- NK1
Cannabinoid
- CB1
What is the cause of motion travel sickness?
Inner ear dysfunction
- conflict of messages to the brain
- involves dopamine D2 receptors in the vestibular nucleus
What is ‘morning sickness’?
Nausea and vomiting associated with pregnancy but can occur at any time of the day
- cause unknown
- thought to be hormonal changes
- symptoms often disappear by the end of the 3rd month
- first trimester
- weeks 16 - 20
- 1 in 10 women still feel sick after week 20
About 50% of pregnant women vomit
More than 80% feel nauseous
- can last all day
How is morning sickness treated?
Generally not treated with drugs but can be used if other methods fail
- harm to foetus
Resting
Eat before getting up
Drinking plenty
- not in large volumes
Small and frequent meals with carbohydrates
Avoid sweet or spicy meals
Cold meals
Avoid food/smells which induce sickness
Distractions from feelings of nausea and vomiting
Avoid tight waistbands
What is hyperemesis gravidarum?
Excessive vomiting during pregnancy
About 1 in 100 women
Symptoms
- dehydration
- ketosis
- weight loss and postural hypotension
- faint when standing up suddenly
How is hyperemesis gravidarum treated?
May need hospitalisation for IV fluids and drugs
- anti-emetics
- vitamin B6
- vitamin B12
- steroids
Which anti-emetics can be used in pregnancy?
Anti-histamines (H1 receptors)
- cyclizine
- promethazine
D2 receptor antagonists
- prochlorperazine
D2 receptor antagonist/5-HT3 receptor antagonist
- metoclopramide hydrochloride
D2/D3 receptor antagonist
- domperidone
- only if potential benefit outweighs risk
5-HT3 receptor antagonist
- ondansetron
- NOT IN FIRST TRIMESTER
- increased risk of oral clefts
- benefits MUST outweigh risks
Steroid
- prednisolone
What are the indications for using D2 receptor antagonists (prochlorperazine) during pregnancy?
Severe nausea and vomiting
Caution in various patient groups
- cardiovascular disease
- elderly
Many side effects
- dystonia
- especially in children
Formulation
- oral
- intramuscular
- buccal
Can be used in combination with a steroid although the mechanism for its anti-emetic action is unknown
- dexamethasone
What are the indications for using D2 receptor antagonists/5-HT3 antagonists (metoclopramide) during pregnancy?
Migraine
Chemotherapy
Radiotherapy
General anaesthetics
Caution in
- elderly
- 15 - 19 year olds
Many side effects
- adverse neurological effects
- extra-pyramidal
MHRA/CHM restrictions
- indications
- dose
- duration
Formulation
- oral
- intramuscular
- intravenous
Also used with dexamethasone
