Pharmacology Flashcards
What muscles contract to cause vomiting?
Abdominal muscles and diaphragm
What is retching?
Reverse peristalsis
What is regurgitation?
Effortless movement of swallowed food contents back into the mouth
Sickness signals through the vestibular pathway are generally caused by what?
Tinnitus or motion sickness
Through what nerve do signals from the vestibular pathway travel?
Vestibulocochlear nerve
Sickness signals through the vagal pathway are generally caused by what?
Bacteria/alcohol/smell and vision/pharynx i.e. excess cough
What is the central pathway with regards to vomiting?
Brainstem emetic control pathway
Where will all drugs acting on the chemoreceptor trigger zone act?
Outside the blood brain barrier
What do enterochromaffin cells in the mucosa do?
Release mediators e.g. 5HT
What do mediators released by enterochromaffin cells in the mucosa cause?
Depolarisation of sensory afferents in the mucosa and AP discharge in vagal afferents to the brainstem
What does AP discharge in vagal afferents to the brainstem cause?
Coordination of vomiting by the vomiting centre
In what state are the stomach, oesophagus and associated sphincters during vomiting?
Relaxed
Where is the vomiting centre found?
Medulla
What state is the glottis in during vomiting?
Closed to prevent aspiration
What usually precedes vomiting?
Profuse salivation, increased HR, sweating and nausea
Does the motor output of vomiting involve efferents or afferents?
Efferents
What do vagal efferents cause in vomiting?
Shortening of the oesophagus, relaxation of the stomach and contraction of small intestine
What do somatic motor neurones cause in vomiting?
Contraction of anterior abdominal muscles and diaphragm
What do autonomic and somatic efferents cause in vomiting?
Increase heart rate and force, increase salivary secretions, pallor and sweaty skin, constriction of bladder and anal sphincters
What are some consequences of vomiting?
Dehydration, metabolic alkalosis, hypokalaemia, Mallory Weiss tear, aspiration
What is a sign of a Mallory Weiss tear?
Reddish streaks of fresh blood in vomit
What are prochlorperazine and droperidol examples of?
Dopamine antagonists
What do dopamine antagonists work as at high doses?
Anti-psychotics
How do dopamine antagonists work?
Block chemoreceptor trigger zone
What are dopamine antagonists used to treat?
Vomiting associated with neoplastic disease, radiation and drug induced sickness
What are side effects of dopamine antagonists?
Sedation and dystonic reactions
Where do prokinetic drugs work?
Dopamine pathways
What do prokinetic drugs do?
Increase gastric peristalsis and lower oesophageal sphincter tone
What is a common anti-emetic in the prokinetic drug class?
Metoclopramide
What are granisetron and ondansetron examples of?
5HT3 Receptor antagonists
What is a frequent side effect of 5HT3 receptor antagonists?
Headaches, and sometimes GI effects
What do 5HT3 antagonists block?
Receptors in the GI tract and CNS
What are 5HT3 antagonists used for?
Management of CINV, radiation induced emesis, PONV
What are promethazine, cyclizine and cinnarize examples of?
H1 Antihistamines
What receptor do H1 antihistamines also often block?
Muscarinic
What effect does cinnazine also have?
Antivertigo (tinnitus and Meniere’s)
What are H1 antagonists most useful for?
Motion sickness, morning sickness, PONV
What can H1 antagonists cause and what is the rule associated with this?
CNS depression and sedation- cannot drive
What are hyoscine, dicyclomine examples of?
Muscarinic antagonists
What are anticholinergics given for?
Motion sickness
What can anticholinergics be associated with?
Blurred vision, dry mouth, urinary retention and sedation
What classes of drugs can be used as adjuvant anti-emetics?
NK1 receptor antagonists, corticosteroids, benzodiazepines, cannibinoids
What drugs are used in anticipatory nausea and vomiting?
Benzodiazepines
How long and wide is the large intestine?
1.5m long and 6cm wide
What controls opening of the ileocaecal valve?
Gastric distension to cause gastro-ileal reflex
What is the ileocaecal valve under control of?
Vagus nerve, sympathetic and enteric nerves
What does the ileocaecal valve allow?
Digested contents of small intestine to move into caecum
what does the ileocaecal valve prevent?
Colonic bacteria entering the ileum
What is absorbed in the large intestine?
H2O, Na+, Cl-, short chain fatty acids