Pharmacology Flashcards
What is nausea
Highly, unpleasant sensation felt in the throat as a sinking sensation. Often relieved by vomiting
What does nausea usually precede
Vomiting
What is retching
Retroperistalsis of the stomach and oesophagus without vomiting
Does stomach contraction cause vomiting (emesis)
No as stomach, oesophagus and associated sphincters relax
What coordinates vomiting in the brain
Vomiting centre in the medulla oblongata of brain stem
What frequently preceedes vomiting
Salivation, increase in heart rate, sweating, nausea
Events in vomiting
Suspension of intestinal slow wave activity, retrograde contractions from ileum to stomach, suspension of breathing, relaxation of lower oesophageal sphincter, abdominal muscles and diaphragm contract, gastric contents ejected through upper oesophageal sphincter
Why does the glottis close during vomiting
To prevent accidental aspiration
Common causes of vomiting
Absorbed toxic material and drugs in blood, mechanical stimuli, vestibular system (motion sickness), stimuli within CNS (pain, repulsive sites, fear)
What part of the medulla controls vomiting
Chemoreceptor trigger zone (CTZ) in the area postrema and nucleus tractus solitarius
Pharyngeal stimulation, gastric/duodenal distention or irritation goes to the medulla via?
Nucleus tractus solitarius
Endogenous toxins ,drugs, vagal afferents stimulate via
Chemoreceptor trigger zone (CTZ) that lacks a blood brain barrier
What do enterochromaffin cells in mucosa release to cause depolarization of sensory afferent terminals
5-HT or serotonin
Motor output of vomiting is co-ordinated by
Group of interconnected neurones within medulla that receives input from nucleus tractus solitarius
Why do sphincters of anus and bladder constrict during emesis
To prevent accidental defecation and micturition
Consequences of severe vomiting
Dehydration, hypochloraemic metabolic alkalosis raising blood pH, hypokalaemia, Mallory-Weiss tear, aspiration of vomitus
What are prokinetic drugs
Increase GI tract motility and lower oesophageal sphincter tone. Ex: Domperidone and Metoclopramide
When do motion sickness H1 antihistamine drugs best
When taken 1-2 hours prior to the journey
Additional effect of cinnarizine
In addition to it’s H1 antihistamine effect, it has an additional antivertigo effect inhibiting calcium influx, helping tinnitus and Meniere disease
Triple drug regime for chemotherapy induced nausea and vomiting (CINV)
5-HT3 receptor antagonist + Dexamethasone (corticosteroid) + Aprepitant (substance P antagonist)
What are NK1 receptors for
Substance P
What does the chemoreceptor trigger zone stimulate
CTZ stimulates vomiting center in the medulla