Classify antiemetic drugs and give an example from each group (60% of marks).
Outline the gastrointestinal effects of metoclopramide (40% of marks).
Antiemetics, as a topic has been frequently asked, in various formats in the past. Candidates who performed well had a good depth and breadth of knowledge as well as sufficient integration of knowledge to be able to classify and understand the basis to the various classifications. Essentially it was expected that candidates mention the classifications of Anticholinergics, Antihistamines, Anti 5HT, Antidopaminergics (benzamides, butyrophenones, phenothiazines), Steroids and other agents with known antiemetic activity (e.g. propofol, benzodiazepines, etc). In relation to metoclopramide it was expected that candidates would mention that it lowers pressure threshold for occurrence of intestinal peristaltic reflex, reduces intestinal muscle fatigue, enhances frequency and amplitude of longitudinal muscle contraction, coordinates gastric, pyloric and duodenal activity to improve GI motility, mechanism of action appears to depend on intramural cholinergic neuron, acts primarily by augmenting release of ACh and perhaps by inhibition of 5-HT release, increases lower oesophageal sphincter pressure, relaxes the pyloric sphincter and antagonize the inhibitory neurotransmitter, dopamine.
Classification of antiemetics:
Gastrointestinal effects of metoclopramide:
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