6582309
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
about 8 years ago
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| Question | Answer |
| Give eg's of & indications for dopamine D2-receptor antagonists. | eg's: metoclopramide, domperidone Indications: • N & V especially in the context of reduced gut motility |
| MOA of dopamine D2-receptor antagonists. | N & V are triggered by a variety of factors, including gut irritation, drugs, motion & vestibular disorders, as well as higher stimuli (sights, smells, emotions). The various pathways converge on a ‘vomiting centre’ in the medulla, which receives inputs from the chemoreceptor trigger zone, the solitary tract nucleus (which is innervated by the vagus nerve), the vestibular system & higher neurological centres. Dopamine, acting via D2 receptors, is relevant in two respects. First, the D2 receptor is the main receptor in the chemoreceptor trigger zone (CTZ), which is the area responsible for sensing emetogenic substances in the blood (e.g. drugs). Second, dopamine is an important neurotransmitter in the gut, where it promotes relaxation of the stomach & LOS & inhibits gastroduodenal coordination. Drugs that block D2 receptors therefore have a prokinetic effect – promoting gastric emptying – which contributes to their antiemetic action. They are effective in N & V due to CTZ stimulation (e.g. due to drugs) & reduced gut motility (eg due to opioids or DM gastroparesis). |
| SE's of dopamine D2-receptor antagonists. | • Diarrhoea • Extrapyramidal syndromes (metoclopramide). In the context of short-term Rx for N & V, this is most likely to take the form of an acute dystonic reaction such as an oculogyric crisis*. • Diarrhoea • Extrapyramidal syndromes (metoclopramide). In the context of short-term treatment for nausea and vomiting, this is most likely to take the form of an acute dystonic reaction such as an oculogyric crisis*. *'An extreme & sustained (usually) upward deviation of the eyes often with convergence causing diplopia(double vision). It is frequently associated with backward & lateral flexion of the neck & either widely opened mouth or jaw clenching. Frequently a result of antiemetics such as the neuroleptics (eg, prochlorperazine) or metoclopramide. Also can be caused by Chlorpromazine.' Wiki. |
| CI's, cautions, & important interactions of dopamine D2-receptor antagonists. | CI's: • GI obstruction • GI perforation • Children Cautions: • Young adults (15-19) - according to BNF Important interactions: The risk of extrapyramidal SE's is ^when metoclopramide is prescribed with antipsychotics. It should not be combined with dopaminergic agents for Parkinson’s disease, as it will antagonise their effects. Domperidone is not subject to these interactions. |
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