SYLAPS SCOPOLAMINE FOR FREE
For the reader who needs a compendium of such short notes but is understandably reluctant to recognise the authority of an unreliable non-peer-reviewed online resource, an excellent anaesthesia-focused paper by Lyons and Ballisat (2016) is available for free and covers all the usual suspects. Instead of carefully dissecting the pharmacokinetics and pharmacodynamics of each substance, short notes on each class will be offered here, as well as links to a monograph dealing with the use of that substance as an antiemetic. There is a lot of overlap in the antihistamine / anticholinergic / dopamine antagonist groups, because many of those drugs are extremely "dirty" and have appreciable antiemetic effects exerted by each of these mechanisms (for example promethazine). Here is a list of antiemetics, arrayed according to their class and year of their commercial availability: DrugĪntiemetics with unclear mechanism of action Markham & Sorkin, 1993, is suggested for ondansetron, and Albibi & McCallum (1983) for metoclopramide. However, metoclopramide and ondansetron have received a lot of attention in past papers, and the savvy candidate will have a detailed familiarity with their properties. Single best reference for further informationįor the pharmacology of antiemetics, Singh et al, 2015 would probably be the best free article, mainly because it only spends about a paragraph on each class, and from the look of previous SAQs we can surmise that this is enough. Galactorrhoea due to dopamine antagonist effects risk of dystonic reaction, especialy with children under 10 Increased lower oesophageal sphincter tone Prokinetic effects are mainly due to the peripheral muscarinic agonist effects dystonic reaction and galactorrhoea) are also mainly antidopaminergic. No anticholinergic or antidopaminergic effects, and therefore no effects on gastric motility or nausea related to vertigoĪntiemetic/antinausea effect is mainly exerted by the antidopaminergic effects centrally. Main mechanism of antiemetic activity is the antagonism of 5-HT3 ligand-gated cation channels at the chemoreceptor trigger zone. Half-life is about 4-6 hours, but the duration of antiemetic effect is only 1-2 hours Half life is about 3.8 hours duration of effect is about 4-8 hours Undergoes some hepatic metabolism, mainly by CYP 2D6Ĭlearance is almost completely hepatic only some minimal amount is eliminated by the kidneysĪbout 20-50%of the drug dose is eliminated unchanged VOD = 3.5L/kg minimally protein-bound (13-22%)ĥ-HT3 serotonin receptor antagonist - which are ligand-gated cation channels and which mainly conduct depolarising sodium and potassium currentsĭ2 dopamine receptor antagonist (Gi-protein coupled) Īlso has activity as a muscarinic agonist (mainly peripherally)ĩ5% of the dose is cleared by hepatic oxidative metabolism Rapidly and completely absorbed, bioavailability ~ 80%
Rapidly and completely absorbed, bioavailability ~ 60%
ondansetron and granisetron are pure, high-affinity 5-HT 3 antagonists.
Phenothiazines and butyrophenones also have strong antimuscarinic effect.Hyoscine, atropine (purely antimuscarinic).Benzamides (metoclopramide), which have a prokinetic effect related to indirect cholinergic activity.Butyrophenones (droperidol), which have slightly less potent anticholinergic and antihistamine effects.Phenothiazines (promethazine), which also have potent activity against muscarinic, H1, 5-HT 3 and dopamine receptors.
0 kommentar(er)
