ANTIEMETICS

Regulation of vomiting medulla oblongatamedulla oblongata –the vomiting centre –chemoreceptor trigger zone (area postrema) emetogenic substances, apomorphine, morphine, chemotherapy, motion sickness –Ach, histamine, 5-HT, Dop

Clinical use of anti-emetic drugs: H 1 -receptor antagonists:  cylizine - motion sickness  cinnarizine - motion sickness, vestibular disorders (e.g. Meniére´s disease)  promethazine - severe morning sickness of pregnancy (only if absolutely essential) D 2 -receptor antagonists:  phenothiazines (e.g. thiethylperazine) - vomiting caused by uraemia, radiation, viral gastroenteritis (drugs of choice); severe morning sickness of pregnancy (if absolutely essential)  metoclopramide - vomiting caused by uraemia, radiation, gastrointestinal disorders, cytotoxic drugs

Muscarinic-receptor antagonists:  hyoscine - motion sickness (drug of choice) 5-HT 3 receptor antagonists:  ondansetron - vomiting caused by cytotoxic anticancer drugs (drug of choice), postoperative vomiting; radiation- induced vomiting Cannabinoids:  nabilone - for vomiting caused by cytotoxic anticancer drugs

laxatives antidiarhoeal drugs

LAXATIVES bulk laxativesbulk laxatives –=increasing the volume, not absorbed –methylcelulose, agar, psyllium seeds –no serious unwanted effects osmotic l.osmotic l. –not absorbed, osmosis - distension of colon –magnesium sulphate, magnesium hydroxide, lactulose –ADR: flatulence, cramps, diarhoea, electrolyte dist., tolerance stimulant l.stimulant l. –stimulation of enteric nerves -  secretion, motility –bisacodyl, senna preparations –! only for short-term use - nerve reduction

antidiarrhoeal agents I secretion, motility, decreased absorption ! fluid and electrolyte balance - rehydration antiinfective agents…gastroenteritis –sever cases of Campylobacter - erythromycin, ciprofloxacin antidiarrhoeal agents

antidiarrhoeal agents II antimotility agentsantimotility agents –opiates, morphine - constipation, sphincter contraction –codeine, diphenoxylate, loperamide –! drowsiness, dizziness, paralytic ileus adsorbentsadsorbents –adsorbing microorganisms and toxins –kaolin, pectin, charcoal

motility stimulants = prokinetic drug domperidone (Motilium) - D 2 antagonist, also antiemetic –  oesophageal sphincter pressure…GERD –! hyperprolactinemia metoclopramide (Paspertin) - DA antagonist and Ach agonist –increases gastric emptying - GERD –! extrapyramidal side effects cisapride (Prepulsid) - 5-HT 4 rec. agonist….Ach release –  gut motility, no antiemetic action –withdrawn due to QT prolongation