This document discusses several classes of drugs used to treat vomiting and regulate gastrointestinal motility. It outlines the mechanisms and clinical uses of antiemetic drugs that act on histamine, dopamine, serotonin, and cannabinoid receptors to treat chemotherapy-induced vomiting and motion sickness. It also summarizes the types and mechanisms of laxative drugs that work by bulking stool, drawing water into the intestines, or stimulating intestinal nerves. Antidiarrheal drugs are discussed that decrease intestinal secretion, motility and absorption to maintain fluid and electrolyte balance.

1. ANTIEMETICS

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

4. 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

5. 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

6. laxatives antidiarhoeal drugs Motility of GIT

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

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

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

11. 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