Antiemetics,Motility

ANTIEMETICS

Regulation of vomitingmedulla oblongata

the vomiting centrechemoreceptor trigger zone (area postrema)emetogenic substances, apomorphine, morphine, chemotherapy, motion sickness Ach, histamine, 5-HT, Dop

Clinical use of anti-emetic drugs:H1-receptor antagonists: cylizine - motion sickness

cinnarizine - motion sickness, vestibular disorders (e.g. Menires disease)

promethazine - severe morning sickness of pregnancy (only if absolutely essential)

D2-receptor antagonists:phenothiazines (e.g. thiethylperazine) - vomiting causedby 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-HT3receptor antagonists:ondansetron - vomiting caused by cytotoxic anticancerdrugs (drug of choice), postoperative vomiting; radiation-induced vomiting

Cannabinoids:nabilone - for vomiting caused by cytotoxic anticancer drugs

laxativesantidiarhoeal drugs

LAXATIVESbulk laxatives=increasing the volume, not absorbedmethylcelulose, agar, psyllium seedsno serious unwanted effectsosmotic l.not absorbed, osmosis - distension of colonmagnesium sulphate, magnesium hydroxide, lactuloseADR: flatulence, cramps, diarhoea, electrolyte dist., tolerancestimulant l.stimulation of enteric nerves - secretion, motilitybisacodyl, senna preparations! only for short-term use - nerve reduction

antidiarrhoeal agents Isecretion, motility, decreased absorption! fluid and electrolyte balance - rehydration

antiinfective agentsgastroenteritissever cases of Campylobacter - erythromycin, ciprofloxacin

antidiarrhoeal agents

antidiarrhoeal agents IIantimotility agentsopiates, morphine - constipation, sphincter contractioncodeine, diphenoxylate, loperamide! drowsiness, dizziness, paralytic ileusadsorbentsadsorbing microorganisms and toxinskaolin, pectin, charcoal

motility stimulants= prokinetic drugdomperidone (Motilium) - D2 antagonist, also antiemetic oesophageal sphincter pressureGERD! hyperprolactinemia

metoclopramide (Paspertin) - DA antagonist and Ach agonistincreases gastric emptying - GERD! extrapyramidal side effects

cisapride (Prepulsid) - 5-HT4 rec. agonist.Ach release gut motility, no antiemetic actionwithdrawn due to QT prolongation