ANTIEMETICS

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ANTIEMETICS
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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

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Clinical use of anti-emetic drugs

• H1-receptor antagonists
• cylizine - motion sickness
• cinnarizine - motion sickness, vestibular
  disorders (e.g.
• Meniéres disease)
• promethazine - severe morning sickness of
  pregnancy (only
• if absolutely
  essential)
• D2-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

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• Muscarinic-receptor antagonists
• hyoscine - motion sickness (drug of choice)
• 5-HT3receptor 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

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Motility of GIT

• laxatives
• antidiarhoeal drugs

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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

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antidiarrhoeal agents I

• secretion, motility, decreased absorption
• ! fluid and electrolyte balance - rehydration
• antiinfective agentsgastroenteritis
• sever cases of Campylobacter - erythromycin,
  ciprofloxacin
• antidiarrhoeal agents

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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

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motility stimulants

• prokinetic drug
• domperidone (Motilium) - D2 antagonist, also
  antiemetic
• ? oesophageal sphincter pressureGERD
• ! hyperprolactinemia
• metoclopramide (Paspertin) - DA antagonist and
  Ach agonist
• increases gastric emptying - GERD
• ! extrapyramidal side effects
• cisapride (Prepulsid) - 5-HT4 rec. agonist.Ach
  release
• ? gut motility, no antiemetic action
• withdrawn due to QT prolongation