Opioids

OPIOIDS

Loperamide

  • Loperamide is a synthetic piperidine opioid
  • It is an opiate analogue with weak anticholinergic property.
  • Because of poor water solubility little is absorbed form the intestine.
  • Entry into brain is negligible.
  • In addition to its opiate like action on motility, it also inhibits secretion.
  • It improves fecal continence by enhancing anal sphincter tone.

Mechanism of action

  • Opiates inhibit ACh release.
  • The resultant increased gastrointestinal rhythmic segmentation and decreased propulsive motility slow the transit time of luminal contents and increase absorption
  • In addition , opiates directly stimulate absorption of fluid and electrolyte via mu -opiate receptors in the CNS and intestinal mucosa.

Codeine

  • Antidiarrheal action is primarily attributed to its peripheral action on small intestine and colon.
  • It does not have central effects , buit produce dependance.
  • It should be used only for a short period.

Diphenoxylate

  • It is an opioid chemically related to pethidine: used exclusively as constipating agent.
  • The antidiarrheal action is prominent, but because it is absorbed systemically and crosses blood brain barrier CNS effects may occur.
  • Atropine is added in a non-pharmacological dose to discourage abuse.
  • Abuse liability is rated low and overdose will produce disturbing atropinic side effects.
  • Use: Opiates are effective in the symptomatic treatment of acute diarrhea.

Administration

  • Paregoric is administered orally 2-3 times daily to dogs and cats once daily to calves and foals
  • Diphenoxylate is administered orally 2-3 times daily to dogs and cats
  • Loperamide is administered orally 1-2 times daily to dogs and cats
  • Codeine is administered orally 2-3 times daily to dogs and cats.
  • Adverse effects: bacterial overgrowth in the intestinal lumen of animals with infectious diarrhea may result from slowed intestinal transit time.
  • In cats, excitatory reactions render opiate use controversial.
  • Paregoric is a camphorated tincture of opium.
  • Diphenoxylate is a synthetic congener of mepridine.
  • Lomotil is diphenoxylate plus atropine.
Last modified: Wednesday, 25 April 2012, 10:30 AM