GIT Drugs

Anti-emetics

Anti-histamines

Diphenhydramine (benadryl)

  • good for motion sickness
  • can cause paradoxical excitement in cats
  • can cause sedation

Meclizine

  • good for motion sickness
  • can cause paradoxical excitement in cats
  • can cause sedation

Dopamine antagonists

Phenothiazines (Prochlorperazine or Acepromazine)

  • block many neurotransmitters involve in vomiting, but main job is to block dopamine receptors in the CTZ
  • adverse effects = hypotension, sedation and can lower seizure threshold in epileptics

Metoclopramide

  • anti emetic effects AND promotes GI motility -> contraindicated in GI obstruction or perforation
  • useful for emesis induced by GI disease and chemotherapy
  • can cause CNS stimulation

Serotonin (5-HT3) Antagonists

Odansetron and Granisetron

  • block central CTZ and peripheral 5-HT3 receptors
  • useful for refractory vomiting (chemotherapy, parvo, post op vomiting and pancreatitis)

Mirtazapine

  • antiemetic effects in cats and appetite stimulation

Neurokinin-1 antagonists

Maropitant (Cerenia)

  • blocks effects of substance P
  • can use in dogs and cats
  • has some analgesia effects

Glucocorticoids

Dexamethasone

  • not indicated for treatment of vomiting but can help to reduce vomiting by inhibiting prostaglandin production (can be added to other antiemetics for refractory vomiting)

Emetics

Peripherally acting

Table salt

Hydrogen peroxide

Ipecac syrup

Centrally acting

Apomorphine

  • dogs

Alpha 2 Agonists (Xylazine, dexmedetomidine)

  • more reliable in cats

Anti-ulcer

H2 (Histamine) Blockers

  • histamine has the greatest effect on ulcers in the stomach
  • histamine binds to H2 receptors on parietal cells to increase cAMP and proton pump activity

Cimetidine

  • least potent and rarely used now

Ranitidine

  • middle potency

Famotidine

  • most potent
  • less rebound hypersecretion compared to others
  • does not inhibit p450 enzymes

Proton Pump Inhibitors

  • most potent gastric antisecretory drugs available

Omeprazole

  • irreversibly binds the parietal cell (sodium potassium proton pump, which is the final step in gastric acid secretion)
  • it is a PROdrug

Mucosal protectants

Sucralfate

  • binds to ulcerated area
  • requires acidic environment for activation
  • good for ulcer healing but not for ulcer prevention

Antacids

  • work by neutralizing pH
  • formulated as hydroxide bases of aluminum, magnesium and calcium

Misoprostol

  • PGE analogue
  • increases mucous production, bicarbonate, re-epithelization of mucosa and increases local blood flow
  • reduces HCL secretion from parietal cells
  • used for the prevention of gastric ulcers
  • contraindicated during pregnancy bc it can cause uterine contractions

Prokinetics

  • dopamine is inhibitory NT
  • Serotonin is excitatory NT

Dopamine Antagonists

Metoclopramide

  • blocks inhibitor (dopamine) receptors and stimulates excitatory (serotonin) receptors) on enteric cholinergic nerves = double whammy to promote motility

Domperidone

Serotonin Receptor Modulators

Cisapride

  • broadest spectrum prokinetic

Miscellaneous

H2-receptor antagonists

Nizatidine

Ranitidine

Cholinergics

Bethanechol

Anti-diarrheals

Bismuth Subsalicylate

Kaolin/Pectin

Opioids

Loperamide (imodium)

Diphenoxylate

Anticholinergics

  • opposite of SLUDGE!
  • help to facilitate rectal exams (calms the rectal muscles)

Atropine, hyoscine butylbromide

Propantheline (synthetic anticholinergic)

Laxatives and Cathartics

  • laxatives produce soft stool and cathartics produce watery stool

Mineral Oil

White petrolatum

Bulk Laxatives

Methylcellulose and psyllium seed

Stool Softeners

Docusate sodium

Hyperosmotics = salts and sugars

  • mannitol, sorbitol and lactulose = the sugars
  • magnesium sulfate and sodium sulfate = the salts