GI Drugs Flashcards
When can aspiration occur?
When barrier pressure (the difference between LES pressure and gastric pressure) decreases
What positing puts patients at risk for aspiration?
Lithotomy
What are patient risk factors for aspiration?
Intestinal obstruction, non-fasted, delayed gastric emptying, hiatal hernia, GERD, pregnancy, obesity, neuromuscular disease, decreased laryngeal reflexes, male, elderly
What is the rule of thumb in prevention of aspiration pneumonitis?
Reduce gastric content acidity pH >2.5
Reduce amount of gastric content
What is the mechanism of action for Reglan?
Acts peripherally as a cholinomimetic (facilitates ACh transmission at selective muscarinic receptors) and centrally as dopamine receptor antagonist
What type of drug is Reglan?
Prokinetic
What are the effects of Reglan use?
Enhances stimulatory effects of ACh on intestinal smooth muscle, increases LES tone, speeds gastric emptying and lowers gastric fluid volume
What is the dose of Reglan?
10-20mg PO or IV
Why is it important to administer Reglan slowly when given IV?
Intense feeling of anxiety and restlessness, followed by drowsiness, may occur with rapid administration.
How is Reglan metabolized and excreted?
Metabolized in the liver and excreted in the urine
How is Reglan metabolized and excreted?
Metabolized in the liver and excreted in the urine
What type of drugs block Reglan effects?
Anticholinergics
What conditions is Reglan contraindicated in?
Bowel obstruction
Parkinson’s disease
Pheochromocytoma (HTN crisis)
How do pheothiazines and droperidol interact with Reglan?
Extrapyramidal effects potentiated with concurrent use
What are two other medications that can be used as a prokinetic?
Erythromycin
Neostigmine
Why isn’t Erythromycin typically used as a prokinetic?
Limited use due to possibility for developing antibiotic resistant bacteria
What is the mechanism of action of proton pump inhibitors?
Selective and irreversible bind to the parietal cells in gastric mucosa causing suppression of gastric acid secretion through inhibition of H+ / K+ ATPase enzyme system at the surface of the parietal cells
What is the dose of Prilosec?
Dose: 20-40mg PO
How is Prilosec metabolized and excreted?
Metabolized by the liver after undergoing extensive first pass effect and excreted in the urine and feces
When should PPIs be given prior to surgery?
The night before and morning of surgery
When should PPIs be given prior to surgery?
The night before and morning of surgery
What kind of drug interactions do PPIs have?
CYP2C19 inducers (St. Johns wart, rifampin), antiretrovirals, clopidogrel (decrease in antiplatelet effects), reduced clearance of diazepam and warfarin
What is the mechanism of action of histamine-2 receptor antagonists?
Selective inhibition of histamine at H2 receptors of the gastric parietal cells resulting in reduced gastric acid secretion, gastric volume and hydrogen ion concentration
How are H2 antagonists metabolized and excreted?
Metabolized in the liver and excreted in the urine
What is the appropriate use of H2 antagonists in an allergic response?
Aids in histamine induced allergic response, but cannot be used for premedication (does NOT prevent histamine release from occurring)
What H2 antagonist has lost favor in its use?
Tagamet due to multiple side effects that accompany its use
How does Tagamet alter other drugs pharmacokinetics?
Alters absorption of some drugs by increasing gastric fluid pH such as lidocaine, propranolol, diazepam, theophylline, phenobarbital, warfarin, phenytoin
How does Tagamet affect the male population?
Can cause gynecomastia and impotence
Why are symptoms such as lethargy, hallucinations, and seizures seen with Tagamet use?
It crosses the BBB in high doses, especially in the elderly
Why are symptoms such as lethargy, hallucinations, and seizures seen with Tagamet use?
It crosses the BBB in high doses, especially in the elderly
What is the mechanism of action of antacids?
Neutralize acidty of gastric contents by providing a base (hydroxide, carbonate, bicarb, citrate) that reacts with H+ ions to form water
What type of antacids are used preoperatively?
Only non-particulate used pre-operatively
Why aren’t particulate antacids used preoperatively?
Aspiration of particulate antacids produces abnormalities in lung function which can result in pulmonary edema, arterial hypoxemia, ARDS
What are two non-particulate antacids that can be used preoperatively?
Bicitra
Polycitra
How can non-particulate antacids affect other drugs?
Alter gastric and urinary pH: slow absorption of digoxin, cimetidine, ranitidine, speed absorption of phenobarbital
Immediate onset
When should non-particulate antacids be given preoperatively?
Should give 15-30 minutes prior to induction (Duration of effectiveness: 30-60 minutes)
What is the dose of bicitra and what electrolyte does it contain?
15-30 mL PO
Each mL contains 1meq of Na and equals 1meq HCO3
What is the dose of polycitra and what electrolyte does it contain?
15-30 mL PO
Each mL contains 1meq of Na, 1meq K, and equals 1meq HCO3
Long term use of antacids can have what kind of effects?
Alterations in acid base status Infections Acid rebound Milk-Alkali Syndrome Phosphorus depletion Drug interactions
Long term use of antacids can have what kind of effects?
Alterations in acid base status Infections Acid rebound Milk-Alkali Syndrome Phosphorus depletion Drug interactions
What is milk-alkali syndrome?
Milk-alkali syndrome is caused by the ingestion of large amounts of calcium and absorbable alkali, with resulting hypercalcemia. If unrecognized and untreated, milk-alkali syndrome can lead to metastatic calcification and renal failure.
