Gastrointestinal Drugs I Flashcards
Basic pathophysiology leading to ulcers?
- Increased acid
- Decreased mucosal resistance
Three receptors on the parietal cell? Overall effect?
- Histamine
- Gastrin
- ACh
Stimulate K+/H+ ATPase activity
By what mechanism does Histamine work to increase stomach acidity?
Histamine hits receptor that causes an increase in cAMP and K+/H+ action
Describe the mechanism of action of gastrin to increase acidity of stomach. ACh?
Both hit their respective receptors and cause an influx of Ca2+ activating K+/H+ ATPase
Where do Gastrin and ACh come from, respectively?
- Gastrin - antrum
- ACh - Vagal inputs
What are the goals of pharmacologic intervention for ulcer Tx?
- Relieft of Syx, especially pain
- Promotion of healing
- Prevention of complications such as perforation, hemorrhage, or scar formation
- Prevention of recurrence
Tx plan for ulcer?
- Neutralize acid
- Decrease acid production
- Increase mucosal resistance
Antacid neutralizing efficacy based on:
- The neutralizing power of the antacid
- The degree or rate of acid secretion
- Rate of stomach emptying
What are the active ingredients of antacid preparations?
- CaCO3
- NaHCO3
- Mg(OH)2 and MgCO3
- Al(OH)2
Mjr SE of CaCO3
Milk-alkali syndrome, nephrocalcinosis, rebound acidity, digitalis antagonism
SE of NaHCO3
Systemic alkalosis and therefore rarely used
SE of Mg(OH)2?
Diarrhea, Hypokalemia, Hypermagnesemia, complexing of enteric iron and therefore iron deficiency
Why is Al(OH)2 less likely to cause electrolyte imbalances?
Al precipitates with enteric phosphate and is not absorbed in the gut
Adverse effects of Al(OH)2?
Constipation, Phosphate depletion and sequelae
What would an equivalent procedure be to using an Anticholinergic agent?
Vagotomy
What are the SE of anticholinergic agents?
- Dryness of mouth
- Blurred vision
- Atony of the bladder
- Constipation
- Drowsiness
- Mental Confusion
What are the anticholinergic drugs?
Atropine, Prpantheline, Metantheline bromide
What are the two big guns of the H2 blocker family? The lesser kids?
- Cimetidine and ranitidine
- Famotidine
- Nizatidine
What is an important consideration when prescribing an H2 blocker?
Cimetidine and ranitidine bind to CP450 interfering with the metabolism of drugs such as theophylline, warfarin, dilantin, or lidocaine
What are the H+/K+ ATPase inhibitors?
- Omeprazole
- Lansoprazole
- Rabeprazole
- Esomeprazole
- Pantoprazole
- Dexlansoprazole
Which H+/K+ ATPase inhibitor has the best bioavailability?
Lansoprazole
Which H+/K+ ATPase inhbitor has the greatest P450 inhbition? Moderate? Least?
- Most - Omeprazole
- Moderate - Rabeprazole
- Least - Pantoprazole
Which H+/K+ ATPase inhibitor has the greatest bioavailability and least P450 inhibition?
Pantoprazole
What are the advantages of H+K+ ATPase inhibitors over the H2 inhibitors?
- Better pain relief
- Faster healing of ulcer
- Heal H2 antagonist refractory ulcers
SE of HKAIs?
- Gynecomastia
- P450 inhibition and delayed metabolism of diazepam, warfarin, dilantin
- Gastric hyperplasia in humans
Not recommended for long term Tx
What are two exogenous agents that can cause ulcers?
- NSAIDS
- H. Pylori
MOA of Bismuth Salts?
In acidic environment, salts precipitate and coat ulcer
MOA of sucralfate?
Al(OH)2 complex of sucrose activated in acidic environment and binds to ulcer
Which ulcer-coating agent is most efficacious?
Bismuth salts
In a patient taking chronic NSAIDs, what would be a good medication to prescribe to prevent ulcers?
Presribe misoprostol to compensate for prostaglandin defciency due to NSAIDs.
What is the adverse effects of misoprostol?
Transient diarrhea, can’t be used in pregnancy
Tx for H. pylori infection?
Bismuth salts, Metrinidazole+ tetracycline/amoxicillin
Preferred Tx for H. pylori infection?
- Twice a day PPI (proton pump inhibitor)
- OR
- Ranitidine bismuth citrate twice a day
- PLUS
- Two of these guys: Amoxicillin, clarithromycin, metronidazole
In what scenario is an advantage in ranitidine bismuth triple Tx observed for H. pylori infection over PPI?
When resistant H. pylori present
What is quadruple Tx for H pylori?
- PPI
- Tetracycline
- Bismuth subsalicylate or subcitrate
- Metronidazole
