Pharmacology Chapter 28 Drugs Acting on the GI tract

Sialagogue

Antisialagogue

Antiemetic

Promote saliva: Pilocarpine hydrochloride

Decrease saliva: Atropine

Antiemetic: Prevent nausea vomiting

The primary symptoms of PUD are related to mucosal exposure to gastric acid and pepsin usually caused by _______  infection or the breakdown of normal mucosal defenses from the use of _______

H. pylori, NSAIDS

PPI are drugs that irreversibly inhibit H, K+ATPase in the _______ _______ cell

gastric parietal

What is the drug of choice for PUD and GERD

PPI

Ends in prazole like omeprazole

Why does PPI still work after the elimination half-life of 0.5 to 2 hours?

They irreversibly bind to the proton pump

PPI should be taken before/after meal

before

What is the side effect of using PPI

Reduced Ca and Mg absorption

Acid is also needed for vitamin B12 release of food

Could also cause C. diff infection

What drug interaction is of concern with the use of PPI?

What is the alternative PPI

Clopidogrel (antiplatelet blood thinner)

Does not work of CYP2C19 (Pantoprazole)

3 mediator of gastric acid secretion

Histamine (stimulate parietal cell for H2 release)

Acetylcholine (muscarinic receptor)

Gastrin (stimulate histamine release)

Nocturnal acid secretion vs Food induced-gastric acid secretion

Nocturnal: Histamine

Food-induced: Acetylcholine Gastrin

What are the problem with long term cimetidine usage?

What to use otherwise

Antiandrogenic effects

Cause gynecomastia in men and galactorrhea in women

Use ranitidine instead

Cimetidine concern in dentist

Strong CYP450 inhibitor 

Toxicity in metabolism of lidocaine and diazepam (liver drugs)

Other tidine are safer

What is the gram stain of H. pylori

What is the best treatment

Gram-negative

Triple regimen: Lansoprazole (PPI) with 2 antibiotic (clarithromycin and either amoxicillin or metronidazole)

Antacids should not be given within 2 hours of dose of what 2 antibiotics

Tetracycline or Fluoroquinolone

4 common antacids

Sodium bicarbonate (Cause CO2 bloating)

Magnesium hydroxide (No CO2) (Disadvantage: laxative effect and tolerance)

Aluminum hydroxide (No CO2 bloating bt cause constipation)

calcium carbonate (Side effect: CO2 bloating and Hypercalcemia)

Alginic acid is used with what

Antacids 

Binds with sodium bicarbonate to form sodium alginate that have viscous gel that is pH neutral

What is simethicone?

Defoaming agent reduce surface tension of gas bubbles in the GI tract and helps relieve symptoms of bloating and discomfort.

What is Misoprostol?

Prostaglandin E1 analogue

Make alkaline mucus and inhibit gastric acid secretion

Inhibit adenylyl cyclase on parietal cells

How to know if GERD pt can be supine position 

how they sleep

(head higher than feet)

What alternative alternative analgesic for GERD pt

What NSAID can be good

Acetaminophen

celecoxib (COX2 selective)

Corticosteroids and ulcers

Systemic corticosteroid can cause ulcers

Topical for oral lesion should be avoided could worsen ulcer

Diazepam in GI pt

Absorption altered by antacid and interaction with cimetidine

Prefer lorazepam or oxazepam

Contraindicatioon of Atropine

Prostatic hypertrophy or narrow-angle glaucoma

Caution with cardiovascular disease

Atropine

Scopolamine

Propantheline

Glycopyrrolate

Last 2 are synthetic and does not cross BBB

Ipecac

Emetic that cause vomiting for acute poisoning

Not used anymore

Use activated charcoal instead

The brainstem vomiting center is located in the ______ ______ ______

lateral medullary reticular formation

The phenothiazines and butyrophenones are central dopamine _______ and inhibit stimulation of the CTZ.

antagonists

For pregnancy nausea not for motion sickness

Castor Oil and Bisacodyl

Stimulants

Irritant of intestinal mucosa 

What are Ducsate and Mineral oil

Lubricant and Stool softeners

What are cathartics

Usually Mg salt

Poorly absorbed that stimulate bowel movement by pulling water

Psyllium and Methylcelluose

Bulk-forming agent absorb water increase bulk

Methylnaltrexone and Alvimopan

Opioid receptor antagonist that does not cross BBB

Opioid cause constipation

Adsorbent vs Motility reducers

Adsorbent bind things in gut to avoid diarrhea (kaolin, bismuth)

Motility reducer: slow gut (opioids: loperamide, diphenoxylate, difenoxin)

That is the prophylaxis antibiotic for traveler’s diarrhea

Fluoroquinolone (ciprofloxacin)

Azithromycin if resistant

What antidiarrhetic have antibiotic effect

Bismuth but should not take with doxycycline 

Treatment for traveler’s diarrhea

Loperamide and fluoroquinolone