gi drug notes

8/8/2019 GI Drug Notes

1/7

y Drugs used to treat GERD PPIs & H2 rec antagonistsy PUD erosion of lower stomach/duodenum from H. pyloriy Risk factors for PUD H. pylori, NSAIDs, acid, pepsin, smokingy These protect against PUD mucus, bicarbonate, blood flow, prostaglandinsy Antibiotics used to treat PUD amoxicillin, Biaxin, tetracycline, Flagyly Other drugs working to treat or defend against PUD bismuth salicylate (pepto), misoprostol, sucralfate, PPIs, H2 rec antagonists,

antacids, muscarinic antag (pirenzepine)

y Tx of H. pylori usually 2-3 antibiotics w/ PPI or H2 rec antag for 10-14 days

Cimetidine

(Tagamet)

Classification H2 receptor antagonist. Others: Ranitidine (Zantac), famotidine (Pepcid), nizatidineMOA (brief) Competitive blocker of histamine H2 rec sites of parietal cells. Diminish effects of gastrin & Ach. Inhibit gastric acid

secretion.

Dosage/Route PO, IV; PO-onset 30 min, peak 1 hr, duration 4-5 hr

Adverse Effects Diarrhea, constipation, gynecomastia, impotence, dec libido, dec sperm count. CNS hepatic/renal problems,

confusion, hallucinations, lethargy

Drug Interactions Meperidine, Phenytoin (dilantin), diazepam, theophylline, warfarin, ETOH, digoxin, ketoconazole, antacids

When is it used? PUD, GERD,

Metabolic Effects Hepatic 1st

pass effect; metabolized by cytochrome p450 will inc the life of theophyllineNursing

considerations

Best if taken with food to slow absorption & prolong effects. H2 rec antag can be taken to prevent GERD from

certain irritating foods.


2/7

y Pirenzepine an anticholinergic drug used to treat PUD. Produces selective blockade of muscarinic receptors that regulate gastric acidsecretion. Inhibits gastric acid secretion without pronounced anticholinergic side effects. Most common SE: dry mouth.

Omeprazole(Prilosec)

TherapeuticClassification

Proton pump inhibitor. Others: Esomeprazole (Nexium), Lansoprazole (Prevacid), Pantoprazole, Rabeprazole,Dexlansoprozole,

MOA Block final step of acid production; nonreversible inhibition of H+/K+ ATPase

Adverse Effects Diarrhea, abdominal pain, n/v, constipation, headache, dizziness, back pain, muscle pain; rare: anemia,

thrombocytopenia, eosinopenia, leukocytosis

Drug Interactions Drugs dependent on gastric pH (iron salts, ampicillin); diazepam, phenytoin, warfarin

When is it used? Hypersecretory disorders, duodenal ulcer, erosive esophagitis (GERD)

Metabolic Effects Rapid absorption in intestine

Nursingconsiderations

Take 30 minutes before morning meal. Taken as maintenance (every day)

Misoprostol

Therapeutic

Classification

Antisecretory Drug that enhances mucosal defenses. (analog of prostaglandin E1)

MOA (brief) Serves as a replacement for endogenous prostaglandins. (NSAIDs cause ulcers by inhibiting pg biosynthesis).

Promotes secretion of bicarbonate and mucus, and maintains submucosal blood flow.

Adverse Effects Diarrhea *, constipation, abdominal pain, n/v, dyspepsia, flatulence, HA. Toxicity: sedation, tremor, convulsions,

dyspnea, fever, palpitations, hypotension, bradycardia

Contraindications Pregnancy category X

Drug Interactions antacids

When is it used? Prevention of gastric ulcers caused by long-term therapy with NSAIDs

Nursingconsiderations

Obtain serum pregnancy test first. Begin on 2nd or 3rd day of period. Give verbal & written instructions of dangers.Comply with birth control measures.


3/7

Antacids MOA Adverse Effects OtherNeutralize stomach acid Caution in pts w/ HTN (antacids

w/ high Na+ content)

Aluminum Hydroxide Has low ANC (anti-neutralizing

capacity

Constipation; dec PO4 absorption. Has high Na+ content

Magnesium Hydroxide

Liquid-milk of magnesia

Has high ANC. Rapid acting w/

long DOA.

Diarrhea Do not give to pts w/ renal

impairment.

Calcium Carbonate High ANC. Rapid acting. Long DOA Rebound acid, belching, flatus,

constipation

Sodium Bicarbonate Elevates urinary pH & excretes

acidic drugs. Rapid acting. Short

DOA.

Belching, flatus. Not good for tx of

ulcers, but good for acidosis.

Do not give to pts w/ HTN.

Sucralfate

Classification Antiulcer Medication Pepto Bismol on steroids

MOA (brief) Paste-like material adheres to ulcer crater creating a barrier to back-diffusion of pepsin and bile salts.

Dosage/Route PO suspension; lasts 6 hours; 4-8 week therapy time

Adverse Effects Constipation, (no severe AE)

Contraindications Chronic renal failure, dialysis pts

Drug Interactions By raising gastric pH above 4, antacids may interfere with sucralfates effects. Administer these at least 30 minapart. Impedes absorption of phenytoin, theophylline, digoxin, warfarin, fluoroquinolones. Cimetidine, Ranitidine,

tetracycline.

When is it used? To treat existing duodenal & gastric ulcers.

Nursing

considerations

Administer 1 hr before meals and at bedtime. Increase fluids and fiber.


4/7

Drugs that cause constipation: analgesics, antacids (Al), anticholinergics*, antidepressants, antidiarrheals, antihistamines*,antihypertensives (some), antiparkinsonian drugs, barium sulfate, diuretics, iron supplements*, muscle relaxants (some)

Anti-constipation drugs MOA Adverse Effects & uses Dose/Response Time

Bulk Forming Laxatives

Methylcellulose, psyllium,

Polycarbophil

Softens stool by pulling more H20

into sm intest & colon, inc fecal

mass & promotes peristalsis.

Fiber!

Take w/ full glass of water. Soft,

formed stool 1-3 days after tx.

Surfactant LaxativesDocusate sodium, calcium

Water penetrates sm intest &colon.

Can take for a while. Producessoft stool 24-72h after tx. Take

with full glass of water.

Stimulant Laxatives

Bisacodyl, senna,

castor oil (quick 2-6h)

Stimulates peristalsis; softens

stool secreting h20 & electrolytes

into intestines

High abuse factor. 2 uses: opioid

induced constip & tx of slow

intest transit.

PO semifluid stool in 6-12h.

supp stool in 15-60 min. not for

long-term use.

Osmotic LaxativesMg, sodium phosphate

Polyethylene glycol (miralax)

Osmosis in sm intest & colon;softening feces & promoting fecal

swelling & peristalsis

Uses: surgery, purge ingestedpoison, evacuate dead parasites

PG prior to colonoscopy

Mg & Na - Low dose 6-12 h;Mg & Na -high dose 2-6 h.

PG-4L, 250ml q 10 min for 2-3 hr

Misc. Laxatives

Mineral oil Lubricates & dec h20 absorb (col) Lipid pneumonia (orally) enema for impaction (5-30 min)

Glycerin suppositories Lubric & causes reflex rectal

contraction (colon)

Used to re-establish normal bowel

fcn after termination of lax abuse.

Evacuation in 30 min.

Lactulose

PEG soln

Similar to osmotic laxatives L: Used in liver dz(ETOH/cirrhosis)

to lower blood ammonia; SE:

cramps, flatus

L: Only use if not responding to

bulk forming lax. Soft stool 1-3

days after tx.

Lubiprostone Opens chloride channels in

intestinal epithelium

Not absorbed no SE Used for idiopathic constipation

and IBS in women over 18.


5/7

Color key from previous table: Red immediate response (5-30 min); Green quick response (2-6hr);Orange semi-quick response (6-12 hr);

Pink delayed response (1-3 days)

Drugs that cause diarrhea: Mg, antihypertensives, antimicrobials*, antineoplastics, bile acids, cardiac glycoside, cholinergics, cholinesterase

inhibitors*, osmotic & stimulant laxatives*, quinidine

*Opioids are most effective anti-diarrheal agents.

Diphenoxylate -

Opioid Antidiarrheal schedule C5 controlled substance. Atropine is given to prevent abuse. Given after loose watery stool for

acute diarrhea. AE CNS depression, euphoria, confusion, sedation, restlessness. Contraindications acute bowel infections, glaucoma, BPH. DI:

alcohol, barbs, tranquilizers, MAOIs.

Loperamide (Imodium) Opioid antagonist OTC -


6/7

Antiemetics MOA

5HT3 rec antagonists Chemo, radi, post-op, pregnancyOndansetron, etc.

Substance P/neurokinin1 antag

aprepitant, fosaprepitant

Block rec in the brain Prevents acute & delayed emesis Chemo. With or without food.

Cannabinoids Unknown. CIII D: THC in pill form (refrigerate) Chemo, sickle cell anemia.

Dronabinol, nabilone Does not produce same high. Caution pts w/ CV dz. AE:

tachycardia, hypotension

Dopamine Antagonists Blocks rec in CTZ Extrapyramidal effects; Chemo, post-op, general.

Phenothiazines: -azines Anticholinergic effects. Can cause Parkinson-like shakes

Butyrophenones: Haloperidol

Other: Metoclopramide,

Domperidone

M: causes long-term nerve

damage

Promethazine: dry mouth, drowsy

Anticholinergics:Antihistamines: - ines

Other: scopolamine

A: block h1 rec

S: Transderm patches S -Use: motion sickness


7/7

Ondansetron

Classification Antiemetic most effective drug to combat n/v

Drug Names Zofran

MOA Blocks 5HT3 rec

Pharmacology

Dosage/Route IV, PO

Therapeutic Range

Adverse Effects Constipation, HA, rash. Rare: bronchospasm, tachycardia, chest pain, hypokalemia, ECG changes, tonic clonic seizure

Contraindications Impaired renal/hepatic fcn; caution in pregnancy, lactation.

Precaution pts:

Drug Interactions More effective with dexamethasone (IV for emesis)

When is it used? Emesis: chemo, perioperative; pregnancy

Metabolic Effects P450 drug metabolizing enzymes

Lab considerations Transient elevations in AST, ALT.

Nursing

considerations

Prevents acute emesis, but not delayed emesis. Monitor bowel fcn & liver enzymes.

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