GI PHARM Flashcards
MOA of Serotonin receptor antagonists
Prevent nausea and vomitting by blocking serotonin receptors at two sites
- chemoreceptor trigger zone
- afferent vagal nerves
Example Sertoninin receptor antagonists
OndanSETRON
ganiSETRON
dolaSETRON
palonoSETRON
Indication for serotonin receptor antagonists
Nausea and vomiting
- post operative
- chemotherapy induced
- pregnancy
- gastritis
Contraindications
Serotonin receptor antagonists
Prolonged QT interval
Cardiac abnormalities:
Bradydysrhythmias
heart failure
MOA
Antihistamines H1 receptor antagonists
Block H1 receptor in the vomiting centre
Prevent signal from inner ear to vomiting centre
Prevention of N/V/motion sickness
SE
H1 receptor antagonists
Muscarinic blockade: dry mouth, constipation, urinary retention, glaucoma, blurred vision, sedation, delirium/paradoxical reaction
H1 receptor blockade: hypertension
Contraindications
H1 receptor antagonists
Third trimester pregnancy - neonatal sedation
breast feeding - neonatal sedation
Conditions made worse by muscarinic blockade: asthma, BPH, constipation, elderly, children
Infants < 6 months
Examples of H1 receptor antagonists
Dimenhydramine (benadryll)
Dimenhydrinate (gravel)
Meclizine
Cyclizine
MOA
Glucocorticoids (for N/V)
unknown mechanism of action
synergistic for N/V if given with other anti-emetics
SE
Glucocorticoids
Bones: osteoporosis, growth suppression, fractures
Skin: infections, striation, poor wound healing
GI: ulcers, perforations, hemorrhages
Cushingoid appearance: central fat, degradation muscles, moon face, hump back; adrenal suppression
Electrolytes: hyperglycaemia, hypernatremia, hypokalemia, FVO, weight gain
Eyes: glaucoma, cataracts
CSN: mania, depression
Contraindications
Glucocorticoids
pregnancy / breastfeeding - teratogenic
Caution: children and elderly, growth suppression, fractures, adrenal insufficiency
Example
Antacids
magnesium hydroxide
aluminum hydroxide
calcium carbonate
sodium bicarbonate
MOA
Ant-acids
- neutralize HCl –> rise in pH
- prevent activation pepsinogen to pepsin
- activation prostaglandin –> increase mucous, bicarb, blood flow mucosa barrier
SE
antacids
calcium carbonate - constipation, acid rebound
magnesium hydroxide - magnesium toxicity, diarrhea
sodium bicarbonate - metabolic alkalosis, hypernatremia
Contraindications
ant-acids
sodium bicarbonate
- metabolic alkalosis, hypernatremia, heart failure or kidney disease
Increase clearance of acidic drugs in urine
prevent absorption of drugs - give 1 hour apart
Magnesium hydroxide
Kidney failure or disease
MOA
H2 receptor antagonists
Prevents gastric acid secretion
Blocks H2 receptors on parietal cells. Prevents cAMP signal which H/K ATPase excretes H+ into gastric lumen (blocked)
increase pH stomach
SE
H2 receptor antagonists
CNS: depression, hallucinations, agitation
pneumonia: increase bacterial colonization stomach, secondary respiratory infections (aspiration)
Contraindications
H2 receptor antagonists
Caution: pregnancy, breast feeding (sedation)
Caution: kidney and hepatic impairment (dose adjustment)
Drug interactions: CYP450 inhibitor (increase warfarin, phenytoin) ; antacids prevent H2 receptor antagonist absorption
Examples
H2 receptor antagonists
raniTIDINE
cimeTIDINE
famoTIDINE
nizaTIDINE
Indication
H2 receptor antagonists
- Treatment PUD
- Ulcer healing
Duration 8-12 weeks gastric
Duration 4-6 weeks duodenal - GERD
MOA
proton pump inhibitors
Prevent secretion and synthesis of HCl
Block H/K ATPase in the parietal cells. Irreversible inhibition. Lasts lifetime of cell (3-5 days)
Indications
PPIs
- Prophylaxis and treatment of PUD
- GERD
- erosive esophagitis
- Zollinger-Ellison syndrome
SE
PPIs
Hypomagnesium - cramps, dysrhythmias, tremors
Hypocalcemia - fractures (convulsions, reflex hyperactive, anorexia, muscle spasms/tetany, positive trauseau, chvostek, parenthesia)
Pneumonia
C. Diff diarrhea
Acid rebound - wean, do not D/C abruptly, PRN H2 receptor antagonist
Contraindications
PPI
pneumonia
osteoporosis
hypomagnesemia, hypocalcemia
C. diff diarrhea
DRUG INTERACTIONS
clopidogrel - decrease conversion to active form (PRN PPI for gastric protection)
Example PPIs
OmePRAZOLE
lansoPRAZOLE
Patient education PPI
Don’t D/C abruptly - hyperacid secretion
Report - diarrhea (c. diff)
Report - dry cough, fatigue, fever (pneumonia)
Report - leg cramps, palpitations, tremors (hypo magnesium)
Take PRN vitamin D and calcium
MOA metoclopromide
- block HT and DA receptors in CTZ = prevention N/V
- Increase Ach in GI = increase GI motility “Pro-kinetic agent”
Indications
Metoclopromide
GERD
Diabetic gastroparesis
N/V chemotherapy, 1st trimester pregnancy
hiccups
SE
Metoclopromide
Diarrhea
Tardive dyskinesia (DA blockade): involuntary movement legs, arms, face
Contraindications Metoclopromide
GI obstruction, perforation, hemorrhage
2nd and 3rd trimester of pregnancy
Start low, go slow (Tardive dyskinesia), shortest duration
MOA
Sucrafalate
Forms a protective gel that coats an ulcer crater at low pH
aluminum hydroxide + sulphated sucrose + low pH = protective gel
SE and contraindications
Sucrafalate
prevention drug absorption
administer 2 hours apart
No systemic SE
No contraindications
Indicaiton
Sucrafalate
PUD
gastric or duodenal ulcers
Protective coating for the ulcers
MOA
Misoprostol
Prostaglandin E1 analog
Binds Prostaglandin E1 receptor on parietal cells
1. prevents cAMP signal which prevents H+ secretion into lumen (H/K ATPase)
2. promotes mucous , bicarbonate secretion, and blood flow
Indications
Misoprostol
- PUD secondary to NSAID therapy
- Induce labour / abortions
SE
Misoprostol
abdominal pain, diarrhea
dysmenorrhea, spotting
induction labour, abortions
Contraindication
Misoprostol
Pregnancy
Written and oral dangers
birth control
HCG negative
start on 2nd day of period
MOA
Clarithromycin
Macrolide antibiotic
Prevent protein synthesis by blocking Ribosome 50S inhibitor
Bacteriostatic
Active against
Gram positive
Some gram negative
Atypicals
Indication
Clarithromycin
H. pylori infections PUD
Triples:
Clarithromycin + amoxicillin/metronidazole + PPI
SE
Clarithromycin
GI: N/V/D, metallic taste
Cardio: Sudden cardiac death, prolonged QT interval
Ottotoxic
Contraindications
Clarithromycin
Drugs that prolong QT interval
Long QT syndrome, ventricular dysrhythmias
CYP3A4 inhibitors (5x cardiac sudden death)
Azole anti fungals
CCB (verapamil, diltiazem)
HIV medications
MOA
Metronidazole
Kills anaerobic bacteria
Anaerobic bacteria convert to active form; causes DNA breaks, prevents nucleic acid synthesis, results in cell death
SE
Metronidazole
N/V/HA
Contraindications
Metronidazole
Alcohol
Disulfram reaction
Wait 3 days before drinking
Indication
Metronidazole
H. pylori infection
Quadruple therapy (Metronidazole + bismuth + tetracycline + PPI)
Triple therapy (Metronidazole + clarithromycin + PPI)
MOA
Bismuth Subsalicylate
- Bacterial cell wall lysis
- inhibits H. pylori urease - preventing adhesion to gastric epithelial cells
SE
Bismuth subsalicylate
Black colour on tongue and in stool (false positive melena stool)
Constipation
Bleeds, acidosis
AE
Bismuth Subsalicylate
Neurotoxicity (high dosage, long term use): tinnitus, loss of hearing
Melena stools (GI bleeds): salicylate
Reye’s syndrome and acidosis
Decreased kidney perfusion, hypertension
Contraindications
Bismuth Subsalicylate
Salicylate: pregnancy, breast feeding, children (Reyes syndrome), acidosis
MOA
Tetracycline
bacteriocidal
Blocks 30S Ribosome preventing protein synthesis
Broad spectrum antibiotic
gram postive, gram negative, MRSA
SE
Tetracycline
Deposition in teeth and long bones
Yellow teeth
Hypoenamel
Fractures
Diarrhea - C. Diff
Phototoxicity
Teratogenic
AE
Tetracycline
C. diff infections
hepatotoxicity (post partum)
phototoxicity
Teratogenic
Contraindications
Tetracycline
pregnancy
post partum (caution)
children < 8 years
liver and kidney disease
Indication
Tetracycline
H. pylori infections
Quadruple therapy
Tetracycline + bismuth subsalicylate + metronidazole + PPI
Can also use for CAP
Monotherapy, dual therapy
Indication
Bismuth Subsalicylate
H. pylori infection
Quadruple therapy
Bismuth subsalicylate + tetracycline + metronidazole + PPI
Travellers diarrhea first line with imodium
MOA
Amoxicillin
- prevent cell wall peptidoglycan cross linking
- promote increase autolysin activity - cell wall degredation
Destruction bacterial cell wall resulting in cell lysis
gram positive, some gram negative infections
SE
Amoxicillin
GI: N/V/D
allergic reactions IgE mediated 7% people (1% cross reactivity with 1st generation cephalosporins)
Neuropsych SE when toxicity (renal impairment)
Contraindications
Amoxicillin
renal impairment
hypersensitivity reactions
MOA
Fluroquinolones
Block DNA gyrase (prevent supercoiling DNA)
Block DNA topoisomerase (prevent separation daughter strands)
Broad spectrum
anaerobic, gram positive, gram negative, pseudomonas
SE
Fluroquinolones
Cardiac: prolonged QT interval
GI: N/V/D/C. diff
MSK: tendon ruptures
SKIN: phototoxicity
Teratogenic
Contraindications
Fluroquinolones
Pregnancy - teratogenic
Children < 18 years
Long QT intervals
Myasthenia Gravis
Caution:
Adults > 60 years
transplants
glucocorticoids
Indication
Levofloxacin
H. Pylori infection
Triples
Amoxicillin + levofloxacin + PPI
Back up for CAP resistant