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GERD - Coggle Diagram
GERD
H2RAs (famotidine)
Duration
6-12 weeks
3 P
PGX
Pharmacogenomic studies are not widely undertaken with H2RAs, partially due to minimal first pass metabolism.
PD
TOXICITY: These medications have a large therapeutic window and no more than minimal toxicity is expected even with very large overdoses
PK
Absorption: 40-45% Bioavailability Distribution: 1.3 L/kg minimal protein binding Metabolism: Minimal first pass Excretion: Renal
MOA
Famotidine, a histamine H(2)-receptor antagonist, primarily inhibits both the concentration and volume of gastric secretion. It inhibits both basal and nocturnal gastric secretion, as well as secretion stimulated by food and pentagastrin.
Adverse Effects
GI: Constipation, Diarrhea Neurologic: Dizziness, Headache
Regimen
40 mg QD: at bedtime 20 mg PO BID: morning and night May give with or without food
Monitoring
Decreased abdominal and/or gastroesophageal discomfort Monitor Renal Function in elderly and those with renal dysfunction
Warnings/Contraindications
Contraindication: hypersensitivity to H2RA, Beer's Criteria: use caution in elderly patients
Interactions
DDIs: cefditoren, dasatinib, delavirdine, fosamprenavir, tizanidine, coumadin, Jantoven
Special Populations
Beer's Criteria: Elderly avoid or use caution, Patients with Renal Dysfunction
Education/Counseling
Tell patient that drug may be taken with antacids, if needed Advise patient to take once daily before bedtime or twice daily in the morning and before bedtime, as directed 30 min before a standardized medium-fat breakfast.
Determinants of Health
Available as generic, so very affordable with coupons; slightly cheaper than PPI. May be more difficult to adhere to if BID dosing is used. Also available as OTC
PPIs (lansoprazole)
3 P
PGX
PPIs are prodrugs that require metabolic activation by CYP2C19. Those with a homozygous extensive metabolizer CYP2C19 genotype will have lower concentrations of active metabolite and lower cure rates for GERD.
PK
F 90%, protein binding 97%, Vd 16 L, t1/2 1.5 h, extensive hepatic metabolism via CYP2C19 and CYP3A4, renal clearance 80% as metabolites
PD
LANSOPRAZOLE: An adult intentionally ingested 600 mg of lansoprazole with no clinical signs or symptoms reported.
MOA
Blocks the final step in acid production by inhibiting the H(+)/K(+)-ATPase (proton pump) in gastric parietal cells, thus decreasing acid secretion
Adverse Effects
Headache, diarrhea, nausea, flatulence, abdominal pain, constipation, somnolence, regurgitation, tachypnea, and dry mouth
Regimen
15mg PO QD
Monitoring
Endoscopy, serum magnesium, calcium, and vit B12
Duration
Up to 8 weeks
Warnings/Contraindications
Contraindications: known hypersensitivity, Precautions: Beer's criteria, severe cutaneous reactions can occur
Interactions
Lots of major drug interactions, including but not limited to mycophenolate mofetil, methotrexate, tacrolimus, octreotide, escitalopram, ketoconazole, amphetamines
Special Populations
Renal impairment: no dose adjustment. Hepatic impairment: only dose adjust for Child Pugh class C (max 20 mg/d). Geriatric: no dose adjustment.
Education/Counseling
Take one hour before meals. Immediately report severe cutaneous reactions, osteoporosis-related fractures, hypomagnesemia, hypocalcemia, or hypokalemia
Report diarrhea that does not improve and consult healthcare professional prior to taking antidiarrheal medicine
Determinants of Health
Available as generic, so very affordable with coupons; slightly more expensive than H2RA. May be easier to adhere to with once daily dosing.