Antacid pharm, H. Pylori eradication: Howden Flashcards
What type of antacids cause constipation?
Aluminum and Ca containing
What type of antacids cause diarrhea?
Magnesium
What is an AE associated with long term use of the absorbable antacid sodium bicarbonate?
Na and water retention and altered acid-base balance
The histamine H2 receptor antagonists (H2RAs) act as competitive antagonists on what cells?
Parietal cells
Briefly describe how histamine stimulates gastric acid secretion.
Hist. binds to H2R on parietal cell—> ^ cAMP—> ^ H+/K+ATPase activity—> ^ acid secretion
List the 4 H2RAs
Which one is also an antacid?
Cime(tidine)
Rani(tidine)
Famo(tidine) - an H2RA + antacid
Niza(tidine)
The H2RAs have their greatest effect…
At night, when parietal cells are not being stimulated more than baseline by anything (food in stomach, yummy thoughts, etc)
Are H2RAs subject to tolerance?
How so?
Yes. Using H2RAs for more than a few days leads to upregulation of the H2 receptors on parietal cells
Are H2RAs really useful for tx of PUD or GERD
Not compared to PPIs (first line tx)
Okay for very mild, infrequent GERD
Better for Asian glow -_-
What is the only known drug interaction of H2RAs?
Cimetidine binds to CYP450 and slows met. of other drugs
The PPIs all end in:
-prazole
How do PPIs make it to the intestine without being degraded by gastric jooce?
Enteric coating
How are PPIs eliminated?
Should we cut the dose back for renal impairment?
What about hepatic impairment?
Hepatic/fecal
No, since the kidneys are not involved in elimination.
No evidence to cut back dose in hepatic impairment.
Nevertheless, you should give minimum effective doses, as with ALL drugs.
MOA of PPIs
Bind to and permanently disable H+/K+ATPase.
Acid will not be secreted until new pumps placed in membrane.
What are some AEs associated with PPIs?
Headache, diarrhea, skin rash, abdominal pain.
Incr. potential for infection due to reduced stomach pH.
Decr. Fe absorption.
