GI Flashcards
H2 Antagonists: Mechanism of Action
Block histamine receptor on parietal cells. Usually histamine activates the proton pump. There are alternate mechanisms so they are not as completely suppressive as PPIs
H2 Antagonists: Indications
PUD, GORD, Dyspepsia
H2 Antagonists: Side effects
Generally well tolerated, diarrhoea, constipation, headaches
H2 Antagonists: Interactions and Warnings
No major interactions
Really excreted, so reduce dose in renal impairment
Can mask signs of gastric cancer
H2 Antagonists: Prescribing
Short term use = OTC
No monitoring
Therapy is guided by symptoms
They have generally been superseded by PPIs, but they do have a faster onset
PPI: Mechanism of Action
Irreversibly inhibit H+/K+ATPase in parietal cells so reduced acid production
PPI: Indications
First line therapy for PUD, GORD, dyspepsia
H.Pylori eradication, as part of triple therapy
PPI: Side Effects
GI Disturbance, headaches, some evidence of increases C.diff risk
PPI: Interactions and Warnings
Omeprazole can decrease the efficacy of clopidogrel. Other PPIs have less of an effect.
They can mask the symptoms of GI cancer
Can increase the risk of osteoporosis
PPI: Prescribing
Oral or injectable available
Mesalazine: Mechanism of Action
It is an aminosalycilate drug. It acts be releasing 5-ASA. Its precise mechanism is unknown, but it acts locally on the gut and has anti-inflammatory and immunosuppressive effects.
Mesalazine: Indications
Mild to moderate UC (First line drug)
Mesalazine: Side Effects
Nausea, dyspepsia, headache
Rare but serious: renal impairment, leukopenia, thrombocytopenia
Mesalazine: Interactions and Warnings
Tablets with a pH sensitive coating may be affected by changes in gastric pH
ASPIRIN ALLERGY!
Mesalazine: Prescribing
Oral or suppository
Renal function should be checked for safety
Efficacy is guided by symptoms
Loperamide: Mechanism of Action
It is an opioid and is chemically similar to pethidine. However, it does not penetrate the CNS so has no analgesic properties. It agonises GI mu-opoid receptors. It slows peristaltic contractions and increases anal tone. The increased transit time means more water can be reabsorbed.
Loperamide: Indications
Diarrhoea, usually viral gastroenteritis or IBD
Loperamide: Side Effects
Predictable: constipation, cramping, flatulance
Loperamide: Interactions and Warnings
Should be avoided in acute ulcerative colitis (inc. risk of toxic megacolon and perforation). Should be avoided in C.Diff and with bloody diarrhoea (could be ETEC) because of the risk of HUS.
It has no clinically significant interactions.
Loperamide: Prescribing
Can be purchased OTC (probably will be cheaper for patient)
Monitored by symptomatic relief
Makes sure to mention it does not treat underlying cause.
