PreOp Meds: H2 Antagonist - Cimetidine, Ranitidine, and Famotidine Flashcards
1
Q
Which H2 antagonist strong inhibits CYP450’s?
A
- Cimetidine
2
Q
What can occur with rapid infusion of cimetidine?
How can this be avoided?
What other adverse effects does cimetidine have?
A
- Bradycardia & hypotension (from cardiac H2 receptors)
- Give over 30 min
- ↑ prolactin & impotence
3
Q
What is the dose for cimetidine?
What is the renal dose?
A
- 150 - 300 mg IV
- 150 mg IV
4
Q
Describe cimetidine, ranitidine, and famotidine’s interactions with CYP450 enzymes.
A
- Cimetidine: strong CYP450 inhibition
- Ranitidine: weak/no CYP450 inhibition
- Famotidine: no CYP450 inhibition
5
Q
What is normal ranitidine dosing?
What is the renal dosing?
A
- 50 mg diluted in 20cc’s over 2 minutes
- 25 mg diluted in 20cc’s over 2 minutes
6
Q
Which H2 antagonist is most potent and has the longest E ½ time? What is this E ½ time?
A
- Famotidine: E½ = 2.5 - 4 hours
7
Q
What adverse effect can occur with famotidine?
A
- Hypophosphatemia (look for fractures)
8
Q
What is the dose of famotidine?
What is the renal dose?
A
- 20mg IV
- 10mg IV
