Fosamprenavir + Famotidine = Precautionary

Effect on Concentration

Fosamprenavir
Decrease
Applies within class?
No
Famotidine
No change
Applies within class?
No

Pharmacologic Effects

Fosamprenavir
Effect
N/A
Applies within class?
No
Famotidine
Effect
N/A
Applies within class?
No

Interaction History

N/A

Last Updated 25-Jun-2018

Summary

This does not take into account ritonavir boosting, which is expected to attenuate the effect

Sources

). Effect of antacids and ranitidine on the single-dose pharmacokinetics of fosamprenavir. ^

Study Design

Twenty-six healthy subjects were given a single dose of Fosamprenavir 1400mg alone, with 40mL of Maalox, or 1 hour after 300mg ranitidine in a randomized, three way cross over study.

Study Results

When given with Maalox, AUC0-24hr and Cmax decreased an average 18 and 35%, respectively while Cmin increased 14%. When given with ranitidine, AUC0-24hr and Cmax decreased 30 and 51%, respectively with no change in Cmin [43]. Concomitant use of H2 receptor antagonists (cimetadine, famotidine, nizatidine, and ranitidine) and fosamprenavir decreases concentrations of fosamprenavir; use with caution and administer fosamprenavir at least 2 hours before an H2 antagonist as a 30% decrease in amprenavir AUC has been noted (consider boosting fosamprenavir).

Study Conclusions

FPV may be coadministered with antacids without concern and without separation in dosing; however, caution is recommended when FPV is coadministered with histamine2- receptor antagonists or proton pump inhibitors. This data does not consider the effect of ritonavir boosting, which is expected to reduce the clinical significance of this effect.

References

Ford SL, Wire MB, Lou Y, Baker KL, Stein DS. Effect of antacids and ranitidine on the single-dose pharmacokinetics of fosamprenavir. Journal Of Antimicrobial Agents And Chemotherapy . 2005; 1: 467-469.