Grapefruit recipe substitute to avoid medicine interaction? A good friend just underwent a kidney transplant and the anti-rejection drugs are known to interact with grapefruit, so while he is of course incredibly grateful for his new kidney, he is a little sad that he will literally never have grapefruit again.

I know this is a weird one but I'm curious if anyone knows of good flavor extracts that contain absolutely no grapefruit but provide a credible grapefruit flavor so I can make him something grapefruity, yet medication-safe.
Two ideas come to mind: 


Artificial grapefruit flavor. Clearly not the most desirable ingredient, but they make it and you can buy it online if you look for it. 
Hoppy beer (IPAs) for aroma. Certain hop varieties have a strong grapefruit aroma. You can seek out West Coast-style IPAs for this (Lagunitas IPA or Lil' Sumpin and Ballast Point Sculpin are some that come to mind). Or homebrew your own beer with hops like Cascade, Amarillo, Centennial, Citra, and there are several others. You can google for grapefruit hops.


Otherwise, you might try meyer lemon. It's sweeter than a lemon, but still has some sourness, though not the same as grapefruit.