Amlodipine/Norvasc and grapefruit. Frenimies or sworn enemies?

November 18, 2015 2:16 PM

I've seen reports that Amlodipine/Norvasc and grapefruit will basically kill you. I've seen reports that you'll be fine as long as grapefruit isn't your only liquid source. My prescription says "don't take with grapefruit products" (emphasis mine). Which is it? Should I avoid grapefruit for 2h? 12h? Forever?
posted by sodium lights the horizon to Health & Fitness (11 answers total)

I was told to avoid grapefruit completely and became very ill when I inadvertently consumed some whilst taking amlodipine. YMMV. :(
posted by Hermione Granger at 2:18 PM on November 18, 2015

Avoid completely. Grapefruit contains compounds that can block the metabolism of some drugs by the liver, which can lead to overdose and/or toxicity from too much active drug in the body.
posted by quince at 2:26 PM on November 18, 2015 [1 favorite]

Grapefruit is notorious for drug interactions. It's best that you not have any grapefruit products at all.
posted by Johnny Wallflower at 2:29 PM on November 18, 2015 [7 favorites]

And be aware that while grapefruit is the most common culprit, there are a few other citrus fruits that can cause similar interactions. I had some pharmaceutical misadventures from bingeing on blood oranges. I asked the pharmacist about it, and he said that star fruit, kiwi fruit and paw paw (?) may also be troublesome.
posted by Corvid at 2:38 PM on November 18, 2015 [3 favorites]

I took amlodipine daily for at least a year, maybe two. I had no idea and got no warning about the grapefruit interactions, and ate grapefruit fairly regularly. For all I know I may have fucked up my inner workings in ways I have yet to discover, but I experienced no effects in the moment.

Of course, big bold disclaimer here: this is not medical advice and my experience may not be typical. I'd hate for you or anyone to become seriously ill just because I said I didn't. Effects would vary depending on your dosage, grapefruit consumption, metabolism, etc. If I had known about the possibility of interaction I would have avoided grapefruit completely.
posted by Metroid Baby at 2:40 PM on November 18, 2015

Sorry, the grapefruit thing is real. I was told to wait a few weeks, but I'm still on the drug that they said this for so I haven't had a chance to try it out. I'm not sure there's anything that "four to six weeks" wouldn't be a safe margin for, though, so it's possible that this prescriber was just making it up.

Grapefruit is as far as I know the most likely natural substance to show up on the interactions list. Probably because so many people got into eating grapefruit when it was a diet fad.

I'm actually probably never going to have it again, because now I see it on the shelf and I immediately think about liver transplants.
posted by SMPA at 2:56 PM on November 18, 2015

Oh, also, apparently the populations of people who are likely to buy grapefruit and people who are likely to be on prescription drugs overlap, and that because both populations are more likely to be over 45 years old they also face a much higher risk of an interaction taking place. It's like a perfect storm!

Anyway, this helps explain why some people have no problem and some people have a massive problem and also why there are so many freaking warnings about grapefruit. It's probably also why some of the effects of grapefruit are confusing to scientists (who normally are rather fond of excluding old people from their studies.)
posted by SMPA at 3:06 PM on November 18, 2015

Here is good information from Harvard health on how grapefruit affects your blood level of the medication, and reccommendations on what to do.
posted by SyraCarol at 3:14 PM on November 18, 2015

Grapefruit drug interactions can be managed for some drugs but it involves careful monitoring and taking the exact same amount of grapefruit every day then tinkering with the dosages until the magic amount of both is found. You can kind of sort of manage it with things like warfarin/coumadin that come in 1mg doses and require frequent blood draws anyway but you're best to live without grapefruit if you're not like super into it.

Like super into it. Into grapefruit in ways most people can only dream of.
posted by the uncomplicated soups of my childhood at 4:41 PM on November 18, 2015 [1 favorite]

Epidemiologist/toxicologist chiming in.

Anecdotal evidence on things like this is totally without value (sorry folks who did just fine chugging grapefruit and contraindicated drugs). Even in situations like this--amlodipine isn't one of the classic "worst case" drugs when it comes to grapefruit interactions--a single person's experience is no guide.

Individuals demonstrate a wide range of rates of expression of the enzymes that do stuff to the drugs we take. The only way you'd know what end of the spectrum you're on would be to subject yourself to coadministration. Even then, you won't always be able to discern if any physiological effects are happening. You can't always feel tissue damage, you know?

These things don't play nice together, so keep them apart as best you can.
posted by late afternoon dreaming hotel at 4:45 PM on November 18, 2015 [7 favorites]

It's a 3A4 inhibitor. So it can increase the serum levels of 3A4 substrates. Most likely you'd be fine with most drugs, but grapefruit isn't worth the possibility of not being fine.
posted by persona au gratin at 1:03 AM on November 19, 2015