They interact with so many drugs, if you take any medication for chronic illnesses, chances are you should not eat any grapefruit for the rest of your life. Also whether a drug is affected by it or not is not clear, so the common advice is just to avoid the fruit whatever the drug you're taking.
It's one of my favourite fruits, and not being able to eat it once in a while hurts. Though I'm not sure how _dangerous_ it really is. Does it affect the half-life of a drug by 5%, or by 100%?
TFA says it increases the bioavailability of felodipine, the drug where the effect was first noticed, by about a factor of 5. For most prescription drugs for chronic illness, you probably do not want to find out what happens when you move to 5x the effective dose.
Even for "some innocent stuff like Tylenol", as the original comment puts it, you do not want to be taking 5x the dose. This is a very harmful drug in (not very) large quantities.
I know of somebody whose boyfriend ended things with her, she took a load of tylenol to end her life, but the doctors managed to resuscitate her. When she came to, she said to her mother "I'm so glad I didn't kill myself over that bastard". A week later she died from liver failure.
That's a standard thing with Tylenol/Paracetamol. You can recover from the initial overdose, but then the metabolites build up in your liver over the next few days and trash it beyond any hope of repair.
At that point it's either a transplant or death.
The scary thing is that it's incredibly easy to overdose by accident. For some people the lethal dose is less than twice the recommended dose, and if you're in a lot of pain - e.g. from a dental abscess - you can easily overdo it.
I'm on a blood pressure drug. My pharmacy ran out of the dose I needed and substituted a 2x size, with instructions to cut the pill in half. I ended up forgetting about the substitution and took the 2x dose daily for a couple of months. Didn't find out until I went to renew the prescription and was told I was trying to refill it too early. Suddenly the recent dizzy spells I had were easily explained.
Adderall/Vyvanse/Amphetamines don't interact well at all with vitamin C, of which grapefruits are full of. So sadly enough, you don't get any 5x intake boost with the enjoyable meds. Would have been way too much fun ;)
The majority of adderall breaks down through the urea cycle due to urine acidity. Enzymes don’t play as significant a role as they do for other drugs. That’s why baking soda is the best potentiator for amphetamines, as it neutralizes urine acidity.
But apparently the effect lasts up to 12 hours, vitamin c should be gone from the stomach by then. Grapefruit has been anecdotally recommended for MDMA (an amphetamine).
The reason it's recommended for MDMA is because it inhibits the CYP3A4 enzyme which metabolizes MDMA (3,4-Methylenedioxymethamphetamine) to MDA (3,4-Methylenedioxyamphetamine). MDA is more neurotoxic than MDMA which is why it's advised to reduce the amount your body intakes.
As someone prescribed Adderall, to my knowledge, grapefruit juice (and citrus in general) will inhibit the absorption so if anything, it would just lower the effectiveness of a typical dose.
They interact with so many drugs, if you take any medication for chronic illnesses, chances are you should not eat any grapefruit for the rest of your life. Also whether a drug is affected by it or not is not clear, so the common advice is just to avoid the fruit whatever the drug you're taking.
It's one of my favourite fruits, and not being able to eat it once in a while hurts. Though I'm not sure how _dangerous_ it really is. Does it affect the half-life of a drug by 5%, or by 100%?