TIL drinking grapefruit juice while on meds may cause serious interactions with your drugs or even kill you

Grapefruit juice inhibits CYP450. Cytochrome P450 is an enzyme, in our livers, that breaks big molecules down into smaller molecules. By inhibiting this enzyme, chemicals which, ordinarily, would be broken down immediately......remain in our blood stream longer because their breakdown has been inhibited.

In truth there are four significant drug interactions---none of which involve narcotics, amphetamines or the benzos!

This information is ancient. Nearly three decades ago, it was exciting when I was a pharmacy school student.

Yes....it is true that grapefruit juice can inhibit CYP450. But for it to have any remotely significant effect on cannabis or any of the synthetic opiates (hydrocodone, oxycodone).....requires massive amounts. It would, if only the grapefruit juice was not acidic, profoundly increase blood levels of amphetamine salts (dexedrine, adderall).

Regarding the meds for ADHD......these drugs are diminished in an acidic environment. This means.....you drink a gallon of grapefruit juice....take your adderall......and you diminish absorption. The acidity prevents it from being absorbed properly. NOW if it was absorbed.....then this CYP450 inhibition would prolong the half-life as well as enhance the blood levels. Problem is....though.....it has to be absorbed. So....no. Do not waste your money on grapefruit juice with hopes of potentiating your adderall (or generic)!!!

Now....speaking scientifically, only (and not with any thought that someone might read these words with ill intent).......Tagamet......cimetidine.....is OTC. Over-the-counter.

Tagamet is about 340% more potent in terms of inhibiting CYP450.

Let me take this opportunity to warn anyone that might take a drug, like oxycodone, hydrocodone, or mixed amphetamines. Tagamet is in the antacid section of your grocery store. YOU must be very cautious......if you take just one tablet an hour before taking your necessary medicine.......what happens is that the tagamet inhibits your livers ability to metabolize (break the molecules) into something inactive. This oversimplifies, but a drug that might ordinarily remain in your system for 4hours.......would remain in the blood stream for around 8hours.

NOT only this.......it elevates the blood levels of the active drug.

Bottom line? If you have acid indigestion.......do not buy Tagamet (cimetidine).......at least not if you take any of the synthetic opiates, benzodiazepines (valium....diazepam or Xanax..alprazolam), or amphetamine salts (adderall, dexedrine)....... It would significantly increase the blood levels as well as the 'half-life' of the drug.

I won't bother including links to references. You folks are highly intelligent......smarter than me, for sure. You can research. I'm merely a PharmD (doctorate in pharmacy) with an MS in toxicology and PhD in nuclear medicine. (NO! I did not get my degrees from the U of Phoenix!).

So....please....warn your families and friends.

Bottom line is there are a handful of drugs that interact with a practical amount of grapefruit juice (ie. someone who drinks a glass, every other day).....but these are drugs for heart or stroke prevention.

Theoretically.....grapefruit juice truly inhibits CYP450. But it requires large volumes and it's acidity often prevents the absorption of drugs....meaning the interaction is merely theoretical.

Cimetidine? OTC.......in the antacid section. It's famous for prolonging the effects of cannabis. It does this quite well (take one or two hours before)......but most especially with ingested cannabis.

I'm happy to have had this opportunity to warn everyone of the dangers of combining cimetidine with other medicines. Be responsible!

/r/todayilearned Thread Link - fda.gov