Grapefruit drug interaction?

[uk_pman]

I've read an account recently about how grapefruit can interact with drugs and either increase or decrease the concentration of the active components in the blood.

I believe the original findings were caused when they were testing the effects of alcohol on blood pressure tablets, and using grapefruit juice to "hide" the alcohol. Subsequently they found the grapefruit had increased the quantity of the blood pressure medication in the blood.

All of which raises the issue - has there been any findings of whether the active ingredient in grapefruit juice which causes this has known impacts on any illegal drugs?

NB- I've used the search function but couldn't find much fact.

 

[Mr Blonde]

This has been covered a lot before, check out the opioid potentiation thread in OD (see the directory or mega threads stickyies).

Any drug that is metabolized by the CYP3A4 enzyme will be 'potentiated' by grapefruit juice, e.g. morphine, heroin, most opioids in fact. Looking up the drugs you use and what enzymes they are metabolized by will get you your answer.

 

[belarki]

This has been covered a lot before, check out the opioid potentiation thread in OD (see the directory or mega threads stickyies).

Any drug that is metabolized by the CYP3A4 enzyme will be 'potentiated' by grapefruit juice, e.g. morphine, heroin, most opioids in fact. Looking up the drugs you use and what enzymes they are metabolized by will get you your answer.

As Mr Blonde said this has been discussed in depth throughout the forums. I think there is still some arguements for and against grapefruit jiuce as a potentiator for codeine though. Try the following thread or even search google or wiki for academic findings.

http://www.bluelight.ru/vb/showthread.php?t=252569

http://en.wikipedia.org/wiki/List_of_drugs_affected_by_grapefruit

 

[Mr Blonde]

For what it's worth, I've never noticed much potentation with grapefruit juice.

 

[person]

I made a poppy brew by just adding some/carton of grapefruit juice then mixing it up with the seeds/crushed pestle in a coffee plunger, was extremely potent!?
But then ive ivd 30mgs of morphine to then drink alot of grapefruit juice to not notice anything or prolonging effects. Could be a million other answers lol, but interesting though.

 

[nabollocks]

It also potentiates some benzos and not others. Here are some examples:

Midazolam

Pretreatment with grapefruit juice is associated with increased bioavailability and changes in the pharmacodynamics of midazolam that may be clinically important, particularly in patients with other causes for increased midazolam bioavailability such as advanced age, cirrhosis of the liver, and administration of other inhibitors of cytochrome P450.

Interaction between grapefruit juice and midazolam in humans (1995)
Clinical Pharmacology and Therapeutics Vol 58 1, Kuperschmidt et al

Alprazolam

Grapefruit juice altered neither the steady-state plasma concentration of alprazolam nor the clinical status in patients. The present study shows that grapefruit juice is unlikely to affect pharmacokinetics or pharmacodynamics of alprazolam due to its high bioavailability.

Effects of Repeated Ingestion of Grapefruit Juice on the Single and Multiple Dose Pharmacokinetics and Pharmacodynamics of Alprazolam (2000) Psychopharmacology (Berl). 2000 Jun;150(2):185-90
Yasui N, Kondo T, Furukori H, Kaneko S, Ohkubo T, Uno T, Osanai T, Sugawara K, Otani K.

For the sake of HR I would suggest that you do not mix grapefruit juice with drugs.

Quite often, the best and safest drug potentiator is simply to have more of the original drug.

 

[Mr Blonde]

^ Oh yeah, I forgot about that.

Also, if you are planning on using grapefruit juice with codeine, forget it; the compounds in the juice inhibit CYP2D6.

 

[Anon Ymous]

Nabollocks, it's all placebo. And by the way buddy, send me a PM regarding what you were implying regarding my 'specialist'. Are you saying that a GP is better than a specialist? It was hard for me to interpret what you meant.

 

[Anon Ymous]

Placebo meaning that grapefruit juice enhances every single drug known to man.

 

[Mr Blonde]

^ It's not a placebo effect, it really does affect enzymes. Whether this causes an appreciable difference in effects may depend on individual body chemistry and, like you said, placebo.

 

[phase_dancer]

For the sake of HR I would suggest that you do not mix grapefruit juice with drugs.

Good advice. While not everyone may be equally affected, GF has the ability to considerably potentiate some opiode drugs, and other drugs which are metabolised via the 3A4 pathway.

 

[nabollocks]

PD, you may be able to correct me on this one:

As far as I know, the only potentiation that is used in practice is the opiate + antihistamine. And only very rarely is this done, normally when trying to keep addiction at bay.

I can just see way to many problems with trying to potentiate substances as the potentiators often are contraindicated with a host of other substances that you may possibly ingest in any one sitting.

Your liver is there to save you guys, don't go shutting it down for no good reason.

 

[phase_dancer]

I'm not sure in what circumstances (if any) that potentiation is used. Grapefruit was widely recognised as a 3A4 inhibiter only relatively recently, around the late 90's if memory serves. I know of no instance where co-administration with GF has been recommended.

 

[Mr Blonde]

The amount of the compounds in grapefruit juice varies anyway, so it would be a messy way to potentiate. You'd be better off getting an OTC CYP3A4 inhibitor of some sort, so you at least know the exact dose of what you are taking.

 

[Anon Ymous]

What exactly is an OTC CYP3A4 inhibitor? Cimetidine is only available by prescription, and oral contraceptives are available by prescription only aswell dude.

 

[Mr Blonde]

Someone mentioned one to me a long time ago in the codeine thread I believe, it may have been an OTC anti-histamine but I can't remember. It worked wonders for him. I'll see if I can find the name of it.