Thursday, July 30, 2015

Grapefruit: Good for You or A Deadly Delight?

I love grapefruit. I eat several a week and would probably eat more if I could. But I just read this article about grapefruits and how they can be toxic for people on medications. It was actually pretty scary how many drugs are affected by grapefruit. The article really focused on the negative effects of how grapefruit can cause overdose and potentially fatal side effects but I think they missed out on the more important issue: why not use grapefruits to supplement for lower dosages of the drugs? 

First a little on how it works.
Supposedly grapefruit contain a chemical called furanocoumarins. It is produced by the grapefruit as a defense mechanism against predators. The furanocoumarins, itself isn't toxic but it interferes with a an enzyme in our intestines called cytochrome P450 3A4 which I will just call the enzyme. 

This enzyme is in the lining of our intestines and helps metabolize many drugs by controlling the amount that enters the bloodstream. Drug companies know about this and purposely increase the dosage of some tablets to compensate for the action of the enzyme.

However, if furanocoumarins are present in the intestine, they stop the enzyme from working.  Therefore, more of the drug gets into the bloodstream and thus the risk of overdose.

A single helping of grapefruit can have an effect, even if consumed hours before the patient takes their medicine. Researchers have shown that taking some drugs with a 200ml glass of grapefruit juice every day for three days nearly tripled the drugs' concentration in the blood.

Can't this be used to our advantage? 
Wouldn't it be great if, since it seems researchers are well aware of this interaction, that people could lower their drug dosages(and probably some of the other side effects of them) by supplementing with grapefruit? It's been nearly ten years since I took pharmacology in college so I definitely don't pretend to know enough about it to know whether there would then be other side effects, but it's such a shame that, likely due to financial reasons, this is unlikely to occur. 

Be Aware 
There really are a lot of medications out there that seem to be impacted to some degree by consuming grapefruit. Now some time in the future, we may be encouraged to eat grapefruit with our medications, for the time being, we need to be cognizant of the potential for a negative drug reaction. Therefore if you're adamant about eating grapefruit it would be worth talking with your doctor if you're taking any drugs. 

Below is a list(probably not comprehensive) of drugs that interact with grapefruit:
  • Dasatinib (leukaemia)
  • Erlotinib (lung cancer and pancreatic cancer)
  • Everolimus (kidney cancer)
  • Lapatinib (breast cancer)
  • Nilotinib  (leukaemia)
  • Pazopanib (kidney cancer)
  • Sunitinib (kidney/gastrointestinal cancer)
  • Vandetanib (thyroid cancer)
  • Venurafenib (skin cancer)
  • Erythromycin (antibiotic)
  • Halofantrine (malaria)
  • Maraviroc (HIV)
  • Primaquine (malaria)
  • Quinine (malaria)
  • Rilpivirine (HIV)
  • Atorvastatin(cholesterol)
  • Lovastatin(cholesterol)
  • Simvastatin(cholesterol)
  • Amiodarone (heart rhythm disorders)
  • Apixaban (anti-clotting)
  • Dronedarone (heart rhythm disorders)
  • Eplerenone (heart failure)
  • Felodipine (high blood pressure/angina)
  • Nifedipine (high blood pressure/angina)
  • Quinidine  (heart rhythm disorder)
  • Rivaroxaban (anti-blood clotting)
  • Ticagrelor (anti-blood clotting after heart attack)
  • Oral Alfentanil (painkiller)
  • Oral fentanyl (painkiller)
  • Oral ketamine (painkiller, sedative)
  • Lurasidone (schizophrenia/mental health problems)
  • Oxycodone (painkiller)
  • Pimozide (schizophrenia/other mental health problems)
  • Ziprasidone (schizophrenia, mania, bipolar disorder)
  • Domperidone (anti-nausea)
  • Cyclosporine (post organ transplant, rheumatoid arthritis, psoriasis)
  • Sirolimus (post organ transplant)
  • Tacrolimus (post organ transplant)
  • Solifenacin (urinary frequency/incontinence)
  • Silodosin (enlarged prostate)
  • Tamsulosin (enlarged prostate)

As you can see the list is fairly long. As there are several malaria drugs on the list, I am definitely going to talk with my doctor before I start eating grapefruit while in Guyana.

Hope you all have explored better ways to spend your down time than reading this blog. If not, check out some suggestions

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