benylin

[Lankidoodles]

Why can't you eat or drink grapefruit while taking Benylin?

[Ethel]

The main ingredient of Benylin is dextromethorphan (dxm) and grapefruit has a strange reaction with it.

Have a read of this:

http://www.erowid.org/experiences/exp.php?ID=1 3856

[theprof]

Grapefruit contains a number of closely related substances called furanocoumarins. These furanocoumarins inhibit the activity of an important enzyme called CYP3A4 in the body. Now one of the functions of CYP3A4 is to metabolise a whole range of medications that we take. One of these medications is Dextromethorphan, the main ingredient in some varieties of Benylin.

Grapefruit can interfere with the action of CYP3A4 within 20 minutes of ingestion and depending on the quantity eaten (or drunk as juice), the effect can last for 3-4 days. Some people are not so sensitive to this action as others, as we all have differing amounts of CYP3AF and related enzymes in our bodies.

When CYP3A4 is unable to function at its working sites in the body, the liver and the large intestine wall, the medications that it normally metabolises in the gut wall enter the bloodstream in hugely increased amounts. The effects and side effects of the medications are then increased as well. In the case of Dextromethorphan, this leads to an increase in drowsiness, dizziness, light-headedness, slurred speech etc over and above what a person might normally experience. Sometimes, the amounts in the bloodstream reach toxic levels and fatalities result. Recreational use of Dextromethorphan as suggested in the link provided by Ethel is extremely dangerous and not to be encouraged.

(continued)

[theprof]

It can take up to 72 hours for CYP3A4 to return to normal operations after drinking grapefruit juice or eating the fruit. There is also another more complicated drug inhibition pathway at work alongside the one I�ve described and grapefruit plays a key role in that as well.

Grapefruit affects many drugs in this way. These include almost all the statins (which the UK government recently suggested should be given to all adults over 40 in the UK), various anti-depressants, analgesics, oral contraceptives and asthma treatments. This is one of the reasons why reading those Patient Information Leaflets that come with your medication is so important.

[himupnorth]

Phew, I thought it was just because the leaflet tells you not to - and they should know!