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22 August 2012
Grapefruit captured the popular consciousness back in the 1930s when the grapefruit diet became all the rage. Post-war things got a little quiet for grapefruit until it became clear that grapefruit juice interfered with an enzyme in the liver called CYP3A4 that is involved in drug metabolism. Now a study has shown that this effect may actually be of benefit in people using a certain cancer medication.
Sirolimus, also known as rapamycin, is a drug used to prevent organ rejection in transplant patients. It is also used in some cancer treatment where it can make chemotherapy more effective. In this study people with incurable cancer were put on one of three regimes; sirolimus alone, sirolimus plus ketoconazole (a drug that slows metabolism), or sirolimus plus grapefruit juice.
The researchers noted that the best cancer-fighting dose of sirolimus was 90mg per week. However, above 45mg per dose there were serious problems with nausea and diarrhoea. So they gave the drug in two 45mg doses. By contrast though when the patients took the sirolimus with ketoconazole optimal blood levels were achieved with 16mg per week and when they took it with grapefruit juice optimal levels were reached with between 25 and 35mg per week.
Grapefruit juice raised blood levels of sirolimus by 350 per cent, so the potential for overdose with other drugs combined with grapefruit juice becomes a positive in this case. It might mean that patients can avoid the side-effects of these drugs by taking lower doses in combination with grapefruit juice.
Of course this is not something you would do without the guidance of a medical practitioner. Grapefruit juice will vary in quality and effect so when dealing with powerful cancer medications every care needs to be taken.
Nevertheless, this points to a potential natural way to reduce the side-effects of chemotherapy. The researchers made the interesting point that all of their funding came from the National Institutes of Health and that such findings will not necessarily be profitable for pharmaceutical companies especially if the study outcome suggests that lower doses of the drug can be effective after the drug has been approved and priced.