Some of the interactions involve medication that have narrow therapeutic window and can therefore cause potent adverse effects such as torsade de pointes, rhabdomyolysis, myelotoxicity, respiratory depression gastrointestinal bleeding, nephrotoxicity and sudden cardiac death. The effects are more pronounced with regular consumption of grapefruit juice prior to ingestion of the drug and there can be a cumulative increase in drug concentrations with continued grapefruit juice intake 7,9.Īs little as 200-250ml may be sufficient to induce its effects 7,10. The half life of the effects of grapefruit juice is estimated to be around 12 hours 7, but these effects may last from 4 hours to 24 hours 8. Further studies have identified similar interactions with more than 85 drugs 6. The interaction of grapefruit juice with medication was first reported by Bailey et al in 1991 after their accidental discovery of up to four fold increase in the blood levels of filodipine when taken with grapefruit juice 5. In the United Kingdom, in terms of fruit juice sales, it ranks second among citrus fruits and the fourth overall. With good publicity, marketing and coverage by health magazines, grapefruit juice has gained widespread use and in most Western Europe and America it is one of the common fruit juices consumed at breakfast. The seed extract is thought to have antimicrobial and antifungal properties. It is found to have antioxidant properties due to the presence of lycopene 1and an ability to inhibit atherosclerosis due to the presence of pectin 2,3. It is a rich source of vitamins C and potassium. The taste is a mixture of the sweetness and tanginess of an orange and the sourness of a citrus fruit. Although the white and pink varieties were being popularly consumed, the ruby red variety has become very popular and commercially successful. Subsequently, different mutant and hybrid varieties were developed. It was first bred in Barbados and brought to Florida in 1820s. Grapefruit (Citrus paradise) is thought to have originated as a cross between the Jamaican sweet orange (Citrus sinensis) and the Indonesian pomelo (Citrus maxima) fruit. More research is necessary to identify the mechanism of such interactions and to identify the active ingredients. Therapeutic doses of the affected drugs may produce serious adverse reactions. Grapefruit juice inhibits the CYP3A4 enzyme of the cytochrome P450 system in the intestinal mucosa, increasing the bioavailability of drugs with a high first pass metabolism. It is necessary for all medical practitioners to be aware of the potential for enhanced serum levels of the affected drugs and the possibility of serious adverse effects. However there has been a lack of awareness of its effects on other medications in patients as well as physicians.
Since the accidental discovery of its interaction with felodipine, more than 85 drugs have been identified to have the potential to cause serious adverse reactions. The use of grapefruit juice on its own or in a mixture with other juices is gradually increasing in UK and grapefruit juice is now a regular part of breakfast consumption in most of Western Europe and America. Grapefruit juice sales are gradually increasing since 1970s and reached an average of 24.9 million litres per annum between 20. Cite this article as: BJMP 2012 5(4):a538
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