Nurses should warn patients taking the antiplatelet drug ticagrelor (which treats acute coronary syndromes, such as unstable angina and myocardial infarction) to avoid grapefruit juice, according to research published in the British Journal of Clinical Pharmacology.
An enzyme, called cytochrome p450 3A (CYP3A), expressed in the liver and intestine metabolises ticagrelor.Grapefruit juice strongly inhibits intestinal CYP3A4. So, ten healthy volunteers drank 200 ml of grapefruit juice or water three times daily for four days. On the third day, volunteers took 90mg ticagrelor. After a two-week washout, those who drank grapefruit juice switched to water and vice versa.
Grapefruit juice increased the peak concentration of ticagrelor in the blood (Cmax) by 165 per cent compared to water. Grapefruit juice also increased the area under the concentration-time curve (AUC) - which indicates total exposure to the drug - by 221 per cent and elimination half-life (the time for blood concentrations to halve) from 6.7 to 7.2 hours.
Grapefruit juice enhanced ticagrelor's antiplatelet effect and delayed recovery of platelet reactivity, potentially increasing the risk of adverse events, complicating preparations for surgery and making management of bleeding side effects more difficult. The authors commented that 'the concomitant use of ticagrelor and grapefruit juice is best to be avoided'.
- British Journal of Clinical Pharmacology (2012) doi: 10.1111/bcp.12026