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Author: Admin | 2025-04-28
Amiodarone Reduction in major metabolite production and increase in serum amiodarone concentration May be clinically significant Poor Major/Delayed A study of 11 healthy volunteers showed that grapefruit juice inhibited the production of N-desmethylamiodarone (the major metabolite of amiodarone) and significantly increased the AUC* and Cmax† of amiodarone. The reductions in PR and QTcintervals caused by amiodarone were also diminished.1 Amlodipine Increased serum amlodipine concentrations. No adverse haemodynamic effects reported. Unlikely to be clinically significant Poor Minor/Delayed A controlled study found a slight interaction between amlodipine and grapefruit juice, the amlodipine AUC was 116% and Cmax was 115% of normal values. There were no differences in blood pressure and heart rate.2 Atorvastatin Increased bioavailability of atorvastatin resulting in increased risk of myopathy or rhabdomyolysis May be clinically significant Fair Moderate/Rapid Grapefruit juice was found to increase the AUC of atorvastatin acid and atorvastatin lactone approximately threefold. AUC of active and total atorvastatin increased by 20-50%.3 Benzodiazepines (see also diazepam and triazolam) No data exists but theoretically none Unlikely to be clinically significant None None/Unknown No data exist for alprazolam, chlordiazepoxide, clonazepam, flurazepam and lorazepam. However, they are all likely to be safe to take with grapefruit juice as their high oral bioavailability leaves little room for elevation by grapefruit juice.4 Buspirone Elevated plasma concentrations resulting in increased risk of adverse effects Clinical significance unknown - there is considerable inter-individual variability with serum levels Poor Minor/Delayed A study of 10 healthy volunteers found that 200 mL of double strength grapefruit juice three times a day increased buspirone's AUC, peak concentration, time to peak concentration and half-life. However, there was considerable inter-individual variability.5 Carbamazepine Increased carbamazepine bioavailability May be clinically significant Fair Moderate/Rapid Grapefruit juice increased peak concentration by 40.4%, trough concentration by 39.2% and AUC by 40.8% during a randomised crossover study.6 Cisapride Increasing serum concentrations increase the risk of adverse effects (e.g. cardiotoxicity, QT prolongation, torsade de pointes) Experimental data are fair but clinical significance unknown. Monitor for adverse effects or avoid grapefruit juice Fair Major/Rapid Grapefruit juice was shown to increase the oral bioavailability of cisapride in 14 volunteers but large inter-individual variations were noted. There was a slight but significant increase in the elimination half-life of cisapride during a two-phase crossover study. No volunteer experienced a change in heart rate, blood pressure or QT interval.7,8 Clarithromycin No increase in drug concentrations noted Insignificant Poor None/Not specified A randomised crossover study of 12 healthy volunteers showed that grapefruit juice increased time to peak concentration but did not affect other pharmacokinetic parameters.9 Clomipramine Increased risk of clomipramine toxicity Clinical significance unknown. Monitor for adverse effects. Poor Moderate/Delayed Clomipramine is metabolised by several different CYP pathways including 1A2, 3A4 and 2D6. Grapefruit
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