What happens when you take seville orange with cyclosporine?
Cyclosporine is a calcineurin inhibitor used to prevent rejection after organ transplantation and to treat several autoimmune conditions. Like tacrolimus, it has a narrow therapeutic window and is metabolized by CYP3A4 and transported by P-glycoprotein in the intestinal wall. Anything that disturbs either system can change cyclosporine blood levels and shift the balance between rejection and toxicity.
Seville orange (Citrus aurantium), also called bitter orange, contains furanocoumarins including bergamottin and 6',7'-dihydroxybergamottin. These are the same compounds responsible for the grapefruit drug interaction, and they act as irreversible inhibitors of intestinal CYP3A4. On chemistry alone, one would expect Seville orange to raise cyclosporine levels just as grapefruit does.
The clinical picture is more nuanced. A controlled crossover study by Edwards and colleagues in 1999 compared the effects of grapefruit juice and Seville orange juice on cyclosporine in healthy volunteers. Seville orange juice reduced enterocyte CYP3A4 protein concentrations by an average of 40%, confirming that it does inhibit the enzyme. But cyclosporine AUC did not rise significantly, in contrast to grapefruit juice, which has been shown to increase cyclosporine exposure in multiple studies.
Why is this important?
The explanation for the discrepancy lies in P-glycoprotein. Grapefruit juice inhibits both intestinal CYP3A4 and intestinal P-glycoprotein, the efflux transporter that pumps cyclosporine back out of enterocytes before it can enter the bloodstream. Seville orange juice inhibits CYP3A4 strongly but appears to leave P-glycoprotein largely intact. Because cyclosporine absorption is rate-limited by P-glycoprotein in addition to CYP3A4 metabolism, knocking out only the enzyme is not enough to produce a meaningful rise in drug exposure.
This is biologically interesting, but it does not change everyday transplant practice much. Most transplant programs counsel patients to avoid all grapefruit-like citrus, including Seville orange, pomelo, and tangelo, because:
- The published data on Seville orange and cyclosporine come from healthy volunteers, not transplant patients with altered intestinal physiology or polypharmacy.
- Furanocoumarin content varies widely between batches of fruit and juice; some Seville orange products contain higher levels than others.
- Other immunosuppressants commonly used alongside cyclosporine, such as tacrolimus and sirolimus, are more sensitive to Seville orange and should be avoided.
- The downside of avoidance is small (no bitter orange marmalade); the downside of a missed interaction is potential organ rejection or toxicity.
Bitter orange is also widely sold as a weight loss supplement under the name Citrus aurantium, often with synephrine listed as the active ingredient. These extracts contain furanocoumarins and sympathomimetic compounds that may carry independent cardiovascular risks. Transplant patients should not take bitter orange supplements without clearing them with their team.
What should you do?
If you are on cyclosporine, the prudent course is to avoid Seville orange products even though the controlled data are reassuring. This includes Seville orange marmalade (most traditional British marmalades), bitter orange in cooking and liqueurs, naranja agria used in Cuban and Mexican cuisine, and bitter orange supplements.
Sweet oranges (navel, Valencia, blood, Cara Cara), mandarins, clementines, tangerines, lemons, and limes do not contain meaningful furanocoumarins and are safe with cyclosporine.
Grapefruit and pomelo are stronger interactions and should be strictly avoided. Tangelos and sweeties (grapefruit-pomelo hybrids) may also carry significant furanocoumarin loads and are best avoided.
If you accidentally consume Seville orange in marmalade or a recipe, the practical risk is likely low based on the Edwards study, but it is reasonable to mention it at your next routine cyclosporine trough check so your transplant team has the context.
Do not start any new supplement, especially weight loss or pre-workout products, without checking the ingredient list for Citrus aurantium, bitter orange, or synephrine and reviewing with your transplant pharmacist.
Which specific products are affected?
This warning concerns cyclosporine formulations including Sandimmune (oil-based), Neoral (microemulsion), and Gengraf (modified). The pharmacokinetic data on Seville orange come from studies using the older Sandimmune formulation; the modified microemulsion formulations are less dependent on bile and on intestinal P-glycoprotein, which may further blunt any interaction.
The food side includes anything made with Citrus aurantium: Seville orange juice, marmalade made from Seville oranges, bitter orange liqueurs, naranja agria mojo and adobo, and bitter orange supplements (often labeled C. aurantium or synephrine).
The bottom line
Seville orange inhibits intestinal CYP3A4, but unlike grapefruit, it does not appear to significantly increase cyclosporine blood levels in controlled studies, likely because cyclosporine also depends on intestinal P-glycoprotein, which Seville orange affects less. Despite this reassuring data, most transplant teams still advise patients on cyclosporine to avoid Seville orange products as a precaution, especially given the wider warnings about furanocoumarin-containing citrus and the high stakes of altered immunosuppressant levels. Skip the bitter orange marmalade and Citrus aurantium supplements, and stick to sweet oranges and other low-furanocoumarin citrus.