Drug & supplement interaction

Grapefruit + Trandolapril, Verapamil

Trandolapril, Verapamil brand name: Tarka.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Trandolapril, Verapamil falls into 4 drug categories that Grapefruit can interact with; the most serious is rated major. Grapefruit juice can increase levels of drugs metabolized by CYP3A4.

Read the full interaction report
SeverityMajor
LikelihoodLikely
Interactions4
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Grapefruit and Trandolapril, Verapamil

These two interact in 4 distinct ways. Each one is explained separately below.

Why Are There 4 Interactions?

Grapefruit interacts with whole categories of medication. Trandolapril, Verapamil falls into 4 of those categories, so it can interact with Grapefruit in 4 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Major).

Major

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

1 of 4

Why this applies to Trandolapril, Verapamil

Trandolapril, Verapamil falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Grapefruit interacts with.

Grapefruit juice can increase levels of drugs metabolized by CYP3A4.
Clinical research shows that grapefruit juice can inhibit CYP3A4 metabolism of drugs, causing increased drug levels and potentially increasing the risk of adverse effects. When taken orally, effects of grapefruit juice on CYP3A4 levels appear to last at least 48 hours. Grapefruit's ability to inhibit CYP3A4 has even been harnessed to intentionally increase levels of venetoclax, which is metabolized by CYP3A4, in an elderly patient with acute myeloid leukemia who could not afford full dose venetoclax. The lower dose of venetoclax in combination with grapefruit juice resulted in serum levels of venetoclax in the therapeutic reference range of full dose venetoclax and positive treatment outcomes for the patient.
Professional consensus recommends the consideration of patient age, existing medical conditions, additional medications, and the potential for additive adverse effects when evaluating the risks of concomitant use of grapefruit juice with any medication metabolized by CYP3A4. While all patients are at risk for interactions with grapefruit juice consumption, patients older than 70 years of age and those taking multiple medications are at the greatest risk for a serious or fatal interaction with grapefruit juice.
Severity Major Likelihood Likely Evidence B

Well-controlled human studies have demonstrated the likely existence of this interaction.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Tarka combines two medicines, and the part that really matters here is verapamil. Your body relies on an enzyme called CYP3A4 to break verapamil down, and grapefruit blocks that enzyme. When that pathway slows, verapamil can build up to higher levels than expected, which makes its effects stronger.

With verapamil, that can mean your blood pressure dropping too low, a slower heart rate, dizziness, lightheadedness, swollen ankles, or constipation. Because verapamil slows the heart's electrical signals, too much can be a real concern, especially if you're older or take other heart or blood pressure drugs. This effect can linger for a couple of days after eating grapefruit. Please don't change anything on your own. Just check with your pharmacist or doctor about whether grapefruit is okay for you.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lilja JJ, Kivisto KT, Neuvonen PJ. Grapefruit juice increases serum concentrations of atorvastatin and has no effect on pravastatin. Clin Pharmacol Ther 1999;66:118-27. DOI
  2. Lilja JJ, Kivisto KT, Neuvonen PJ. Grapefruit juice-simvastatin interaction: effect on serum concentrations of simvastatin, simvastatin acid, and HMG-CoA reductase inhibitors. Clin Pharmacol Ther 1998;64:477-83. PubMed
  3. Jetter A, Kinzig-Schippers M, Walchner-Bonjean M, et al. Effects of grapefruit juice on the pharmacokinetics of sildenafil. Clin Pharmacol Ther 2002;71:21-9. PubMed
  4. Fuhr U, Muller-Peltzer H, Kern R, et al. Effects of grapefruit juice and smoking on verapamil concentrations in steady state. Eur J Clin Pharmacol 2002;58:45-53. PubMed
  5. Kanazawa S, Ohkubo T, Sugawara K. The effects of grapefruit juice on the pharmacokinetics of erythromycin. Eur J Clin Pharmacol 2001;56:799-803. PubMed
  6. Charbit, B., Becquemont, L., Lepere, B., Peytavin, G., and Funck-Brentano, C. Pharmacokinetic and pharmacodynamic interaction between grapefruit juice and halofantrine. Clin Pharmacol Ther 2002;72(5):514-523. PubMed
  7. Tanaka S, Uchida S, Miyakawa S, Inui N, Takeuchi K, Watanabe H, Namiki N. Comparison of inhibitory duration of grapefruit juice on organic anion-transporting polypeptide and cytochrome P450 3A4. Biol Pharm Bull. 2013;36(12):1936-41. PubMed
  8. Bailey DG. Predicting clinical relevance of grapefruit-drug interactions: a complicated process. J Clin Pharm Ther. 2017 Apr;42(2):125-27. PubMed
  9. Mouly S, Lloret-Linares C, Sellire PO, Sene D, Bergmann JF. Is the clinical relevance of drug-food and drug-herb interactions limited to grapefruit juice and Saint-John's Wort? Pharmacol Res. 2017 Apr;118:82-92. PubMed
  10. Loretz C, Ho MD, Alam N, Mitchell W, Li AP. Application of cryopreserved human intestinal mucosa and cryopreserved human enterocytes in the evaluation of herb-drug interactions: evaluation of CYP3A inhibitory potential of grapefruit juice and commercial f
  11. Long Z, Ruan M, Wu W, Zeng Q, Li Q, Huang Z. The successful combination of grapefruit juice and venetoclax in an unfit acute myeloid leukemia patient with adverse risk: A case report. Front Oncol 2022;12:912696. PubMed
Major

CALCIUM CHANNEL BLOCKERS

2 of 4

Trandolapril, Verapamil also falls under CALCIUM CHANNEL BLOCKERS.

Grapefruit juice can increase blood levels of oral calcium channel blockers, potentially increasing the effects and adverse effects of these drugs.
Clinical research shows that grapefruit juice increases absorption and plasma concentrations of amlodipine, nifedipine, nisoldipine, verapamil, felodipine, nimodipine, nicardipine, diltiazem, pranidipine, nitrendipine, and manidipine, This interaction is likely the result of the inhibition of intestinal metabolism of these drugs by CYP3A4, although some research suggests grapefruit may alter plasma drug levels by reducing the rate of gastric emptying. Consuming grapefruit juice 1 liter daily increases steady state concentrations of verapamil by as much as 50%. However, some references dispute the clinical relevance of the interactions with amlodipine, diltiazem, and verapamil. Other research in healthy individuals suggests plasma levels of felodipine and nifedipine are not affected when given intravenously. There is considerable interindividual variability in the effect of grapefruit juice on drug metabolism, which might account for inconsistent study results. In healthy older adults, the hemodynamic response to felodipine plus grapefruit juice might be influenced by altered autonomic regulation. In older healthy adults, a single dose of grapefruit juice and felodipine enhanced the blood pressure-lowering effects of felodipine. However, after a week of grapefruit juice and felodipine (steady state), the hypotensive activity was reduced, possibly due to compensatory tachycardia. Research indicates it is necessary to withhold grapefruit juice for as long as 3 days to avoid interactions with felodipine and nisoldipine.
Severity Major Likelihood Likely Evidence B

Well-controlled human studies have demonstrated the likely existence of this interaction.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Your Tarka pill combines two medicines, and the one that matters most here is verapamil. Your gut wall normally breaks down a good chunk of verapamil before it reaches your bloodstream, using an enzyme called CYP3A4. Grapefruit blocks that enzyme, so more verapamil gets through. In one study, drinking about a liter of grapefruit juice daily raised verapamil levels by as much as 50%.

What that can feel like: more blood pressure lowering than expected, dizziness or lightheadedness, a slower heartbeat, flushing, headache, or constipation. The trandolapril part isn't affected this way. Effects vary a lot from person to person, so don't stop anything on your own. Just check with your pharmacist or doctor before making grapefruit a regular habit.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Josefsson M, Zackrisson AL, Ahlner J. Effect of grapefruit juice on the pharmacokinetics of amlodipine in healthy volunteers. Eur J Clin Pharmacol 1996;51:189-93. PubMed
  2. Garg SK, Kumar N, Bhargava VK, Prabhakar SK. Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy. Clin Pharmacol Ther 1998;64:286-8. PubMed
  3. Bailey DG, Spence JD, Munoz C, Arnold JM. Interaction of citrus juices with felodipine and nifedipine. Lancet 1991;337:268-9. PubMed
  4. Bailey DG, Arnold JM, Strong HA, et al. Effect of grapefruit juice and naringin on nisoldipine pharmacokinetics. Clin Pharmacol Ther 1993;54:589-94. PubMed
  5. Bailey DG, Dresser GK, Kreeft JH, et al. Grapefruit juice-felodipine interaction: Effect of segments and an extract from unprocessed fruit. Clin Pharmacol Ther 2000;67:107 (abstract PI-71).
  6. Dresser GK, Bailey DG, Carruthers SG. Grapefruit juice-felodipine interaction in healthy seniors. Clin Pharmacol Ther 1998;65:(abstract PIII-63).
  7. Zaidenstein R, Dishi V, Gips M, et al. The effect of grapefruit juice on the pharmacokinetics of orally administered verapamil. Eur J Clin Pharmacol 1998;54:337-40. PubMed
  8. Fuhr U. Drug Interactions with Grapefruit Juice. Drug Saf 1998;18:251-72. DOI
  9. Takanaga H, Ohnishi A, Murakami H, et al. Relationship between time after intake of grapefruit juice and the effect on pharmacokinetics and pharmacodynamics of nisoldipine in healthy subjects. Clin Pharmacol Ther 2000:67:201-14. PubMed
  10. Takanaga H, Ohnishi A, Matsuo H, et al. Pharmacokinetic analysis of felodipine-grapefruit juice interaction based on an irreversible enzyme inhibition model. Br J Clin Pharmacol 2000;49:49-58. PubMed
  11. Dresser GK, Bailey DG, Carruthers SG. Grapefruit juice-felodipine interaction in the elderly. Clin Pharmacol Ther 2000;68:28-34. PubMed
  12. Erlund I, Meririnne E, Alfthan G, Aro A. Plasma kinetics and urinary excretion of the flavanones naringenin and hesperetin in humans after ingestion of orange juice and grapefruit juice. J Nutr 2001;131:235-41. PubMed
  13. Ho PC, Ghose K, Saville D, Wanwimolruk S. Effect of grapefruit juice on pharmacokinetics and pharmacodynamics of verapamil enantiomers in healthy volunteers. Eur J Clin Pharmacol 2000;56:693-8. PubMed
  14. Uno T, Ohkubo T, Sugawara K, et al. Effects of grapefruit juice on the stereoselective disposition of nicardipine in humans: evidence for dominant presystemic elimination at the gut site. Eur J Clin Pharmacol 2000;56:643-9. PubMed
  15. Fuhr U, Muller-Peltzer H, Kern R, et al. Effects of grapefruit juice and smoking on verapamil concentrations in steady state. Eur J Clin Pharmacol 2002;58:45-53. PubMed
  16. Bailey DG, Dresser GK, Bend JR. Bergamottin, lime juice, and red wine as inhibitors of cytochrome P450 3A4 activity: comparison with grapefruit juice. Clin Pharmacol Ther 2003;73:529-37 . PubMed
  17. Sigusch, H., Hippius, M., Henschel, L., Kaufmann, K., and Hoffmann, A. Influence of grapefruit juice on the pharmacokinetics of a slow release nifedipine formulation. Pharmazie 1994;49(7):522-524.
  18. Bailey, D. G., Arnold, J. M., Munoz, C., and Spence, J. D. Grapefruit juice--felodipine interaction: mechanism, predictability, and effect of naringin. Clin Pharmacol Ther 1993;53(6):637-642. PubMed
  19. Bailey, D. G., Arnold, J. M., Bend, J. R., Tran, L. T., and Spence, J. D. Grapefruit juice-felodipine interaction: reproducibility and characterization with the extended release drug formulation. Br J Clin Pharmacol 1995;40(2):135-140.
  20. Christensen, H., Asberg, A., Holmboe, A. B., and Berg, K. J. Coadministration of grapefruit juice increases systemic exposure of diltiazem in healthy volunteers. Eur J Clin Pharmacol 2002;58(8):515-520. PubMed
  21. Edgar, B., Bailey, D., Bergstrand, R., Johnsson, G., and Regardh, C. G. Acute effects of drinking grapefruit juice on the pharmacokinetics and dynamics of felodipine--and its potential clinical relevance. Eur J Clin Pharmacol 1992;42(3):313-317.
  22. Goosen, T. C., Cillie, D., Bailey, D. G., Yu, C., He, K., Hollenberg, P. F., Woster, P. M., Cohen, L., Williams, J. A., Rheeders, M., and Dijkstra, H. P. Bergamottin contribution to the grapefruit juice-felodipine interaction and disposition in humans. Cl PubMed
  23. Fuhr, U., Maier-Bruggemann, A., Blume, H., Muck, W., Unger, S., Kuhlmann, J., Huschka, C., Zaigler, M., Rietbrock, S., and Staib, A. H. Grapefruit juice increases oral nimodipine bioavailability. Int J Clin Pharmacol Ther 1998;36(3):126-132.
  24. Hashimoto, K., Shirafuji, T., Sekino, H., Matsuoka, O., Sekino, H., Onnagawa, O., Okamoto, T., Kudo, S., and Azuma, J. Interaction of citrus juices with pranidipine, a new 1,4-dihydropyridine calcium antagonist, in healthy subjects. Eur J Clin Pharmacol 1 PubMed
  25. Lundahl, J., Regardh, C. G., Edgar, B., and Johnsson, G. Effects of grapefruit juice ingestion--pharmacokinetics and haemodynamics of intravenously and orally administered felodipine in healthy men. Eur J Clin Pharmacol 1997;52(2):139-145. PubMed
  26. Lundahl, J., Regardh, C. G., Edgar, B., and Johnsson, G. Relationship between time of intake of grapefruit juice and its effect on pharmacokinetics and pharmacodynamics of felodipine in healthy subjects. Eur J Clin Pharmacol 1995;49(1-2):61-67. PubMed
  27. Rashid, T. J., Martin, U., Clarke, H., Waller, D. G., Renwick, A. G., and George, C. F. Factors affecting the absolute bioavailability of nifedipine. Br J Clin Pharmacol 1995;40(1):51-58. PubMed
  28. Soons, P. A., Vogels, B. A., Roosemalen, M. C., Schoemaker, H. C., Uchida, E., Edgar, B., Lundahl, J., Cohen, A. F., and Breimer, D. D. Grapefruit juice and cimetidine inhibit stereoselective metabolism of nitrendipine in humans. Clin Pharmacol Ther 1991; PubMed
  29. Rashid, J., McKinstry, C., Renwick, A. G., Dirnhuber, M., Waller, D. G., and George, C. F. Quercetin, an in vitro inhibitor of CYP3A, does not contribute to the interaction between nifedipine and grapefruit juice. Br J Clin Pharmacol 1993;36(5):460-463.
  30. Uno, T., Ohkubo, T., Motomura, S., and Sugawara, K. Effect of grapefruit juice on the disposition of manidipine enantiomers in healthy subjects. Br J Clin Pharmacol 2006;61(5):533-537. DOI
  31. Paine, M. F., Widmer, W. W., Hart, H. L., Pusek, S. N., Beavers, K. L., Criss, A. B., Brown, S. S., Thomas, B. F., and Watkins, P. B. A furanocoumarin-free grapefruit juice establishes furanocoumarins as the mediators of the grapefruit juice-felodipine in
  32. Sigusch, H., Henschel, L., Kraul, H., Merkel, U., and Hoffmann, A. Lack of effect of grapefruit juice on diltiazem bioavailability in normal subjects. Pharmazie 1994;49(9):675-679.
  33. Odou, P., Ferrari, N., Barthelemy, C., Brique, S., Lhermitte, M., Vincent, A., Libersa, C., and Robert, H. Grapefruit juice-nifedipine interaction: possible involvement of several mechanisms. J Clin Pharm Ther 2005;30(2):153-158. PubMed
  34. Bailey, D. G., Dresser, G. K., Kreeft, J. H., Munoz, C., Freeman, D. J., and Bend, J. R. Grapefruit-felodipine interaction: effect of unprocessed fruit and probable active ingredients. Clin Pharmacol Ther 2000;68(5):468-477. PubMed
  35. Guo, L. Q., Chen, Q. Y., Wang, X., Liu, Y. X., Chu, X. M., Cao, X. M., Li, J. H., and Yamazoe, Y. Different roles of pummelo furanocoumarin and cytochrome P450 3A5*3 polymorphism in the fate and action of felodipine. Curr Drug Metab 2007;8(6):623-630. PubMed
Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

3 of 4

Trandolapril, Verapamil also falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES.

Theoretically, grapefruit juice might increase levels of drugs metabolized by CYP1A2.
In vitro research suggests that grapefruit juice might inhibit CYP1A2 enzymes. So far, this interaction has not been reported in humans.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the honest picture with Tarka (the trandolapril and verapamil combo). The interaction on file is based on the idea that grapefruit might block a liver enzyme called CYP1A2. But that's really a side note for this medicine. The bigger, well-known concern is that grapefruit strongly affects a different enzyme (CYP3A4), which is the main one that clears verapamil. When grapefruit slows that breakdown, verapamil levels can climb.

If that happens, you might feel more of verapamil's effects: dizziness, lightheadedness, a slower heartbeat, low blood pressure, or constipation. The CYP1A2 piece itself is only theoretical and hasn't been seen in real people. Still, because of the verapamil component, I'd run your grapefruit habit by your pharmacist or doctor before making it a regular thing.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Unger M, Frank A. Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction. Rapid Commun Mass Spectrom 2004;1 PubMed
Minor

P-GLYCOPROTEIN SUBSTRATES

4 of 4

Trandolapril, Verapamil also falls under P-GLYCOPROTEIN SUBSTRATES.

Grapefruit juice does not seem to affect renal P-glycoprotein (P-gp). Theoretically, it might inhibit intestinal P-gp, but evidence is conflicting.
While most in vitro research shows that grapefruit products inhibit P-gp,, research in humans is less clear. Two small clinical studies in healthy adults using digoxin as a probe substrate show that grapefruit juice does not inhibit P-gp in the kidneys. It is unclear whether this applies to intestinal P-gp, for which digoxin is not considered to be a sensitive probe. Grapefruit juice has been shown to reduce levels of fexofenadine, and increase levels of quinidine. However, as both of these drugs are also substrates of other enzymes and transporters, it is unclear what role, if any, intestinal P-gp has in these findings.
Severity Minor Likelihood Possible Evidence B

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing about Tarka (the verapamil plus trandolapril combo) and grapefruit. The interaction on file is about P-glycoprotein, a transporter that moves drugs around. Honestly, the evidence for that specific transporter effect is weak and conflicting, so it's rated minor. But there's a bigger reason I'd raise an eyebrow: verapamil is also broken down by CYP3A4 in your gut, and grapefruit is a well-known blocker of that enzyme. That can let more verapamil into your bloodstream.

More verapamil can mean a slower heart rate, dizziness, lightheadedness, low blood pressure, or swelling in the ankles. Trandolapril can add to that blood-pressure drop. I wouldn't panic over an occasional slice, but regular grapefruit or its juice is worth a quick chat with your pharmacist or doctor before you make it a habit.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Soldner A, Christians U, Susanto M, et al. Grapefruit juice activates P-glycoprotein-mediated drug transport. Pharm Res 1999;16:478-85. PubMed
  2. Damkier P, Hansen LL, Brosen K. Effect of diclofenac, disulfiram, itraconazole, grapefruit juice and erythromycin on the pharmacokinetics of quinidine. Br J Clin Pharmacol 1999;48:829-38. PubMed
  3. Bailey DG, Dresser GK, Munoz C, et al. Reduction of fexofenadine bioavailability by fruit juices. Clin Pharmacol Ther 2001;69:P21.
  4. Edwards DJ, Fitzsimmons ME, Schuetz EG, et al. 6',7'-Dihydroxybergamottin in grapefruit juice and Seville orange juice: effects on cyclosporine disposition, enterocyte CYP3A4, and P-glycoprotein. Clin Pharmacol Ther 1999;65:237-44. PubMed
  5. Becquemont L, Verstuyft C, Kerb R, et al. Effect of grapefruit juice on digoxin pharmacokinetics in humans. Clin Pharmacol Ther 2001;70:311-6. DOI
  6. Dresser GK, Bailey DG, Leake BF, et al. Fruit juices inhibit organic anion transporting polypeptide-mediated drug uptake to decrease the oral availability of fexofenadine. Clin Pharmacol Ther 2002;71:11-20. PubMed
  7. Parker RB, Yates CR, Soberman JE, Laizure SC. Effects of grapefruit juice on intestinal P-glycoprotein: evaluation using digoxin in humans. Pharmacotherapy 2003;23:979-87. PubMed
  8. Di Marco MP, Edwards DJ, Wainer IW, Ducharme MP. The effect of grapefruit juice and seville orange juice on the pharmacokinetics of dextromethorphan: the role of gut CYP3A and P-glycoprotein. Life Sci 2002;71:1149-60. PubMed
  9. Dresser GK, Kim RB, Bailey DG. Effect of grapefruit juice volume on the reduction of fexofenadine bioavailability: possible role of organic anion transporting polypeptides. Clin Pharmacol Ther 2005;77:170-7. PubMed
  10. Min, D. I., Ku, Y. M., Geraets, D. R., and Lee, H. Effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of quinidine in healthy volunteers. J Clin Pharmacol 1996;36(5):469-476. PubMed
  11. Jia Y, Liu J, Xu J. Influence of grapefruit juice on pharmacokinetics of triptolide in rats grapefruit juice on the effects of triptolide. Xenobiotica. 2017 Apr 16:1-5. PubMed
  12. Guideline on the investigation of drug interactions. CPMP/EWP/560/95/Rev. 1 Corr. 2. European Medicines Agency, 2015. Available at: https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-investigation-drug-interactions-revision-1_en.pdf (As
  13. Piscitelli J, Nikanjam M, Capparelli EV, et al. Fexofenadine Plasma Concentrations to Estimate Systemic Exposure in Healthy Adults Using a Limited Sampling Strategy with a Population Pharmacokinetic Approach. Ther Drug Monit 2023;45(4):539-545. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Grapefruit Also Interacts With Other Medications

Grapefruit has 775 major, 151 moderate, 63 minor known drug interactions in our database — the Trandolapril, Verapamil one above is among them. If you take anything else, check it against the full list below.

Major 775 Moderate 151 Minor 63 No known interaction 1,841 (incl. Trandolapril, Verapamil)
Taking anything else?

Check Another of Your Medications Against Grapefruit

Covers the 2,830 medications we’ve checked against Grapefruit. Pick one to open its full report.

From our Q&A

Questions About Grapefruit or Trandolapril, Verapamil

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Grapefruit or Trandolapril, Verapamil, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Trandolapril, Verapamil

This page covers Grapefruit only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Trandolapril, Verapamil page lists 304 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Asarabacca (major) and Beer (major).

By severity: 11 major · 250 moderate · 43 minor.

From our pharmacist’s overview on the Trandolapril, Verapamil page

“This is one of the supplement lists I would want a patient to read closely, not skim. Tarka combines trandolapril and verapamil to lower blood pressure, and most of these interactions pull on that same lever, either dropping pressure further than intended or working against the medicine altogether.”

Reviewed by 2 · Jul 18, 2026

Open the Trandolapril, Verapamil interaction page

One more smart check

Taking Grapefruit as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,144 real supplement products containing Grapefruit, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Grapefruit. Your product may carry other ingredients that interact with Trandolapril, Verapamil too, on top of Grapefruit — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Grapefruit and Trandolapril, Verapamil Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Grapefruit
Top 10%

#110 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Trandolapril, Verapamil
Top half

#731 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Grapefruit

What is Grapefruit?

Grapefruit
  • Source of vitamin C
  • Digestive complaints
  • Antimicrobial (seed extract)
  • Weight management
  • Skin and cosmetic uses

Grapefruit is a nutritious citrus fruit rich in vitamin C and other nutrients, and it is generally safe to eat. However, grapefruit is famous for serious interactions with many prescription medicines, so anyone taking medication should check with a pharmacist or doctor before consuming it regularly.

Read the full Grapefruit monograph & all interactions
Keep checking

Other Drugs & Grapefruit

Browse every other medication we’ve checked against Grapefruit — both the ones with a known interaction and the ones without. Select any drug for the full detail.

775Major
151Moderate
63Minor
1,840No known interaction
775 Major 151 Moderate 63 Minor 1,840 No interaction
Major

775 interactions

Showing 60 of 775 major interactions — see all 775 on the Grapefruit page.

Moderate

151 interactions

Showing 60 of 151 moderate interactions — see all 151 on the Grapefruit page.

Minor

63 interactions

Showing 60 of 63 minor interactions — see all 63 on the Grapefruit page.

No interaction 1,840 drugs checked — show the list

We also checked Grapefruit against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,840 medications checked with no known interaction — see the full Grapefruit list.

See the full Grapefruit interactions page
See every supplement checked against Trandolapril, Verapamil, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

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Taking Grapefruit and Trandolapril, Verapamil Together: Common Questions

Can you take Grapefruit with Trandolapril, Verapamil?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 4 interactions listed for Grapefruit and Trandolapril, Verapamil?
Trandolapril, Verapamil belongs to more than one drug category, and Grapefruit interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Grapefruit and Trandolapril, Verapamil interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.