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Drug Interactions between fosphenytoin and Tri-Sprintec

This report displays the potential drug interactions for the following 2 drugs:

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Major

ethinyl estradiol fosphenytoin

Applies to: Tri-Sprintec (ethinyl estradiol / norgestimate) and fosphenytoin

ADDITIONAL CONTRACEPTION RECOMMENDED: Coadministration with certain anticonvulsants such as carbamazepine, eslicarbazepine, oxcarbazepine, phenobarbital, phenytoin, and primidone may reduce the efficacy of contraceptive hormones. There have been numerous case reports of menstrual abnormalities (e.g., breakthrough bleeding, amenorrhea, irregular menses) and unintended pregnancy occurring in women who received oral contraceptives with anticonvulsants. The incidence of menstrual irregularities associated with this combination has been reported to be as high as 65% in some studies. The interaction stems from accelerated clearance of contraceptive hormones as well as decreased plasma concentrations of unbound (active) hormones due to induction of hepatic CYP450 enzymatic activity and hormone-binding globulin capacity by some anticonvulsants. Pharmacokinetic studies have found that normally recommended dosages of carbamazepine, oxcarbazepine, phenobarbital, and phenytoin can individually reduce ethinyl estradiol and levonorgestrel systemic exposure (AUC) by a third or more. Eslicarbazepine acetate 1200 mg once daily for 2 weeks decreased the mean AUC of single-dose ethinyl estradiol (30 mcg) and levonorgestrel (150 mcg) by 32% and 24%, respectively, while eslicarbazepine 800 mg once daily decreased the mean AUCs by 25% and 11%, respectively.

MANAGEMENT: Women using hormonal contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant therapy with enzyme-inducing anticonvulsants. Alternative or additional methods of birth control should be used during and for at least two weeks after short-term and 4 weeks after long-term (greater than 4 weeks) anticonvulsant therapy. If a combination oral contraceptive pill is used, a regimen containing at least 50 mcg of ethinyl estradiol per day or equivalent should be considered. Although breakthrough bleeding is not necessarily indicative of low ethinyl estradiol serum levels or increased risk of ovulation, some clinicians suggest that women who experience breakthrough bleeding during enzyme-inducing therapy may be prescribed an increased dose of ethinyl estradiol above 50 mcg daily by combining more than one formulation of contraceptive pill if necessary. For emergency contraception in patients who have used an hepatic enzyme inducer in the past 4 weeks, a non-hormonal emergency contraceptive (e.g., copper intrauterine device) is considered preferable. If this is not possible, some authorities recommend that the usual dose of levonorgestrel (1.5 mg) should be doubled to 3 mg and taken as a single dose as soon as possible (within 72 hours of unprotected sexual intercourse). However, there are no data on efficacy, compliance, or side effects of this regimen. For women with the etonogestrel subdermal implant, the addition of a barrier method is recommended during concomitant use and for 28 days after discontinuation of hepatic enzyme inducing drugs. It is recommended to remove the implant and to prescribe a nonhormonal method in women who require long-term treatment with hepatic enzyme inducing drugs. No precautions or recommendations are available for women using hormone-releasing intrauterine systems, but a significant interaction with these systems is thought to be unlikely due to their local action. Injectable progestin-only contraceptives are also thought to be unaffected by enzyme-inducing drugs.

References

  1. Crawford P, Chadwick DJ, Martin C, et al. (1990) "The interaction of phenytoin and carbamazepine with combined oral contraceptive steroids." Br J Clin Pharmacol, 30, p. 892-6
  2. Odlind V, Olsson SE (1986) "Enhanced metabolism of levonorgestrel during phenytoin treatment in a woman with norplant implants." Contraception, 33, p. 257-61
  3. Baciewicz AM (1985) "Oral contraceptive drug interactions." Ther Drug Monit, 7, p. 26-35
  4. Back DJ, Bates M, Bowden A, et al. (1980) "The interaction of phenobarbital and other anticonvulsants with oral contraceptive steroid therapy." Contraception, 22, p. 495-503
  5. Dossetor J (1975) "Drug interactions with oral contraceptives." Br Med J, 4, p. 467-8
  6. Furlan AJ, Rothner AD (1974) "Anti-epileptic drugs and failure of oral contraceptives." Lancet, 1, p. 1113
  7. Coulam CB, Annegers JF (1979) "Do anticonvulsants reduce the efficacy of oral contraceptives?" Epilepsia, 20, p. 519-26
  8. Szoka PR, Edgren RA (1988) "Drug interactions with oral contraceptives: compilation and analysis of an adverse experience report database." Fertil Steril, 49, s31-8
  9. Mattson RH, Cramer JA, Darney PD, Naftolin F (1986) "Use of oral contraceptives by women with epilepsy." JAMA, 256, p. 238-40
  10. Laengner H, Detering K (1974) "Letter: Anti-epileptic drugs and failure of oral contraceptives." Lancet, 2, p. 600
  11. Janz D, Schmidt D (1974) "Letter: Anti-epileptic drugs and failure of oral contraceptives." Lancet, 1, p. 1113
  12. Back DJ, Orme ML (1990) "Pharmacokinetic drug interactions with oral contraceptives." Clin Pharmacokinet, 18, p. 472-84
  13. Diamond MP, Greene JW, Thompson JM, VanHooydonk JE, Wentz AC (1985) "Interaction of anticonvulsants and oral contraceptives in epileptic adolescents." Contraception, 31, p. 623-32
  14. D'Arcy PF (1986) "Drug interactions with oral contraceptives." Drug Intell Clin Pharm, 20, p. 353-62
  15. Rapport DJ, Calabrese JR (1989) "Interactions between carbamazepine and birth control pills." Psychosomatics, 30, p. 462-4
  16. Notelovitz M, Tjapkes J, Ware M (1981) "Interaction between estrogen and dilantin in a menopausal woman." N Engl J Med, 304, p. 788-9
  17. Saano V, Glue P, Banfield CR (1995) "Effects of felbamate on the pharmacokinetics of a low-dose combination oral contraceptive." Clin Pharmacol Ther, 58, p. 523-31
  18. Back DJ, Breckenridge AM, Crawford FE, MacIver M, Orne ML, Rowe PH (1981) "Interindividual variation and drug interactions with hormonal steroid contraceptives." Drugs, 21, p. 46-61
  19. Shane-McWorter L, Cerveny JD, MacFarlane LL, Osborn C (1998) "Enhanced metabolism of levonorgestrel during phenobarbital treatment and resultant pregnancy." Pharmacotherapy, 18, p. 1360-4
  20. Haukkamaa M (1986) "Contraception by Norplant subdermal capsules is not reliable in epileptic patients on anticonvulsant treatment." Contraception, 33, p. 559-65
  21. Fattore C, Cipolla G, Gatti G, Limido GL, Sturm Y, Bernasconi C, Perucca E (1999) "Induction of ethinylestradiol and levonorgestrel metabolism by oxcarbazepine in healthy women." Epilepsia, 40, p. 783-7
  22. Klosterskov Jensen P, Saano V, Haring P, Svenstrup B, Menge GP (1992) "Possible interaction between oxcarbazepine and an oral contraceptive." Epilepsia, 33, p. 1149-52
  23. (2001) "Product Information. Trileptal (oxcarbazepine)." Novartis Pharmaceuticals
  24. (2001) "Product Information. Norplant System (levonorgestrel)." Wyeth-Ayerst Laboratories
  25. Wilbur K, Ensom MHH (2000) "Pharmacokinetic drug interactions between oral contraceptives and second-generation anticonvulsants." Clin Pharmacokinet, 38, p. 355-65
  26. Kenyon IE (1972) "Unplanned pregnancy in an epileptic. (Letter to the editor)." Br Med J, 1, p. 686
  27. (2005) "FFPRHC Guidance (April 2005). Drug interactions with hormonal contraception." J Fam Plann Reprod Health Care, 31, p. 139-51
  28. Back DJ, Grimmer SF, Orme ML, Proudlove D, Mann RD, Breckenridge AM (1988) "Evaluation of Committee on Safety of Medicines yellow card reports on oral contraceptive-drug interactions with anticonvulsants and antibiotics." Br J Clin Pharmacol, 25, p. 527-32
  29. Schindlbeck C, Janni W, Friese K (2006) "Failure of Implanon contraception in a patient taking carbamazepin for epilepsia." Arch Gynecol Obstet, 273, p. 255-6
  30. O'Brien MD, Guillebaud J (2006) "Contraception for women with epilepsy." Epilepsia, 47, p. 1419-22
  31. (2012) "Product Information. Fycompa (perampanel)." Eisai Inc
  32. (2013) "Product Information. Aptiom (eslicarbazepine)." Sunovion Pharmaceuticals Inc
  33. Faculty of Sexual & Reproductive Healthcare (2016) "FSRH Clinical Guidance: Drug Interactions with Hormonal Contraception. file:///C:/Users/df033684/Downloads/ceuguidancedruginteractionshormonal.pdf"
View all 33 references

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Major

norgestimate fosphenytoin

Applies to: Tri-Sprintec (ethinyl estradiol / norgestimate) and fosphenytoin

ADDITIONAL CONTRACEPTION RECOMMENDED: Coadministration with certain anticonvulsants such as carbamazepine, eslicarbazepine, oxcarbazepine, phenobarbital, phenytoin, and primidone may reduce the efficacy of contraceptive hormones. There have been numerous case reports of menstrual abnormalities (e.g., breakthrough bleeding, amenorrhea, irregular menses) and unintended pregnancy occurring in women who received oral contraceptives with anticonvulsants. The incidence of menstrual irregularities associated with this combination has been reported to be as high as 65% in some studies. The interaction stems from accelerated clearance of contraceptive hormones as well as decreased plasma concentrations of unbound (active) hormones due to induction of hepatic CYP450 enzymatic activity and hormone-binding globulin capacity by some anticonvulsants. Pharmacokinetic studies have found that normally recommended dosages of carbamazepine, oxcarbazepine, phenobarbital, and phenytoin can individually reduce ethinyl estradiol and levonorgestrel systemic exposure (AUC) by a third or more. Eslicarbazepine acetate 1200 mg once daily for 2 weeks decreased the mean AUC of single-dose ethinyl estradiol (30 mcg) and levonorgestrel (150 mcg) by 32% and 24%, respectively, while eslicarbazepine 800 mg once daily decreased the mean AUCs by 25% and 11%, respectively.

MANAGEMENT: Women using hormonal contraceptives should be advised of the risk of breakthrough bleeding and unintended pregnancy during concomitant therapy with enzyme-inducing anticonvulsants. Alternative or additional methods of birth control should be used during and for at least two weeks after short-term and 4 weeks after long-term (greater than 4 weeks) anticonvulsant therapy. If a combination oral contraceptive pill is used, a regimen containing at least 50 mcg of ethinyl estradiol per day or equivalent should be considered. Although breakthrough bleeding is not necessarily indicative of low ethinyl estradiol serum levels or increased risk of ovulation, some clinicians suggest that women who experience breakthrough bleeding during enzyme-inducing therapy may be prescribed an increased dose of ethinyl estradiol above 50 mcg daily by combining more than one formulation of contraceptive pill if necessary. For emergency contraception in patients who have used an hepatic enzyme inducer in the past 4 weeks, a non-hormonal emergency contraceptive (e.g., copper intrauterine device) is considered preferable. If this is not possible, some authorities recommend that the usual dose of levonorgestrel (1.5 mg) should be doubled to 3 mg and taken as a single dose as soon as possible (within 72 hours of unprotected sexual intercourse). However, there are no data on efficacy, compliance, or side effects of this regimen. For women with the etonogestrel subdermal implant, the addition of a barrier method is recommended during concomitant use and for 28 days after discontinuation of hepatic enzyme inducing drugs. It is recommended to remove the implant and to prescribe a nonhormonal method in women who require long-term treatment with hepatic enzyme inducing drugs. No precautions or recommendations are available for women using hormone-releasing intrauterine systems, but a significant interaction with these systems is thought to be unlikely due to their local action. Injectable progestin-only contraceptives are also thought to be unaffected by enzyme-inducing drugs.

References

  1. Crawford P, Chadwick DJ, Martin C, et al. (1990) "The interaction of phenytoin and carbamazepine with combined oral contraceptive steroids." Br J Clin Pharmacol, 30, p. 892-6
  2. Odlind V, Olsson SE (1986) "Enhanced metabolism of levonorgestrel during phenytoin treatment in a woman with norplant implants." Contraception, 33, p. 257-61
  3. Baciewicz AM (1985) "Oral contraceptive drug interactions." Ther Drug Monit, 7, p. 26-35
  4. Back DJ, Bates M, Bowden A, et al. (1980) "The interaction of phenobarbital and other anticonvulsants with oral contraceptive steroid therapy." Contraception, 22, p. 495-503
  5. Dossetor J (1975) "Drug interactions with oral contraceptives." Br Med J, 4, p. 467-8
  6. Furlan AJ, Rothner AD (1974) "Anti-epileptic drugs and failure of oral contraceptives." Lancet, 1, p. 1113
  7. Coulam CB, Annegers JF (1979) "Do anticonvulsants reduce the efficacy of oral contraceptives?" Epilepsia, 20, p. 519-26
  8. Szoka PR, Edgren RA (1988) "Drug interactions with oral contraceptives: compilation and analysis of an adverse experience report database." Fertil Steril, 49, s31-8
  9. Mattson RH, Cramer JA, Darney PD, Naftolin F (1986) "Use of oral contraceptives by women with epilepsy." JAMA, 256, p. 238-40
  10. Laengner H, Detering K (1974) "Letter: Anti-epileptic drugs and failure of oral contraceptives." Lancet, 2, p. 600
  11. Janz D, Schmidt D (1974) "Letter: Anti-epileptic drugs and failure of oral contraceptives." Lancet, 1, p. 1113
  12. Back DJ, Orme ML (1990) "Pharmacokinetic drug interactions with oral contraceptives." Clin Pharmacokinet, 18, p. 472-84
  13. Diamond MP, Greene JW, Thompson JM, VanHooydonk JE, Wentz AC (1985) "Interaction of anticonvulsants and oral contraceptives in epileptic adolescents." Contraception, 31, p. 623-32
  14. D'Arcy PF (1986) "Drug interactions with oral contraceptives." Drug Intell Clin Pharm, 20, p. 353-62
  15. Rapport DJ, Calabrese JR (1989) "Interactions between carbamazepine and birth control pills." Psychosomatics, 30, p. 462-4
  16. Notelovitz M, Tjapkes J, Ware M (1981) "Interaction between estrogen and dilantin in a menopausal woman." N Engl J Med, 304, p. 788-9
  17. Saano V, Glue P, Banfield CR (1995) "Effects of felbamate on the pharmacokinetics of a low-dose combination oral contraceptive." Clin Pharmacol Ther, 58, p. 523-31
  18. Back DJ, Breckenridge AM, Crawford FE, MacIver M, Orne ML, Rowe PH (1981) "Interindividual variation and drug interactions with hormonal steroid contraceptives." Drugs, 21, p. 46-61
  19. Shane-McWorter L, Cerveny JD, MacFarlane LL, Osborn C (1998) "Enhanced metabolism of levonorgestrel during phenobarbital treatment and resultant pregnancy." Pharmacotherapy, 18, p. 1360-4
  20. Haukkamaa M (1986) "Contraception by Norplant subdermal capsules is not reliable in epileptic patients on anticonvulsant treatment." Contraception, 33, p. 559-65
  21. Fattore C, Cipolla G, Gatti G, Limido GL, Sturm Y, Bernasconi C, Perucca E (1999) "Induction of ethinylestradiol and levonorgestrel metabolism by oxcarbazepine in healthy women." Epilepsia, 40, p. 783-7
  22. Klosterskov Jensen P, Saano V, Haring P, Svenstrup B, Menge GP (1992) "Possible interaction between oxcarbazepine and an oral contraceptive." Epilepsia, 33, p. 1149-52
  23. (2001) "Product Information. Trileptal (oxcarbazepine)." Novartis Pharmaceuticals
  24. (2001) "Product Information. Norplant System (levonorgestrel)." Wyeth-Ayerst Laboratories
  25. Wilbur K, Ensom MHH (2000) "Pharmacokinetic drug interactions between oral contraceptives and second-generation anticonvulsants." Clin Pharmacokinet, 38, p. 355-65
  26. Kenyon IE (1972) "Unplanned pregnancy in an epileptic. (Letter to the editor)." Br Med J, 1, p. 686
  27. (2005) "FFPRHC Guidance (April 2005). Drug interactions with hormonal contraception." J Fam Plann Reprod Health Care, 31, p. 139-51
  28. Back DJ, Grimmer SF, Orme ML, Proudlove D, Mann RD, Breckenridge AM (1988) "Evaluation of Committee on Safety of Medicines yellow card reports on oral contraceptive-drug interactions with anticonvulsants and antibiotics." Br J Clin Pharmacol, 25, p. 527-32
  29. Schindlbeck C, Janni W, Friese K (2006) "Failure of Implanon contraception in a patient taking carbamazepin for epilepsia." Arch Gynecol Obstet, 273, p. 255-6
  30. O'Brien MD, Guillebaud J (2006) "Contraception for women with epilepsy." Epilepsia, 47, p. 1419-22
  31. (2012) "Product Information. Fycompa (perampanel)." Eisai Inc
  32. (2013) "Product Information. Aptiom (eslicarbazepine)." Sunovion Pharmaceuticals Inc
  33. Faculty of Sexual & Reproductive Healthcare (2016) "FSRH Clinical Guidance: Drug Interactions with Hormonal Contraception. file:///C:/Users/df033684/Downloads/ceuguidancedruginteractionshormonal.pdf"
View all 33 references

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Drug and food interactions

Moderate

norgestimate food

Applies to: Tri-Sprintec (ethinyl estradiol / norgestimate)

MONITOR: Grapefruit juice may increase the plasma concentrations of orally administered drugs that are substrates of the CYP450 3A4 isoenzyme. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Because grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4, the magnitude of interaction is greatest for those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability). In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: Patients who regularly consume grapefruit or grapefruit juice should be monitored for adverse effects and altered plasma concentrations of drugs that undergo significant presystemic metabolism by CYP450 3A4. Grapefruit and grapefruit juice should be avoided if an interaction is suspected. Orange juice is not expected to interact with these drugs.

References

  1. Edgar B, Bailey D, Bergstrand R, et al. (1992) "Acute effects of drinking grapefruit juice on the pharmacokinetics and dynamics on felodipine and its potential clinical relevance." Eur J Clin Pharmacol, 42, p. 313-7
  2. Jonkman JH, Sollie FA, Sauter R, Steinijans VW (1991) "The influence of caffeine on the steady-state pharmacokinetics of theophylline." Clin Pharmacol Ther, 49, p. 248-55
  3. Bailey DG, Arnold JM, Munoz C, Spence JD (1993) "Grapefruit juice--felodipine interaction: mechanism, predictability, and effect of naringin." Clin Pharmacol Ther, 53, p. 637-42
  4. Bailey DG, Arnold JMO, Spence JD (1994) "Grapefruit juice and drugs - how significant is the interaction." Clin Pharmacokinet, 26, p. 91-8
  5. Sigusch H, Hippius M, Henschel L, Kaufmann K, Hoffmann A (1994) "Influence of grapefruit juice on the pharmacokinetics of a slow release nifedipine formulation." Pharmazie, 49, p. 522-4
  6. Bailey DG, Arnold JM, Strong HA, Munoz C, Spence JD (1993) "Effect of grapefruit juice and naringin on nisoldipine pharmacokinetics." Clin Pharmacol Ther, 54, p. 589-94
  7. Yamreudeewong W, Henann NE, Fazio A, Lower DL, Cassidy TG (1995) "Drug-food interactions in clinical practice." J Fam Pract, 40, p. 376-84
  8. (1995) "Grapefruit juice interactions with drugs." Med Lett Drugs Ther, 37, p. 73-4
  9. Hukkinen SK, Varhe A, Olkkola KT, Neuvonen PJ (1995) "Plasma concentrations of triazolam are increased by concomitant ingestion of grapefruit juice." Clin Pharmacol Ther, 58, p. 127-31
  10. Min DI, Ku YM, Geraets DR, Lee HC (1996) "Effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of quinidine in healthy volunteers." J Clin Pharmacol, 36, p. 469-76
  11. Majeed A, Kareem A (1996) "Effect of grapefruit juice on cyclosporine pharmacokinetics." Pediatr Nephrol, 10, p. 395
  12. Clifford CP, Adams DA, Murray S, Taylor GW, Wilkins MR, Boobis AR, Davies DS (1996) "Pharmacokinetic and cardiac effects of terfenadine after inhibition of its metabolism by grapefruit juice." Br J Clin Pharmacol, 42, p662
  13. Josefsson M, Zackrisson AL, Ahlner J (1996) "Effect of grapefruit juice on the pharmacokinetics of amlodipine in healthy volunteers." Eur J Clin Pharmacol, 51, p. 189-93
  14. Kantola T, Kivisto KT, Neuvonen PJ (1998) "Grapefruit juice greatly increases serum concentrations of lovastatin and lovastatin acid." Clin Pharmacol Ther, 63, p. 397-402
  15. Ozdemir M, Aktan Y, Boydag BS, Cingi MI, Musmul A (1998) "Interaction between grapefruit juice and diazepam in humans." Eur J Drug Metab Pharmacokinet, 23, p. 55-9
  16. Bailey DG, Malcolm J, Arnold O, Spence JD (1998) "Grapefruit juice-drug interactions." Br J Clin Pharmacol, 46, p. 101-10
  17. Bailey DG, Kreeft JH, Munoz C, Freeman DJ, Bend JR (1998) "Grapefruit juice felodipine interaction: Effect of naringin and 6',7'-dihydroxybergamottin in humans." Clin Pharmacol Ther, 64, p. 248-56
  18. Garg SK, Kumar N, Bhargava VK, Prabhakar SK (1998) "Effect of grapefruit juice on carbamazepine bioavailability in patients with epilepsy." Clin Pharmacol Ther, 64, p. 286-8
  19. Lilja JJ, Kivisto KT, Neuvonen PJ (1998) "Grapefruit juice-simvastatin interaction: Effect on serum concentrations of simvastatin, simvastatin acid, and HMG-CoA reductase inhibitors." Clin Pharmacol Ther, 64, p. 477-83
  20. Fuhr U, Maier-Bruggemann A, Blume H, et al. (1998) "Grapefruit juice increases oral nimodipine bioavailability." Int J Clin Pharmacol Ther, 36, p. 126-32
  21. Lilja JJ, Kivisto KT, Neuvonen PJ (1999) "Grapefruit juice increases serum concentrations of atorvastatin and has no effect on pravastatin." Clin Pharmacol Ther, 66, p. 118-27
  22. Eagling VA, Profit L, Back DJ (1999) "Inhibition of the CYP3A4-mediated metabolism and P-glycoprotein-mediated transport of the HIV-I protease inhibitor saquinavir by grapefruit juice components." Br J Clin Pharmacol, 48, p. 543-52
  23. Damkier P, Hansen LL, Brosen K (1999) "Effect of diclofenac, disulfiram, itraconazole, grapefruit juice and erythromycin on the pharmacokinetics of quinidine." Br J Clin Pharmacol, 48, p. 829-38
  24. Lee AJ, Chan WK, Harralson AF, Buffum J, Bui BCC (1999) "The effects of grapefruit juice on sertraline metabolism: An in vitro and in vivo study." Clin Ther, 21, p. 1890-9
  25. Dresser GK, Spence JD, Bailey DG (2000) "Pharmacokinetic-pharmacodynamic consequences and clinical relevance of cytochrome P450 3A4 inhibition." Clin Pharmacokinet, 38, p. 41-57
  26. Gunston GD, Mehta U (2000) "Potentially serious drug interactions with grapefruit juice." S Afr Med J, 90, p. 41
  27. Takanaga H, Ohnishi A, Maatsuo H, et al. (2000) "Pharmacokinetic analysis of felodipine-grapefruit juice interaction based on an irreversible enzyme inhibition model." Br J Clin Pharmacol, 49, p. 49-58
  28. Libersa CC, Brique SA, Motte KB, et al. (2000) "Dramatic inhibition of amiodarone metabolism induced by grapefruit juice." Br J Clin Pharmacol, 49, p. 373-8
  29. Bailey DG, Dresser GR, Kreeft JH, Munoz C, Freeman DJ, Bend JR (2000) "Grapefruit-felodipine interaction: Effect of unprocessed fruit and probable active ingredients." Clin Pharmacol Ther, 68, p. 468-77
  30. Zaidenstein R, Soback S, Gips M, Avni B, Dishi V, Weissgarten Y, Golik A, Scapa E (2001) "Effect of grapefruit juice on the pharmacokinetics of losartan and its active metabolite E3174 in healthy volunteers." Ther Drug Monit, 23, p. 369-73
  31. Sato J, Nakata H, Owada E, Kikuta T, Umetsu M, Ito K (1993) "Influence of usual intake of dietary caffeine on single-dose kinetics of theophylline in healthy human subjects." Eur J Clin Pharmacol, 44, p. 295-8
  32. Flanagan D (2005) "Understanding the grapefruit-drug interaction." Gen Dent, 53, 282-5; quiz 286
View all 32 references

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Minor

ethinyl estradiol food

Applies to: Tri-Sprintec (ethinyl estradiol / norgestimate)

Coadministration with grapefruit juice may increase the bioavailability of oral estrogens. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In a small, randomized, crossover study, the administration of ethinyl estradiol with grapefruit juice (compared to herbal tea) increased peak plasma drug concentration (Cmax) by 37% and area under the concentration-time curve (AUC) by 28%. Based on these findings, grapefruit juice is unlikely to affect the overall safety profile of ethinyl estradiol. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability. Also, the effect on other estrogens has not been studied.

References

  1. Weber A, Jager R, Borner A, et al. (1996) "Can grapefruit juice influence ethinyl estradiol bioavailability?" Contraception, 53, p. 41-7
  2. Schubert W, Eriksson U, Edgar B, Cullberg G, Hedner T (1995) "Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17B-estradiol." Eur J Drug Metab Pharmacokinet, 20, p. 219-24

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Minor

ethinyl estradiol food

Applies to: Tri-Sprintec (ethinyl estradiol / norgestimate)

The central nervous system effects and blood levels of ethanol may be increased in patients taking oral contraceptives, although data are lacking and reports are contradictory. The mechanism may be due to enzyme inhibition. Consider counseling women about this interaction which is unpredictable.

References

  1. Hobbes J, Boutagy J, Shenfield GM (1985) "Interactions between ethanol and oral contraceptive steroids." Clin Pharmacol Ther, 38, p. 371-80

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Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

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Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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