Drug Interaction Report
8 potential interactions and/or warnings found for the following 2 drugs:
- Lo/Ovral (ethinyl estradiol / norgestrel)
- MY-E (erythromycin)
Interactions between your drugs
erythromycin ethinyl estradiol
Applies to: MY-E (erythromycin), Lo/Ovral (ethinyl estradiol / norgestrel)
MONITOR: Coadministration of chloramphenicol, dalfopristin, erythromycin, or fusidic acid may increase the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme, by reducing their clearance, as these antibiotics are moderate inhibitors of this isoenzyme. Many estrogen and progestin type medications are CYP450 3A4 substrates. These medications are used for a variety of purposes including, but not limited to, contraception, acne treatment, hormone replacement therapy, and appetite stimulation. When telithromycin, a potent CYP450 3A4 inhibitor, was co-administered with oral contraceptives containing ethinyl estradiol and levonorgestrel, studies showed that the systemic concentration (AUC) of ethinyl estradiol did not change and the AUC of levonorgestrel increased by 50%. The study showed that telithromycin did not interfere with the anti-ovulatory effect of oral contraceptives containing ethinyl estradiol and levonorgestrel.
MANAGEMENT: Caution is advised if chloramphenicol, dalfopristin, erythromycin, or fusidic acid must be used concurrently with medications that undergo metabolism by CYP450 3A4. Patients should be monitored for increased adverse effects from the hormonal treatment if it must be co-administered with one of these antibiotics. Some serious side effects associated with hormonal treatment include, but are not limited to, cardiovascular disease (e.g., venous thromboembolism, myocardial infarction, and stroke); breast cancer; loss of bone mineral density; changes in mood; cholestatic jaundice; and dementia. Some of these side effects are affected by other factors such as medication dosage, concurrent medications, age, smoking status, and other disease states. If concurrent therapy with any of these antibiotics is necessary, please refer to the product labeling for more specific adverse effects to monitor for and counsel the patient and/or the patient's caregiver on the risks and benefits of concurrent therapy.
MONITOR: Estrogenic steroids, but not progestins, undergo enterohepatic cycling. It is possible that antimicrobials may interfere with the enterohepatic recirculation of estrogens by decreasing bacteria in the gastrointestinal tract that are responsible for regenerating parent estrogen molecules following first-pass metabolism. Most of the research regarding this possible interaction has been done with oral contraceptives; however, all estrogens appear to undergo enterohepatic recirculation so theoretically this interaction is a possibility with estrogen containing medications that are being used for alternative purposes. The risk appears to be small, and supportive data are primarily limited to anecdotal evidence from case reports and findings from uncontrolled or poorly controlled studies. Most antimicrobials, except for enzyme inducing medications like the rifamycins and possibly griseofulvin, have not been shown to significantly increase the clearance of estrogens present in combined hormonal contraceptives. It is possible that a small number of women may be more sensitive to the effects of antimicrobials on estrogen disposition in vivo, but risk factors or genetic predispositions have yet to be identified.
MANAGEMENT: If a person is using estrogen for a purpose other than contraception, it is important to note that there is a theoretical possibility of lower levels of systemic estrogen available during treatment with an antibiotic due to interference with enterohepatic cycling. These patients should be counseled to report any changes in efficacy of the hormonal product to their healthcare provider. In the case of contraception specifically, the Centers for Disease Control and Prevention do not consider most broad-spectrum antibiotics to significantly interfere with the effectiveness of combined hormonal contraception. However, the manufacturers of certain combined hormonal contraceptives and/or certain antibiotics do recommend using a back-up method of birth control for varying amounts of time; therefore, consulting the product labeling of each medication involved is advised. Some illnesses, as well as some antibiotics, may cause nausea, vomiting, and/or diarrhea. If the patient vomits within a few hours of taking an oral contraceptive pill, consult the product labeling for instructions on what to do in the event of a missed pill. Some authorities recommend a back-up method of birth control if an individual has persistent vomiting or diarrhea.
References
- (2022) "Product Information. Ery-Tab (erythromycin)." Abbott Pharmaceutical
- (2001) "Product Information. Premarin (conjugated estrogens)." Wyeth-Ayerst Laboratories
- (2001) "Product Information. Ortho-Est (estropipate)." Ortho McNeil Pharmaceutical
- (2001) "Product Information. Yasmin (drospirenone-ethinyl estradiol)." Berlex Laboratories
- (2005) "Product Information. Angeliq (drospirenone-estradiol)." Berlex Laboratories
- Faculty of Sexual & Reproductive Healthcare (2016) "FSRH Clinical Guidance: Drug Interactions with Hormonal Contraception. file:///C:/Users/df033684/Downloads/ceuguidancedruginteractionshormonal.pdf"
- Curtis KM, Tepper NK, Jatlaoui TC, et al. (2023) U.S. medical eligibility criteria (US MEC) for contraceptive use. https://www.cdc.gov/reproductivehealth/contraception/mmwr/mec/index.html
- Faculty of Sexual & Reproductive Healthcare (2023) FSRH CEU response to study: analysis of reports of unintended pregnancies associated with the combined use of non-enzyme inducing antibiotics and hormonal contraceptives - february 2021 https://www.fsrh.org/standards-and-guidance/documents/fsrh-ceu-respo
- Faculty of Sexual & Reproductive Healthcare (2023) FSRH CEU guidance: drug interactions with hormonal contraception (may 2022) https://www.fsrh.org/standards-and-guidance/documents/ceu-clinical-guidance-drug-interactions-with-hormonal/
- Simmons KB, Haddad LB, Nanda K, Curtis KM (2018) "Drug interactions between non-rifamycin antibiotics and hormonal contraception: a systemic review." Am J Obstet Gynecol, 218, 88-97.e14
- Zhanel GG, Siemens S, Slayter K, Mandell L (1999) "Antibiotic and oral contraceptive drug interactions: is there a need for concern?" Can J Infect Dis, 10, p. 429-33
- Black A, Francoeur D, Rowe T, et al. (2023) SOGC clinical practice guidelines canadian contraception consensus https://www.jogc.com/article/S1701-2163(16)30260-2/pdf
- Allen K (2012) "Contraception - common issues and practical suggestions." Aust Fam Physician, 41, p. 770-2
- (2023) "Product Information. Erythromycin Lactobionate (erythromycin)." Nexus Pharmaceuticals Inc
- (2023) "Product Information. Erythromycin Ethylsuccinate (erythromycin)." Zydus Pharmaceuticals (USA) Inc
- (2018) "Product Information. Erythro-Base (erythromycin)." AA Pharma Inc
- (2019) "Product Information. Erythro-S (erythromycin)." AA Pharma Inc
- (2020) "Product Information. Erythrocin Lactobionate (erythromycin)." Amdipharm Limted
- (2023) "Product Information. ERYthromycin (Mayne Pharma) (ERYthromycin)." Mayne Pharma International Pty Ltd, 5.0
- (2023) "Product Information. Erythromycin (erythromycin)." Strides Pharma UK Ltd
- (2023) "Product Information. Erythromycin Lactobionate (erythromycin)." Advanz Pharma
- (2016) "Product Information. Chloramphenicol Sodium Succinate (chloramphenicol)." Fresenius Kabi USA, LLC
- (2022) "Product Information. Chloromycetin (chloramphenicol)." Pfizer Canada Inc
- (2015) "Product Information. Chloromycetin Succinate (chloramphenicol)." Link Medical Products Pty Ltd T/A Link Pharmaceuticals
- (2023) "Product Information. Chloramphenicol (chloramphenicol)." Eramol (UK) Ltd
erythromycin norgestrel
Applies to: MY-E (erythromycin), Lo/Ovral (ethinyl estradiol / norgestrel)
MONITOR: Coadministration of chloramphenicol, dalfopristin, erythromycin, or fusidic acid may increase the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme, by reducing their clearance, as these antibiotics are moderate inhibitors of this isoenzyme. Many estrogen and progestin type medications are CYP450 3A4 substrates. These medications are used for a variety of purposes including, but not limited to, contraception, acne treatment, hormone replacement therapy, and appetite stimulation. When telithromycin, a potent CYP450 3A4 inhibitor, was co-administered with oral contraceptives containing ethinyl estradiol and levonorgestrel, studies showed that the systemic concentration (AUC) of ethinyl estradiol did not change and the AUC of levonorgestrel increased by 50%. The study showed that telithromycin did not interfere with the anti-ovulatory effect of oral contraceptives containing ethinyl estradiol and levonorgestrel.
MANAGEMENT: Caution is advised if chloramphenicol, dalfopristin, erythromycin, or fusidic acid must be used concurrently with medications that undergo metabolism by CYP450 3A4. Patients should be monitored for increased adverse effects from the hormonal treatment if it must be co-administered with one of these antibiotics. Some serious side effects associated with hormonal treatment include, but are not limited to, cardiovascular disease (e.g., venous thromboembolism, myocardial infarction, and stroke); breast cancer; loss of bone mineral density; changes in mood; cholestatic jaundice; and dementia. Some of these side effects are affected by other factors such as medication dosage, concurrent medications, age, smoking status, and other disease states. If concurrent therapy with any of these antibiotics is necessary, please refer to the product labeling for more specific adverse effects to monitor for and counsel the patient and/or the patient's caregiver on the risks and benefits of concurrent therapy.
MONITOR: Estrogenic steroids, but not progestins, undergo enterohepatic cycling. It is possible that antimicrobials may interfere with the enterohepatic recirculation of estrogens by decreasing bacteria in the gastrointestinal tract that are responsible for regenerating parent estrogen molecules following first-pass metabolism. Most of the research regarding this possible interaction has been done with oral contraceptives; however, all estrogens appear to undergo enterohepatic recirculation so theoretically this interaction is a possibility with estrogen containing medications that are being used for alternative purposes. The risk appears to be small, and supportive data are primarily limited to anecdotal evidence from case reports and findings from uncontrolled or poorly controlled studies. Most antimicrobials, except for enzyme inducing medications like the rifamycins and possibly griseofulvin, have not been shown to significantly increase the clearance of estrogens present in combined hormonal contraceptives. It is possible that a small number of women may be more sensitive to the effects of antimicrobials on estrogen disposition in vivo, but risk factors or genetic predispositions have yet to be identified.
MANAGEMENT: If a person is using estrogen for a purpose other than contraception, it is important to note that there is a theoretical possibility of lower levels of systemic estrogen available during treatment with an antibiotic due to interference with enterohepatic cycling. These patients should be counseled to report any changes in efficacy of the hormonal product to their healthcare provider. In the case of contraception specifically, the Centers for Disease Control and Prevention do not consider most broad-spectrum antibiotics to significantly interfere with the effectiveness of combined hormonal contraception. However, the manufacturers of certain combined hormonal contraceptives and/or certain antibiotics do recommend using a back-up method of birth control for varying amounts of time; therefore, consulting the product labeling of each medication involved is advised. Some illnesses, as well as some antibiotics, may cause nausea, vomiting, and/or diarrhea. If the patient vomits within a few hours of taking an oral contraceptive pill, consult the product labeling for instructions on what to do in the event of a missed pill. Some authorities recommend a back-up method of birth control if an individual has persistent vomiting or diarrhea.
References
- (2022) "Product Information. Ery-Tab (erythromycin)." Abbott Pharmaceutical
- (2001) "Product Information. Premarin (conjugated estrogens)." Wyeth-Ayerst Laboratories
- (2001) "Product Information. Ortho-Est (estropipate)." Ortho McNeil Pharmaceutical
- (2001) "Product Information. Yasmin (drospirenone-ethinyl estradiol)." Berlex Laboratories
- (2005) "Product Information. Angeliq (drospirenone-estradiol)." Berlex Laboratories
- Faculty of Sexual & Reproductive Healthcare (2016) "FSRH Clinical Guidance: Drug Interactions with Hormonal Contraception. file:///C:/Users/df033684/Downloads/ceuguidancedruginteractionshormonal.pdf"
- Curtis KM, Tepper NK, Jatlaoui TC, et al. (2023) U.S. medical eligibility criteria (US MEC) for contraceptive use. https://www.cdc.gov/reproductivehealth/contraception/mmwr/mec/index.html
- Faculty of Sexual & Reproductive Healthcare (2023) FSRH CEU response to study: analysis of reports of unintended pregnancies associated with the combined use of non-enzyme inducing antibiotics and hormonal contraceptives - february 2021 https://www.fsrh.org/standards-and-guidance/documents/fsrh-ceu-respo
- Faculty of Sexual & Reproductive Healthcare (2023) FSRH CEU guidance: drug interactions with hormonal contraception (may 2022) https://www.fsrh.org/standards-and-guidance/documents/ceu-clinical-guidance-drug-interactions-with-hormonal/
- Simmons KB, Haddad LB, Nanda K, Curtis KM (2018) "Drug interactions between non-rifamycin antibiotics and hormonal contraception: a systemic review." Am J Obstet Gynecol, 218, 88-97.e14
- Zhanel GG, Siemens S, Slayter K, Mandell L (1999) "Antibiotic and oral contraceptive drug interactions: is there a need for concern?" Can J Infect Dis, 10, p. 429-33
- Black A, Francoeur D, Rowe T, et al. (2023) SOGC clinical practice guidelines canadian contraception consensus https://www.jogc.com/article/S1701-2163(16)30260-2/pdf
- Allen K (2012) "Contraception - common issues and practical suggestions." Aust Fam Physician, 41, p. 770-2
- (2023) "Product Information. Erythromycin Lactobionate (erythromycin)." Nexus Pharmaceuticals Inc
- (2023) "Product Information. Erythromycin Ethylsuccinate (erythromycin)." Zydus Pharmaceuticals (USA) Inc
- (2018) "Product Information. Erythro-Base (erythromycin)." AA Pharma Inc
- (2019) "Product Information. Erythro-S (erythromycin)." AA Pharma Inc
- (2020) "Product Information. Erythrocin Lactobionate (erythromycin)." Amdipharm Limted
- (2023) "Product Information. ERYthromycin (Mayne Pharma) (ERYthromycin)." Mayne Pharma International Pty Ltd, 5.0
- (2023) "Product Information. Erythromycin (erythromycin)." Strides Pharma UK Ltd
- (2023) "Product Information. Erythromycin Lactobionate (erythromycin)." Advanz Pharma
- (2016) "Product Information. Chloramphenicol Sodium Succinate (chloramphenicol)." Fresenius Kabi USA, LLC
- (2022) "Product Information. Chloromycetin (chloramphenicol)." Pfizer Canada Inc
- (2015) "Product Information. Chloromycetin Succinate (chloramphenicol)." Link Medical Products Pty Ltd T/A Link Pharmaceuticals
- (2023) "Product Information. Chloramphenicol (chloramphenicol)." Eramol (UK) Ltd
Drug and food interactions
erythromycin food
Applies to: MY-E (erythromycin)
ADJUST DOSING INTERVAL: Food may variably affect the bioavailability of different oral formulations and salt forms of erythromycin. The individual product package labeling should be consulted regarding the appropriate time of administration in relation to food ingestion. Grapefruit juice may increase the plasma concentrations of orally administered erythromycin. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In an open-label, crossover study consisting of six healthy subjects, the coadministration with double-strength grapefruit juice increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of a single dose of erythromycin (400 mg) by 52% and 49%, respectively, compared to water. The half-life was not affected. The clinical significance of this potential interaction is unknown.
MANAGEMENT: In general, optimal serum levels are achieved when erythromycin is taken in the fasting state, one-half to two hours before meals. However, some erythromycin products may be taken without regard to meals.
References
- Welling PG, Huang H, Hewitt PF, Lyons LL (1978) "Bioavailability of erythromycin stearate: influence of food and fluid volume." J Pharm Sci, 67, p. 764-6
- Welling PG, Elliott RL, Pitterle ME, et al. (1979) "Plasma levels following single and repeated doses of erythromycin estolate and erythromycin stearate." J Pharm Sci, 68, p. 150-5
- Welling PG (1977) "Influence of food and diet on gastrointestinal drug absorption: a review." J Pharmacokinet Biopharm, 5, p. 291-334
- Coyne TC, Shum S, Chun AH, Jeansonne L, Shirkey HC (1978) "Bioavailability of erythromycin ethylsuccinate in pediatric patients." J Clin Pharmacol, 18, p. 194-202
- Malmborg AS (1979) "Effect of food on absorption of erythromycin. A study of two derivatives, the stearate and the base." J Antimicrob Chemother, 5, p. 591-9
- Randinitis EJ, Sedman AJ, Welling PG, Kinkel AW (1989) "Effect of a high-fat meal on the bioavailability of a polymer-coated erythromycin particle tablet formulation." J Clin Pharmacol, 29, p. 79-84
- Kanazawa S, Ohkubo T, Sugawara K (2001) "The effects of grapefruit juice on the pharmacokinetics of erythromycin." Eur J Clin Pharmacol, 56, p. 799-803
norgestrel food
Applies to: Lo/Ovral (ethinyl estradiol / norgestrel)
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
- 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
- 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
- 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
- Bailey DG, Arnold JMO, Spence JD (1994) "Grapefruit juice and drugs - how significant is the interaction." Clin Pharmacokinet, 26, p. 91-8
- 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
- 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
- Yamreudeewong W, Henann NE, Fazio A, Lower DL, Cassidy TG (1995) "Drug-food interactions in clinical practice." J Fam Pract, 40, p. 376-84
- (1995) "Grapefruit juice interactions with drugs." Med Lett Drugs Ther, 37, p. 73-4
- 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
- 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
- Majeed A, Kareem A (1996) "Effect of grapefruit juice on cyclosporine pharmacokinetics." Pediatr Nephrol, 10, p. 395
- 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
- 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
- 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
- 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
- Bailey DG, Malcolm J, Arnold O, Spence JD (1998) "Grapefruit juice-drug interactions." Br J Clin Pharmacol, 46, p. 101-10
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- Dresser GK, Spence JD, Bailey DG (2000) "Pharmacokinetic-pharmacodynamic consequences and clinical relevance of cytochrome P450 3A4 inhibition." Clin Pharmacokinet, 38, p. 41-57
- Gunston GD, Mehta U (2000) "Potentially serious drug interactions with grapefruit juice." S Afr Med J, 90, p. 41
- 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
- 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
- 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
- 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
- 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
- Flanagan D (2005) "Understanding the grapefruit-drug interaction." Gen Dent, 53, 282-5; quiz 286
ethinyl estradiol food
Applies to: Lo/Ovral (ethinyl estradiol / norgestrel)
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
- Weber A, Jager R, Borner A, et al. (1996) "Can grapefruit juice influence ethinyl estradiol bioavailability?" Contraception, 53, p. 41-7
- 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
erythromycin food
Applies to: MY-E (erythromycin)
Ethanol, when combined with erythromycin, may delay absorption and therefore the clinical effects of the antibiotic. The mechanism appears to be due to slowed gastric emptying by ethanol. Data is available only for erythromycin ethylsuccinate. Patients should be advised to avoid ethanol while taking erythromycin salts.
References
- Morasso MI, Chavez J, Gai MN, Arancibia A (1990) "Influence of alcohol consumption on erythromycin ethylsuccinate kinetics." Int J Clin Pharmacol, 28, p. 426-9
ethinyl estradiol food
Applies to: Lo/Ovral (ethinyl estradiol / norgestrel)
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
- Hobbes J, Boutagy J, Shenfield GM (1985) "Interactions between ethanol and oral contraceptive steroids." Clin Pharmacol Ther, 38, p. 371-80
norgestrel food
Applies to: Lo/Ovral (ethinyl estradiol / norgestrel)
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
- Hobbes J, Boutagy J, Shenfield GM (1985) "Interactions between ethanol and oral contraceptive steroids." Clin Pharmacol Ther, 38, p. 371-80
Therapeutic duplication warnings
No duplication warnings were found for your selected drugs.
Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.
Drug Interaction Classification
Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. | |
Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. | |
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. | |
No interaction information available. |
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