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Drug Interactions between tamoxifen and Zagam

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

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Major

tamoxifen sparfloxacin

Applies to: tamoxifen and Zagam (sparfloxacin)

CONTRAINDICATED: Sparfloxacin may cause dose-related prolongation of the QT interval in some patients. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death. Torsade de pointes has been reported in a few patients receiving sparfloxacin alone and with antiarrhythmic agents like amiodarone and disopyramide.

MANAGEMENT: Coadministration of sparfloxacin with other drugs that can prolong the QT interval is considered contraindicated.

References

  1. Thomas M, Maconochie JG, Fletcher E "The dilemma of the prolonged QT interval in early drug studies." Br J Clin Pharmacol 41 (1996): 77-81
  2. Jaillon P, Morganroth J, Brumpt I, Talbot G "Overview of electrocardiographic and cardiovascular safety data for sparfloxacin. Sparfloxacin Safety Group." J Antimicrob Chemother 37(suppl a) (1996): 161-7
  3. Zix JA, GeerdesFenge HF, Rau M, Vockler J, Borner K, Koeppe P, Lode H "Pharmacokinetics of sparfloxacin and interaction with cisapride and sucralfate." Antimicrob Agents Chemother 41 (1997): 1668-72
  4. "Product Information. Zagam (sparfloxacin)." Rhone Poulenc Rorer PROD (2001):
  5. Demolis JL, Charransol A, Funck-Brentano C, Jaillon P "Effects of a single oral dose of sparfloxacin on ventricular repolarization in healthy volunteers." Br J Clin Pharmacol 41 (1996): 499-503
  6. Dupont H, Timsit JF, Souweine B, Gachot B, Wolff M, Regnier B "Torsades de pointe probably related to sparfloxacin." Eur J Clin Microbiol Infect Dis 15 (1996): 350-1
  7. Lipsky BA, Dorr MB, Magner DJ, Talbot GH "Safety profile of sparfloxacin, a new fluoroquinolone antibiotic." Clin Ther 21 (1999): 148-59
  8. Owens RC "Risk assessment for antimicrobial agent-induced QTc interval prolongation and torsades de pointes." Pharmacotherapy 21 (2001): 301-19
  9. Iannini PB, Doddamani S, Byazrova E, Curciumaru I, Kramer H "Risk of torsades de pointes with non-cardiac drugs." BMJ 322 (2001): 46-7
  10. Ball P "Quinolone-induced QT interval prolongation: a not-so-unexpected class effect." J Antimicrob Chemother 45 (2000): 557-9
  11. Kang J, Wang L, Chen XL, Triggle DJ, Rampe D "Interactions of a series of fluoroquinolone antibacterial drugs with the human cardiac K+ channel HERG." Mol Pharmacol 59 (2001): 122-6
  12. Oliphant CM, Green GM "Quinolones: a comprehensive review." Am Fam Physician 65 (2002): 455-64
  13. Owens RC Jr, Ambrose PG "Torsades de pointes associated with fluoroquinolones." Pharmacotherapy 22 (2002): 663-8; discussion 668-72
  14. Iannini PB "Cardiotoxicity of macrolides, ketolides and fluoroquinolones that prolong the QTc interval." Expert Opin Drug Saf 1 (2002): 121-8
  15. Owens RC "QT Prolongation with Antimicrobial Agents : Understanding the Significance." Drugs 64 (2004): 1091-124
  16. Katritsis D, Camm AJ "Quinolones: cardioprotective or cardiotoxic." Pacing Clin Electrophysiol 26 (2003): 2317-20
  17. Stahlmann R "Clinical toxicological aspects of fluoroquinolones." Toxicol Lett 127 (2002): 269-77
  18. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  19. Canadian Pharmacists Association "e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink" (2006):
  20. Falagas ME, Rafailidis PI, Rosmarakis ES "Arrhythmias associated with fluoroquinolone therapy." Int J Antimicrob Agents 29 (2007): 374-9
  21. Cerner Multum, Inc. "Australian Product Information." O 0
View all 21 references

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Drug and food interactions

Moderate

tamoxifen food

Applies to: tamoxifen

GENERALLY AVOID: Due to their estrogenic effect, isoflavones present in soy such as genistein and daidzein may stimulate breast tumor growth and antagonize the antiproliferative action of tamoxifen. Supportive data are derived primarily from in vitro and animal studies. In vitro, low concentrations of these phytoestrogens have been found to promote DNA synthesis and reverse the inhibitory effect of tamoxifen on estrogen-dependent breast cancer cell proliferation. In contrast, high concentrations of genistein greater than 10 microM/L have been found to enhance tamoxifen effects by inhibiting breast cancer cell growth. It is not known if these high concentrations are normally achieved in humans. Plasma concentrations below 4 microM/L have been observed in healthy volunteers given a soy diet for one month or large single doses of genistein. These concentrations are comparable to the low plasma concentrations associated with tumor stimulation reported in animals. In a study of 155 female breast cancer survivors with substantially bothersome hot flashes, a product containing 50 mg of soy isoflavones (40% to 45% genistein; 40% to 45% daidzein; 10% to 20% glycitein) taken three times a day was found to be no more effective than placebo in reducing hot flashes. No toxicity or recurrence of breast cancer was reported during the 9-week study period.

Green tea does not appear to have significant effects on the pharmacokinetics of tamoxifen or its primary active metabolite, endoxifen. In a study consisting of 14 patients who have been receiving tamoxifen treatment at a stable dose of 20 mg (n=13) or 40 mg (n=1) once daily for at least 3 months, coadministration with green tea supplements twice daily for 14 days resulted in no significant differences in the pharmacokinetics of either tamoxifen or endoxifen with respect to peak plasma concentration (Cmax), systemic exposure (AUC), and trough plasma concentration (Cmin) compared to administration of tamoxifen alone. The combination was well tolerated, with all reported adverse events categorized as mild (grade 1) and none categorized as serious or severe (grade 3 or higher) during the entire study. Although some adverse events such as headache, polyuria, gastrointestinal side effects (e.g., constipation, dyspepsia), and minor liver biochemical disturbances were reported more often during concomitant treatment with green tea, most can be attributed to the high dose of green tea used or to the caffeine in green tea. The green tea supplements used were 1000 mg in strength and contained 150 mg of epigallocatechin-3-gallate (EGCG), the most abundant and biologically active catechin in green tea. According to the investigators, the total daily dose of EGCG taken by study participants is equivalent to the amount contained in approximately 5 to 6 cups of regular green tea. However, it is not known to what extent the data from this study may be applicable to other preparations of green tea such as infusions, since the bioavailability of EGCG and other catechins may vary between preparations.

MANAGEMENT: Until more information is available, patients treated with tamoxifen may consider avoiding or limiting the consumption of soy-containing products. Consumption of green tea and green tea extracts during tamoxifen therapy appears to be safe.

References

  1. Therapeutic Research Faculty "Natural Medicines Comprehensive Database. http://www.naturaldatabase.com" (2008):
  2. Braal CL, Hussaarts KGAM, Seuren L, et al. "Influence of green tea consumption on endoxifen steady-state concentration in breast cancer patients treated with tamoxifen." Breast Cancer Res Treat 184 (2020): 107-13

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Therapeutic duplication warnings

No 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.

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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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