Docetaxel/folic acids/cyanocobalamin interaction
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Increased PSA levels in an elderly patient: case report A 71-year-old man with prostate cancer experienced elevated PSA levels during concomitant treatment with docetaxel and an oral supplement containing cyanocobalamin, folic acid and methyltetrahydrofolic acid [Intrinsi B12/folate]. The man’s PSA level slowly increased into the 3 ng/mL range in 2007, and he began receiving docetaxel 30 mg/m2 [route not stated] for 3 out of every 4 weeks. However, his PSA level continued to increase exponentially for 18 weeks, and docetaxel resistance was suspected. He then revealed that he was also ingesting 10 dose units of Intrinsi B12/folate each day; each dose unit contained cyanocobalamin [vitamin B12] 500µg, folic acid 400µg, methyltetrahydrofolic acid 400µg and porcine intrinsic factor [indication and duration of treatment not stated]. His PSA level reached 21.3 ng/mL on 11 February 2010. Four days later, his serum folic acid and cyanocobalamin levels were determined to be 134 ng/mL and > 1500 pg/mL, respectively; his serum testosterone level had remained at < 20 ng/mL and his serum homocysteine level was 12.0 µmol/L. The oral supplement was discontinued on day 900, and the man’s serum PSA level started to decrease within the next 2 weeks. At the time of the report, he had a PSA level of 2.08 ng/mL and continued to receive weekly docetaxel. His last recorded serum folic acid, cyanocobalamin and serum homocysteine levels were 4.0 ng/mL, 377 pg/mL and 17.8 µmol/L, respectively. Author comment: "We therefore consider the reversal of docetaxel resistance by folate/vitamin B12-mediated changes in DNA epimethylation to be possible." Tisman G, et al. Control of prostate cancer associated with withdrawal of a supplement containing folic acid, L-methyltetrahydrofolate and vitamin B12: A case report. Journal of Medical Case Reports 5: No. 413, 2011. Available from: 803064799 URL: http://dx.doi.org/10.1186/1752-1947-5-413 - USA
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Editorial comment: A search of AdisBase, Medline and Embase did not reveal any previous case reports associated with an interaction between docetaxel and either folic acid, methyltetrahydrofolic acid or cyanocobalamin. The WHO ADR database contained five reports associated with the concomitant use of docetaxel and folic acid, but none associated with the concomitant use of docetaxel and 5-methyltetrahydrofolate or docetaxel and cyanocobalamin.
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Reactions 7 Jan 2012 No. 1383
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