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Rapid Responses: Rapid Responses published:
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Vitamin B6 supplements may prevent DNA damage
- Ellen CG Grant (27 February 2004)
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A useful approach!
- Truls W. Gedde-Dahl (27 February 2004)
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Dose of pyridoxine
- Kenneth Ch'ng (19 April 2004)
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vitamin B-6, n-of-1-trial, and mymop
- Vincent Vinh-Hung (15 August 2004)
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Ellen CG Grant, physician and medical gynaecologist 20 Coombe Ridings, Kingston-upon-Thames, Surrey KT2 7JU
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This is my fourth response to this n-1 trial of vitamin B6 in pregnancy sickness which I did not expect to show an effect. An essential nutrient is not an anti-emetic drug. Vitamin B6 deficiency is common even in symptomless individuals. A functional deficiency can be diagnosed by a blood test. Professor Bruce Ames has emphasised the importance for supplements in optimizing health. He states that deficiency of some essential nutriients, including vitamin B6, appears to mimic radiation in damaging DNA by causing single- and double-strand breaks, oxidative lesions or both. He says the amount that is truly "required" is the amount that minimises DNA damage and maximises a healthy lifespan. This is particuarly true for the health of a pregnant women and her child. I hope not a single pregnant woman will be deprived of supplemental vitamin B6 because of this inappropriate study. 1. Ames BN. A role for supplements in optimising health: the metabolic tune-up. Arch Biochem Biophys 2004; 423:227-234. Competing interests: None declared |
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Truls W. Gedde-Dahl, Retired epidemiologist Foundation for Local Health Trials
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The commentary of Ed Peile (1) on applying the principle of n of 1 trials as n of 1 learning seems very appropriate. Such thinking of finding the individual response on different learning methods adds validity to its application for finding the likely best treatment option for an individual patient who deviates from the average. Thus, in the life-long learning in professional (general) practice it should probably be used much more in the way of Harker et al. (2) even in instances when one is not able to overcome the uncertainty of random errors. In the long run they will give much more unbiased estimates of the right answers than “come back if that doesn’t work and we will try another thing”. In addition to being a more fair method in itself, it will give both physician and patient more experience in assessing treatment effects in the grey zone between documented and undocumented & tacit evidence.
---------------------------- References: (1) Nicola Harker, Alan Montgomery, Tom Fahey. Interactive case report: Treating nausea and vomiting during pregnancy: case outcome. http://bmj.com/cgi/content/full/328/7438/503?etoc (2) Ed Peile, Commentary: n of 1 learning. http://bmj.com/cgi/content/full/328/7438/505?etoc Competing interests: None declared |
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Kenneth Ch'ng, Pharmacist 3818 (Australia)
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I followed with great interest the n of 1 trials for the case of treating nausea and vomiting during pregnancy. However, pyridoxine dosage we generally use in our organisation is 25mg qid and often in conjunction with metoclopramide 10mg tds if nausea is severe (Reference: Therapeutic Guidelines: Gastrointestinal 2nd Edition 1999)your case report elected to use 10mg tds which I think is sub-therapeutic. Your n of 1 trials will probably benefit from a dose titration upwards. Thanks you. Competing interests: None declared |
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Vincent Vinh-Hung, adjunct, Oncology Center, AZ-VUB, 1090 Jette, Belgium
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Dear Editor, At first, I had some difficulties understanding Harker et al's paper (Treating nausea and vomiting during pregnancy: case outcome. BMJ 2004; 328: 503). I was unsure whether it was a humoristic tale, or else. The incomprehension was further compounded by reference 5's link which, instead of the purported Cochrane Database, led to a Homo sapiens cDNA clone's cryptic sequence of letters. It seemed a riddle. Probing further, it finally dawned on me that it was a serious didactic case. If the goal is to introduce the n-of-1-trial, then I've learned something. Instead of merely saying to the patient "try this prescription", the n-of-1-trial introduces a formal testing procedure. This is a clever approach. The Cochrane's abstract mentions that "...Of newer treatments, pyridoxine (vitamin B6) appears to be more effective in reducing the severity of nausea" (http://www.update- software.com/abstracts/ab000145.htm). Harker et al's report suggests that results from grouped data do not necessarily apply to the individual patient. The paper's results Table mentions the MYMOP scores, with a missing reference. I guess the correct reference should be http://www.hsrc.ac.uk/mymop/. Congratulations, and thank you for the enlightening theme issue on non-working treatments [1]. [1] Doust J, Del Mar C. Why do doctors use treatments that do not work? BMJ 2004;328:474-475, http://bmj.bmjjournals.com/cgi/content/full/328/7438/474 Competing interests: None declared |
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