It has long been known that vitamin B6 has anti-emetic effects; it is often recommended for use in pregnancy to reduce morning sickness, and has been used in antiemetic drugs.
A review of therapies to manage nausea and vomiting in pregnancy noted vitamin B6 as an effective anti-nausea and antiemetic treatment.[1] Newer research has gone on to demonstrate that it is the activated form of vitamin B6, namely, pyridoxal-5-phosphate (P5P), which is the critical compound for antiemesis.[2]
The findings come after 283 pregnant women experiencing morning sickness were enrolled in this double- blind, randomised, multicenter, placebo-controlled study.[2] The participants were randomised to receive either a drug containing pyridoxine hydrochloride or a placebo for 14 days, with a dosage schedule of 2-4 tablets per day.[2]
Effectiveness of treatment was assessed via the Pregnancy-Unique Quantification of Emesis (PUQE) scoring system; blood samples were drawn on days zero, four, eight and 14 to measure plasma concentrations of doxylamine, pyridoxine, pyridoxal, and P5P.[2]
Among the 131 women in the treatment group, PUQE scores improved steadily during the 14 days, confirming this to be an effective anti-nausea and antiemetic drug.[2] The blood sample analysis indicated that blood levels of pyridoxine and pyridoxal remained low throughout treatment, while P5P concentrations rose in association with the antiemetic effect.[2] This suggests that pyridoxine and pyridoxal are prodrugs for P5P, and that it is P5P which has the intended therapeutic effect.[2]
It can be surmised from this that taking P5P directly in supplemental form may be a more efficient therapy for morning sickness than vitamin B6 in its unactivated forms.
References
- King TL. Evidence-based approaches to managing nausea and vomiting in early pregnancy. J Midwifery Womens Health 2009;54(6):430-444. [Abstract]
- Matok I, Clark S, Caritis S, et al. Studying the antiemetic effect of vitamin B6 for morning sickness: pyridoxine and pyridoxal are prodrugs. J Clin Pharmacol 2014;24(12):1429-1433. [Abstract]
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