Treating nausea and vomiting during pregnancy: case outcome

Five weeks ago (31 January, p 276) we presented the case of Ms Reynolds, a 25 year old woman who presented to her general practitioner when eight weeks pregnant complaining of nausea and vomiting with light headedness.After an unsuccessful trial of prochlorperazine, she asked about alternatives to conventional drugs, and we suggested a trial of vitamin B-6 (pyridoxine) to relieve her symptoms (7 February, p 337). Because of the paucity of evidence for or against the use of vitamin B-6, we suggested an n of 1 trial as an objective way to assess whether it was effective. The table shows that vitamin B-6 did not have a significant treatment effect compared with placebo for Ms Reynolds's four most important symptoms. After being shown the results of her n of 1 study, Ms Reynolds stopped taking vitamin B-6.

Vitamin B-6 in the form of pyridoxal-5-phosphate acts as an important coenzyme in the transamination of amino acids, with deficiency leading to polyneuropathy and convulsions.2 Vitamin B-6 has an important role in protein metabolism and transporting many amino acids across cell membranes. The mode of action in alleviating nausea in pregnancy is not known. No clear relation has been found between indicators of vitamin B-6 status and nausea and vomiting.2

Nausea and vomiting are the commonest symptoms experienced in the first trimester of pregnancy, affecting 70-85% of women.3 Hyperemesis gravidarum, persistent vomiting that is sufficient to cause fluid and electrolyte disturbance, is much less common, with an incidence of 3.5/1000 deliveries.3 Despite the relative lack of evidence, use of complementary or alternative medicines, including vitamins and herbal remedies, is popular. One study found that nearly a third of pregnant women use such remedies, with 13% of women specifically taking them to alleviate symptoms of nausea and vomiting in pregnancy.1 In most instances patients do not tell their doctors that they are taking complementary medicines.1

An n of 1 trial in a patient with hyperemesis gravidarum showed that prednisolone 50 mg daily was no more effective than ascorbic acid.4 The results of our n of 1 trial—that vitamin B-6 had no clinically important effect on vomiting—concurred with those of a systematic review, based on evidence from three randomised controlled trials.5 Vitamin B-6 was also ineffective in alleviating our patient's three other most important symptoms of dizziness, daily activities, and general wellbeing. We believe an n of 1 trial is a useful means of helping patients decide on which treatment to take in situations where evidence is poor or equivocal.

This is the final part of a 3 part case report, which describes the outcome and summarises the comments made by readers during the case presentation