Nausea and vomiting in pregnancy

For several years now I have been particularly interested in the management of nausea and vomiting in pregnancy (NVP). This interest was sparked by the fact that there seemed to be too large a number of admissions to our hospital for management of hyperemesis gravidarum (HG). A similar rise in admissions for HG was reported in the UK – three-fold in the 15 years from 1990 to 2005. It seemed likely that the reason was inadequate early management of ‘morning sickness’ resulting in deterioration to the point of ketosis and dehydration, in other words, HG. On checking what these unfortunate women had been treated with before admission, it became strikingly clear that, almost without exception, they had been on metoclopramide. This suggested to me that metoclopramide was not particularly good at treating the problem. I found, on asking patients who had been prescribed it what they thought of metoclopramide, that their assessment was quite low and that frequently they had given up on it altogether.

Pregnancy Sickness Support, an association in the UK, to do what its name suggests, advises on its website that first steps should be to use a phenothiazine combined with pyridoxine and specifically mention cyclizine and promethazine. They also point out that American and Canadian guidelines suggest doxylamine and pyridoxine as the first step. Once we started to use doxylamine with pyridoxine we found excellent results, which seemed to make a difference to the rates of admission – from about 45 per cent of presenters to the emergency department down to about 25 per cent. The rationale for using doxylamine is that it was one of the ingredients of the best treatment for NVP of all time, Debendox, and is now available in combination with pyridoxine, as Diclectin, or separately as Restavit.

I carried out a survey of prescribing habits for NVP with the results published in ANZJOG.¹ The number-one choice for NVP, whether mild or severe, was metoclopramide – even ranking ahead of pyridoxine. For HG it was even more stark – first was metoclopramide and second choice was ondansetron. This seems to suggest that my colleagues have been prescribing irrationally and by rote. Because metoclopramide enhances gastric emptying, and NVP is worse when the stomach is empty, it doesn’t seem logical to use it at all.

As for steroids, one good double blind trial² showed they were no better than a placebo. There was, however, an improvement in sense of well-being. Another study³ claimed that a short course of methylprednisolone was better than promethazine, despite the fact that three in the steroid group failed to stop vomiting in two days, versus two in the promethazine group. Nevertheless, there have certainly been some rapid improvements reported anecdotally. I have never used dexamethasone as I have found phenothiazines quite satisfactory even in the severe end of HG. As a general principle, by the time you get there you are likely to need a combination anyway and prochlorperazine with ondansetron has not failed me.

Drs Lakhdir and McDougall, in their article in O&G Magazine Vol 16 No 2 25–26, mention metoclopramide first in their list of drugs to be considered and don’t mention doxylamine at all. They quote the National Women’s Hospital guideline as saying metoclopramide is a first-line choice. This is a surprising claim in view of the guidelines from the USA, Canada and the UK that do not mention metoclopramide until at least the second line. I challenge the authors of the article, the authors of the National Women’s guideline and, indeed, all O&G Magazine readers to run a little comparison on their next few sufferers of NVP to see which is more effective, Maxolon (metoclopramide) or Restavit (doxylamine) and it is my prediction that it will become obvious quickly that metoclopramide is inferior. Indeed, the widespread use of it may well be responsible for the rise in admissions for treatment of HG that has characterised the last two decades.