Today, I was prescribing for a pregnant woman with vomiting and thought it worth checking what the latest recommendations were. According to the RCOG guidelines, the two main classes of drugs recommended are:
- Phenothiazines (e.g. prochlorperazine)
(If neither does the trick, it seems trying them in combination may help.)
Obviously I’m familiar with using prochlorperazine for nausea, but not so much antihistamines. Looked that up for more info and came up with emedicine.com article on motion sickness (unrelated to pregnancy) which advised that this only works with the sedating ones as they’re the ones that cross the BBB. According to this article (which, again, was dealing with the use of antihistamines for nausea in situations other than pregnancy) several studies show cinnarizine to be the most effective one with the fewest side-effects; dimenhydrinate and meclizine don’t seem to cause too much sedation; and promethazine can also work but is obviously quite a sedating antihistamine.
Metoclopramide is now recommended only as second-line due to the increased risk of extrapyramidal symptoms (which please note phenothiazines also have, to some extent) but can still be used as effective and safe for fetus. Ondansetron may help and appears safe, but evidence is limited so shouldn’t be first choice. Pyridoxine is no longer recommended. Steroids are only recommended when other treatments have failed.
Non-pharmacological treatments with some evidence behind them include ginger and acustimulation. Hypnosis is not recommended.