Rational drug management of nausea and vomiting depends on:

• Inferring or demonstrating what mechanisms are at work.
• Understanding what receptors are likely to be involved.
• Understanding what non-receptor mechanisms are likely to be involved.

Pharmacologically, a logical approach is:

• Choose a rational first line drug (that is, one likely to block the appropriate receptors).
• Review the effectiveness of this approach.
• If this fails, choose a rational second line.  This can be one of three things:
• An alternative drug, because in the meantime an alternative explanation for the problem has become clear.
• A complementary drug, i.e. one that blocks some of the receptors that were not blocked by your first choice drug.
• An alternative antiemetic that blocks a much wider range of receptors.  Phenothiazines, and in particular Levomepromazine, are ‘broad spectrum’ antiemetics and can be useful second line agents.

Table 3 shows the receptor antagonist properties of common antiemetics.  On the basis of an understanding of those receptor properties, and of the likely mechanism of nausea and vomiting in your patient, it should be possible to derive a logical approach.

Steroids

Long-term steroids should be avoided in paediatric palliative medicine as their benefits are quickly outweighed by their adverse effects.  Short courses of steroids may, however, be helpful adjuvants in managing nausea and vomiting.  Steroids probably do not work directly through a drug receptor interaction, but by:

• Reducing oedema, particularly in the brain (for example due to brain tumour), or in the liver (for example infection or metastatic disease).
• Reducing inflammation.  By moderating the inflammatory response, steroids can reduce the amount of cell damage and release of mediators of emesis.