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Evidence‐based approaches

Medicines should only be administered by injection when no other route is suitable or available, or administration by injection is clinically indicated. As injections avoid the GI tract, this is described as parenteral administration. Injections are administered when:
  • the medication might be destroyed by the stomach
  • rapid first‐pass metabolism may be extensive
  • the drug is not absorbed if given orally
  • precise control over dosage is required
  • the drug cannot be given by mouth
  • there is a need to achieve high drug plasma levels (Downie et al. [82], Ostendorf [277]).
There are disadvantages as injections are invasive, cause pain and discomfort, and can put patients at risk of infection and (in the case of intravenous injections) infiltration and extravasation.

Methods for injection or infusion

There are a number of routes for injection or infusion (see Box 15.8). The selection may be predetermined, for example in the cases of intra‐arterial or intra‐articular injections. The choice of other routes will normally depend on the desired therapeutic effect and the patient's safety and comfort.
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