<P> Disadvantages of injections include potential pain or discomfort for the patient and the requirement of trained staff using aseptic techniques for administration . However, in some cases, patients are taught to self - inject, such as SC injection of insulin in patients with insulin - dependent diabetes mellitus . As the drug is delivered to the site of action extremely rapidly with IV injection, there is a risk of overdose if the dose has been calculated incorrectly, and there is an increased risk of side effects if the drug is administered too rapidly . </P> <P> Neural drug delivery is the next step beyond the basic addition of growth factors to nerve guidance conduits . Drug delivery systems allow the rate of growth factor release to be regulated over time, which is critical for creating an environment more closely representative of in vivo development environments . </P>

Why are some medicines not able to be given orally