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. 
TPN increases the risk of having liver disease and damage. Infants and yound child on TPN are more at risk for liver disease than older children and adults. The organs of infants and younger children are still developing. They are not as capable of handling the burden and strain that TPN puts on them. Children who are on TPN for a long time are also more at risk than those who are on TPN temporarily or for a short time. Some children who require an intestinal transplant may also receive a liver transplant at the same time due to liver disease associated with their use of TPN.