It is important to detect
injection site reactions during the nonclinical phases of drug development. However, differentiating between normal changes following needle
trauma and changes due to the toxicity of injected drugs can be challenging. Therefore, we used the Sprague-Dawley rat model to evaluate the pathological findings expected following a single
subcutaneous injection of
normal saline. Rats were subcutaneously administered with
normal saline, and the injection sites were examined microscopically.
Inflammation was evident in most of the injection sites, mostly in minimal severity.
Parakeratosis/epithelial crust was also seen in several sites, and
necrosis was observed in a minority of the cases. These findings indicate that needle
puncture trauma can present with some degree of
inflammation and
necrosis. Although limited to a specific time point and strain, this study shows that
inflammation following
subcutaneous injection can be attributed in part to the needle
trauma and not necessarily to the drug itself.