Are unintended intramuscular injections possible?

No. The pressure and speed are calculated in such a way that the medication only enters into the subcutaneous adipose tissue. Accidental administration of the medication into the muscle is virtually impossible.
In contrast to insulin injections in diabetic children that frequently and unintentionally are performed intramuscular when using a needle syringe (30,5 % of performed injections). (literature review: POLAK et al., 1996)