Sometimes we can’t avoid giving an IM injection, even though they are painful. Some vaccines should be given IM, and the routine needle in the thigh of every baby for vitamin K is a rite of passage, that has become standard everywhere. There has been very little study of analgesia for this procedure in the newborn, compared to studies of heelsticks, for example.
Liaw J-J, Zeng W-P, Yang L, Yuh Y-S, Yin T, Yang M-H. Nonnutritive Sucking and Oral Sucrose Relieve Neonatal Pain During Intramuscular Injection of Hepatitis Vaccine. Journal of Pain and Symptom Management. 2011;42(6):918-30. http://www.sciencedirect.com/science/article/pii/S0885392411001606
In the neonatal pain literature this is a fairly large study (165 babies in 3 groups, control NNS and sucrose) both the intervention groups were much better than the controls. For other procedures the combination of a soother and sucrose is better than either alone.
As a result, the standard of care should be to give sucrose and a soother before intramuscular injections.
But also, many intramuscular injections can be avoided. Vitamin K can be given intravenously to babies that have an IV, such as many preterm babies.
Finally a question, is it ethically appropriate to include untreated controls in a study of pain relief in the newborn?