A narrative review of the success of intramuscular gluteal injections and its impact in psychiatry

Abstract

There are 12 billion injections given worldwide every year. For many injections, the intramuscular route is favoured over the subcutaneous route due to the increased vascularity of muscle tissue and the corresponding increase in the bioavailability of drugs when administered intramuscularly. This paper is a review of the variables that affect the success of intramuscular injections and the implications that these success rates have in psychiatry and general medicine. Studies have shown that the success rates of intended intramuscular injections vary between 32 and 52%, with the rest potentially resulting in inadvertent subcutaneous drug deposition. These rates are found to be even lower for certain at-risk populations, such as obese patients and those on antipsychotic medications. The variables associated with an increased risk of injection failure include female sex, obesity, site of injection, and subcutaneous fat depth. New guidelines and methods are needed in order to address this challenge and ensure that patients receive optimum care. Looking forward, the best way to improve the delivery of intramuscular injections worldwide is to develop uniform algorithms or innovative medical devices to confirm or guarantee successful delivery at the bedside.

Keywords: Antipsychotic; Computed tomography; Gluteal; Intramuscular injection; Subcutaneous; Ultrasound.

Fig. 1

An outline of the dorsogluteal and ventrogluteal injection sites

Fig. 2

Summary image of the techniques used to landmark the various regions on the buttock prior to intramuscular injections. (Reproduced with permission from [22])

Fig. 3

Comparison of subcutaneous fat thickness and successful intramuscular injections in males (top) and females (bottom). (Reproduced with permission from [1])

Fig. 4

Relationship between BMI and subcutaneous tissue thickness in males (top) (Spearman’s r = 0.51, P < 0.01) and females (bottom) (Spearman’s r = 0.19, P = 0.37). (Reproduced with permission from [1])