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Intramuscular (IM) injection is one of many routes for administering medications, including antibiotics, vaccines, hormonal therapies, and corticosteroids.1,2 Even when alternate routes of administration are available, IM injections may be preferred when a patient cannot tolerate oral medication or when adherence is a concern.2 IM injections also may be beneficial for absorption compared with other routes of administration (ie, faster than subcutaneous injection and slower than intravenous administration). In addition, some medications contain components that can irritate subcutaneous tissue but not muscle tissue, which also can tolerate larger fluid volumes with minimal discomfort.3,4

Large-volume injections (3 mL or greater), however, are not frequently administered; and many clinicians may not be familiar with their appropriate use, possible side effects, and potential efficacy. Medications administered via large-volume IM injections include ceftazidime (Fortaz, Tazicef, generics), cefuroxime (Ceftin, Zinacef, generics), ertapenem (Invanz), penicillin G benzathine (Bicillin L-A, Permapen), and fulvestrant (Faslodex).5-9 This article discusses the practical issues related to administration of large-volume IM injections, in the setting of administering fulvestrant for the treatment of breast cancer, with a focus on best practices for efficacy and safety.

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IM injections are administered in five potential sites: deltoid (commonly used for adult vaccinations), dorsogluteal, ventrogluteal, rectus femoris, and vastus lateralis3,10,11 (Figure 1). Maximum volumes have been proposed across the various IM sites for adult patients3,12-16 (Table 1). Overall, 5 mL has been cited for adults as the maximum volume for a single IM injection, with lower maximums proposed for adult patients with less-developed or small muscle mass.3,13,14


Once administered exclusively by physicians, IM injections became a primary-nurse responsibility during the 1960s.1 However, few evidence-based guidelines for IM injections are available, and discrepancies within nursing textbooks have been noted.10-13 In addition, current guidelines do not address administration of large-volume injections.

The dorsogluteal site for IM injections is the one nurses have the most experience using, as this is what is traditionally taught in nursing schools and covered in nursing textbooks.16-18 A recent study found that acute care nurses in Canada preferentially selected the dorsogluteal IM injection site over the ventrogluteal IM injection site.19 The majority of respondents cited their own level of comfort as the predominant reason for this preference. However, nurses who were older than 30 years, were diploma prepared, and had more than 4 years of nursing experience were more likely to choose the dorsogluteal site; whereas nurses who were age 20 to 24 years, were degree prepared, and had 1 to 4 years of nursing experience were more like to choose the ventrogluteal site.19 This finding supports the idea that the ventrogluteal site may be used more often by those who received specific guidance in administering at that site.