BackgroundIntravenous (IV), intramuscular (IM), and subcutaneous (SC) are the three most frequently used injection routes in medication administration. Comparative studies of SC versus IV, IM versus IV, or IM versus SC have been sporadically conducted, and some new findings are completely different from the dosage recommendation as described in prescribing information. However, clinicians may still be ignorant of such new evidence-based findings when choosing treatment methods.MethodsA literature search was performed using PubMed, MEDLINE, and Web of Sciences™ Core Collection to analyze the advantages and disadvantages of SC, IV, and IM administration in head-to-head comparative studies.Results“SC better than IV” involves trastuzumab, rituximab, antitumor necrosis factor medications, bortezomib, amifostine, recombinant human granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, recombinant interleukin-2, immunoglobulin, epoetin alfa, heparin, and opioids. “IV better than SC” involves ketamine, vitamin K1, and abatacept. With respect to insulin and ketamine, whether IV has advantages over SC is determined by specific clinical circumstances. “IM better than IV” involves epinephrine, hepatitis B immu-noglobulin, pegaspargase, and some antibiotics. “IV better than IM” involves ketamine, morphine, and antivenom. “IM better than SC” involves epinephrine. “SC better than IM” involves interferon-beta-1a, methotrexate, human chorionic gonadotropin, hepatitis B immunoglobulin, hydrocortisone, and morphine. Safety, efficacy, patient preference, and pharmacoeconomics are four principles governing the choice of injection route. Safety and efficacy must be the preferred principles to be considered (eg, epinephrine should be given intramuscularly during an episode of systemic anaphylaxis). If the safety and efficacy of two injection routes are equivalent, clinicians should consider more about patient preference and pharmacoeconomics because patient preference will ensure optimal treatment adherence and ultimately improve patient experience or satisfaction, while pharmacoeconomic concern will help alleviate nurse shortages and reduce overall health care costs. Besides the principles, the following detailed factors might affect the decision: patient characteristics-related factors (body mass index, age, sex, medical status [eg, renal impairment, comorbidities], personal attitudes toward safety and convenience, past experience, perception of current disease status, health literacy, and socioeconomic status), medication administration-related factors (anatomical site of injection, dose, frequency, formulation characteristics, administration time, indication, flexibility in the route of administration), and health care staff/institution-related factors (knowledge, human resources).ConclusionThis updated review of findings of comparative studies of different injection routes will enrich the knowledge of safe, efficacious, economic, and patient preference-oriented medication administration as well as...
