Upper arm administration is associated with higher injection site pain with romosozumab: a randomized controlled trial and a self-controlled study

These 2 prospective studies investigated whether the injection site influences pain and local reactions with romosozumab treatment for osteoporosis. In Study 1, 169 patients were randomly assigned to receive monthly romosozumab 210 mg (2 vials) injections for 12 mo in either the abdomen (Abd group) or upper arm (Arm group). In Study 2, 55 patients received 105 mg (1 vial) injections in both sites to directly compare pain at each location. Pain was evaluated using a Visual Analog Scale (VAS, mm), and secondary outcomes included BMD, bone turnover markers (BTMs) (total P1NP and TRACP-5b), and injection site reactions (ISRs). In the randomized trial, 70 of 85 patients (82.4%) in the Abd group and 69 of 84 (82.1%) in the Arm group completed the study. The Arm group reported significantly greater pain than the Abd group, starting after the fifth injection (mean difference, 6.8 mm [95% CI, 0.7-12.8]; <i>p</i> = .029) and continuing through the 12th injection (9.5 mm [95% CI, 2.9-16.1]; <i>p</i> = .005). Although crude ISR rates were similar (Abd, 26.2% vs Arm, 35.8%; <i>p</i> = .24), multivariable analysis showed a higher ISR incidence in the Arm group (incidence rate ratio: 1.73 [95% CI, 1.01-2.95]; <i>p</i> = .045). In Study 2, pain was consistently greater at the upper arm, beginning with the first injection (mean difference, 5.2 mm [95% CI, 1.7-8.7]; <i>p</i> = .004) and continuing through the 12th (8.1 mm [95% CI, 4.2-11.9]; <i>p</i> < .001). BMD and BTMs did not differ between sites. In conclusion, upper arm injections were associated with greater pain and higher ISR incidence without affecting bone metabolism. Selecting an injection site based on comfort may improve patient experience during romosozumab therapy.