An Investigation Into Local Infusion Site Pain After Infusion of Ultra Rapid Lispro Excipients Across Sites and Depths

Background: This phase 1, randomized, one-day, five-period crossover study in adults with type 1 diabetes on continuous subcutaneous insulin infusion investigated local infusion site pain following infusion of the excipients of ultra rapid lispro (URLi; without insulin) across infusion sites and depths. Methods: Forty participants (mean age, 40.5 years; body mass index [BMI], 27.5) were randomized to one of five infusion site sequences consisting of the arm, thigh, buttock (6 mm cannula depth), and abdomen (6 and 9 mm depth). Basal infusion of sodium citrate and treprostinil in diluent with magnesium chloride was initiated (10 μL/h) and at three, six, and nine hours after basal initiation, 15 unit-equivalent boluses (150 μL) were given. Participants rated their pain on a 0 to 100 mm validated visual analog scale (VAS) at 5 minutes pre-bolus and 1 and 15 minutes post-bolus. Results: At one minute post-bolus, increased VAS scores were occasionally reported. Most one minute post-bolus scores were ≤10 mm (little to no discomfort) while 7 of 577 were >45 mm (generally considered clinically meaningful pain). Painful infusions were reported more frequently for the arm, and mean VAS scores were higher for the arm compared with the thigh and abdomen. The VAS score distributions were similar between cannula depths. By 15 minutes post-bolus, VAS scores returned to pre-bolus levels. Conclusions: Local infusion site discomfort after infusion of URLi excipients was reported by a small subset of participants; it was transient, tolerable, and dependent on infusion site but not infusion depth. Given differences within individuals, patients may consider using a different infusion site if they experience discomfort. Clinicaltrial.gov identifier: NCT05067270.