Pain on injection from propofol may be avoided by changing its formulation.

Background: After using propofol for a decade, pain on injection had been considered routine by patients and medical personnel. When given propofol from a different manufacturer, patients did not complain. Two preparations of propofol were compared.

Methods: A comparative, double-blind, randomized study was conducted in 22 adult patients undergoing pain relief procedures; they received sedation by an intravenous injection of 1.7 mg/kg of propofol and then were treated with paravertebral injections. Pain on injection was assessed by verbal complaint, movement of the extremity, of the whole body and recollection of pain at induction, when discharged. Propofol from Baxter Laboratories, mixed with either 5 ml of 2% lidocaine or 5 ml of NaCl 0.9%, was compared with propofol Laboratorios Gray, which was similarly mixed. Injections were randomly administered four times, blindly, to each of 22 patients. Statistical analysis was conducted using the analysis of variance method.

Results: A total of 352 propofol injections were given. Each of the four propofol solutions was administered 88 times; of patients receiving Baxter propofol+saline, 74 (84%) had pain; when mixed with 2% lidocaine 45 (50.2%) complained. After propofol Gray with NaCl 0.9% was given, two patients (2.2%) experienced pain. Propofol Gray with 2% lidocaine produced no pain. None of the latter group remembered having pain, whereas, those given propofol Baxter 54 (61.3%) and 26 (29.5%) remembered experiencing pain at injection. Pain on injection was prevented and statistically reduced (<0.01) with the propofol from Laboratorios Gray.

Conclusions: By changing the formulation (size of molecules and their dispersion) of propofol, pain on injection was avoided.