Separation of Components of Methylprednisolone Acetate Solution for Safe Intrathecal Administration

Abstract

To the Editor In a recent study by Candido et al. the concentration of polyethylene glycol (PEG) in a vial of methylprednisolone acetate (Depo-Medrol) (Depo-Medrol, Pharmacia & Upjohn Company, Kalamazoo, MI) was reduced >75% by extracting and aspirating only the steroid component after keeping the vial inverted for >2 hours.1 The method described by the authors, albeit effective, requires a very precise insertion of the hypodermic needle into a vial containing a small quantity of drug (1 mL) with approximately only half of it to be aspirated carefully.2 A slight inadvertent upward movement of the needle may lead to inclusion of a larger percentage of PEG into the steroid base. We have found that it may still be better to first aspirate the entire contents of the vial into a 1-mL syringe and keeping this syringe vertical (needle up and plunger down with no air) under all sterile precautions for >2 hours. The 2 phases separate quite well within the syringe, and the upper aqueous phase being PEG can be discarded just before intrathecal injection of the steroid base. We loaded 10 vials of Depo-Medrol into 1-mL syringes and found that the mean volume of supernatant, i.e., PEG, was approximately 0.6 mL with remaining 0.4 mL of steroid seen as white base (Fig. 1).Figure 1: Showing the 2 phases being clearly demarcated in 1-mL syringe.Rajesh Mahajan, MD Anuradha Bali, MD Department of Anesthesia Government Medical College Jammu, India [email protected] Shivani Mehta, MD Department of Pathology Government Medical College Jammu, India Firdose Shafi, MD Department of Anesthesia Acharya Chander College of Medical Sciences Jammu, India