In Response

Abstract

We agree with Mahajan et al.1 that keeping a vial of Depo-Medrol® (Pharmacia & Upjohn Company, Kalamazoo, MI) inverted for 2 hours as we described2 is not the only way to separate 2 phases from a methylprednisolone acetate (MPA) suspension. Besides aspirating the entire contents into a 1-mL syringe and keeping the syringe “suspended” vertically for more than 2 hours as Mahajan et al.1 describe, there is the possibility of separating these 2 phases by centrifugation as Rijsdijk et al. have shown in a recent publication.3 The question is, “Which one of these three methods is more suitable for use in a busy clinical practice?” The advantage of centrifugation is that it is the quickest method but requires the centrifuge and a laminar flow hood for processing samples with sterile precautions. The method suggested by Mahajan et al.1 requires the use of a sterile (autoclaved) metallic test tube stand in the regional anesthesia tray. We are not aware of any commercial manufacturers who include a sterile test tube stand in their standardized kits, which begs the question of the clinical feasibility of Mahajan et al.'s suggestion. The 2 methods proposed by Mahajan et al.1 and by us2 require at least 2 hours of separation and the awareness that the upcoming patient may be a candidate for intrathecal injection using methylprednisolone with a reduced concentration of preservatives. We agree with Mahajan et al.1 that our method requires very careful insertion of the needle and aspiration from the small vial containing a total of 1 mL of contents. However, if practitioners choose the proposed method of Mahajan et al.1 and if either their prediction is not correct that the patient is a suitable candidate for intrathecal injection of corticosteroids, or if the patient does not agree to proceed with such an injection, they cannot sterilely reinject the contents back into the vial for subsequent use at a later time. However, by using our method2 in the case of someone not being a candidate for intrathecal MPA, one can always mix these 2 phases again by merely reverting the vial back upright. However, before using intrathecal MPA for managing postherpetic neuralgia-related pain, we should consider the recently published study of Rijsdijk et al.,3 performed on 12 dogs showing a dose-dependent intrathecal inflammation after MPA and recommending that MPA not be administered intrathecally to patients. These findings do not necessarily nullify the clinical work of Kotani et al.4 in 277 humans who underwent MPA intrathecal injections. Those authors observed no clinical complications, no abnormal findings on repeated lumbar magnetic resonance imaging scans taken postinjection, and no pleocytosis or proteinosis (which typically occurs as a prelude to arachnoiditis).5,6 Therefore, further clinical study is decidedly warranted concerning intrathecal MPA before either embracing or discarding this therapy for patients with postherpetic neuralgia. Kenneth D. Candido, MD Nebojsa Nick Knezevic, MD, PhD Department of Anesthesiology Advocate Illinois Masonic Medical Center Chicago, IL Department of Anesthesiology University of Illinois Chicago, IL [email protected]