Medications and therapeutic apheresis procedures: are we doing our best?

Therapeutic apheresis refers to a group of extracorporeal therapies commonly used in the treatment of a variety of neurological, renal, hematological, and other systemic diseases caused by circulating "toxic agents" that cannot be cleared by other means. This article presents an overview of the concepts underlying the effect of therapeutic apheresis procedures on prescription drugs taken by patients and describes key drug-related and procedure-related factors that may impact drug disposition during therapeutic apheresis. Therapeutic apheresis, and specifically therapeutic plasma exchange (TPE), is the process involving the extracorporeal separation of plasma from the cellular components of blood, discarding the plasma and exchanging it with replacement physiologic fluids such as albumin or fresh frozen plasma to maintain oncotic pressure and blood volume, and then returning this and the original cellular components of blood back to the patient's circulatory system (Ibrahim and Balogun, Semin Dial 2012;25:176-189). Over the last 4 decades, modern therapeutic apheresis has been used clinically for the treatment of a host of renal, hematological, and neurological diseases such as Goodpasture's syndrome, thrombotic thrombocytopenic purpura, and myasthenia gravis to name a few (Ibrahim et al., Pharmacotherapy 2007;27:1529-1549). Because of its ability to remove plasma, TPE can extract circulating drugs residing in this compartment, thereby affecting their disposition and potentially their therapeutic action (Ibrahim and Balogun, Semin Dial 2012;25:176-189; Ibrahim et al., Pharmacotherapy 2007;27:1529-1549; Kale-Pradhan and Woo, Pharmacotherapy 1997;17:684-695; Kintzel et al., J Clin Apher 2003;18:194-205). The aim of this article is to shed light on drug-related and TPE-related factors that may influence drug removal by TPE. Emphasis is put on areas needing improvement in the way of assessing drug removal by TPE. In addition, a call for an expanded investigation of TPEs influence on select compounds is enlisted.