Impact of plasmapheresis on disopyramide elimination

The impact of plasmapheresis on the disposition of disopyramide was investi gated in a 16-year-old female with systemic lupus erythematosus. Determinat ion of total disopyramide plasma concentrations immediately prior to and fo llowing a 4-h plasmapheresis treatment revealed a significant reduction (i. e., 1.77 to 0.7 mg/l or approximately 60%). However, reassessment of the to tal serum concentration after 1.5 h (i.e., post equilibrium) revealed a reb ounding of the value to 1.64 mg/l. Associated with this reduction in total serum levels was a decrease in the protein-bound fraction of disopyramide f rom 69.5% (pre treatment) to 48.6% (post treatment) that corresponded to a commensurate reduction in the concentration of alpha(1)-acid glycoprotein ( i.e., 119 mg/dl pre treatment to 48.9 mg/dl post treatment). Despite these alterations in disopyramide concentrations, the procedure removed only 2.7% of the disopyramide dose and was not associated with the appearance of a c ardiac dysrhythmia.