Abstract
Background. Ritodrine hydrochloride is frequently used in pregnant patients receiving dialysis. Though its blood concentration reportedly decreases during hemodialysis (HD), its dialysability remains unclear. We calculated the clearance of ritodrine hydrochloride during HDF and dialysability in pregnant patients receiving HD and hemodiafiltration (HDF). Methods. We measured the concentrations of ritodrine hydrochloride before and after dialysis during HD (APS-15MD, QB of 180 mL/min, QD of 500 mL/min) and HDF (pre-dilution, APS-15MD, QB of 180 mL/min, QD of 450-500 mL/min, QF of 33 mL/min). Additionally, we measured blood concentrations during HDF; before dialysis, 2 hours later, and after 4 hour dialysis. The initial ritodrine hydrochloride dose was 126 μg/min, but was increased to 160 μg/min during dialysis. Results. During HDF, the blood concentration of ritodrine before dialysis was 62.03 ng/mL, at 2 hours later was 69.08 ng/mL, and after dialysis was 68.48 ng/mL. Therefore, only a slight increase was observed. During HD, its concentration was 68.52 ng/mL before dialysis and 40.35 ng/mL after. Plasma clearance was 52.3 mL/min. During HDF, the concentration was 75.82 ng/mL before dialysis and 37.10 ng/mL after. Plasma clearance was 81.3 mL/min. These clearances were lower than expected. The duration of pregnancy can be extended by increasing ritodrine hydrochloride during dialysis. Ritodrine hydrochloride has low dialysability during HDF; however, the dose should be increased on the day of HDF because dialysis may confound threatened premature labor. Conclusions. Ritodrine hydrochloride has a low dialysability during HD and HDF. However, the dose of ritodrine hydrochloride should be increased for pregnant patients receiving HD and HDF on the day of HD and HDF.
