The Relationship of Plasma Concentration of Doxylamine and Rhabdomyolysis in Doxylamine Overdose

Ahn, Nam Kyu; Han, Seung Baik; Kim, Jun Sig; Paik, Jin Hui; Jung, Hyun Min; Kim, Ji Hye

Abstract

PURPOSE
The relationship between plasma concentration of doxylamine and rhabdomyolysis in doxylamine overdose has not yet been reported. The aim of this study was to determine if the plasma concentration of doxylamine can predict the occurrence of rhabdomyolysis.
METHODS
We reviewed the medical records of patients whose plasma concentration of doxylamine were checked during a state of doxylamine overdose. Variables, including the measured concentration (Ct) of drug, were compared between the rhabdomyolysis and the non-rhabdomyolysis group. We calculated the hypothetical initial concentration (C0) based on first order pharmacokinetics and measurement of each patient's plasma concentration of doxylamine (Ct). C0 values were compared based on the occurrence of rhabdomyolysis.
RESULTS
A total of 41 blood samples were taken; all were taken more than two hours after the ingestion of doxylamine. Of the 41, 14 of the subjects showed rhabdomyolysis and 15 of the subjects did not. The rest were excluded from the study. Average values of Ct and C0 in the rhabdomyolysis and non-rhabdomyolysis groups were, respectively, 4.18+/-5.17 mg/L Vs 4.18+/-2.23 mg/L, for Ct; 6.21+/-7.92 mg/L Vs 15.53+/-17.97 mg/L for C0. Ct levels between the two groups were not different (p=1.00), but the difference in C0 was marginally significant (p=0.08). Blood sampling time showed a significant difference between the two groups (p=0.03).
CONCLUSION
We can not confirm a relationship of plasma doxylamine concentration and rhabdomyolysis but it appears that the development of rhabdomyolysis in doxylamine overdose has a tendency to increase at high plasma concentration.