Highly Sensitive LC-MS/MS Method for Determinationof Memantine in Rat Plasma: Application to Pharmacokinetic Studies in Rats

Background: A rapid and highly sensitive assay method has been developed and validated for the estimation of
memantine (MEM) in rat plasma using liquid chromatography coupled to tandem mass spectrometry with electro
spray ionization in the positive-ion mode. Method validation was performed as per United States Food and Drug
Administration (US FDA) guidelines. Methods: The assay procedure involves a simple liquid-liquid extraction of
MEM and phenacetin (internal standard, IS) from rat plasma using methyl tert-butyl methyl ether. Chromatographic
separation was achieved with 0.2% formic acid: acetonitrile (40:60, v/v) at a flow rate of 0.50 ml/min on
an Atlantis dC18 column with a total run time 3.0 min. The MS/MS ion transitions monitored were 180.10
® 163.30 for MEM and 180.10 ® 110.10 for IS. Results: The results met the acceptance criteria mentioned
in the guidelines. The lower limit of quantitation achieved was 0.025 ng/ml and the linearity was observed
from 0.025 to 220 ng/ml. The intra- and inter-day precision was in the range of 0.88–6.84 and 2.57–6.79%,
respectively. Conclusions: An LC-ESI-MS/MS for the determination of MEM in rat plasma employing simple liquid- liquid extraction was developed and validated with high sensitivity and selectivity. This novel method has been
applied to a pharmacokinetic study in rats.