A MODIFIED GAS-LIQUID-CHROMATOGRAPHIC ASSAY TO MONITOR PLASMA MEXILETINE IN A TINNITUS STUDY

  • 1 January 1982
    • journal article
    • research article
    • Vol. 4  (4) , 243-247
Abstract
In a clinical study of .beta.-histidine, diazepam and mexiletine for the oral chemotherapy of tinnitus, a double-blind triple cross-over trial including a placebo was devised. As mexiletine is a potent cardiovascular drug and also a measure of compliance, a rapid and sensitive GLC method was developed to monitor its plasma concentration in patients who took part in the trial. This assay involved a preliminary ethereal extraction of the drug and internal marker (3-N,N-diethyl carbamyloxy pyridine) in a 1-ml plasma or urine sample under alkaline condition. The concentrated extract was redissolved in distilled methanol (10 .mu.l) and an aliquot (2 .mu.l) was analyzed by a GLC system (3% OV17 on Gas Chrome Q, 10-100 mesh) linked to a N-sensitive detector. The calibration graphs relating peak height ratios of the drug to the internal marker and concentration were linear and reproducible over the ranges of 5.0-100.0 ng/ml and 1.0-10.0 .mu.g/ml for both plasma and/or urine samples. The steady-state plasma concentrations of mexiletine in 5 patients, from whom blood samples were obtained as a measure of compliance, ranged between 570-1911 ng/ml which were similar to those reported from treatment of ventricular arrhythmias with similar dosage regimen of 200 mg mexiletine hydrochloride 3 times/day.

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