A simple and sensitive high-performance liquid chromatography assay of diltiazem and main metabolites in renal transplanted patients.
A sensitive and specific reversed-phase high-performance liquid chromatographic method was developed for determination of the benzothiazepine calcium channel blocker diltiazem and three of its main metabolites in human plasma. A solid-phase extraction method (C18) is described for isolating diltiazem and the metabolites N-demethyl-diltiazem (M(A)), deacetyldiltiazem (M1) and N-demethyl-deacetyl-diltiazem (M2) from human plasma spiked with trans-diltiazem as internal standard. Chromatographic analysis of the eluate was accomplished using a reversed-phase column (C8) and a mobile phase consisting of acetonitrile, potassium dihydrogen phosphate-buffer (pH 2.9), triethylamine and methanol (280:598:2:90 v/v/v/v). The limit of detection was 5 ng/ml for diltiazem and 2.5 ng/ml for the metabolites (UV detection). Recoveries were > 75% for all substances. Precision analysis indicated a coefficient of variation below 5% for both diltiazem and metabolites at plasma concentrations ranging from 30 to 120 ng/ml for diltiazem and from 15 to 60 ng/ml for the metabolites. The accuracy was < 3% for diltiazem at all concentrations investigated. Metabolites showed an accuracy of < 7% at higher concentrations, however at low concentration the accuracy was < 16%. A pilot study has been performed in order to study whether the method was applicable to patients and volunteers. Plasma samples from renal transplanted patients treated with cyclosporin A and healthy volunteers did not show any interference by cyclosporin A with the determination of diltiazem and metabolites.
Department of Pharmacology, School of Pharmacy, University of Oslo, Norway. h.s.christensen@farmasi.uio.no
H
H
Christensen
E
E
Carlson
A
A
Asberg
L
L
Schram
K J
KJ
Berg
D000328:Adult; D000368:Aged; D002121:Calcium Channel Blockers / Q000097:blood* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D016572:Cyclosporine / Q000097:blood / Q000627:therapeutic use; D004110:Diltiazem / Q000097:blood* / Q000378:metabolism; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000097:blood / Q000627:therapeutic use; D016030:Kidney Transplantation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity
D002121:Calcium Channel Blockers; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D004110:Diltiazem