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D W Holt

Publications and source records attributed to D W Holt.

206 records · Page 12Linked to original sources
PubMedDate not supplied

Validation of high-performance liquid chromatographic-mass spectrometric method for the analysis of lidocaine in human plasma.

A sensitive and simple liquid chromatography-tandem mass spectrometry method is developed and validated for the determination of lidocaine in human plasma. Bupivacaine is used as an internal standard, and the plasma extraction is performed by a simple liquid-liquid extraction. The limit of quantitation (LOQ) is 0.5 ng/mL with a signal-to-noise ratio greater than 5. The calibration curve is linear from 0.5 to 250 ng/mL with an r2 greater than 0.99. The coefficients of variation for within- and between-assay imprecision, including LOQ, are < or = 13% and < or = 8%, respectively. The percentage of inaccuracy for within- and between-assay, including LOQ, are < or = 9% and < or = 5%, respectively. The absolute recovery of lidocaine and bupivacaine are greater than 84% and 82%, respectively. The higher sensitivity and accuracy of this method allow the measurement of low concentrations of lidocaine in plasma from a clinical study of topically applied lidocaine in healthy subjects.

Anesthetics, Local↗
PubMedDate not supplied

Sirolimus: has it gained from experience with older drugs?

The immunosuppressive drug sirolimus, recently licensed in Europe for use following kidney transplantation, was developed against a background in which it was common practice to use blood concentration measurements as a guide to therapy. This article sets out to document the use of blood concentration measurements in the assessment of the early and pivotal clinical trials of the drug and the attention that has been paid to the validation of analytical techniques used to measure the drug. It is concluded that, building on experience from the older drugs used for immunosuppression, data relating drug concentrations with efficacy outcomes have played a significant role in formulating guidelines on sirolimus dosing.

Chromatography, Liquid↗
PubMedDate not supplied

Creatine kinase MB isoforms: a potential predictor of acute cardiac allograft rejection.

BACKGROUND: Noninvasive studies to detect or predict acute allograft rejection after heart transplantation have failed to be sufficiently reliable to substitute for endomyocardial biopsy. Isoforms of creatine kinase MB isoenzyme (MB2 and MB1) are extremely sensitive markers of ischemic myocardial damage and, in theory, may be elevated in cardiac allograft rejection when myocardial necrosis is visible on microscopy (International Society for Heart and Lung Transplantation grade 2 or greater). METHODS: We examined, prospectively, the endomyocardial biopsy specimens (n = 256) of 50 consecutive patients undergoing orthotopic heart transplantation. Blood samples for creatine kinase MB isoforms (n = 527) were taken immediately before endomyocardial biopsy and at intervals between biopsies. RESULTS: The median ratio of MB2/MB1 in plasma samples taken at the time of biopsy for grades 2 and 3 was not significantly different from the ratio from biopsy specimens graded 0 and 1 (1.65 versus 1.33; p = Not significant). The sensitivity for diagnosing a moderately severe rejection was 47% with a specificity of 58%. However, in patients with significant acute rejection (grades 2 and 3) in whom consecutive samples were collected, the MB2/MB1 ratio was significantly increased before histologic changes seen on biopsy in 13 of 16 rejection episodes by a mean of 14 days. The sensitivity for predicting rejection (grade 2 or 3) before endomyocardial biopsy was 60% with a specificity of 71% (positive predictive value 43%, negative predictive value 86%). CONCLUSIONS: Creatine kinase MB isoforms may predict the occurrence of acute rejection before histologic evidence seen on endomyocardial biopsy.

Adolescent↗
PubMedDate not supplied

Mitochondrial calcium deposition in association with cyclosporine therapy and myocardial magnesium depletion: a serial histologic study in heart transplant recipients.

Intramitochondrial calcification has been reported in heart transplant recipients treated with high-dose cyclosporine. Myocardial magnesium depletion is common in this group and, on the basis of extensive data from animal studies, would be expected to produce similar mitochondrial deposition of calcium. This prospective study investigated the occurrence of such calcification in biopsy specimens obtained serially in nine heart transplant recipients with simultaneous analysis of myocardial magnesium. During a mean follow-up of 32 weeks, 24 biopsy specimens were analyzed from nine patients. Mitochondrial calcium deposition was more marked in biopsy specimens from recipients with magnesium depletion (p < 0.025). Early toxic cyclosporine levels occurred in three recipients associated with a significant but reversible increase in mitochondrial calcification (p < 0.0001). Histologic rejection and use of calcium antagonists did not modify these findings. It is concluded that although cyclosporine toxicity does induce mitochondrial calcium deposition, such deposition can occur in the absence of toxicity should myocardial magnesium depletion be concurrent. Long-term follow-up will establish the clinical sequelae of such observations. However, when taken together with the results of this study, recent reports of attenuation of accelerated graft atherosclerosis by calcium antagonists may suggest that cyclosporine-induced myocardial magnesium depletion may have an etiologic role in this multifactorial process.

Biopsy↗