William C. Griffiths

Elevated nicotine levels in patients undergoing hemodialysis: A role in cardiovascular mortality and morbidity?

The incidence of cardiovascular disease in patients with end-stage renal disease undergoing long-term maintenance hemodialysis is excessively high. The reason for this excess morbidity and mortality has remained unclear. Cigarette smoking is one factor that has been associated with increased cardiovascular risk. To learn more about the effects of tobacco smoking in these patients, nicotine levels were assayed in the serum of 10 patients with end-stage renal disease undergoing maintenance hemodialysis. Specimens were obtained before and after smoking one cigarette and following dialysis or an equivalent period in control subjects. Serum nicotine levels (+/-SEM) in control subjects measured 19.0 +/- 7.2 ng/ml initially, 36.1 +/- 8.2 ng/ml after smoking, and 9.3 +/- 3.5 ng/ml after a period of 4.35 hours. These compare with respective values of 76.6 +/- 16.8 ng/ml (p less than 0.004), 132.9 +/- 19.7 ng/ml (p less than 0.001), and 51.9 +/- 10.5 ng/ml (p less than 0.001) in patients undergoing hemodialysis. These data demonstrate markedly higher nicotine levels in hemodialysis patients compared with control subjects, which may have serious implications regarding morbidity and mortality.

Simultaneous assay of diazepam, chlordiazepoxide, N-desmethyldiazepam, N-desmethylchlordiazepoxide, and demoxepam in serum by high performance liquid chromatography

A method is presented for simultaneously determining diazepam and chlordiazepoxide along with their respective major active serum metabolites N-desmethyldiazepam, and N-desmethylchlordiazepoxide and demoxepam. The drugs are extracted from one ml of buffered serum using chloroform containing 5-(p-methylphenyl)-5-phenylhydantoin as an internal standard. The elution is accomplished using a reversed-phase column with a mobile phase consisting of an acetonitrile/methanol/acetate buffer pH 5.0 (200/225/500) at a flow rate of 2.0 ml/min. Absorbance is monitored at 240 nm using a variable wavelength detector. Each chromatographic separation requires approximately 15 minutes at ambient temperature. Of more than twenty drugs tested for possible interference with this procedure, only methaqualone interferes with the internal standard, and phenytoin with demoxepam.

Comparison of an Enzyme Immunoassay and a High Performance Liquid Chromatographic Method for Quantitation of Quinidine in Serum

AbstractThe need to monitor serum or plasma levels of quinidine in the treatment of cardiac arrhythmia is well documented [1-3] Quinidine has been assayed by fluorometry [4, 5], chromatographic methods [6, 7, 9], and, most recently, an enzyme immunoassay technique (EMIT). We have compared the enzyme immunoassay method with a reverse-phase high performance liquid chromatographic method [7, 9]

The albumin binding of unconjugated bilirubin in serum

1. The limited bilirubin binding capacity of human serum albumin, and the fact that kernicterus can occur once the serum unconjugated bilirubin concentration exceeds this capacity, makes the assessment of non-albumin bound free bilirubin valuable in cases of severe neonatal hyperbilirubinemia. 2. Present methodology for this assessment utilizes Sephadex column chromatography, and is somewhat tedious and slow. 3. We have developed a procedure for assessing the albumin binding capacity of serum by titrating a sample of the serum with T-20 Dextran coated charcoal. 4. The method requires 2 ml of serum, takes 90 minutes to complete and is highly reproducible. 5. By this method, we can determine the reported secondary loose binding capacity of the albumin as well as the tight binding capacity which is determined by existing methods. 6. The tight binding capacity of a pool of normal adult human serum was found to be 20 mg/dl of serum. 7. This is in agreement with existing methods. The loose binding capacity was found to be an additional 10 mg/dl of serum. Added phenobarbital was found to lower the tight binding capacity, but not the secondary capacity.

False positive urine drug screens from quinine in tonic water

Urine surveillance of patients is a universal procedure in drug treatment programs for monitoring frequency and type of illicit drug use. The method is also being increasingly utilized by employers to screen employees for drug use. The presence of a prescribed substance in a subjects urine is considered objective evidence of illicit drug use, and is used to confront subjects. However, studies have demonstrated that urine surveillance is not infallible. The presence of inaccuracy in urine surveillance has definite negative consequences of both individuals and the testers. In this paper, we report that a positive urine test for quinine, which may be evidence of illicit drug use, results from the consumption of the amount of tonic water present in a mixed drink. The implications of this finding are discussed.

A procedure for estimating bias between quantitative analytical methods

Before quality control techniques and protocols can be applied to a laboratory procedure, the quality itself must be evaluated. This involves among other considerations an assessment of analytical accuracy. Some, but not all (and perhaps not even many), clinical laboratory analytical procedures can be considered accurate in the sense that every laboratory should get the same quantitative result for the analyte in question, regardless of the composition of the sample medium (for example potassium). That most methods are to one degree or another inaccurate does not invalidate their use. But the burden is on the laboratory, in choosing a method, to knowjust how accurate that method is.

On the difference between colonic and small intestinal alkaline phosphatase.

Colonic and small intestinal alkaline phosphatase extracts were studied biochemically and electrophoretically to elucidate the source of a reported difference in cellulose acetate electrophoretic mobility. Both preparations were inactivated with 0.5 mmol/L L-phenylalanine but retained full activity in the presence of 1.0 mmol/L tetramisole. Treatment with neuraminidase changed a minor fraction of the small intestinal but the major portion of the colonic alkaline phosphatase to a cathodically migrating form. The most likely explanation for our findings is that the colon and small intestinal alkaline phosphatase are mixtures of the same multiple forms but in different proportions.