Quantitative analysis of buprenorphine and norbuprenorphine in urine using liquid chromatography tandem mass spectrometry.

Buprenorphine is an opioid analgesic drug that is used as an alternative to methadone to treat heroin addiction. Established methods for the analysis of buprenorphine and its metabolites in urine such as gas chromatography-mass spectrometry (GC-MS) involve complicated sample extraction procedures. The aim of the present study was to develop a sensitive yet straightforward method for the simultaneous analysis of buprenorphine and norbuprenorphine in urine using liquid chromatography-MS-MS. The method comprised an enzymatic hydrolysis using Patella vulgata b-glucuronidase, followed by centrifugation and direct analysis of the supernatant. The limits of detection and quantitation were < 1 microg/L for buprenorphine and < 1 and 4 microg/L, respectively, for norbuprenorphine. Assay coefficients of variation (CVs) were < 15%, with the exception of concentrations close to the limit of quantitation, where CVs were below 20%. In direct comparison with an established GC-MS protocol, the method showed minimal negative bias (8.7% for buprenorphine and 1.8% for norbuprenorphine) and was less susceptible to sample carryover. The extent of conjugation in unhydrolyzed urine was investigated and found to be highly variable, with proportions of unconjugated buprenorphine and norbuprenorphine of 6.4% [range 0% to 67%; standard deviation (SD) 9.7%] and 34% (range 0% to 100%; SD 23.8%), respectively.

Rapid determination of amphetamine stereoisomer ratios in urine by gas chromatography-mass spectroscopy.

We describe a method for the determination of amphetamine optical isomer ratios. A simple basic extraction of amphetamine from urine is followed by on-column derivatization with (S)-(-)-N-(trifluoroacetyl)-L-prolyl chloride and analysis by gas chromatography-mass spectroscopy. This approach has been shown to be satisfactory for the separation of d- and l-amphetamine isomers and precision data shows the method to be reproducible. Patient data is presented to demonstrate the ability to differentiate between patients taking d-amphetamine and those using illicit (racemic) amphetamine by their l/d amphetamine ratio.

Observations on the BT PABA/14C-PABA tubeless test of pancreatic function.

The diagnostic accuracy of the BT PABA/14C-PABA tubeless test of pancreatic function was assessed in a prospective study of 140 patients. Drug or isotopic interference invalidated 16 tests (11.4%). The sensitivity of the PABA/14C excretion index was 76.7% and the specificity 85.7% using the mean -2 SD value of 0.82 as the cut-off point; 74.4% sensitivity and 95.7% specificity using the mean -3 SD value of 0.76. The potential usefulness and limitations of this modern version of the PABA test are discussed.

Relationship between PABA and Lundh tests: lack of influence of duodenal pH in vivo.

Twenty-five patients with chronic pancreatitis and 25 patients with non-pancreatic abdominal disorders were investigated by Lundh and BT PABA/14C-PABA tests of pancreatic function. The following results emerged: (1) There was a strong positive linear relationship between mean trypsin activity (MTA) and mean chymotrypsin activity (MCA) in duodenal aspirates after a Lundh test meal. (2) There was a strong positive linear relationship between chymotrypsin activity measured with BTEE, or BT PABA as substrate. (3) There was a strong positive correlation between MTA, or MCA, in duodenal juice after a Lundh meal and urinary PABA recovery, or the PABA/14C excretion index (PEI) in patients with chronic pancreatitis, but not in controls. (4) There was no correlation between the pH of duodenal juice in Lundh tests and PABA recovery, or PEI, in patients with or without pancreatic disease. We conclude that the Lundh and BT PABA/14C-PABA tests are equally discriminatory methods of assessing pancreatic exocrine function. The rate limiting effect of pH on BT PABA hydrolysis reported in in-vitro studies does not affect the practical clinical value of the BT PABA/14C-PABA test.

Plasma 25-hydroxyvitamin D concentrations in preterm infants receiving oral vitamin D supplements.

Plasma 25-hydroxy-cholecalciferol (25-OHD) was measured serially in two groups of preterm infants receiving either 400 IU or 1000 IU oral vitamin D3 daily. All the babies were able to absorb and hydroxylate vitamin D3 adequately by 36 weeks' gestational age. The higher daily supplement had no advantage over the lower dose.