Salivary clearance and urinary metabolic pattern of caffeine in healthy children and in pediatric patients with hepatocellular diseases

Measurement of salivary clearance and urinary metabolites of caffeine is an excellent noninvasive tool for assessing liver function, particularly the activity of cytochrome P4501A2 (CYP1A2), N-acetyltransferase (NAT), and xanthine oxidase (XO). This study was undertaken to measure the clearance of caffeine using saliva as a biological fluid and to assess the activities of the above-mentioned enzymes in healthy children and pediatric patients with liver diseases using urinary molar ratios of different caffeine metabolites. The well-established two-sample saliva approach was used to measure the clearance of caffeine in nine pediatric patients with liver diseases (LD) and in nine healthy children. The caffeine metabolites were also measured in the urine of these subjects by high-performance liquid chromatography, and urinary molar ratios of 5-acetylamino-6-formylamino-3-methyluracil (AFMU), 1-methylxanthine (1X), 1-methyluric acid (1U), and 1,7-dimethyluric acid (17U) were employed to estimate the activities of CYP1A2, NAT, and XO. The caffeine salivary clearance and the percentage of the dose excreted in the form of various metabolites were significantly (p < 0.035) smaller in the LD patients than those in healthy children. The urinary molar ratio of [AFMU + 1U + 1X]/17U, which reflects the activity of CYP1A2, was also significantly (p < 0.0005) reduced in these patients. However, there were no significant differences between the two groups in the ratios of AFMU/1X and 1U/1X, which estimate the activities of NAT and XO, respectively. In conclusion, the data obtained suggest that liver disease in pediatric subjects significantly reduces the salivary clearance of caffeine and the activity of cytochrome P4501A2, but it has no impact on the activities of NAT and XO.

Simultaneous high-performance liquid chromatography analysis of azithromycin and two of its metabolites in human tears and plasma

This article describes a high-performance liquid chromatographic (HPLC) method for the measurement of azithromycin (AZI) and two of its metabolites, 9a-N-desmethylazithromycin (ADES) and N-desmethylazithromycin (NDES), in human tears and plasma. The drug, metabolites, and internal standard (n-propylazithromycin [IS]) were detected electrochemically after injection of the extracted sample into the HPLC system. The peak height ratio (AZI, ADES, or NDES to IS) varied linearly, with concentrations in the ranges of 0.1 mg/L to 2.0 mg/L (tears) and 0.01 mg/L to 2.0 mg/L (plasma) of AZI, ADES, and NDES; the correlation coefficient (r) was more than 0.994 mg/L for all of the compounds (n=6). The analysis of tear samples collected at different intervals within 12 hours to 144 hours after a dose of 20 mg/kg of AZI from a trachoma patient yielded concentrations ranging from 1.52 mg/L to 0.34 mg/L for AZI, 0.79 mg/L to 0.27 mg/L for ADES, and 1.99 mg/L to less than 0.20 mg/L for NDES. The concentration of AZI in plasma ranged from 0.15 mg/L to 0.01 mg/L, whereas ADES and NDES were undetectable.

Seismic upgrades of healthcare facilities

Before 1989 seismic upgrading of hospital structures was not a primary consideration among hospital owners. However, after extensive earthquake damage to hospital buildings at Loma Prieta in Northern California in 1989 and then at Northridge in Southern California in 1994, hospital owners, legislators, and design teams become concerned about the need for seismic upgrading of existing facilities. Because the damage hospital structures sustained in the earthquakes was so severe and far-reaching, California has enacted laws that mandate seismic upgrading for existing facilities. Now hospital owners will have to upgrade buildings that do not conform to statewide seismic adequacy laws. By 2030, California expects all of its hospital structures to be sufficiently seismic-resistant. Slowly, regions in the Midwest and on the East Coast are following their example. This article outlines reasons and ways for seismic upgrading of existing facilities.

Transient inhibition by orotic acid does not abolish the in vivo response of rat hepatocytes to a direct mitogen, lead nitrate

BACKGROUND

Orotic acid (OA) is able to inhibit hepatocyte proliferation in vivo induced by 2/3 partial hepatectomy. The present studies were aimed at establishing: (i) whether OA also inhibits hepatocyte proliferation induced by a direct mitogen and, if so (ii) whether the stimulus provided by the mitogen is still expressed following transient inhibition by OA.

METHODS/RESULTS

In the first experiment male Wistar rats were injected with either lead nitrate (100 mumol/kg, i.v.) or saline and 20 h later some animals receiving the mitogen were also implanted with a 400-mg OA tablet (as OA-methyl ester. i.p.). Multiple injections of 3H-thymidine were given to each rat (50 microCi each, 6 h apart, i.p.) until 2 h before killing. All groups were killed 3 days after the initial treatment. Results indicated that OA almost completely inhibited hepatocyte DNA synthesis and labelling induced by lead nitrate (e.g. labelling index was 1.9 +/- 0.5% in the saline-treated group, 44.7 +/- 4.0% in the lead nitrate group and 1.4 +/- 0.3% in the group receiving lead nitrate + OA). Based on the above results, in a second experiment rats were given a similar dose of lead nitrate and a subset of animals was implanted 20 h later with a 400-mg OA tablet, as previously described. Multiple doses of 3H-thymidine were again given to each rat (20 microCi each, 6 h apart) until 2 h before killing. Animals from both groups were killed at 3, 6 or 8 days after lead nitrate. Results indicated that, while at day 3 lead nitrate-induced DNA synthesis was effectively inhibited by OA, at day 6 the proliferative response was resumed in the group receiving OA. Cumulative labelling index over 6 days was 30.3 +/- 1.4 in rats given the mitogen alone and 52.1 +/- 2.2 in the group exposed to lead nitrate + OA.

CONCLUSIONS

These data indicate that: (i) OA is also able to inhibit hepatocyte proliferation induced by a direct mitogen such as lead nitrate; this, in turn, suggests that its inhibitory effect is not unique to the stimulus elicited by partial hepatectomy. (ii) The proliferative response triggered by the mitogen is not abolished by the transient (3-4 days) inhibitory phase imposed by OA. Possible mechanisms underlying these effects are considered in the discussion.

Expedient liquid chromatographic assay for paclitaxel in plasma after its administration to cancer patients

A rapid and expedient liquid chromatographic method for the analysis of paclitaxel in plasma is described. Paclitaxel and the internal standard (IS, N-nitrosodiphenylamine) were separated on a 10-microns particle, 8 mm x 10 cm C18 cartridge in conjunction with a radial compression system preceded by Guard Pak with a C18 insert. The mobile phase was a mixture of 1 mM sodium phosphate buffer (pH 5) and acetonitrile (55.5:45.5 per volume), and the flow rate was 4.5 ml/min. The compounds were extracted from plasma with ethyl acetate and were detected in the effluent spectrophotometrically at 227 nm. The recovery of paclitaxel from plasma at concentrations equivalent to 50, 400, and 800 micrograms/L paclitaxel in plasma was 79.1, 75.2, and 74.3%, respectively, and the retention times of the drug and IS under these conditions were 5.26 and 6.45 min, respectively. The relationship between the concentration and peak height ratio (drug/IS) was linear (r = 0.9938-0.9998) in the range of 10-1,600 micrograms/L, and no interference in the assay was observed. The intrarun coefficient of variations (CV) at 50, 250, and 800 micrograms/L were 4.9, 5.4, and 4.1%, respectively, and the deviations from theoretical accuracy at these concentrations were 1.2, 0.5, and 5.4%, respectively. We are currently using this assay to investigate the pharmacokinetics of paclitaxel in cancer patients treated with this agent in a combined chemotherapy.

The enhancing effect of fasting/refeeding on the growth of nodules selectable by the resistant hepatocyte model in rat liver

Caloric restriction causes a generalized decrease in growth rate and has been shown to delay the development of both spontaneous and induced neoplasia. In contrast to chronic food restriction, the extreme condition of fasting/refeeding is associated with an overall increase in cell turnover in several organs, including liver, compared with regular feeding. The present study was therefore designed to investigate the effect of complete food withdrawal followed by refeeding on the growth of hepatocyte nodules in initiated rat liver. Male Fischer 344 rats were given a single dose of diethylnitrosamine (DEN, 200 mg/kg i.p.) and then, starting 1 wk later, they were exposed to one or three cycles of fasting (3 days) followed by refeeding (11 days). The control group was fed continuously. Seven weeks after DEN administration all rats were subjected to the resistant hepatocyte model (2-acetylaminofluorene coupled with CCl4) and 2 weeks later 2/3 partial hepatectomy (PH) was performed. All animals were killed 2 weeks after surgery. At PH rats given one cycle of fasting/refeeding had significantly larger glutathione S-transferase 7-7-positive hepatic lesions compared with controls (mean area 0.73 +/- 0.04 versus 0.50 +/- 0.05 mm2, P < 0.025; mean percent area 25.6 +/- 3.2 versus 12.4 +/- 0.9, P < 0.005), while no significant change was observed in their number. The observed differences were more pronounced with three cycles of fasting/refeeding. A similar pattern of results was obtained at the time of killing. It is concluded that fasting/refeeding can exert a positive effect on the growth of rat hepatocyte foci and nodules, in contrast to the general inhibitory effect on carcinogenesis caused by food restriction.

Liquid chromatographic analysis of mesna and dimesna in plasma and urine of patients treated with mesna

We describe in this report an expedient and accurate liquid chromatographic method for measurement of mesna and dimesna in plasma and urine. The separation of mesna and the internal standard (p-aminobenzoic acid, IS) was achieved on a 10-microns, 8 mm (i.d.) x 10-cm C18-Resolve cartridge in conjunction with radial compression system. An aqueous solution of sodium citrate (0.1 M), tetrabutyl ammonium phosphate (0.001 M), and triethylamine (1:10,000, vol/vol), adjusted to pH 5 with 85% phosphoric acid was used at a flow rate of 2 ml/min as a mobile phase. The compounds were detected in the effluent electrochemically at +450 mV. After an appropriate amount of IS was added, the plasma sample (100 microliters or fraction thereof) was deproteinized with an equal volume of 0.0825 M sulfuric acid containing sodium hexametaphosphate (1.25% wt/vol), whereas urine was diluted 1:50 with water and mixed 1:1 with an aqueous solution of sodium hexametaphosphate (1.25% wt/vol). Dimesna was reduced back to mesna with sodium borohydride before analysis of the total mesna. The peak height ratio (drug/IS) varied linearly with the concentration, and the correlation coefficient was > 0.992 for both mesna and dimesna. The intrarun precision at different concentrations of mesna was equally good and the coefficient of variation was consistently < 4.5%. No interference from endogenous substances or any concomitantly used drug was observed. This assay is currently being used for measurement of mesna and dimesna in plasma of bone marrow recipients who receive high doses of cyclophosphamide.

A comparison of three ported cannulae available in New Zealand

A comparison was made of the three 22-gauge ported intravenous cannulae available in New Zealand--Venflon 2, Vasofix Braunule and Insyte. All cannulae performed satisfactorily in terms of overall success of cannulation although significant differences were apparent in both clinical and laboratory performance. Anaesthetists' clinical preference was for Insyte and Venflon 2 brands, perceiving these to have greater ease of handling and better packaging. In a series of laboratory studies, Vasofix was found to have the highest flowrate, the fastest time to flashback and the lowest valve opening pressure. Insyte required the least force of penetration. Venflon 2 had the greatest margin of safety between pressure to inject through the port and pressure required to blow the syringe/port assembly apart. Potential problems were identified with the Insyte port valve mechanism.

Effect of orotic acid on in vivo DNA synthesis in hepatocytes of normal rat liver and in hepatic foci/nodules

One of the proposed mechanisms by which orotic acid (OA) promotes liver carcinogenesis is by differentially mito-inhibiting the normal hepatocytes while permitting the initiated ones to respond to growth stimuli to form foci/nodules. In an attempt to examine this hypothesis, the present study was designed to determine (i) whether OA inhibits DNA synthesis in normal hepatocytes in vivo, and (ii) whether hepatocytes from hepatic foci/nodules are relatively resistant to the mito-inhibitory effects of OA. The results of this study indicate that OA given i.p. as a tablet of 300 mg at the time of partial hepatectomy (PH) almost completely inhibited liver DNA synthesis. Three days later--a time period by which the implanted tablet disappeared--the hepatocytes resumed DNA synthesis. Exposure to OA results in an accumulation of uridine nucleotides and a decrease in adenosine nucleotides. Creation of such an imbalance in nucleotide pools appears to be important for OA to inhibit DNA synthesis. Adenine (a tablet of 300 mg), an agent that inhibits the metabolism of OA to uridine nucleotides, counteracted the mito-inhibitory effects of OA. To determine whether the hepatocytes in foci/nodules are resistant to the mito-inhibitory effects of OA, rats were initiated with diethylnitrosamine (DENA; 150 mg/kg) and promoted by the resistant-hepatocyte model. Fourteen weeks after the administration of DENA, the rats were subjected to PH in the presence of absence of OA (300 mg tablet). The results indicated that, in contrast to hepatocytes in normal or surrounding non-nodular liver, a subpopulation of hepatocyte foci/nodules appear to be relatively resistant to the mito-inhibitory effects of OA. These findings support the hypothesis that differential mito-inhibition is a possible component in the promoting effect of OA. However, whether this is the mechanism by which OA promotes liver carcinogenesis needs to be further investigated.

Impaired elimination of atenolol in a nephropathic patient with self-medication overdose

A case of intoxication with atenolol (plasma concentration of 2.71 mg/L) caused by an improper self-medication combined with impaired renal function is presented. The patient was supported with atropine, isoproterenol, dopamine, and dobutamine, and a thorough pharmacokinetic monitoring of atenolol was conducted. As the serum creatinine concentration returned slowly to baseline with good diuresis, the concentration of atenolol decreased (biologic half-life = 2.95 days) and the blood pressure gradually recovered. The patient improved and was subsequently discharged in good health. Had pharmacokinetic monitoring of atenolol not been performed, hemodialysis would have been indicated.

Alteration of taurine homeostasis in acute heatstroke

OBJECTIVE

To investigate the potential role of taurine as a hypothermic modulator during heatstroke.

DESIGN

Prospective analyses.

SETTING

Heatstroke Center in makkah, Saudi Arabia.

PATIENTS

Twenty-nine adult patients with heatstroke.

INTERVENTIONS

High-performance liquid chromatography was used to measure plasma and urine taurine concentrations in heatstroke patients on admission (precooling) and 24 hrs after complete cooling (postcooling).

MEASUREMENTS AND MAIN RESULTS

There were 18 males and 11 females with a mean rectal temperature of 42.2 +/- 0.14 degrees C. At the precooling time period, the taurine concentrations were increased (plasma 180 +/- 14 mumol/L; urine 4142 +/- 720 mumol/L [normal ranges 45.5 to 138.2 and 168 to 1890 mumol/L, respectively]). At the postcooling time period, taurine concentrations were significantly (p < .0001) decreased (54 +/- 6 and 802 +/- 160 mumol/L for plasma and urine, respectively). No correlation was found between taurine and creatine kinase activity, or between precooling temperature and taurinemia or taurinuria.

CONCLUSIONS

The source and clinical significance of the increased taurine concentrations are to be determined. The involvement of taurine in the regulation of core body temperature suggests that it may have an adaptive role in heatstroke.

An expedient liquid chromatographic micromeasurement of isoniazid in plasma by use of electrochemical detection

We describe a sensitive and expedient microassay of isoniazid in plasma by use of electrochemical detection in conjunction with a radial compression liquid chromatography. Diphenylcarbazide was used as an internal standard and the separation was achieved on a 10-micron, 8 mm x 10 cm C18 (12% carbon load) cartridge. A mixture of 10 mM sodium dibasic phosphate solution (adjusted to pH 7 with phosphoric acid) and methanol (93.5:6.5, by volume) was used as a mobile phase at a flow rate of 4 ml/min. After dilution with an equal volume of aqueous solution of the internal standard (6.667 microM), the plasma sample (50-150 microliters) was deproteinized by use of an Amicon Centrifree-MS ultrafilter at 2,000 g. No interference from any endogenous substance or concomitantly used drug was observed, and the assay was highly linear (r greater than 0.9994) in the concentration range examined (0.146-145.8 microM). The intra- and interrun precision was equally good, with coefficients of variation of less than 3.13 and less than 5.4%. We are currently using this method for monitoring isoniazid in patients treated with this drug for tuberculosis.

Steady state pharmacokinetics of propranolol in Saudi Arabian patients and comparison with data for different populations

The steady state pharmacokinetics of propranolol was examined in 48 Saudi Arabian patients chronically treated with oral doses [mean (SEM) = 85.8 (5) mg] of this drug. The mean (SEM) of the steady state concentration (Css) per mg/kg daily dose was 21.8 (3.1) ng.ml-1/mg.kg-1. A 6-fold variability in Css was observed between patients treated with 40 mg every 8 hours and 14-fold between patients treated with 40 mg twice daily. The frequency distribution of the apparent oral clearance (TCLor) of propranolol was bimodal with 88% of the patients showing TCLor of 18 to 372 l.hr-1 while the remainder had TCLor of 471 to 749 l.hr-1. The mean (SEM) of the TCLor per kg body weight for all 48 patients was 3.16 (0.38) l.hr-1.kg-1. Both Css and TCLor obtained for Saudi Arabian patients are not significantly different from those reported for subjects from Western populations. While Css increased proportionally (P less than .001) with dosing, a near-significant (P less than .06), inverse, linear relationship was found between age and TCLor. No significant effect of sex, body weight, or disease state (i.e., heart diseases, hypertension, depression, migraine) on Css or TCLor was detected.

Rapid liquid chromatographic analysis of mitoxantrone in plasma with C18 sample purification

A useful and rapid method for the analysis of mitoxantrone in human plasma is described. We purified the sample with a C18 Sep Pak cartridge pre-treated with methanol, water and 0.05 M ammonium phosphate (pH = 2.75). The drug and internal standard (Methylene Blue) were eluted from the cartridge with 1 M acetic acid in methanol and were separated on a 10 microns particle size CN Resolve cartridge in conjunction with a radial compression liquid chromatograph. The mobile phase consisted of a mixture of 0.05 M ammonium phosphate, acetonitrile and methanol (60:35:5, by vol), and the detection was performed spectrophotometrically at 660 nm. The peak height ratio (drug/internal standard) varied linearly (r greater than 0.993) with concentration over the range examined 0.01-3 micrograms ml-1, and the inter- and intra-run precision at high, medium and low concentrations were good; CV ranged from 2.52 to 7.2%. There was no interference from other anticancer drugs or analgesics. We applied the described method to investigate the pharmacokinetics of mitoxantrone using a rabbit as an in vivo model.

Direct, simultaneous measurement of chloramphenicol and its monosuccinate ester in micro-samples of plasma by radial-compression liquid chromatography

A simple method of simultaneous analysis for chloramphenicol and chloramphenicol succinate in 10-microL samples of plasma is described. We injected the plasma samples directly into a radial-compression liquid chromatograph equipped with a precolumn module and a C18 insert. A mixture of acetic acid solution (pH 3)/acetonitrile (75/25, by vol) was used as mobile phase, at a flow rate of 4 mL/min. We separated the compounds in a 10-micron (particle size) C18 cartridge with a radial compression separation system and detected them in the effluent at 280 nm. The peak height for both compounds was linearly (r greater than 0.9993) related to concentration over the range investigated, 1-50 mg/L. We also performed the analysis with use of an internal standard (methylprednisolone) and obtained equally good results (r greater than 0.9995). We observed no interference from other antibiotics or drugs in the assay, and the inter- and intra-run precision at different concentrations was good (CV, 0 to 5.6%). We analyzed microsamples of plasma from an infant treated for meningitis with chloramphenicol sodium succinate intravenously. Total analysis time for each sample was less than 8 min.

Direct, simultaneous measurement of chloramphenicol and its monosuccinate ester in micro-samples of plasma by radial-compression liquid chromatography

A simple method of simultaneous analysis for chloramphenicol and chloramphenicol succinate in 10-microL samples of plasma is described. We injected the plasma samples directly into a radial-compression liquid chromatograph equipped with a precolumn module and a C18 insert. A mixture of acetic acid solution (pH 3)/acetonitrile (75/25, by vol) was used as mobile phase, at a flow rate of 4 mL/min. We separated the compounds in a 10-micron (particle size) C18 cartridge with a radial compression separation system and detected them in the effluent at 280 nm. The peak height for both compounds was linearly (r greater than 0.9993) related to concentration over the range investigated, 1-50 mg/L. We also performed the analysis with use of an internal standard (methylprednisolone) and obtained equally good results (r greater than 0.9995). We observed no interference from other antibiotics or drugs in the assay, and the inter- and intra-run precision at different concentrations was good (CV, 0 to 5.6%). We analyzed microsamples of plasma from an infant treated for meningitis with chloramphenicol sodium succinate intravenously. Total analysis time for each sample was less than 8 min.