High-pressure Liquid Chromatographic Assay Research Articles

Quantification of neuroreceptors in the living human brain: III. D2-like dopamine receptors: theory, validation, and changes during normal aging.

Dopamine receptor density is believed to decline in normal aging. To test this hypothesis, we measured the density of dopamine D2-like receptors in vivo in the neostriatum of normal living humans by using the graphical method. This method determines the D2-like dopamine receptor density in the human brain with an occupying ligand (unlabeled haloperidol) and a radioligand (labeled 3-N-methylspiperone). The method was examined critically, and the assumptions underlying the method were shown to be valid. The validation included comparison of the representation of tracer metabolism by high-pressure liquid chromatography and model assays, calculation of the lumped constant Dw from the value of its components, and comparable tracer partition coefficients in vitro and in vivo. In error analysis, the method consistently performed as well as the direct least-squares regression at statistical noise levels appropriate for the tomograph used in these studies. The method revealed that the density of the D2-like receptors that bind haloperidol in the caudate nucleus of normal humans declined 1% per year after the age of 18 years.

Interaction of β2-adrenoceptor agonists with native cyclodextrins: Application to the development of chiral assays for terbutaline

The enantioselectivity of the complexation between β2-adrenoceptor agonists of different structural types and native cyclodextrins (α, β and γ-CDs) has been examined by including CDs as chiral modifiers in high pressure liquid chromatography (HPLC) and in capillary zone electrophoresis (CZE). The best enantiomer separation was obtained for terbutaline with β-CD in both HPLC and CZE systems (resolution (Rs) of 1.0 and 1.1 respectively). The chiral HPLC assay for terbutaline was validated and gave linear standard curves of peak height versus concentration for both enantiomers (r2 > 0.99) with y-intercepts through the origin and intra- and interday coefficients of variation of less than 3% at 100 μg ml−1. Only the enantiomers of the resorcinol type β2-agonists terbutaline and orciprenaline were separated in the CZE and HPLC systems, suggesting the position of substituents in the aromatic ring of β2-agonists has a profound effect on the enantioselectivity of complexation of these drugs with β-CD.

High-pressure liquid chromatographic assay for the determination of thyrotropin-releasing hormone and its common metabolites in a physiological salt solution circulated through the isolated perfused rat lung

A specific and sensitive assay for TRH ( l-pyroglutamyl- l-histidyl- l-proline amide), 3H-TRH ( l-proline 3,4- 3H(N),histidyl-3- 3H(N)), and four possible metabolites of TRH, present in the recirculated perfusate of an isolated perfused rat lung preparation, was developed. Unlike previous methods, the method developed does not require extraction of the analytes from the biological matrix. The crude sample was adjusted to a pH of 3.2 with concentrated trifluoroacetic acid and injected on to a PRP-1 (polystyrene divinylbenzene) column (10 μm, 25 cm × 4.6 mm i.d.). The mobile phase was 10% v/v acetonitrile and 90% v/v 0.75 g l −1 1-hepantanesulfonic acid in 0.004 M trifluoroacetic acid, adjusted to a pH of 2.4 with concentrated NaOH. The flow rate was 0.5 ml min −1 and the analytes were detected by UV absorption at a wavelength of 26 nm and by radiochemical detection utilizing a liquid scintillation counter. The nominal retention times for l-PRO, l-PRO-NH 2, TRH, cyclo(HIS-PRO) and TRH-OH were 4.0 ± 0.9, 10.0 ± 0.2, 15.5 ± 0.4, 19.2 ± 0.5 and 25.3 ± 0.5 min respectively. The assay performs well in terms of precision and accuracy as indicated by linear regression and intra-assay variability analysis.

Identification of the α Chain Lysine Donor Sites Involved in Factor XIIIa Fibrin Cross-linking

Biochemical studies of fibrin cross-linking were conducted to identify the specific Aalpha chain lysine residues that potentially serve as Factor XIIIa amine donor substrates during alpha polymer formation. A previously characterized Factor XIIIa fibrin lysine labeling system was employed to localize sites of donor activity based on their covalent incorporation of a synthetic peptide acceptor substrate analog modelled after the NH2-terminal cross-linking domain of alpha2 antiplasmin. Peptide-decorated fibrin was prepared using purified fibrinogen as the starting material. Cyanogen bromide digestion, immunoaffinity chromatography, high pressure liquid chromatography (HPLC), and enzyme-linked immunosorbent assay (anti-peptide) methodologies were employed to isolate purified CNBr fibrin fragments whose structures included the acceptor probe in cross-linked form and, therefore, represented regions of (amine) donor activity. Five alpha chain CNBr fragments (within Aalpha 208-610) and one gamma chain CNBr fragment (gamma 385-411) were the only portions of fibrin found associated with the acceptor peptide, based on collective sequencing, mass, and compositional data. Trypsin digestion, HPLC, and enzyme-linked immunosorbent assay (anti-peptide) methodologies were used to isolate smaller derivatives whose structures included an alpha chain tryptic cleavage product (the donor arm) cross-linked to the trypsin-resistant synthetic peptide (the acceptor arm). Biochemical characterization and quantitative peptide recovery data revealed that 12 of the 23 potential lysine donor residues within alpha 208-610 had incorporated the peptide probe, whereas gamma chain donor activity was due solely to peptide cross-linking at (gamma) Lys406; the alpha chain lysines, Lys556 and Lys580, accounted for 50% of the total alpha chain donor cross-linking activity observed, with Lys539, Lys508, Lys418, and Lys448 contributing an additional 28% and Lys601, Lys606, Lys427, Lys429, Lys208, Lys224, and/or Lys219 responsible for the remaining proportion (2-5%, each). The collective findings extend current models proposed for the mechanism of alpha polymer formation, raise questions concerning the physiological role of multiple alpha chain donor sites, and, most importantly, provide specific information that should facilitate future efforts to identify the respective lysine and glutamine partners involved in native fibrin alpha chain cross-linking.

Isolation and characterization of Rhizobium tropici Nod factor sulfation genes.

Rhizobium tropici produces a mixture of sulfated and non-sulfated Nod factors. The genes responsible for the sulfation process in R. tropici strain CFN299 were cloned and sequenced. These genes are homologous to the nodP, nodQ, and nodH genes from R. meliloti. The identity among the two species is 75% for nodP, 74% for nodQ, and 69% for nodH. NodH resembles sulfotransferases in general and NodQ has the characteristic purine-binding motifs and the PAPS 3'-phosphoadenosine 5'-phosphosulfate) motif. Mutants of NodP and NodH were obtained by site-directed mutagenesis. They are no longer able to synthesize the sulfated Nod factor, as was demonstrated in high-pressure liquid chromatography and thin-layer chromatography assays. The NodP- mutant had a decreased nodulation capacity in Phaseolus vulgaris Negro Xamapa bean plants. In contrast, NodH- and NodP- mutants acquired an increased capacity to nodulate the high-nitrogen-fixing bean cultivars N-8-116 and BAT-477. Nodulation was restored to normal levels when the mutants were complemented with a 16-kb clone carrying the wild-type genes. The role of the sulfate on Nod factors in R. tropici was dependent on the bean cultivar and the conditions assayed.

有害物質・障害生物の水環境への影響と制御 河川水マイクロコズムによるビスフェノールＡ（ＢＰＡ）の分解

Biodegradability of bisphenol (BPA) in aquatic environments was evaluated by a river die-away method using a variety of river water microcosms. Among 44 microcosms examined, 40 microcosms (ca. 90% of the total) exhibited BPA-degrading capability to a certain degree in an artificial river water. It suggested ubiquitous presence of BPA-degraders. However, among them only 6 samples showed complete degradation or mineralization of BPA shown as complete removal of TOC, and the other 34 microcosms accumulated common metabolites, which were detected as two peaks according to high-pressure liquid chromatography assay. As a result, more than 10% of the initial TOC remained in test microcosms. Eight BPA-degrading bacteria were isolated from river waters and all the isolates accumulated the same metabolites as those accumulated by river water microcosms during BPA degradation. These results suggest that recalcitrant metabolites are produced even if partial degradation of BPA can proceed easily. In some aquatic environments the metabolite(s)-degraders coexist together with the BPA-degraders and they seems essential for the complete degradation or mineralization of BPA.

Effect of R-verapamil on the pharmacokinetics of paclitaxel in women with breast cancer.

To study the effect of the multidrug-resistance reversal agent R-verapamil on the pharmacokinetic behavior of paclitaxel. Six women with breast cancer who received paclitaxel as a 3-hour infusion with and without R-verapamil were monitored with frequent plasma sampling up to 24 hours postinfusion. Paclitaxel concentrations were measured using a reverse-phase high-pressure liquid chromatography assay. Concomitant administration of R-verapamil resulted in a decrease in mean (+/- SD) paclitaxel clearance from 179 +/- 67 mL/min/m2 to 90 +/- 34 mL/min/m2 (P < .03) and in a twofold increase in paclitaxel exposure (area under the curve [AUC]). The mean end-infusion paclitaxel concentration was also twofold higher: 5.1 +/- 1.8 mumol/L versus 11.3 +/- 4.1 mumol/L (P < .03). The alteration in paclitaxel pharmacokinetics when paclitaxel and R-verapamil are coadministered complicates the interpretation of response and toxicity data from clinical trials of this drug combination.

Near-patient rapid assay of carbamazepine concentration

Rapid turnaround testing of carbamazepine (CBZ) concentration helps the clinician assess patients efficiently. The Biotrack (BT) therapeutic drug monitor uses an automated turbidimetric latex agglutination assay of hemolyzed whole blood and reports the corresponding serum drug concentration within 3 min of sample application. We compared BT results for 53 patients with serum CBZ measurements made with the Abbott TDx fluorescence polarization immunoassay (FPIA) system. Mean BT concentration was 9.5 μg/ml (range, 2.8–18.3 μg/ml); one sample was reported “below 2.0 μg/ml” (FPIA = 1.1 μg/ml). Mean FPIA concentration of the 52 BT-quantifiable samples was 8.7 μg/ml (range, 2.8–18.0 μg/ml). Correlation of BT with FPIA was high ( r = 0.96). BT results had a bias of 0.8 μg/ml [95% confidence intervals (CI) = 0.6 to 0.9 μg/ml]; median absolute error relative to FPIA was 0.6 μg/ml. Variations within the normal range for hematocrit, albumin, and creatinine had minimal effect on accuracy. As compared with a high-pressure liquid chromatographic (HPLC) assay, the BT assay showed less cross-reactivity than did FPIA to increased concentrations of the CBZ metabolite, carbamazepine-10,11-epoxide (CBZE). Assays performed on samples from 15 other patients not receiving CBZ were all <2.0 μg/ml. The BT assay is sufficiently accurate for clinical monitoring of CBZ concentrations

Forms of cobalamin and vitamin B 12 analogs in maternal plasma, milk, and cord plasma

Corrinoids are nutrients synthesized by microorganisms, both as biologically active compounds (cobalamins: hydroxo-, cyano-[vitamin B 12], and the two vitamin B 12 coenzymatic forms: 5′ adenosyl- and methyl-cobalamin) and as biologically inactive molecules, the so-called analogs (cobinamides). Though the transport system in humans favors the biologically active forms of vitamin B 12, numerous studies have indicated the presence of analogs in human material. The present study was undertaken to compare the number of analogs present in maternal plasma and milk and in cord plasma, and to determine if milk secretion is contaminated with potentially harmful vitamin B 12 analogs. The concentrations of cobalamin and of cobinamides were measured in maternal milk, maternal plasma, and cord plasma. Cobalamin analogs were found in maternal plasma (34.6 ± 28.1 pmol/L) and in cord plasma (62.1 ± 32.0 pmol/L; P < 0.005), but not in maternal milk (0.6 ± 0.7 pmol/L). A combination of reverse phase high pressure liquid chromatography and radioisotopic dilution assay was used to identify the individual cobalamins. The major peak in cord plasma was identified as CH 3-cobalamin (39%), while the peaks of CH 3-cobalamin (29.75%) and ado-cobalamin (29.56%) were similar in the maternal plasma. The ado-cobalamin peak was higher in milk (41%) than in maternal or umbilical plasma. We have confirmed the presence of analogs in plasma, but shown that milk is protected from vitamin B 12 analogs, as none were found in the exocrine mammary secretion. Thus, biologically active vitamin B 12 is selectively transported into milk. We found cord plasma to contain significantly higher amounts of analogs than maternal plasma. Whether this represents conversion of active forms of the vitamin within the fetus or accumulation of analogs transferred during pregnancy remains to be elucidated.

High-Pressure Liquid Chromatography Assay for Quantitatively Monitoring Spore Photoproduct Repair Mediated by Spore Photoproduct Lyase during Germination of uv-Irradiated Bacillus subtilis Spores

The major DNA photoproduct formed upon uv irradiation of Bacillus subtilis spores is the thymine dimer 5-thyminyl-5,6-dihydrothymine, informally referred to as spore photoproduct (SP). A rapid separation technique for detecting and quantitating SP by HPLC was developed to replace traditional paper chromatography. Tritiated thymine and thymine-containing photoproducts from trifluoroacetic acid-hydrolyzed DNA purified from uv-irradiated cells or spores of B. subtilis were identified and isolated from paper chromatograms, subjected to HPLC on a Microsorb phenyl 5-μm column using 100% water as the mobile phase, and detected by scintillation counting of collected fractions. At a flow rate of 1.8 ml per minute, thymine-containing compounds eluted in the order thymine (T; 5.5 min), cis-syn cyclobutyl thymine-thymine dimers (TT; 7.5 min), cyclobutyl uracil-thymine dimers (UT, the acid breakdown product of cytosine-thymine (CT) dimers; 9.5 min), and SP (14.5 min). The method was used to quantitate the amount of SP produced upon irradiation of B. subtilis spores and to monitor repair of SP in vivo by the enzyme SP lyase during spore germination.

Evaluation of assays for the identification and quantitation of muconic acid, a benzene metabolite in human urine.

Muconic acid (MA) is a urinary metabolite of benzene and has been used as a biomarker of exposure to benzene in humans exposed to levels as low as 1 ppm. We have modified a high-pressure liquid chromatography (HPLC) based assay for urinary MA (Ducos et al., 1990) by the use of a diode array detector. This modification increases the specificity of the HPLC-based assay by identifying false positives. In addition, we have developed a gas chromatography (GC) based assay that uses a flame ionization detector (GC-FID). Both assays identified and quantified MA in human urine at concentrations greater than 40-50 ng/ml. Assay precision was within 10% relative standard deviation for MA concentrations above 90 ng/ml using the HPLC assay and above 40 ng/ml using the GC-FID assay. Quantitative accuracy of the assays was evaluated by determining MA in human urine samples using both methods and also a gas chromatography-mass spectrometry (GC-MS) procedure. Numerical correlation among the three assays was good at MA concentrations above 100 ng/ml.

Human Alveolar Macrophage Mediated Vasodilation and the Role of Arginine Compounds

To determine whether human alveolar macrophages (AM) generate a compound similar to the endothelium-derived relaxing factor, we studied the effect of AM on the isometric response of the pre-contracted rat aorta preparation in the presence and absence of L-arginine or N-substituted L-arginine compounds. Addition of AM to the pre-contracted aorta preparation was ineffective even in the presence of millimolar concentrations of L-arginine. But, AM in the presence of the substituted L-arginine, N alpha-benzoyl L-arginine ethyl ester, significantly increased vasodilation. The enhanced relaxation was associated with an increase in vascular cyclic guanosine 3,5'-monophosphate formation. Hemoglobin and N omega-nitro L-arginine methyl ester are inhibitors of the endothelium-dependent relaxation, and both attenuated the vasodilation elicited by AM. Human AM were found to metabolize N alpha-benzoyl L-arginine ethyl ester to a citrulline derivative. No such metabolism was observed with L-arginine. A specific, high-pressure liquid chromatographic assay for guanidines revealed that the lack of effect of external L-arginine is not due to the presence of an excess amount of endogenous L-arginine in AM. These results demonstrate that nonactivated human AM, unlike rodent macrophages, possess an enzyme system(s) that metabolize(s) arginine derivatives but not L-arginine to a vasodilator, and this vasodilator has properties similar to that of endothelium-derived relaxing factor. This human AM-derived vasodilator may have an important role in regulating airway smooth muscle function.

Pharmacokinetics, metabolism and distribution of 1,2-dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo [1,2-al pyrido [3,2-el pyrazine-5-oxide in C3H mice

Purpose: 1,2-Dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo [1,2- a] pyrido [3,2- e] pyrazine-5-oxide (RB90740) is a bioreductive drug with an oxic to hypoxic toxicity ratio of 16 in cultured V79 cells in vitro. The aim of this study was to examine the pharmacokinetics, metabolism and distribution of the drug in tumor bearing C3H mice. Methods and Materials: A high pressure liquid chromatography assay for the quantitative determination of concentrations of the drug and its metabolites has been developed and used to examine their distribution in blood, RIF-1 and KHT tumors, brain, muscle, and liver tissue. Urine and feces collected for 24 h after drug administration have been examined for the drug and its metabolism products. Results: Three metabolites, two of which have been identified, have been observed in mouse tissue. 1,2-Dihydro-8-(4-methylpiperazinyl)-4-phenylimidazo [1,2- a]pyrido[3,2- e]pyrazine (RB92815) is the two-electron reduced species, which is observed in liver, urine and occassionally in tumor samples. 1,2-dihydro-8-(4-piperazinyl)-4-phenylimidazo [1,2- a]pyrido[3,2-elpyrazine-5-oxide (11131739), the N-demethylated compound, is observed in urine and liver. Elimination of the drug after an intraperitoneal dose of 50 mg/kg is biphasic with t 12 α = 3 min and t 12 β = 219 min. The area under the curve for blood concentration vs. time is 1.4 mg ml min −1. The drug is preferentially taken up into tumor tissue as is apparent from the area under the curve values for RIF-1 (28.3 mg ml min −1) and KHT (18.4 mg ml min −1) tumors. Conclusion: From these values of the area under the curve it is suggested that the drug is present in tumor tissue at concentrations sufficient to eliminate the hypoxic fraction provided reduction to a toxic species occurs. Bioreduction by the addition of two electrons to form RB92815 occurs in some tumors, but it is not known if this is due to an obligate two-electron detoxifying step or if reduction occurs by single electron additions via a toxic free radical species.

Determination of fostriecin pharmacokinetics in plasma using high-pressure liquid chromatography assay.

Fostriecin is an antitumor antibiotic with marked activity against ovarian, breast, and lung cancer cell lines in the human tumor clonogenic assay. The mechanism of cytotoxicity in vivo is unknown; in vitro it has been shown to inhibit macromolecular synthesis, interact with the reduced folate carrier system, and inhibit topoisomerase II. Phase I testing of fostriecin in a daily for 5 days schedule has begun in cancer patients. A high-pressure liquid chromatographic method to measure fostriecin in plasma samples was developed using sulfaquinoxaline as an internal standard and ultraviolet detection (268 nm). The extraction efficiency is 70% and the sensitivity limit is 100 ng/ml. The pharmacokinetics of fostriecin were determined in six rabbits following intravenous injection of 12 mg/m2. The mean distribution space was 4.44 L/m2 and the mean plasma clearance was 302 ml/min/m2. The elimination half-life was 11.95 +/- 8.55 min. All rabbits exhibited a 10-60-fold increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) that resolved within 48 h of drug administration.

Pharmacokinetics of sparfloxacin in patients with renal impairment

The pharmacokinetics of sparfloxacin were studied in 14 renal failure patients (group I, 7 with creatinine clearance of > 10 to 30 ml/min; and group II, 7 with creatinine clearance of < or = 10 ml/min) after a single oral dose of 400 mg. Plasma and urine samples were collected up to 144 h postdosing for determination of parent and total (parent-plus-glucuronide-conjugated) sparfloxacin levels, by high-pressure liquid chromatography assay and UV detection. The elimination of the drug in patients compared with that in healthy volunteers was markedly impaired. The mean elimination half-lives of sparfloxacin were 34.9 and 38.5 h in group I and group II, respectively, versus 19.1 h in healthy volunteers. Conjugated drug half-lives were 23.7, 35.0, and 15.3 h, respectively. The renal clearance of the drug was markedly reduced in the patients, with values of 6.8, 4.8, and 21.2 ml/min determined for group I, group II, and healthy subjects, respectively, for parent sparfloxacin and with values of 31.5, 14.0, and 327 ml/min for conjugated sparfloxacin. The nonrenal clearance of sparfloxacin was moderately, but not significantly, decreased in group II renal failure patients. No difference between the two groups of patients was detected in sparfloxacin levels in plasma. A significant relationship between pharmacokinetic parameters and creatinine clearance was observed only for renal clearance of parent or conjugated sparfloxacin.

High-Pressure Liquid Chromatographic Assay of Theophylline in Dog Feces following Oral Administration of Sustained-Release Products

A solid-phase-extraction reversed-phase HPLC assay is described for the determination of theophylline embedded in dog feces as powder, sustained-release tablets, or capsules. The feces is extracted with 5% isopropyl alcohol in chloroform in the presence of β-hydroxypropyl-theophylline as the internal standard. Separation and quantitation are achieved with a C18 analytical column. UV absorbance is monitored at 280nm. Recovery of theophylline was >50%. The assay is linear between 10 and 400mg amounts of theophylline in 50g of feces. Inter- and intraday coefficients of variation of the chromatographic assay were <3%, and the extraction procedure was highly reproducible with coefficients of variation of <10% at amounts of drug from 10 to 400mg. By keeping the stool/solvent extraction ratio constant, the method is equally effective in extracting theophylline from different sizes of stool samples (50 versus g of stool). The assay was applied to evaluate the theophylline content in feces following oral administration of the drug to dogs as tablet (Theo-Dur) and capsule (Slo-Bid) dosage forms. The resulting fecal recovery values of each product were inversely related to the corresponding bioavailability values obtained from the literature.

Cefotam concentrations in the sinus fluid of patients with chronic sinusitis after administration of cefotiam hexetil

Cefotiam hexetil is a prodrug of cefotiam. The concentrations of cefotiam in plasma and sinus secretions were determined in 18 patients (10 males, 8 females, aged 39.3 +/- 13.0 years) with chronic sinusitis. All patients received two 200 mg oral doses of cefotiam hexetil 12 h apart and were divided into four groups according to the time which elapsed between the last dose and collection of secretion samples. The last dose was given 2 h (group I), 3 h (group II), 4 h (group III) or 6 h (group IV) before sinus puncture. Cefotiam concentrations were measured by high-pressure liquid chromatography and microbiological assay, results being very similar with both methods. Mean concentrations of cefotiam with the standard deviation in sinus exudates were 1.04 +/- 0.60 mg/l at 2 h (n = 6), 1.04 +/- 0.33 mg/l at 3 h (n = 4), 0.75 +/- 0.74 mg/l at 4 h (n = 4) and < 0.10 mg/l at 6 h (n = 4). Mean sinus fluid concentrations were higher than mean plasma concentrations in all groups. These results suggest that cefotiam concentrations higher than the MICs for common pathogens are found in sinus secretions up to 4 h after oral administration of cefotiam hexetil.

A rapid HPLC assay for zearalenone in laboratory cultures ofFusarium graminearum

A high pressure liquid chromatographic (HPLC) method to determine zearalenone in corn contaminated withFusarium graminearum is described. After extraction with methanol-water and solvent partition, samples were cleaned up by applying the extract to a disposable silica cartridge and by eluting the toxin with a mixture of hexane/dry ethyl ether (5/5). Separation was achieved by a reverse phase μBondapak C18 column followed by fluorescence detection using an excitation wavelength at 274 nm and an emission wavelength at 440 nm. Detection limit was about 5 ng. Recoveries ranging from 85.37 to 100.97%, in standard solutions range 30–0.5 µg/ml, were found.

PHARMACOKINETICS OF MIVACURIUM N NORMAL PATIENTS AND IN THOSE WITH HEPATIC OR RENAL FAILURE

We have determined the pharmacokinetics and duration of action of a bolus dose of mivacurium (0.15 mg kg-1) during isoflurane and nitrous oxide anaesthesia in nine patients with normal renal and liver function, nine patients undergoing cadaveric kidney transplantation and nine patients undergoing cadaveric liver transplantation. Total plasma concentrations of mivacurium were measured for 2.5 h after administration using a high-pressure liquid chromatographic assay. Plasma concentration vs time data for what were presumed to be the two active mivacurium isomers were analysed by a non-compartmental method based on statistical moments. Neuromuscular block was assessed by measuring the electromyographic evoked response of the adductor pollicis muscle to train-of-four stimulation of the ulnar nerve. The mean time to recovery of 25% neuromuscular transmission, T25, was greater in the patients with liver failure (57.2 min) than in control patients (18.7 min). The volume of distribution at steady rate (Vdss) was comparable in the three groups. Patients with impaired liver function had significantly longer mean residence time and smaller plasma clearance than did patients with renal failure or control patients. There were significant negative correlations between plasma cholinesterase activity and both T25 (r = 0.79) and mean residence time (r = 0.62).

Pharmacokinetics of meropenem (ICI 194,660) and its metabolite (ICI 213,689) in healthy subjects and in patients with renal impairment.

The pharmacokinetics of meropenem (ICI 194,660) and its open-ring metabolite (ICI 213,689) were studied in 6 healthy volunteers and 16 patients with moderate to severe renal impairment after a single intravenous dose of 500 mg given as a 30-min infusion. Concentrations of unchanged meropenem in plasma and urine were measured by both microbiological and high-pressure liquid chromatographic (HPLC) assays. A good correlation was found between the two techniques. Pharmacokinetic parameters of unchanged meropenem were determined by using the HPLC data. The terminal half-life of unchanged meropenem increased in relation to the degree of renal impairment, being 1.2 h in subjects with normal renal function and 10 h in patients with end-stage renal failure. Total body clearance and renal clearance of unchanged meropenem are linearly related to creatinine clearance. The concentrations of the metabolite in plasma, which are very low in healthy subjects, significantly increased in uremic patients. The apparent half-life of ICI 213,689 increased in uremic patients and was about 35 h in patients with severe renal insufficiency. Meropenem and its metabolite are effectively removed by hemodialysis. The dialysis clearance of the unchanged drug was 81 +/- 22 ml/min. Dosage adjustments of meropenem will be necessary in patients with severe renal impairment.