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J H Proost

Publications and source records attributed to J H Proost.

At least 19 recordsLinked to original sources
PubMed2001

Pharmacokinetics and whole body distribution of elastase derived angiostatin (K1-3) in rats.

In the current study, we determined short-term pharmacokinetics and whole body distribution of elastase derived angiostatin [angiostatin(k1-3)] in rats after i.v. injection of radiolabelled protein. Since in gamma-camera studies, no tumor specific angiostatin(k1-3) accumulation was observed, general pharmacokinetics were studied in tumor free rats. By one-compartment model fitting of the data, Km 7.3 +/- 1.7 microg x ml(-1), Vmax 0.94 +/- 0.19 microg x min(-1), V, 10.9 +/- 2.5 ml and intrinsic clearance (Vmax/Km) 0.128 ml x min(-1) were calculated. Of the injected dose (I.D.) of angiostatin(k1-3), 12.1 +/- 2.1% per gram tissue was present in the kidneys 10 min after injection. Accumulation of angiostatin(k1-3) was detectable in spleen, liver, lungs and heart 10 min after injection. Sixty minutes after injection, kidney associated angiostatin(k1-3) had decreased, whereas in stomach and small intestines a small increase was seen. Immunohistochemical analysis demonstrated specific staining of interstitial cells of the kidney, liver Kupffer cells and endothelium of larger blood vessels of the lungs. Renal clearance of angiostatin(k1-3) and/or fragments is a major route of elimination, whereas lack of accumulation of radioactivity in the faeces indicates little hepatic elimination or hepatic elimination followed by enterohepatic cycling of the protein's degradation products. Instant blood coagulation at the site of vascular activation and the occurrence of respiratory problems upon administration of higher doses of angiostatin(k1-3) warrants further investigation of the protein's potential side effects. The data presented can be applied to study the relation between angiostatin(k1-3) treatment regimens, blood concentration levels, anti-tumor activity and harmful effects.

Angiostatins↗
PubMed2001

Effect of hypothermia on the hepatic uptake and biliary excretion of vecuronium in the isolated perfused rat liver.

BACKGROUND: Hypothermia prolongs the time course of action of nondepolarizing muscle relaxants. It is not known whether this prolongation is caused by a reduced rate of extrahepatic distribution or elimination, liver uptake, metabolic clearance, or biliary excretion. Therefore, the authors studied the effects of hypothermia on the net hepatic uptake, metabolism, and biliary excretion of vecuronium in isolated perfused rat liver. METHODS: Livers of Wistar rats were perfused with Krebs Ringer solution (1% albumin, 3.3% carbon dioxide in oxygen, pH 7.36-7.42, 38 degrees C). Each perfusion experiment (recirculatory perfusion system) was divided into three phases. In phase 1, a bolus dose of vecuronium (950 microg) was followed by a continuous infusion of vecuronium (63 microg/min) throughout the perfusion experiment. In phase 2, the temperature was reduced to 28 degrees C. In phase 3, temperature was restored. In controls, the temperature was kept constant throughout the perfusion. Concentrations of vecuronium and its metabolites were measured in perfusion medium, bile, and liver homogenate. Parameters of a multicompartmental liver model were fitted to the concentration patterns in perfusion medium and in bile. RESULTS: Hypothermia increased vecuronium concentrations in the perfusion medium from 4.0 microg/ml (range, 2.5-6.6) to 15.6 microg/ml (11.5-18.4 microg/ml; P = 0.018). Hypothermia reduced the biliary excretion rate of 3-desacetyl vecuronium from 18% (range, 6-37%) to 16% (range, 4-19%) of that of vecuronium (P = 0.018). Pharmacokinetic analysis confirmed that hypothermia reduced the rate constants of hepatic uptake and metabolism from 0.219 to 0.053 and from 0.059 to 0.030, respectively. CONCLUSIONS: Hypothermia significantly and reversibly reduced the net hepatic uptake of vecuronium. Hypothermia reduced the metabolism of vecuronium and the biliary excretion rate of 3-desacetyl vecuronium.

Animals↗
PubMed2000

Clinical efficacy, safety and pharmacokinetics of a newly developed controlled release morphine sulphate suppository in patients with cancer pain.

OBJECTIVE: To compare the efficacy, safety and pharmacokinetics of a newly developed controlled-release suppository (MSR) with MS Contin tablets (MSC) in cancer patients with pain. METHODS: In a double-blind, randomised, two-way cross-over trial, 25 patients with cancer pain were selected with a morphine (M) demand of 30 mg every 12 h. Patients were divided into two groups. Group 1 received active MSC (30 mg) and placebo MSR, followed by placebo MSC and active MSR (30 mg) each for a period of 5 days. Group 2 started with active MSR and placebo MSC, followed by active MSC and placebo MSR, each for a period of 5 days. Blood for determination of plasma concentration of morphine (M) and its 3- and 6-glucuronides (M3G, M6G) was collected, and area under the plasma concentration-time curve (AUC)0-12 h, peak plasma concentration (Cmax), time to reach Cmax (tmax), and CO and C12 of M, M6G and M3G were determined on day 5 and day 10. Intensity of pain experienced by each patient was assessed every 2 h on a 0-10 scale, while side effects and rescue medication were recorded. RESULTS: Twenty patients (ten patients in each group) completed the study. A pronounced inter-patient variability in plasma concentrations of M, M3G and M6G was observed after administration of both forms. Apart from the C0 and C12, no significant differences in AUC0-12 h, tmax and Cmax of morphine between the rectal and oral route of administration were found. In the case of the metabolites, it was found that AUC0-12 h and Cmax of M6G, and AUC0-12 h, Cmax, C0 and C12 of M3G after rectal administration were significantly lower than after oral administration. However, apart from the tmax of M6G, none of the pharmacokinetic parameters of M, M6G or M3G met the criteria for bioequivalence. There were no significant (P = 0.44) differences in pain intensity score between the oral and rectal forms within the two groups, regardless of the treatment sequence. No treatment differences in nausea, sedation or the demand on escape medication (acetaminophen tablets) between the rectal and oral forms were observed. CONCLUSION: The newly developed controlled-release M suppository is safe and effective and may be a useful alternative for oral morphine administration in patients with cancer pain.

Adult↗
PubMed2000

Pharmacokinetic studies of neuromuscular blocking agents: good clinical research practice (GCRP).

In September 1997, an international consensus conference on standardization of studies of neuromuscular blocking agents was held in Copenhagen, Denmark. Based on the conference, a set of guidelines for good clinical research practice (GCRP) in pharmacokinetic studies of neuromuscular blocking agents is presented. Guidelines include: design of the study; relevant patient groups to investigate; test drug administration, sampling and analysis; pharmacokinetic analysis; pharmacokinetic/pharmacodynamic modeling; population pharmacokinetics; statistics; and presentation of pharmacokinetic data. The guidelines are intended to aid those working in this research area; it is hoped that they will assist researchers, editors of scientific papers, and pharmaceutical companies in improving the quality of pharmacokinetic studies.

Body Temperature↗
PubMed2000

Urinary, biliary and faecal excretion of rocuronium in humans.

The excretion of rocuronium and its potential metabolites was studied in 38 anaesthetized patients, ASA I-III and 21-69 yr old. Rocuronium bromide was administered as an i.v. bolus dose of 0.3 or 0.9 mg kg-1. In Part A of the study, the excretion into urine and bile, and the liver content were studied. Plasma kinetics (n = 19) were similar to those reported previously. Urinary recovery within 48 h after administration was 26 (8)% (mean (SD)) (n = 8) of the dose. In bile obtained from T-drains, the recovery within 48 h was 7 (6)% (n = 11). The rocuronium concentration in bile declined bi-exponentially, with half-lives of 2.3 (0.7) and 16 (11) h respectively (n = 6). In three patients from whom stoma fluid was collected, the amount of rocuronium recovered ranged from 0.04 to 12.0% of the dose. In liver tissue obtained from four patients undergoing hemihepatectomy, the estimated amount of rocuronium at 2-5 h after administration ranged between 6.3 and 13.2% (n = 4). In the second part of the study (Part B), urine and faeces were collected over 4-8 days and the recovery was 27 (13)% and 31 (23)% of the dose respectively (n = 10). In most samples, irrespective of the type of biological material, only small amounts of the metabolite 17-desacetyl-rocuronium was found. The results demonstrate that rocuronium is taken up by the liver and excreted into bile in high concentrations. The faecal and urinary excretion of unchanged rocuronium are the major routes of rocuronium elimination.

Adult↗
PubMed2000

Structure-pharmacokinetics relationship of series of aminosteroidal neuromuscular blocking agents in the cat.

To obtain more insight in the relationship between physicochemical properties of neuromuscular blocking agents (NMBAs) and their pharmacokinetic characteristics, a series of 12 aminosteroidal NMBAs, supplemented with data on five related NMBAs from the literature, was investigated in anaesthetized cats. After i.v. bolus injection, plasma concentration decreased very rapidly, showing a biphasic pattern, with half-lives ranging from 0.4 to 1.4 min, and from 3 to 10 min, respectively. Clearance was in the range from 24 to 58 ml. min(-1). kg(-1). Compounds containing an acetyl-ester group at position 3 were partly metabolized to the 3-OH derivative. The urinary excretion of the parent drug and metabolites amounted to <10% for each of the compounds. The parent drugs were excreted in large amounts into bile, along with smaller amounts of 3-OH derivatives. The terminal half-life of the urinary and biliary excretion rate were markedly longer than the apparent terminal half-life in plasma, ranging from 11 to 40 min, and from 119 to 489 min in urine and bile, respectively. Lipophilicity of the NMBAs, expressed as the partition coefficient octanol/Krebs (log P), was found to be correlated positively with unbound plasma clearance and unbound initial plasma clearance, and negatively with plasma half-life, volume of distribution at steady state, and mean residence time. The increase of the unbound plasma clearance with increasing lipophilicity is counteracted by the concurrent increase in plasma protein binding.

Animals↗
PubMed1999

Do plasma concentrations obtained from early arterial blood sampling improve pharmacokinetic/pharmacodynamic modeling?

In pharmacokinetic/pharmacodynamic (PK/PD) modeling the first blood sample is usually taken 1 to 2 min after drug administration (late sampling). Therefore, investigators have to extrapolate the plasma concentration to Time 0. Extrapolation, however, erroneously assumes instantaneous and complete mixing of drug in the central volume of distribution. We investigated whether plasma concentrations obtained from early arterial blood sampling would improve PK/PD modeling. In 14 pigs, one of five neuromuscular blocking agents (NMBAs) was administered into the right ventricle within 1 sec and arterial sampling was performed every 1.2 sec (1st min). The response of the tibialis muscle was measured mechanomyographically. The influence of inclusion of data from early arterial sampling on PK/PD modeling was determined. Furthermore, the concentrations in the effect compartment at 50% block (EC50) derived from modeling were compared to the measured concentration in plasma during a steady state 50% block. A very high peak in arterial plasma concentration was seen within 20 sec after administration of the NMBA. Extensive modeling revealed that plasma concentrations obtained from early arterial blood sampling improve PK/PD modeling. Independent of the type of modeling, the EC50 and KeO based on data sets that include early arterial blood sampling were, for all five NMBAs, significantly higher and lower respectively, than those based on data sets obtained from late sampling. Early arterial sampling shows that the mixing of the NMBA in the central volume of distribution is incomplete. A parametric PD (sigmoid Emax) model could not describe the time course of effect of the NMBAs adequately.

Animals↗
PubMed1999

Pharmacokinetics and pharmacokinetic-dynamic relationship between rapacuronium (Org 9487) and its 3-desacetyl metabolite (Org 9488).

UNLABELLED: Rapacuronium (Org 9487) is a rapid-onset and short- to intermediate-acting muscle relaxant. Its 3-desacetyl metabolite, Org 9488, also exerts neuromuscular-blocking activity that may become apparent after prolonged maintenance of relaxation with rapacuronium. In this study, the pharmacokinetic behavior (n = 7) of this metabolite and the pharmacokinetic/pharmacodynamic (PK/PD) relationship of rapacuronium (n = 10) and Org 9488 (n = 7) were investigated in humans. Similar protocols were used for three study groups regarding the anesthetic technique, blood and urine sampling, and pharmacokinetic and PK/PD analyses. The time course of action was measured mechanomyographically using the adductor pollicis muscle. The median clearance of rapacuronium was 7.28 mL x kg(-1) x min(-1) x with an excretion fraction in the urine of 6.2%. The clearance (studied in two groups) of Org 9488 was 1.28 and 1.06 mL x kg(-1) x min(-1) with an excretion fraction in the urine of 51.9% and 53.5%, respectively. The median rate constant of transport between plasma and the biophase of rapacuronium (0.449 min(-1)) is markedly larger than that for Org 9488 (0.105 min(-1)). The modeled concentration in the biophase at 50% effect as a measure of potency is higher for rapacuronium (4.70 microg/mL) than for Org 9488 (1.83 microg/mL). The lower clearance of the metabolite will gradually prolong the time course of the neuromuscular blockade during maintenance with rapacuronium. IMPLICATIONS: We investigated the concentration-time-effect relationship of the relaxant rapacuronium and the contribution of its metabolite. Clearance, rate constant of transport between plasma and the biophase, and modeled concentration in the biophase at 50% effect of rapacuronium are consistent with its rapid onset and short to intermediate duration. The lower clearance of the metabolite will gradually prolong the time course of the neuromuscular blockade during maintenance with rapacuronium.

Adult↗
PubMed1999

The pulmonary first-pass uptake of five nondepolarizing muscle relaxants in the pig.

BACKGROUND: It is not known whether the lungs influence the early pharmacokinetics of muscle relaxants and, if they do, whether differences in pulmonary uptake contribute to the differences in potency and/or onset time among muscle relaxants. Because the lungs are uniquely positioned, receive the entire cardiac output, have a large capillary surface area, and can temporarily store various basic drugs, the authors determined whether substantial pulmonary first-pass uptake of muscle relaxants occurs. METHODS: In 14 pigs, rocuronium, vecuronium, Org 9487, Org 7617, or d-tubocurarine were administered simultaneously with indocyanin green within 1 s into the right ventricle, and then arterial blood was sampled every 1.2 s (in the first min). The tibialis muscle response was registered mechanomyographically. RESULTS: The maximum block was 93% (68-100% [median and range]). Onset times ranged from 83 s (78-86 s) for rocuronium to 182 s (172-192 s) for d-tubocurarine. Fraction-versus-time outflow curves showed that the peak of muscle relaxants and indocyanin green occurred almost simultaneously. Pulmonary first-pass retention was negligible. The retention of muscle relaxants at 95% passage of indocyanin green was -9% (-31 to 18%). The difference in the mean transit time between muscle relaxant and indocyanin green was 1.0 (0.8 to 1.4), 0.2 (-0.8 to 0.3), 0.3 (0.2 to 0.4), 0.5 (0.2 to 1.3), and -2.2 s for rocuronium, vecuronium, Org 9487, Org 7617, and d-tubocurarine, respectively. CONCLUSIONS: There is no substantial pulmonary first-pass uptake of rocuronium, vecuronium, Org 9487, Org 7617, or d-tubocurarine in pigs. Therefore, differences in pulmonary first-pass uptake do not contribute to the differences in potency and/or onset time among muscle relaxants.

Androstanols↗
PubMed1998

Absorption kinetics of oral sotalol combined with cisapride and sublingual sotalol in healthy subjects.

AIMS: To study the absorption kinetics of sotalol following administration of different formulations. A formulation which results in fast absorption might be useful in the episodic treatment of paroxysmal supraventricular tachycardia (SVT), atrial fibrillation (Afib) or atrial flutter (Afl). METHODS: In an open randomized crossover study seven healthy male volunteers were given an intravenous infusion of 20 mg sotalol, for assessing the absolute bioavailability, an oral solution containing 80 mg sotalol, an oral solution containing both 80 mg sotalol and 20 mg cisapride and an 80 mg sotalol tablet, which was taken sublingually. RESULTS: The addition of cisapride decreased the time at which maximum serum concentrations were reached (tmax) from 2.79 (1.85-4.34) h to 1.16 (0.68-2.30) h (P=0.009) [95% CI: -2.59, -0.55] and increased the absorption rate constant (ka) from 0.49 (0.31-0.69) h(-1) to 1.26 (0.52-5.61) h(-1) (P=0.017). The absolute bioavailability of sotalol was reduced by cisapride from 1.00+/-0.15 to 0.70+/-0.26 (P=0.006), while maximum serum concentrations of both oral solutions were not significantly different. Compared with the sublingually administered tablet with a median tmax of 2.12 (0.89-3.28) h, the sotalol/cisapride oral solution gave a smaller tmax (p=0.009) [95% CI: -1.64, -0.36]. The ka of the sotalol/cisapride solution was significantly (P=0.010) larger than the ka of 0.56 (0.33-0.75) h(-1) found after sublingual administration of the tablet. CONCLUSIONS: The sotalol/cisapride oral solution might be suitable for the episodic treatment of SVT, Afib or Afl.

Administration, Oral↗
PubMed1998

Inhibition of the enzymic degradation of suxamethonium and mivacurium increases the onset time of submaximal neuromuscular block.

BACKGROUND: The factors that influence the onset time of submaximal (<100%) neuromuscular block are not fully known. The authors hypothesized that differences in the rate of decrease in the plasma concentration result in differences in the rate of equilibration between plasma and biophase and thus in different onset times. If this hypothesis is valid, inhibition of the enzymic degradation of muscle relaxants should increase the onset time of neuromuscular block. METHODS: Twenty pigs received either suxamethonium or mivacurium. Dose finding (70% block) was done for each pig. The enzymic degradation of the muscle relaxant was randomly inhibited by selective inhibition of plasma cholinesterase activity by tetraisopropyl pyrophosphoramide (10 pigs) or was not inhibited (10 pigs). Plasma cholinesterase activities and the mechanomyographic muscle response after peroneal nerve stimulation (0.1 Hz) were measured. RESULTS: Inhibition of plasma cholinesterase activity (by 93% and 89%, respectively) increased the onset time of suxamethonium from a median of 40 s (range, 20-45 s) to 131 s (range, 114-166 s; P = 0.009) and of mivacurium from a median of 52 s (range, 40-59 s) to 105 s (range, 90-125 s; P = 0.009). Inhibition of degradation decreased the effective dose of suxamethonium that resulted in 70% depression of the initial twitch height from 900 microg/kg (range, 400-1,000 microg/kg) to 150 microg/kg (range, 135-150 microg/kg) and of mivacurium from 100 microg/kg (range, 80-150 microg/kg) to 35 microg/kg (range, 20-50 microg/kg). CONCLUSIONS: Inhibition of the enzymic degradation of suxamethonium and mivacurium increases the onset time of submaximal neuromuscular block. Therefore, pharmacokinetics influence the onset time of submaximal neuromuscular block. These results imply that to obtain an ultrashort onset time, muscle relaxants should be developed that not only have a low affinity for the receptor but also rapidly disappear from plasma.

Animals↗
PubMed1998

Characterization of the uptake of rocuronium and digoxin in human hepatocytes: carrier specificity and comparison with in vivo data.

Mechanisms of drug transport in the liver have been investigated predominantly in rodents. Most of the in vitro drug research in the liver is performed in liver preparations of animals. The results of such experiments frequently are discussed in relation to anticipated metabolic profiles in man, but these extrapolations are often inappropriate because of large interspecies differences in drug metabolism. In the present study, the mechanisms and specificity of the uptake of the organic cation rocuronium and the cardiac glycoside digoxin were investigated in human hepatocytes and were compared with results obtained in rat hepatocytes. The extraction ratio for the intact liver was calculated from the measured uptake rates of the compounds in the human cells in vitro and compared with published in vivo data. The initial hepatic extraction ratio, calculated from the in vitro uptake data for digoxin and rocuronium, very well reflected the initial extraction ratio for distribution in the liver in vivo in man. Uptake of 100 microM rocuronium was inhibited by 40 microM K-strophantoside (80% inhibition), and although not significantly, by 160 microM procainamide ethobromide, whereas no inhibitory effect was found in the presence of 160 microM taurocholic acid. In a previous study in rat hepatocytes, marked inhibition of digoxin uptake by quinine and only minimal inhibition by the diastereomer quinidine was demonstrated, showing clear stereoselectivity in transport inhibition. Unexpectedly, the uptake of digoxin in human hepatocytes was not inhibited significantly by quinidine or quinine, which indicates clear species differences. This is the first study to investigate the uptake mechanisms of organic cations and cardiac glycosides in human hepatocytes in some detail. The results show that uptake characteristics of drugs found in rats can not be extrapolated directly to humans.

Androstanols↗
PubMed1997

Comparison of vecuronium with ORG 9487 and their interaction.

PURPOSE: To compare the pharmacodynamic behaviour of vecuronium with that of ORG 9487, we measured the time-course of action of equipotent doses of ORG 9487 and vecuronium and investigated their mutual interaction when given in succession. METHODS: Sixty ASA I-II patients were anaesthetized with thiopentone, fentanyl, halothane and nitrous oxide and assigned randomly to four groups. Each patient received an initial dose (ID) of either vecuronium (V) or ORG 9487 (O) followed by maintenance doses (MDn) of either V or O (ID/MD: O/O, V/O, O/V, and V/V). The time course of action was measured mechanomyographically, determining the duration until 25% recovery of the single twitch (DUR25). RESULTS: The onset time of an ID of ORG 9487 was shorter than that of an ID of vecuronium (96 vs 203 sec, P < 0.001). The DUR25 of the ID of ORG 9487 was less than half that of vecuronium (10.7 +/- 2.8 vs 28.8 +/- 6.1 min, P < 0.001). The DUR25 of MD1 and MD2 of ORG 9487 were shorter than those of vecuronium (O/O: 7.3 +/- 2.8 and 8.5 +/- 2.4 min; V/O: 12.7 +/- 3.3 and 11.5 +/- 3.5 min, vs O/V: 16.4 +/- 4.5 and 20.6 +/- 4.7 min; V/V: 18.8 +/- 3.0 and 20.1 +/- 3.8 min, respectively, P < 0.05). AN ID of vecuronium prolonged the DUR25 of MD1 and MD2 of ORG 9487 (P < 0.05). CONCLUSION: ORG 9487 is a muscle relaxant with a shorter duration of action than vecuronium. Maintenance doses of ORG 9487 are also shorter acting than roughly equipotent maintenance doses of vecuronium, irrespective of which relaxant is given initially.

Adolescent↗
PubMed1997

Pharmacokinetics and anti-HIV-1 efficacy of negatively charged human serum albumins in mice.

Negatively charged albumins (NCAs, with the prototypes succinylated human serum albumin (Suc-HSA) and aconitylated human serum albumin (Aco-HSA)), modified proteins with a potent anti-human immunodeficiency virus type 1 (anti-HIV-1) activity in vitro, were studied for their pharmacokinetic behaviour in mice and their in vivo anti-HIV-1 efficacy in an HIV-1 infection model in mice. In contrast to the saturation kinetics found in rats, intravenous injections of 10-300 mg/kg for both NCAs showed a linear correlation between the area under the curve (AUC) and the dose. The elimination t1/2 was 25 and 30 min for Suc-HSA and Aco-HSA, respectively. Preinjections of an excess of formaldehyde-treated albumin (Form-HSA) resulted in plasma levels that were 3- and 4-fold higher for Aco-HSA and Suc-HSA, respectively. These data indicate that elimination is at least partly (scavenger) receptor-mediated. Organ distribution studies 10 min after injection showed an accumulation in liver (Suc-HSA 17.3 +/- 6.6% of the dose; Aco-HSA 20.9 +/- 2.3%) and lungs (Suc-HSA 12.7 +/- 10.5%; Aco-HSA 16.0 +/- 13.6). Intraperitoneal injection of 300 mg/kg Suc-HSA resulted in a final bioavailability of about 0.45. Suc-HSA was also evaluated for its in vivo neutralizing capacity in a human-to-mouse chimeric model for HIV-1 infection. Intraperitoneal injections of 300 and 3 mg/kg Suc-HSA, given 15-30 min before the mice were challenged with the virus, sufficed to protect these mice against infection with the HIV-1 IIIB strain.

Animals↗
PubMed1997

Pharmacodynamics and pharmacokinetics of rocuronium in intensive care patients.

We have studied dose requirements, recovery times and pharmacokinetics of rocuronium in 32 intensive care patients. After an initial dose of 50 mg, rocuronium was administered as maintenance doses of 25 mg whenever two responses to train-of-four (TOF) stimulation reappeared (bolus group; n = 27) or by continuous infusion to maintain one response in the TOF (infusion group; n = 5). Median requirements for rocuronium were 27.4 (range 14.5-68.3) mg h-1 and 43.7 (30.9-50.3) mg h-1 in patients in the bolus and infusion groups, respectively. Median total duration of rocuronium administration was 29.0 (12.4-95.5) h and 63.4 (24.0-140.3) h, respectively. Median time from administration of the last bolus dose and end of infusion to recovery of the fourth twitch in the TOF was 100 (45-300) min and 60 (15-155) min, respectively. Arterial blood samples were obtained for up to 10 h after cessation of rocuronium administration, and concentrations of the parent compound and its putative metabolites were measured using high pressure liquid chromatography (HPLC). The plasma concentration profile (n = 12) was described adequately by a two-compartment model. Mean plasma clearance (Cl), steady-state distribution volume (Vss), mean residence time (MRT) and elimination half-life (T1/2 beta) were 3.16 (SD 1.15) ml kg-1 min-1, 769 (334) ml kg-1, 262 (120) min and 337 (163) min, respectively. Recovery times, Vss, MRT, and T1/2 beta differed from previously published data obtained after rocuronium infusion of moderate duration in surgical patients.

Adolescent↗