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Biomedical subjects

G Geisslinger

Publications and source records attributed to G Geisslinger.

143 records · Page 8Linked to original sources
PubMed1991

Pharmacokinetics of ibuprofen enantiomers in dogs.

Inversion of inactive (R)-ibuprofen to active (S)-ibuprofen has been suggested to occur presystemically only. In order to investigate the site of inversion in dogs we administered both enantiomers either intravenously or intraduodenally (10 mg/kg) to adult, male beagle dogs (n = 3) in a crossover design. Plasma, urine, and bile were collected for up to 6 h and analyzed stereospecifically by HPLC, according to a previously published method. Pharmacokinetic parameters were calculated using a linear computer program. Absorption after intraduodenal administration occurred rapidly, resulting in maximum plasma concentrations 0.2 h after giving the enantiomer. Approximately 70% of the (R)-enantiomer (according to AUC) was inverted to the S-enantiomer independent of route of administration. No R-ibuprofen could be detected in plasma after (S)-ibuprofen administration. Mean residence time was found to be 2 to 3 times longer for (S)- than for (R)-ibuprofen. Total systemic clearance from plasma was twice as high for (R)- than for (S)-ibuprofen. There were no differences between plasma clearances after intravenous and intraduodenal administration. Between 8 and 17% of dose was recovered in bile [especially as free and conjugated (S)-ibuprofen] and 3-12% in urine [as (S)-ibuprofen, hydroxy- and carboxyibuprofen, free and conjugated forms]. Small amounts of (R)-ibuprofen were detected in bile after intraduodenal administration of (R)-ibuprofen only (1.8% of dose). In short, the unidirectional inversion of R-ibuprofen appears to occur systemically rather than presystemically in dogs.

Animals↗
PubMed1991

S-ibuprofen versus ibuprofen-racemate. A randomized double-blind study in patients with rheumatoid arthritis.

Ibuprofen (ibu) is a racemic 2-arylpropionic acid non-steroidal anti-inflammatory drug whose activity is due mainly to the S-enantiomer. So far only the racemic compound is in clinical use. A double-blind randomized trial was carried out for a 2-week period in 50 patients with classical rheumatoid arthritis (RA) (Steinbrocker II-III) to compare the effectiveness and tolerance of S-ibu (400 mg T.I.D.) with that of the racemic compound (600 mg T.I.D.). Ritchie-index, limitation of movement, joint pain on pressure and pain at night decreased significantly in both groups. Due to lack of effectiveness, the dose had to be increased in 3 patients from the S-ibu group as well as in 6 patients from the racemic group resulting in mean daily doses of 1220 mg S-ibuprofen and 1870 mg racemic ibu. No statistically significant difference could be found between both groups concerning efficacy and unwanted effects. Therefore, S-ibu given alone may be advantageous because the metabolic load to the human body is reduced and patients are more likely to comply with drug doses of 1.2 g/day as compared to 1.8 g/day.

Adult↗
PubMed1991

[Possibilities and limitations of intravenous anesthesia].

The increasing importance of intravenous anaesthesia is based on two developments, namely the synthesis of substances capable of acting selectively and over the short term, and which are rapidly eliminated (good control), and a desire on the part of the anaesthetist to have an anaesthetic whose actions can be controlled in various ways. Efforts in this area are aimed at ensuring not only a minimum of stressing of organs by the anaesthetic, but also a minimisation of risks during the intra-operative phase, and a non-problematic maximally pleasant post-operative course. There are two problems that militate against the realization of these objectives. Although the substances presented here ideally permit the realization of some of these aims, at the same time they are associated with side effects that prevent their use from ever being completely non-problematical, and which should always prompt the exercise of particular care when employing these medications. In addition, the differentiable control made possible by the use of these drugs is (partly) offset by inadequate monitoring with respect to the qualities of the anaesthetic--a fact that modifies the potential advantages of intravenous anaesthesia.

Analgesics, Opioid↗
PubMed1990

Stereoselective high-performance liquid chromatographic determination of ketoprofen, ibuprofen and fenoprofen in plasma using a chiral alpha 1-acid glycoprotein column.

The effect of mobile phase composition, pH and temperature on the chiral resolution and retention of some 2-arylpropionic acids using the chiral alpha 1-acid glycoprotein column EnantioPac is described. Furthermore, a direct stereoselective high-performance liquid chromatographic assay to determine the enantiomers of ketoprofen, ibuprofen and fenoprofen in plasma is presented. Detection was at 260, 220 and 220 nm for ketoprofen, ibuprofen and fenoprofen, respectively. The limit of detection was 0.1 micrograms/ml for the enantiomers of ketoprofen and ibuprofen, and 0.25 micrograms/ml for the enantiomers of fenoprofen. The method was demonstrated to be applicable for stereoselective pharmacokinetic studies of ketoprofen, ibuprofen and fenoprofen after administration under clinical conditions.

1-Propanol↗
PubMed1990

Pharmacokinetics of S(+)- and R(-)-ibuprofen in volunteers and first clinical experience of S(+)-ibuprofen in rheumatoid arthritis.

S(+)-, R(-)- or racemic ibuprofen was administered orally to volunteers in doses of 150 mg, 300 mg and 500 mg pure S(+)-, 300 mg pure R(-)- and 600 mg racemic ibuprofen. The pharmacokinetic parameters in humans showed that S(+)-ibuprofen was not inverted to R(-)-ibuprofen, whereas R(-)-ibuprofen was inverted to S(+)-ibuprofen to a variable degree. S(+)-ibuprofen and R(-)-ibuprofen given alone more rapidly reached significantly higher maximal plasma concentrations than after the same doses of the racemic compound. The elimination half-lives and clearance values for all three forms of ibuprofen were comparable. The mean residence time of S(+)-ibuprofen after R(-)- and racemic ibuprofen was significantly longer than after administration of the pure S(+)-enantiomer. Judged by the AUC, the bioavailability of S(+)-ibuprofen was independent of the dose within the range tested. Administration of S(+)-ibuprofen to 6 rheumatic patients showed that the pharmacokinetic behaviour of S(+)-ibuprofen in patients was similar to that found in volunteers. S(+)-ibuprofen proved to be an effective analgesic antirheumatic drug in the dose range 1 to 1.5 g/day.

Adult↗
PubMed1990

The biliary elimination and enterohepatic circulation of ibuprofen in rats.

The biliary and urinary excretion of ibuprofen and its metabolites were determined in rats after intravenous and peroral administration of 25 and 100 mg/kg of the drug. Within 24 hours 48% of the low i.v. dose and 59% of the high i.v. dose were eliminated via bile as ibuprofen and its metabolites. Following oral administration 40 to 41% of the dose were recovered in bile, whereas 16 to 32% of the dose were eliminated in urine, resulting in an overall drug recovery of 66 to 79% within 24 hours. Upon infusion of bile containing ibuprofen and its metabolites into the duodenum substantial enterohepatic cycling of the drug occurred in the rat.

Animals↗
PubMed1989

High-performance liquid chromatographic determination of ibuprofen, its metabolites and enantiomers in biological fluids.

An isocratic high-performance liquid chromatographic method to determine racemic ibuprofen (assay I) and its major metabolites (assay II) in biological fluids (plasma, urine, bile) using a conventional reversed-phase column is described. A third assay using beta-cyclodextrin as stationary phase (Cyclobond I) for the separation of the ibuprofen enantiomers is also described. A wavelength of 220 nm was used to monitor the substances. The sensitivity of the method was 0.1 microgram/ml for all three assays. The method was demonstrated to be suitable for stereoselective pharmacokinetic studies of ibuprofen in humans and animals.

Bile↗
PubMed1989

Pharmacological differences between R(-)- and S(+)-ibuprofen.

Ibuprofen (IBU) is a non-steroidal anti-inflammatory drug exhibiting optical isomerism. Only the racemate is in clinical use. In in vitro studies it has been demonstrated that only the S(+)-enantiomer inhibits the PG synthetase system. Nevertheless, it is widely believed that the sole use of the active isomer does not comprise any advantages since the inactive isomer is converted within the human body. In a triple cross-over study (300 mg S(+), 300 mg R(-), 600 mg racemic IBU; n = 8), we could show that the converted R(-)-IBU after racemate administration provides for only one third of the AUC of S(+)-IBU obtained after S(+)-application. Highest S(+)-peak plasma levels were reached after S(+)-IBU, lower ones after racemate. We, therefore, studied 4 patients with classical rheumatoid arthritis treated with 2-3 doses of 500 mg of S(+)-IBU/day over a two week period. Significant clinical recovery (Ritchie-index p less than 0.01; analogue scale pain p less than 0.05, motion p less than 0.01) was reached after one week. The results indicate that a reduction of dose and of metabolic load is possible if the S(+)-enantiomer is administrated.

Administration, Oral↗
PubMed1989

Therapeutically relevant differences in the pharmacokinetical and pharmaceutical behavior of ibuprofen lysinate as compared to ibuprofen acid.

The pharmacokinetic properties of ibuprofen p.o. given either as a lysine salt or as acid to eight young, healthy male volunteers was investigated. Ibuprofen lysinate, administered after overnight fasting, produced peak plasma concentrations significantly earlier and higher than ibuprofen acid. A similar difference was observed when the drugs were given following a standardized breakfast. Under these conditions the lat-time was significantly shorter for the lysine salt than for the acid. The pharmacokinetic differences are likely to result from the faster dissolution rate of ibuprofen lysinate. They indicate that the administration of ibuprofen as lysine salt before meals may be advantageous if rapid and reliable onset of pain relief is required.

Adult↗
PubMedDate not supplied

Relevance of frequent mu-opioid receptor polymorphisms for opioid activity in healthy volunteers.

Polymorphisms in the mu-opioid receptor gene (OPRM1) are primary candidate sources of clinical variability in opioid therapy. Apart from the 118A>G single nucleotide polymorphism, nothing is known about the role of OPRM1 mutations in opioid therapy. The influence of the OPRM1 mutations on opioid pharmacodynamics was assessed in pooled data from 31 healthy volunteers obtained in previous studies with available plasma concentrations and pupil diameters after intravenous administration of morphine or morphine-6-glucuronide (M6G). A total of 24 candidate ORPM1 mutations were screened for and those found at an allelic frequency of at least 5% in the 31 subjects were analyzed for functional consequences, using population pharmacokinetic-pharmacodynamic modeling of the miotic effects of the opioids as a reliable and sensitive surrogate parameter of the central nervous opioid effects. Polymorphisms at an allelic frequency of > or =5% (n=310) were 118A>G in exon 1 (11.5%), the IVS2-31G>A (8.9%) and IVS2-691C>G (44.5%) SNPs in intron 2. The 118A>G SNP significantly increased the values of EC50 by a factor of more than 2 (non-mutated: EC50,morphine=30 nmol/l, EC50,M6G=750 nmol/l, 118G carriers: EC50,morphine=66 nmol/l, EC50,M6G=1650 nmol/l), whereas the IVS2-691C>G SNP had no effect. Based on morphine and M6G, the present analysis encourages focusing on the 118A>G SNP when investigating the role of OPRM1 mutations for the activity of opioid analgesics. Other OPRM1 mutations are probably less important either owing to low allelic frequency or due to poor indications for functional consequences. This applies to opioid potency in the context of opioid therapy but not to pain processing or substance addiction, in which opioid receptors are involved but other or additional OPRM1 mutations may be important.

Alleles↗
PubMedDate not supplied

Isolation and pharmacological characterization of microsomal human liver flumazenil carboxylesterase.

PURPOSE: In vivo the biotransformation of the imidazobenzodiazepine antagonist flumazenil leads to the formation of two metabolites, flumazenil acid and N-demethylated flumazenil. In the present study we investigated the role of carboxylesterases for the metabolism of flumazenil. METHODS: We purified a non-specific carboxylesterase (EC 3.1.1.1) from human liver microsomes that catalyzes the hydrolysis of flumazenil to flumazenil acid and, in presence of methanol the formation of flumazenil methyl ester an in vivo unknown metabolite. The purification procedure included solubilization of the microsomes obtained from human livers with Triton X-100 and subsequent chromatography of the 100,000 x g supernatant on blue-sepharose, DEAE-sepharose, hydroxyapatite and final chromatofocusing. RESULTS: The purified esterase isozyme exhibited an apparent subunit molecular weight of 59 kDa as estimated by SDS gelelectrophoresis, a native molecular weight of 170 kDa determined by a calibrated gel filtration column suggesting that the active enzyme is a trimer. The isoelectric point of the enzyme was approximately 5.4. The specific activities of the purified enzyme were 5.8 nmol/(min*mg protein) protein for the formation of flumazenil acid and 31 nmol/(min*mg protein) for the synthesis of the flumazenil methylester. The purified enzyme obeys simple Michaelis-Menten kinetics with K(M) values of 665 microM for flumazenil acid, 1011 mM for methanol and 900 microM for the flumazenil methylester. PMSF, a specific inhibitor for serine proteases and mammalian acetylcholinesterase, completely inhibited the formation of flumazenil -acid and the flumazenil methylester at a concentration of 100 microM. No synthesis of the flumazenil -methylester could be observed by incubation of the purified esterase with flumazenil acid in the presence of methanol leading to the conclusion that the enzymatically catalyzed reaction is a transesterification. The purified esterase was digested with endoproteinase LysC. A 15 amino acid long peptide was isolated and showed identical matches to carboxylesterase cDNAs from human liver and lung. CONCLUSION: Our results show that carboxylesterase isozymes play an important role in the detoxification and metabolism of flumazenil. Because of enzymatic, catalytic and structural properties a similarity of the characterized flumazenil carboxylesterase with human liver cocaine carboxylesterase is possible.

Animals↗
PubMedDate not supplied

Effects of sodium salicylate on elimination kinetics of indomethacin and bile production in dogs.

We investigated the effects of sodium salicylate on the elimination kinetics of indomethacin in bile duct-cannulated beagles. Indomethacin and metabolites were quantified by HPLC in plasma, bile, and urine. Indomethacin was administered as iv bolus injection and iv infusion to yield a steady-state plasma concentration of approximately 1 microgram/ml. Following sodium salicylate, given either iv (25 mg/kg) or via duodenal fistula (50 mg/kg), the indomethacin plasma level dropped instantaneously by 60-70%. Concomitantly, total systemic clearance from the plasma and biliary clearance were increased significantly. In addition, a reduced plasma protein binding of indomethacin and a significant increase in the volume of distribution were observed. The amount of indomethacin, excreted as free and conjugated drug in bile, was significantly increased temporarily by sodium salicylate. The total amount eliminated in bile (approximately 70% of the dose), however, was not changed by sodium salicylate co-administration. The bile flow was significantly enhanced for at least 4 hr. Both phase 1 metabolism and renal excretion of indomethacin remained practically unaffected by sodium salicylate treatment.

Animals↗
PubMedDate not supplied

Lymph distribution of different non-steroidal anti-inflammatory drugs assessed by microsurgical cannulation of the thoracic duct in rat.

The motility of lymphatic vessels is regulated by arachidonate metabolites and, therefore, can be altered by cyclo-oxygenase blockers such as non-steroidal anti-inflammatory drugs (NSAIDs). In order to investigate the lymphotropic properties of different NSAIDs, pharmacokinetics in plasma and lymph following intragastric administration of three model compounds, namely racemic ibuprofen, tenoxicam and nabumetone, were investigated in rats. Microsurgical cannulation of the thoracic duct allowed cumulative sampling of lymph fluid up to 48 hrs (n = 16). Pharmacokinetic parameters in plasma were determined in a control group (n = 12). Concentrations of R-, S-ibuprofen, tenoxicam, nabumetone and the metabolites OH-ibuprofen, COOH-ibuprofen and 6-methoxy-2-naphthyl-acetic acid (6MNA, metabolite of nabumetone) were monitored in lymph and plasma by HPLC. To quantify the lymphotropic properties of the investigated compounds, a "lymphatic clearance" was defined by dividing the amount recovered in lymph fluid by the corresponding area under the plasma concentration-time curve (AUCP). The "lymphatic clearance" substantially differed between the investigated compounds (mean +/- SD: R-ibuprofen 6.71 +/- 3.15 microliters/min, S-ibuprofen 3.24 +/- 1.20 microliters/min, tenoxicam 8.74 +/- 8.11 microliters/min, nabumetone 46.05 +/- 26.08 microliters/min and 6MNA 6.32 +/- 2.96 microliters/min). The overall recovery of the investigated compounds in lymph did not exceed 5% of the doses given. The known fact that lymphatic drainage is regulated by arachidonate metabolites might suggest that NSAIDs differing in their lymphotropic properties could result in different responses of lymphatic vessels to an inflammatory fluid load.

Animals↗
PubMedDate not supplied

[A microsurgical approach to drainage of the thoracic duct in the rat].

Study of thoracic lymph flow is still of interest in gastrointestinal absorption and lymph distribution of different drugs or in immunological studies. A microsurgical experimental model for cannulation of the thoracic duct in rats is described. The principle of the method is the end fistula described by Bollman, allowing the sampling of the total thoracic duct lymph output. A simple method of collecting lymph under free moving conditions was used. The lymph cannulations were one with 0.9 mm outer diameter silicone tubing in 24 Sprague-Dawley rats with an average preoperative weight of 300 +/- 30 g. The daily lymph output measured for up to 10 days in the awake and unrestrained rats varied between 24.4 ml and 97.7 ml/day (average 45.6 ml/ day). The hourly lymph output varied between 0.55 ml and 5.8 ml (average 1.9 ml/h). Patency of the lymph fistulas was 87.5% at five days and 64.3% at the end of the experiment. The rats with failed fistulas presented various degrees of thickening of the lymphatic vessel wall. The average weight loss at the time of euthanasia was 72 g (24%). An accurate technique under the operation microscope and the use of silicone tubing may offer a reliable method in experiments requiring the sampling of the whole thoracic duct lymph output for limited periods of time.

Anesthesia, Inhalation↗
PubMedDate not supplied

No contribution of morphine-6-glucuronide to clinical morphine effects after short-term administration.

The primary metabolite of morphine, morphine-6-beta-glucuronide (M-6-G), is reported to contribute to the effects of morphine. The authors investigated the effects of M-6-G on the central nervous system (CNS) after short-term intravenous (i.v.) administration by employing both electroencephalograph (EEG) power spectra analyses and clinical signs as indicators of opioid effects. Three dosages of M-6-G, one dosage of morphine (bolus 10 mg/70 kg and 3.5 mg/70 kg/hour for 4 hours), a combination of morphine and M-6-G, and placebo were administered to 20 healthy volunteers as i.v. bolus plus i.v. infusion for 4 hours. M-6-G was dosed to produce steady state plasma concentrations that were either identical, 2 times, or 3 times higher than the M-6-G plasma concentrations observed after administration of morphine. The EEG background activity and clinical effects were recorded 3.5 hours after the infusion started. M-6-G failed to produce effects on any of the investigated EEG or clinical parameters at the doses tested. In contrast, morphine produced a significant increase in the alpha 1 and delta power of the EEG. In addition, morphine increased the subjects' ratings of tiredness, sickness, vertigo, and drowsiness, and decreased their level of performance in a tracking task. It was concluded that after short-term i.v. administration, M-6-G does not affect the CNS at the doses tested. Therefore, its contribution to clinical effects of morphine after short-term administration is questionable. The missing CNS effects were probably caused by the slow brain permeability of M-6-G, which in short-term treatment might not attain effective CNS concentrations.

Adult↗