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Carsten Skarke

Publications and source records attributed to Carsten Skarke.

At least 19 recordsLinked to original sources
PubMed2006

Evidence for morphine-independent central nervous opioid effects after administration of codeine: contribution of other codeine metabolites.

OBJECTIVE: Our objective was to investigate whether codeine or one of its metabolites contributes substantially to central nervous effects independent from the cytochrome P450 (CYP) 2D6-mediated O-demethylation to morphine. METHODS: After oral administration of codeine, plasma concentrations of codeine and its metabolites, as well as pupil size as a measure of central nervous effects, were measured in 11 healthy volunteers representing poor, intermediate, extensive, and ultrarapid metabolizers for CYP2D6. Subsequently, the observed plasma morphine concentrations were mimicked by use of computerized morphine infusion, and the miotic effects were compared with those observed after codeine administration. The contribution of codeine, codeine-6-glucuronide, norcodeine, morphine, morphine-6-glucuronide, and normorphine to the miotic effects was analyzed by means of pharmacokinetic-pharmacodynamic modeling. RESULTS: The areas under the curve of the miotic effects after codeine were 1.7 +/- 2 times greater than after morphine (P <0.01). This contrasted to similar or even lower morphine concentrations after codeine than after morphine (area under the curve ratio, 0.5 +/- 0.4; P =.21). A pharmacokinetic-pharmacodynamic fit of the miotic effects by use of morphine as the only active moiety was most significantly (P <.0001) improved when codeine-6-glucuronide as a second active moiety was added. CONCLUSION: CYP2D6-dependent formation of morphine does not explain exclusively the central nervous effects of codeine. Codeine-6-glucuronide is the most likely additional active moiety.

Adult↗
PubMed2006

Modulation of the central nervous effects of levomethadone by genetic polymorphisms potentially affecting its metabolism, distribution, and drug action.

AIM: Our aim was to judge the importance of candidate pharmacogenetic modulators of the central nervous effects of levomethadone by both magnitude of the modulatory effect and frequency of the mutation to assess the utility of genotyping for clinical levomethadone therapy in a random sample of subjects that, by distribution of genotypes, resembled the clinical setting. METHODS: Candidate pharmacogenetic modulators were polymorphisms reported to be of functional consequence and therefore potentially important for metabolism, distribution, or pharmacodynamic action of levomethadone, consisting of genes coding for cytochrome P450 (CYP) 2B6 and 3A, as well as 1A2, 2C8, 2C9, 2C19, and 2D6, for P-glycoprotein (ABCB1), and for mu-opioid receptors (OPRM1). The central nervous effects of levomethadone were investigated by means of measuring pupil size in a random sample of 51 healthy volunteers for 9 hours after oral administration of 0.075 mg/kg levomethadone. Plasma concentrations of levomethadone and its metabolites were assessed concomitantly, and to judge the role of metabolites, the affinities of levomethadone and its metabolites at mu-opioid receptors were estimated by use of displacement of the selective mu-opioid receptor agonist [(3)H]-DAMGO ((3)H-[D-Ala(2),N-MePhe(4),Gly-ol(5)]-enkephalin). RESULTS: Pupil size decreased to -41.8% +/- 9.6% from baseline at 3.5 +/- 1.1 hours after levomethadone administration. Miosis was still manifest to a lower degree (-25.1% +/- 12.3%) at the end of the observation period. In carriers of the variant 118G allele (118A>G single-nucleotide polymorphism) of the mu-opioid receptor gene (OPRM1), levomethadone had a 1.74 times (95% confidence interval, 1.4-2.2 times) lower miotic potency (P < .001) as compared with noncarriers (concentration at half-maximum effects, 52.3 nmol/L; 95% confidence interval, 36.7-66.2 nmol/L). The maximum percent decrease in pupil diameter from baseline was 44.9% +/- 7.6%, 33% +/- 6.5%, and 24% +/- 6.9% for carriers of the OPRM1 118AA, AG, and GG genotypes, respectively (P < .001 for AG and GG versus wild type, without significant differences between AG and GG). Other candidate polymorphisms in the ABCB1 or in CYP genes had no significant influence on the effects of levomethadone, either because of lack of functional consequences or because of their low allelic frequency. The metabolites of levomethadone did not contribute to the effects as indicated by low metabolite plasma concentrations and their 120- to 1300-fold lower affinities at mu-opioid receptors as compared with levomethadone. CONCLUSIONS: Among polymorphisms in OPRM1, ABCB1, and CYP genes previously associated with functional consequences in a different context, the most important pharmacogenetic factor modulating the short-term effects of levomethadone is a polymorphism (OPRM1 118A>G) affecting mu-opioid receptors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2006

The cyclooxygenase 2 genetic variant -765G>C does not modulate the effects of celecoxib on prostaglandin E2 production.

OBJECTIVE: Our objective was to assess the role of the reportedly functional PTGS2 (prostaglandin-endoperoxide synthase 2/cyclooxygenase [COX] 2) promoter mutation -765G>C for the COX-2-inhibiting effects of celecoxib. METHODS: Twenty healthy carriers of the -765GG genotype and -765CC genotype (n = 10 each) received 200 mg of celecoxib orally. Blood samples were drawn at baseline and at 1, 3, 6, 9, and 24 hours after administration. Plasma concentrations of celecoxib and concentrations of prostaglandin E(2) (PGE(2)) produced by peripheral blood monocytes stimulated ex vivo with bacterial lipopolysaccharide (LPS) were analyzed by liquid chromatography-tandem mass spectrometry. Expression of COX-2 messenger ribonucleic acid and protein expression with and without LPS stimulation were analyzed by real-time polymerase chain reaction and Western blotting, respectively. RESULTS: LPS induced PGE(2) production (P < .001), and celecoxib reduced PGE(2) production from 19.3 +/- 7.2 ng/mL at baseline to 7.4 +/- 4.8 ng/mL at 1 hour (P < .001). The effect of celecoxib lasted for 9 hours (repeated-measures ANOVA, P .28). LPS up-regulated COX-2 messenger ribonucleic acid expression (P = .016) but was independent of genotype (P = .36). COX-2 protein expression was similar for both -765G>C genotypes (P = .63). CONCLUSION: The PTGS2 -765G>C single-nucleotide polymorphism does not modulate COX-2 inhibitory effects of celecoxib as assessed by an ex vivo whole blood assay. Thus the results indicate the need for further investigation toward PTGS2 pharmacogenetics-based prescription of celecoxib.

Adult↗
PubMed2006

Rapid identification of three functionally relevant polymorphisms in the OATP1B1 transporter gene using Pyrosequencing.

INTRODUCTION: Clinical evidence suggests there are three single nucleotide polymorphisms (SNPs) of the solute carrier organic anion transporter family member B1 (SLCO1B1) gene for which in vivo evidence for a functional relevance for organic anion transporter polypeptides subgroup C (OATP1B1, formerly OATP-C) has been provided. These genetic variants have been shown to lead to altered pharmacokinetics of OATP1B1 substrates, mainly pravastatin, but also the irinotecan metabolite SN-38, estrone-3-sulfate, and estradiol-17beta-glucuronide. The authors therefore developed reliable and quick screening assays to identify the SLCO1B1 SNPs -11187G>A, 388A>G and 521T>C, in order to facilitate the judgment of their clinical role and to identify allelic frequencies of SNPs and haplotypes in a Caucasian random sample. METHODS: Three simplex Pyrosequencing assays were developed and the three selected SLCO1B1 SNPs were screened for in 250 DNA samples from healthy young female and male unrelated volunteers of Caucasian ethnicity. SLCO1B1 haplotypes involving DNA positions -11187, 388 and 521 were identified by in silico haplotyping. RESULTS: A clear identification of the three single nucleotide polymorphisms in the 250 DNA samples was possible and was verified by routine implementation of 40 control samples obtained by conventional sequencing. The frequencies of the variant alleles -11187A, 388G and 521C were 0.09, 0.47 and 0.12, respectively. All observed frequencies of heterozygous of homozygous carriers of SLCO1B1 alleles were in agreement with the Hardy-Weinberg equilibrium. SLCO1B1 haplotypes reportedly associated with altered substrate pharmacokinetics, i.e., SLCO1B1*15B (-11187G/388G/521C) and *17 (-11187A/388G/521C), were found at allelic frequencies of 0.09 and 0.02, respectively. CONCLUSION: The presently developed Pyrosequencing assays allowed for quick and reliable identification of those SLCO1B1 SNPs that had been proposed to cause functional alternations in OATP1B1 with shown consequences for the pharmacokinetics of drugs that are OATP1B1 substrates.

Adult↗
PubMed2005

Rapid genotyping for relevant CYP1A2 alleles by pyrosequencing.

OBJECTIVE: To develop a rapid and reliable screening method for identifying the relevant cytochrome P450 (CYP) 1A2 alleles CYP1A2*1D (-2467Tdel), *1F (-163A>C), and *1K (-739T>G, -729C>T, -163A>C) that are in linkage disequilibrium with the functionally relevant CYP1A2 polymorphisms and therefore are considered to be predictive for the CYP1A2 phenotype. METHODS: CYP1A2 single nucleotide polymorphisms (SNPs) -2467Tdel, -739T>G, -729C>T, and -163A>C were screened for in 495 healthy Caucasian volunteers using newly developed pyrosequencing duplex and simplex assays. Conventional sequencing of randomly selected samples served as quality control. RESULTS: Frequencies were 7.9% for CYP1A2*1D, 31.8% for *1F, and 0.4% for *1K. The observed distribution of homozygous and heterozygous carriers of the alleles corresponded to the predicted one according to the Hardy-Weinberg law. It also corresponded to reported allelic frequencies from Caucasians but differed significantly from the distribution seen in other ethnicities. The most frequent haplotype was -2467T/-739T/-729C/-163A (allelic frequency 61.6%), followed by -2467T/-739T/-729C/-163C (30.5%), -2467Tdel/-739T/-729C/-163A (5.1%), -2467Tdel/-739G/-729C/-163A (1.2%), and -2467Tdel/-739T/-729C/-163C (1.1%). Complete linkage disequilibrium (value of D' nearly 1) existed between -2467Tdel, -739T>G, and -729C>T and between -729T>G and -163A>C. CONCLUSIONS: Pyrosequencing facilitates rapid and reliable detection of those CYP1A2 alleles that, based on current knowledge, can be considered predictive for the CYP1A2 phenotype.

Alleles↗
PubMed2005

The 5-hydroxytryptamine 4 receptor agonist mosapride does not antagonize morphine-induced respiratory depression.

BACKGROUND: On the basis of experiments in rats, serotonin 4 receptor (5-hydroxytryptamine 4 [5-HT4]) agonists have been proposed as a novel therapeutic strategy for the selective treatment of respiratory depression caused by opioids while leaving analgesic effects unaffected. The effects in rats have been seen with the 5-hydroxytryptamine 4a (5-HT4a) agonist BIMU8, which is currently not available for use in humans. METHODS: In a proof-of-applicability study, the clinically recommended dose of 5 mg mosapride, currently the only 5-HT4 agonist available for clinical use, was given in a placebo-controlled manner 3 times daily for 5 days to 12 healthy men and women. During the actual experiments, a further 15 mg mosapride was administered. After baseline measurements of respiratory depression, by use of a carbon dioxide rebreathing method, and of pain, by use of electrical and chemical pain stimuli, 30 mg morphine per 70 kg body weight was administered intravenously within 2 hours. After assessment of respiratory depression and pain, 2 mg naloxone was intravenously administered within 20 minutes, followed by a third assessment of respiratory depression and pain. In ancillary experiments 10 rats received 100 mg/kg mosapride orally or placebo 50 minutes before intraperitoneal injection of 10 mg/kg morphine, followed 20 minutes later by injection of naloxone, and the respiratory frequency was monitored. RESULTS: With placebo coadministration, the slope of the relationship between expiratory volume and CO2 concentration in the inspired air was significantly reduced, from 1.11 +/- 0.46 L/mm Hg CO2 at baseline to 0.39 +/- 0.25 L/mm Hg CO2 at the end of the morphine infusion (P < .001). Coadministration of mosapride had no effect on respiratory depression induced by morphine (slope of 0.39 +/- 0.19 L/mm Hg CO2, P > .7). In contrast, naloxone significantly reversed the slope to 0.78 +/- 0.36 L/mm Hg CO2 (P = .001). Morphine produced significant effects on electrical and chemical pain stimuli, which were partially reversed by naloxone, but mosapride did not affect the analgesic effects of morphine. In rats mosapride similarly failed to prevent a slowing of the breathing frequency after morphine administration but naloxone reversed the respiratory depression. CONCLUSION: Our results show that, with mosapride, opioid-induced respiratory depression cannot be prevented, and because other 5-HT4 agonists are not currently available for clinical use, a cure for opioid-induced respiratory depression as promised by the previous successful experiments in laboratory animals is not yet available in clinical practice.

Adult↗
PubMed2004

Probenecid interacts with the pharmacokinetics of morphine-6-glucuronide in humans.

BACKGROUND: Evidence obtained from porcine cell cultures and experiments in laboratory animals indicates that transmembrane transporters may play a role in the distribution of the active morphine metabolite morphine-6-glucuronide (M6G). This was evaluated in a study in healthy volunteers. METHODS: Ten subjects received an intravenous M6G infusion for 30 min at a dosage of 0.5 mg/kg body weight, leading to M6G plasma concentrations approximately two to three times higher than those observed with analgesic morphine doses in subjects with normal kidney function. In a randomized, double-blind, three-way crossover fashion, subjects received 800 mg quinidine for inhibition of P-glycoprotein; 500 mg probenecid for inhibition of other transporters, including organic anion transporter peptide, multidrug resistance-related protein, and organic anion transporter families; or placebo 1 h before the start of M6G administration. Plasma concentrations of M6G and pupil size were measured for 7 h. RESULTS: Probenecid pretreatment resulted in a decrease in the clearance of M6G from 8.3 +/- 1 l/h to 6.7 +/- 1.3 l/h (factor of 0.8; P < 0.05 vs. placebo cotreatment). This was paralleled by an increase by a factor of 1.2 of the area under the miotic effect-versus-time curves (P < 0.05 vs. placebo). In contrast, quinidine pretreatment had no influence on the pharmacokinetics of M6G. CONCLUSIONS: The active morphine metabolite is subject to transmembrane transport by transporters inhibited by probenecid in humans.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Genetic predictors of the clinical response to opioid analgesics: clinical utility and future perspectives.

This review uses a candidate gene approach to identify possible pharmacogenetic modulators of opioid therapy, and discusses these modulators together with demonstrated genetic causes for the variability in clinical effects of opioids. Genetically caused inactivity of cytochrome P450 (CYP) 2D6 renders codeine ineffective (lack of morphine formation), slightly decreases the efficacy of tramadol (lack of formation of the active O-desmethyl-tramadol) and slightly decreases the clearance of methadone. MDR1 mutations often demonstrate pharmacogenetic consequences, and since opioids are among the P-glycoprotein substrates, opioid pharmacology may be affected by MDR1 mutations. The single nucleotide polymorphism A118G of the mu opioid receptor gene has been associated with decreased potency of morphine and morphine-6-glucuronide, and with decreased analgesic effects and higher alfentanil dose demands in carriers of the mutated G118 allele. Genetic causes may also trigger or modify drug interactions, which in turn can alter the clinical response to opioid therapy. For example, by inhibiting CYP2D6, paroxetine increases the steady-state plasma concentrations of (R)-methadone in extensive but not in poor metabolisers of debrisoquine/sparteine. So far, the clinical consequences of the pharmacogenetics of opioids are limited to codeine, which should not be administered to poor metabolisers of debrisoquine/sparteine. Genetically precipitated drug interactions might render a standard opioid dose toxic and should, therefore, be taken into consideration. Mutations affecting opioid receptors and pain perception/processing are of interest for the study of opioid actions, but with modern practice of on-demand administration of opioids their utility may be limited to explaining why some patients need higher opioid doses; however, the adverse effects profile may be modified by these mutations. Nonetheless, at a limited level, pharmacogenetics can be expected to facilitate individualised opioid therapy.

Analgesics, Opioid↗
PubMed2003

Respiratory and miotic effects of morphine in healthy volunteers when P-glycoprotein is blocked by quinidine.

AIM: Our objective was to evaluate whether P-glycoprotein inhibition after quinidine pretreatment results in modified central nervous effects of morphine. METHODS: Twelve healthy volunteers received 7.5 mg morphine as an intravenous infusion over a 3-hour period. In a randomized, double-blind, 2-way crossover fashion, subjects received either 800 mg quinidine or placebo 1 hour before the start of morphine administration. The miotic and respiratory depressive effects of morphine were assessed by means of pupillometry and the respiratory response to carbon dioxide rebreathing, respectively. Quinidine effects were assessed by electrocardiogram recordings. Plasma concentrations of morphine and its glucuronide metabolites were measured throughout the observation period of 5 hours. RESULTS: Morphine significantly reduced both the respiratory response to carbon dioxide and the pupil diameter. Throughout the observation period, quinidine had significant effects on the corrected QT interval (QTc increase of >60 milliseconds), indicating clinically relevant quinidine action. However, quinidine pretreatment did not enhance the respiratory depressive effects of morphine, nor did it alter the miotic effects of morphine to a statistically significant or clinically relevant extent. Plasma concentrations of morphine and its glucuronides were not significantly changed by quinidine pretreatment. CONCLUSIONS: Whereas morphine clearly produced miosis and respiratory depression, pretreatment with quinidine as an inhibitor of P-glycoprotein did not result in an enhancement of central nervous opioid effects in healthy volunteers.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Simultaneous screening for three mutations in the ABCB1 gene.

A noncoding C3435T mutation in exon 26 of the ABCB1 gene was found to be often associated with a G2677T(A) mutation in exon 21 encoding an Ala893Ser P-glycoprotein and with a noncoding C1236T mutation in exon 12. We developed a Pyrosequencing screening method that simultaneously detects all three mutations. After separate PCRs for each exon, the sequences around the potentially mutated nucleotide positions were simultaneously analyzed in a multiplex assay. The method was tested with DNA from 100 volunteers. Allele frequencies of the T1236, T2677, and T3435 alleles were 44, 42, and 50%, respectively. A mutation at position 3435 occurred together with a mutation at position 2677 or 1236 in 64 and 65% of the subjects, respectively. The most frequent haplotype, with 44.4%, was not mutated at all three positions, i.e., C1236, G2677, C3435. The second most frequent haplotype, with 37.1%, was mutated at all three positions, i.e., T1236, T2677, T3435. The most frequent genotype, with 36%, was heterozygously mutated at all three positions, i.e., C/T1236, G/T2677, C/T3435. The next most frequent genotypes were a homozygous nonmutated genotype, with 20%, and a homozygous mutated genotype, with 13%.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2003

Pharmacokinetics of morphine are not altered in subjects with Gilbert's syndrome.

AIMS: To verify that Gilbert's syndrome, which is caused by decreased glucuronidation capacity of the UDP-glucuronosyl transferase (UGT)1A1, does not account for impaired morphine clearance. METHODS: Noncompartmental pharmacokinetic parameters for morphine and its glucuronide metabolites were compared between five carriers of Gilbert's syndrome and six noncarriers after a 7.5 mg (19.8 micro mol) intravenous injection of morphine sulphate pentahydrate. To estimate the amount of morphine-6-glucuronide (M6G) formed from morphine, 1 mg of deuterized M6G was injected intravenously at the same time. RESULTS: No differences were detected between carriers and noncarriers of Gilbert's syndrome in the clearance of morphine (80.1 +/- 12 l h(-1) vs 87.9 +/- 22 l h(-1)) and in the percentage of morphine that was metabolized to M6G (10.9 +/- 1.4 vs 13 +/- 2). The areas under the plasma concentration vs time curves of morphine, M6G and morphine-3-glucuronide also did not differ between carriers and noncarriers of Gilbert's syndrome. CONCLUSIONS: Gilbert's syndrome is not a factor to be considered when prescribing morphine.

Adult↗
PubMed2003

Analgesic effects of morphine and morphine-6-glucuronide in a transcutaneous electrical pain model in healthy volunteers.

OBJECTIVE: Our objective was to quantify the extent and time course of the effects of morphine-6-glucuronide and morphine on pain threshold, pain tolerance, pupil diameter, and side effects. METHODS: In a double-blind, placebo-controlled, randomized, 3-way crossover study, 12 healthy volunteers (6 men and 6 women) received 63 to 112 mg of morphine-6-glucuronide or 26 to 66 mg of morphine as an intravenous bolus, followed by an infusion of the same medication for 1.8 to 6.4 hours. Analgesia was assessed every 30 minutes for up to 16 hours by means of transcutaneous electrical stimulation (sine wave, 5 Hz; intensity, 0-9.99 mA). Pupil diameter and side effects were recorded concomitantly. RESULTS: At the administered doses, morphine-6-glucuronide and morphine had comparable effects on pain tolerance, pupil diameter, and side effects. The delay between the time course of the plasma concentrations and the time course of the effects was longer for morphine-6-glucuronide than for morphine (transfer half-life, 8.2 hours versus 2.6 hours for pain tolerance and 7.7 hours versus 2.8 hours for pupil diameter). The slope of the linear concentration versus effect relationship for pain tolerance was flatter for morphine-6-glucuronide than for morphine (0.05% versus 0.6% increase in pain tolerance per nanomole per liter of morphine-6-glucuronide and morphine at effect site, respectively). Morphine-6-glucuronide was less potent than morphine in producing pupil constriction (mean concentration at half-maximum effect, 745 nmol/L versus 26.4 nmol/L for morphine-6-glucuronide and morphine, respectively). In carriers of the mutated G118 allele of the mu-opioid receptor, the potency of the pupil-constricting effects of morphine-6-glucuronide and morphine was significantly smaller, and carriers of the G118 allele reported less nausea and vomited less often after administration of morphine-6-glucuronide. CONCLUSIONS: Morphine-6-glucuronide clearly produced analgesic effects in healthy volunteers. However, the high amounts of systemic morphine-6-glucuronide needed to produce the same effects as morphine suggest that morphine-6-glucuronide barely contributes to the central nervous opioid effects after administration of analgesic doses of morphine.

Adult↗
PubMed2003

Effects of ABCB1 (multidrug resistance transporter) gene mutations on disposition and central nervous effects of loperamide in healthy volunteers.

OBJECTIVE: Mutations in the ABCB1 gene have been associated with decreased expression and net function of P-glycoprotein (P-gp). We investigated the modulation of the central nervous effects of loperamide resulting from ABCB1 genetic variants. METHODS: On two occasions, 20 healthy volunteers received 24 mg loperamide suspension orally and, in a double-blind randomized two-way crossover fashion, 800 mg quinidine or placebo orally 1 h before loperamide. Pupil size was measured for 5 h following loperamide administration, and plasma concentrations of loperamide and quinidine were measured for 6 h. Single nucleotide polymorphisms and haplotypes including G2677T(A) (exon 21) and C3435T (exon 26) were analysed for their relation to plasma concentrations of quinidine and loperamide and to the miotic effects of loperamide. RESULTS: Loperamide plasma concentrations with quinidine co-administration were about twice as high as those without quinidine. The ABCB1 haplotype G2677/T3435 was associated with the highest loperamide plasma concentrations, which were about 1.5 times higher than in non-carriers of this haplotype. Plasma concentrations of quinidine did not differ among carriers and non-carriers of genetic variants. When quinidine was co-administered with loperamide, pupil size decreased. Without quinidine it changed only minimally. The ABCB1 TT3435 genotype was associated with the most pronounced increase of the miotic effects of loperamide when quinidine was co-administered. This was accompanied by a tendency toward higher plasma loperamide in TT3435 carriers. CONCLUSIONS: Our data support a functional importance of the ABCB1 mutations for plasma concentrations and central nervous actions of the opioid loperamide.

Administration, Oral↗
PubMed2003

Olfactory function in mild cognitive impairment and Alzheimer's disease: an investigation using psychophysical and electrophysiological techniques.

OBJECTIVE: To clarify the olfactory deficit hypothesis regarding Alzheimer's disease, the authors compared olfactory function in patients with Alzheimer's disease, subjects with mild cognitive impairment, and healthy comparison subjects. METHOD: Olfactory function of 14 patients with mild Alzheimer's disease, eight subjects with mild cognitive impairment, and eight healthy age-matched comparison subjects was assessed with both psychophysical tests and olfactory event-related potentials. RESULTS: Group comparison of the psychophysical test results showed a significant main effect of diagnosis for odor detection threshold, odor discrimination, and odor identification. These results correlated only partially with those obtained from olfactory event-related potentials. Seven Alzheimer's disease patients and four with mild cognitive impairment showed no olfactory event-related potentials, suggesting hyposmia, while all comparison subjects had clearly discernible responses. Patients with Alzheimer's disease were significantly more likely to be nonresponders. In the four Alzheimer's disease patients and four subjects with mild cognitive impairment who had clear electrophysiological responses, amplitudes and latencies of the various event-related potential components were normal, i.e., similar to those of the comparison subjects, although 12 of the 14 Alzheimer's disease patients and seven of the eight mildly impaired subjects were classified as functionally anosmic with psychophysical methods. CONCLUSIONS: The electrophysiological results confirm prior findings of olfactory dysfunction in patients with Alzheimer's disease and preclinical Alzheimer's disease. Investigations of larger study groups with detailed cognitive examination and postmortem diagnosis may resolve the intriguing possibility of early diagnosis and discrimination of Alzheimer's disease subtypes through chemosensory event-related potentials in addition to existing biomarkers.

Aged↗
PubMed2002

The influence of inhibition of probenecid sensitive transporters on the central nervous system (CNS) uptake and the antinociceptive activity of morphine-6-glucuronide in rats.

In light of a recent demonstration that probenecid enhanced the central nervous system (CNS) uptake of morphine-3-glucuronide (M3G), we investigated the consequences of probenecid co-administration for the spinal cord concentrations and antinociceptive effects of morphine-6-glucuronide (M6G) in rats. Spinal cord tissue concentrations of M6G were assessed by in-vivo microdialysis. Ten rats were administered M6G by intravenous infusion for 8 h, five of them additionally received an infusion of probenecid. Antinociceptive effects of M6G were assessed by means of formalin tests during the 8th h of the M6G infusion in another five rats that received M6G together with probenecid. Five additional rats per groups received probenecid only, M6G only and placebo. The inhibition of probenecid-sensitive transporters caused a raise in both plasma (statistically significant) and spinal cord tissue (not statistically significant) concentrations of M6G by a factor of 1.3, without affecting the tissue to plasma concentration ratio of M6G (0.0812 +/- 0.034 for M6G alone, 0.0824 +/- 0.021 for M6G plus probenecid). Co-administration of probenecid with M6G resulted in a significant reduction of the number of flinches by a factor of 2.5 as compared to M6G alone. The study showed that probenecid sensitive transporters play a role for the CNS concentrations of M6G via an increase of its plasma concentrations, but the effect of probenecid co-administration is small as compared to the reported effects on the CNS concentrations of M3G in rats.

Analgesics↗
PubMed2002

Pharmacokinetic modeling to predict morphine and morphine-6-glucuronide plasma concentrations in healthy young volunteers.

OBJECTIVE: This investigation focused on the development of a predictive model of morphine, including morphine-6-glucuronide (M6G) for healthy young volunteers after morphine administration. METHODS: Population compartmental pharmacokinetic modeling with NONMEM was applied to the plasma concentration-time data of morphine and M6G obtained from 8 healthy volunteers (4 men and 4 women; age range, 23 to 30 years) after intravenous bolus injection of 5.64 mg morphine base (7.5 mg morphine sulfate) and of 1 mg deuterium-labeled M6G. RESULTS: Two models were identified that described the plasma concentration versus time courses of morphine and M6G after administration of morphine. The model consisted of a standard 3-compartment model for morphine and a standard 2-compartment model for M6G, with input into and output from the central compartments. The formation of M6G from morphine was modeled as a fraction of morphine clearance of about 14%, which accounted for the formation of M6G, and a delay of the appearance of M6G in plasma modeled as a first-order process, with a mean metabolic transit time of 17.2 minutes. An alternative model assigned the formation of M6G among the first peripheral compartment of morphine and the central compartment of M6G. Therefore the alternative 3-compartment model of morphine had the input into the central compartment and renal excretory elimination from the central compartment, but the metabolic clearance of morphine started from the first peripheral compartment. M6G was again modeled with a standard 2-compartment model. Both models predicted morphine and M6G plasma concentrations available from an independent study with acceptable accuracy and without bias. CONCLUSIONS: Two models are provided that can predict plasma concentrations of morphine and M6G with acceptable accuracy in healthy young volunteers.

Adult↗