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- Bastami, Salumeh, 1967-
(författare)
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Practical and clinical use of opioids
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pain is a common symptom of a number of conditions including cancer and one of the most frequent reasons for seeking healthcare. Acute and chronic pain result in considerable discomfort with a detrimental impact on the quality of life. Opioids are the mainstay of pain management for many patients with severe pain. Opioids are, unfortunately, also commonly abused drugs, and are well-represented in forensic toxicology investigations.Side effects related to the central nervous system are the major reasons fordiscontinuation of opioid treatment. In this thesis, we tested the hypothesis that local analgesic treatment by opioids, without the usual opioid-related side effects, could be a potential alternative to systemic opioid treatment. We examined the analgesic effect of topically applied morphine in a randomized, double blind, cross over study in patients with painful leg ulcers. Significant reduction of pain was obtained after application of both morphine and placebo gel. Morphine reduced pain more than placebo but the difference was not statistically significant. However, morphine could reduce pain considerably more than placebo in those cases where VAS (Visual analog scale) was higher initially.Another issue with opioid therapy is the substantial individual variability in response to opioids including morphine and tramadol. We investigated the significance of UGT2B7, CYP2D6, OPRM1 and ABCB1 polymorphisms for pharmacokinetic and pharmacodynamic properties of morphine and tramadol. We showed that genetic variants in CYP2D6 and UGT2B7 have an important role in the metabolism of tramadol and morphine respectively. While the role of SNPs in ABCB1 remained unclear, genetic variants in OPRM1 gene were correlated with the required dose of morphine. Taken together, these findings suggest that genotypes should be taken into consideration when interpreting clinical pharmacology and forensic toxicology results.Opioids, besides their analgesic properties, have other pharmacological effects including effects on immune system. We evaluated potential differences between commonly used opiates with regard to their effect on the immune system. We found an inhibition of cytokine release, in the order of potency as follows: tramadol > ketobemidone >morphine >fentanyl. All opioids with the exception of fentanyl were capable of inhibiting production of mRNAs for TNF-alpha and IL-8. Further studies are needed to understand the clinical implications of the observed immunosuppressive effects of opioids and to improve opioid treatment strategies in patients with cancer.Here, we have found that individual genotype matters and affects the individual response. Further research is warranted to tailor individualized treatment. Personalized medicine has increased in importance and will hopefully in the near future become standard procedure to improve and predict the outcome of treatment by opioids.
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| 2. |
- Karlsson, Louise
(författare)
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P-glycoprotein and chiral antidepressant drugs : Pharmacokinetic, pharmacogenetic and toxicological aspects
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The blood-brain barrier (BBB) is formed by the capillary endothelial cells, joined together by tight junctions, with transporter proteins. BBB acts to regulate the brain concentrations of substances including many drugs. Transport across the cells is necessary for a drug to ensure that the drug reaches the site of action and transport proteins such as P-glycoprotein (P-gp; ABCB1) can limit the entrance into various tissues, including the brain.Molecules that are not superimposable on their mirror images and thus exist in two enantiomeric forms (enantiomers) are said to be chiral. A racemic compound is one composed of a 50:50 mixture of two enantiomers, S- and R-enantiomers. Two examples of frequently prescribed racemic drugs are the chiral antidepressants venlafaxine (VEN) and citalopram (CIT). The enantiomers of VEN possess different pharmacodynamic profiles where the R-enantiomer is a potent inhibitor of both serotonin and noradrenaline reuptake (SNRI), while the S-enantiomer is more selective in inhibiting serotonin reuptake (SSRI). The SSRI effect of CIT resides in the S-enantiomer, whereas the R-enantiomer is considered to be therapeutically inactive, or even that it counteracts the effects. The S-enantiomer of CIT is now available as a separate SSRI (escitalopram, EsCIT). VEN and CIT are also among the most commonly found drugs in forensic autopsy cases.Few previous studies have examined a possible enantioselective activity of P-gp. Thus, the general aim of this thesis was to study the enantiomeric distribution of chiral antidepressant drugs, focusing on the role of P-gp in the BBB. For this purpose, a mouse model disrupted of the genes coding for P-gp (abcb1ab (-/-) mice) was used. Brain and serum concentrations of the enantiomers of VEN and CIT, and their major metabolites, were compared to the corresponding wild-type mice (abcb1ab (+/+) mice). The open-field locomotor and rearing activities were examined after chronic VEN administration. In addition to the animal studies, genetic and toxicological aspects of P-gp were studied in a forensic autopsy material, where intoxication cases were compared with cases that were not related to intoxications.The brain to serum concentration ratios for VEN, CIT and EsCIT differed between knockout mice and wild-type mice, with 2-3 fold higher brain concentrations in mice with no expression of P-gp. Hence, all studied drugs, and their major metabolites, were substrates for P-gp. There was no evidence for a stereoselective P-gp mediated transport. The P-gp substrate properties were reflected in the open-field behavior test where the knockout mice displayed increased center activity compared with wild-type mice following chronic VEN exposure. The genotype distribution of ABCB1 SNPs C1236T, G2677T and C3435T in VEN positive cases was significantly (or borderline) different between the intoxication cases and the non-intoxication cases. This difference in genotype distribution was not observed for the CIT positive cases.To conclude, the present work has led to an increased knowledge about how the enantiomers of VEN and CIT are affected by the BBB transporter P-gp. Using an animal model, VEN and CIT have proved to be actively transported out of the brain by P-gp and no difference was observed for the enantiomers with regard to P-gp transport. Further, the ABCB1 genotype distribution was different in intoxication cases compared with non-intoxication cases. Taken together, these findings offer the possibility that the expression of P-gp in humans may be a contributing factor for limited treatment response and increased risk of side-effects following antidepressant drug treatment.
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| 3. |
- Nilsson, Gunnel, 1950-
(författare)
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Zopiclone degradation in biological samples : Characteristics and consequences in forensic toxicology
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bio-analytical results are influenced by in vivo factors such as genetics, pharmacological and physiological conditions and in vitro factors such as specimen composition, sample additives and storage conditions. Zopiclone (ZOP) is a short-acting hypnotic drug (Imovane®) used for treatment of insomnia. ZOP is metabolized by three major pathways; oxidation to the active zopiclone N-oxide (ZOPNO), demethylation to the inactive N-desmethylzopiclone (NDZOP) and oxidative decarboxylation to other inactive metabolites. ZOP is increasingly being encountered in forensic cases and is a common finding in samples from drug-impaired drivers, users of illicit recreational drugs, victims of drug facilitated sexual assaults and forensic autopsy cases. ZOP is a notoriously unstable analyte in biological matrices and analytical results depend on pre-analytical factors, such as storage time and temperature. The overall aim of this thesis was to investigate the stability of ZOP and the factors of importance for degradation during storage in biological samples and to identify consequences for interpretation of results in forensic toxicology.In paper I, different stability tests in spiked samples were performed including short-term, longterm, freeze-thaw and processed stability. Analyses of ZOP were performed by gas chromatography with nitrogen phosphorous detection and ZOP concentrations were measured at selected time intervals. The degradation product 2-amino-5-chloropyridine (ACP) was identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The stability investigations showed a very poor short-term storage stability of ZOP.Therefore, in paper II, the influence of pre-analytical conditions was further investigated in dosed subjects. Whole blood from volunteers was obtained before and after oral administration of Imovane®. In this study, the influence from physiological factors such as drug interactions, matrix composition and plasma protein levels were minimized. The results showed that ZOP was stable in whole blood for only one day at room temperature, one week in a refrigerator and at least three months frozen in authentic as well as in spiked whole blood. The rapid degradation of ZOP at ambient temperature can cause an underestimation of the true concentration and consequently flaw the interpretation. However, by also analyzing the degradation product ACP the original concentration of ZOP may be estimated.In papers III and IV, two LC-MS-MS methods were validated for the quantitation of ACP, ZOP and NDZOP in blood and ACP, ZOP, NDZOP and ZOPNO in urine. These methods were used in a controlled pharmacokinetic study where whole blood and urine were obtained after oral administration of Imovane®. Samples of blood and urine were aliquoted, analyzed and stored under different conditions and the formation of ACP was monitored. Additionally, at each studied time point the pH of the blood and urine samples was measured using i-STAT® system. The results showed that ACP was formed in equimolar amounts to the degradation of ZOP and its metabolites.In urine samples, the formation of ACP occurred at elevated pH or temperature and mirrored the degradation of ZOP, NDZOP and ZOPNO. The high concentrations of metabolites, which also degraded to ACP, made it impossible to estimate the original ZOP concentration.The results from analysis of blood samples containing ACP were also used to develop mathematical models to estimate the original ZOP concentration. Both models showed strong correlation to the original ZOP concentration (r=0.960 and r=0.955) with p<0.01. This study showed that the equimolar degradation of ZOP and NDZOP to ACP could be used to estimate the original concentration of ZOP in blood samples.Absence of ACP in the blood or urine samples analysed strongly suggests that degradation has not occurred and that the measured concentration of ZOP is reliable. For proper interpretation in forensic cases, it is strongly recommended that ZOP and its metabolites as well as ACP are included in the analysis.
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| 4. |
- Vikingsson, Svante, 1983-
(författare)
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Development of new methodology for therapeutic drug monitoring of thiopurine treatment
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The three thiopurine drugs azathioprine (AZA), 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG) are used to treat several diseases, including inflammatory bowel disease (IBD). They are pro-drugs and are believed to act through the formation of thioguanine nucleotides (TGNs). Other important metabolites are the methylthioinosine nucleotides (meTINs). These metabolites are active in the white blood cells (WBCs).Most patients respond well to the thiopurine drugs but up to a third have to modify or discontinue their treatment due to adverse events or a lack of therapeutic effects. This could be caused by inter-patient variability in the metabolism of the drugs. Therapeutic drug monitoring (TDM) of thiopurine nucleotides in red blood cells (RBCs) is used to guide treatment. Current routine assays measure the nucleotides after hydrolysation to nucleic bases and are therefore unable to distinguish between mono-, di-, and triphosphates. Recently it was shown that these assays failed to predict the clinical outcome in about 40% of the patients. It has been suggested that measuring thioguanosine triphosphate (TGTP) (believed to be the most active of the TGNs) separately might increase the clinical value.An assay suitable for measuring thioguanosine mono- (TGMP) and diphosphate (TGDP) and TGTP, as well as methylthioinosine mono- (meTIMP), di- (meTIDP) and triphosphate (meTITP) separately in RBCs in clinical samples has been developed. In clinical studies of 82 IBD patients, we found no correlation between the thiopurine dose and metabolite levels in RBCs, thus illustrating the importance of metabolite measurements in the TDM of thiopurines.The TGN peak measured by the routine assay during TDM of patients treated with thiopurines consisted of TGTP and TGDP with a small contribution from TGMP. The meTIN also consisted of mono-, di- and triphosphates, but in different proportions, indicating differences in the formation. The inter-individual differences in nucleotide distribution were very small and a strong correlation between the different nucleotides and their respective sums was observed. As a consequence, measuring the mono-, di- and triphosphates separately was not beneficial in predicting remission, which was confirmed by the results from the clinical study.Further research into the metabolism and mode of action of thiopurine drugs is needed to understand the inter-patient variability in response and metabolite formation. An assay suitable for such studies, measuring TGNs and meTINs in cultured cells, has also been developed.
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