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The Effect of Peripheral Enzyme Inhibitors on Levodopa Concentrations in Blood and CSF
Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Reconstruction Centre, Department of Neurosurgery UHL.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
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2010 (English)In: Movement Disorders, ISSN 0885-3185, E-ISSN 1531-8257, Vol. 25, no 3, 363-367 p.Article in journal (Refereed) Published
Abstract [en]

Levodopa combined with a dopa-decarboxylase inhibitor, such as carbidopa. shifts the metabolism to the COMT pathway. Adding the peripheral acting COMT inhibitor entacapone provides improvement for patients with PD suffering from motor fluctuations. We studied the effects of the enzyme inhibitors entacapone and carbidopa on the levodopa concentrations in CSF and in blood. Five PD patients with wearing-off underwent lumbar drainage and intravenous microdialysis. Samples were taken 12 h daily for 3 days. Day I; intravenous levodopa was given, day 2; additional oral entacapone 200 mg tid, day 3; additional oral entacapone 200 mg bid and carbidopa 25 mg bid. Levodopa in CSF and in dialysates was analysed. The AUC for levodopa increased both in blood and CSF when additional entacapone was given alone and in combination with carbidopa. The C-max of levodopa in both CSF and blood increased significantly. Additional entacapone to levodopa therapy gives an increase of C-max in CSF and in blood. The increase is more evident when entacapone is combined with carbidopa.

Place, publisher, year, edition, pages
John Wiley & Sons, 2010. Vol. 25, no 3, 363-367 p.
Keyword [en]
Parkinsons Disease, levodopa, continuous infusion, COMT
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-54855DOI: 10.1002/mds.22613ISI: 000276136900016OAI: oai:DiVA.org:liu-54855DiVA: diva2:310859
Available from: 2010-04-16 Created: 2010-04-16 Last updated: 2017-06-19
In thesis
1. Biochemical and pharmacokinetic studies in vivo in Parkinson’s disease
Open this publication in new window or tab >>Biochemical and pharmacokinetic studies in vivo in Parkinson’s disease
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Parkinson’s disease (PD) is a neurodegenerative disease affecting approximately 25000 people in Sweden. The main cause of the disease is the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc) projecting to the striatum. The motor symptoms of PD, due to decreased levels of dopamine, includes bradykinesia, rigidity and tremor.

During the 1960ies oral L-dopa treatment was introduced increasing quality of life for PD patients. In recent decades, enzyme inhibitors have been introduced, increasing bioavailability of L-dopa in plasma. After 5-10 years of L-dopa treatment, 50% of PD patients develop disabling dyskinesias. This can be due to rapid changes in L-dopa conentrations with non physiological stimulation of the dopamine receptor.

For over 20 years deep brain stimulation (DBS) has grown to be a good neurosurgical procedure for improving quality of life in advanced PD with disabling dyskinesias. With stereotactic technique, electrodes are implanted in the brain and connected to a pacemaker sending electrical impulses. The most common target in PD is the subthalamic nucleus (STN). The knowledge about DBS mechanism(s) and its interaction with L-dopa is unsatisfactory.

The aims of this thesis were; to study the effect of the enzyme inhibitor entacapone on the L-dopa concentration over the blood brain barrier (BBB); to study possible interactions between L-dopa and DBS; to study alterations in neurotransmitters during DBS; to visualize microdialysis catheters in anatomical targets and to estimate sampling area of the catheters.

In all four papers the microdialysis technique was used. It is a well-established technique for continuous sampling of small water-soluble molecules within the extracellular fluid space in vivo, allowing studies of pharmaceutical drugs and neurotransmitters.

We showed that entacapone increases the bioavailability of L-dopa in blood with a subsequent increase of L-dopa peak levels in the cerebrospinal fluid. This in turn may cause a larger burden on the dopaminergic neurons causing an increased degeneration rate and worsening of the dyskinesias; we showed that 18% of L-dopa crosses the BBB and that there is a possible interaction between L-dopa and DBS, L-dopa concentrations increase during concomitant STN DBS, which can clarify why its possible to decrease L-dopa medication after DBS surgery. The research has also shown that STN DBS has an effect on various neurotransmitter systems, mainly L-dopa, dopamine and GABA. We showed that STN DBS may have an effect on the SNc, resulting in putaminal dopamine release.

We have shown that with stereotactic technique, it is safe to do microdialysis sampling in specific areas in the human brain. Simulations with the finite element method combined with patient specific preoperative MRI and postoperative CT images gave us exact knowledge about the positions of the catheters and that the studied structures were the intended. The research has given an assumption of the maximum tissue volume that can be sampled around the microdialysis catheters.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 78 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1345
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-91294 (URN)978-91-7519-737-1 (ISBN)
Public defence
2013-05-17, Berzeliussalen, Hälsouniversitetet, Campusu US, Linköpings universitet, Linköping, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2013-04-19 Created: 2013-04-19 Last updated: 2017-04-15Bibliographically approved
2. Levodopa pharmacokinetics -from stomach to brain: A study on patients with Parkinson’s disease
Open this publication in new window or tab >>Levodopa pharmacokinetics -from stomach to brain: A study on patients with Parkinson’s disease
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders and it is caused by a loss of dopamine (DA) producing neurons in the basal ganglia in the brain. The PD patient suffers from motor symptoms such as tremor, bradykinesia and rigidity and treatment with levodopa (LD), the precursor of DA, has positive effects on these symptoms. Several factors affect the availability of orally given LD. Gastric emptying (GE) is one factor and it has been shown to be delayed in PD patients resulting in impaired levodopa uptake. Different enzymes metabolize LD on its way from the gut to the brain resulting in less LD available in the brain and more side effects from the metabolites. By adding dopa decarboxylase inhibitors (carbidopa or benserazide) or COMT-inhibitors (e.g. entacapone) the bioavailability of LD increases significantly and more LD can pass the blood-brain-barrier and be converted to DA in the brain. It has been considered of importance to avoid high levodopa peaks in the brain because this seems to induce changes in postsynaptic dopaminergic neurons causing disabling motor complications in PD patients. More continuously given LD, e.g. duodenal or intravenous (IV) infusions, has been shown to improve these motor complications. Deep brain stimulation of the subthalamic nucleus (STN DBS) has also been proven to improve motor complications and to make it possible to reduce the LD dosage in PD patients.

In this doctoral thesis the main purpose is to study the pharmacokinetics of LD in patients with PD and motor complications; in blood and subcutaneous tissue and study the effect of GE and PD stage on LD uptake and the effect of continuously given LD (CDS) on LD uptake and GE; in blood and cerebrospinal fluid (CSF) when adding the peripheral enzyme inhibitors entacapone and carbidopa to LD infusion IV; in brain during STN DBSand during oral or IV LD treatment.

To conclude, LD uptake is more favorable in PD patients with less severe disease and GE is delayed in PD patients. No obvious relation between LD uptake and GE or between GE and PD stage is seen and CDS decreases the LD levels. Entacapone increases the maximal concentration of LD in blood and CSF. This is more evident with additional carbidopa and important to consider in avoiding high LD peaks in brain during PD treatment. LD in brain increases during both oral and IV LD treatment and the DA levels follows LD well indicating that PD patients still have capacity to metabolize LD to DA despite probable pronounced nigral degeneration. STN DBS seems to increase putaminal DA levels and together with IV LD treatment also increases LD in brain possibly explaining why it is possible to decrease LD medication after STN DBS surgery.

Abstract [sv]

Parkinsons sjukdom (PS) är en av de vanligaste s.k. neurodegenerativasjukdomarna och orsakas av förlust av dopamin(DA)producerande nervceller i hjärnan. Detta orsakar motoriska symptom såsom skakningar, stelhet och förlångsammade rörelser. Levodopa (LD) är ett ämne, som kan omvandlas till DA i hjärnan och ge symptomlindring och det är oftast förstahandsval vid behandling av patienter med PS. Flera faktorer påverkar tillgängligheten av LD, bl.a. den hastighet som magsäcken tömmer sig med och denna verkar förlångsammad hos personer med PS vilket ger sämre tillgänglighet av LD i blodet och därmed i hjärnan. LD bryts även ner i hög grad av olika enzym ute i kroppen vilket leder till mindre mängd LD som hamnar i hjärnan och till fler nedbrytningsprodukter som orsakar biverkningar. Tillägg av enzymhämmare leder till ökad mängd LD som kan nå hjärnan och omvandlas till DA. Det anses viktigt att undvika höga toppar av LD i hjärnan då dessa verkar bidra till utvecklandet av besvärliga motoriska komplikationer hos patienter med PS. Om LD ges mer kontinuerligt, exempelvis som en kontinuerlig infusion in i tarmen eller i blodet, så minskar dessa motoriska komplikationer. Inopererande av stimulatorer i vissa delar av hjärnan (DBS) har också visat sig minska dessa motoriska komplikationer och även resultera i att man kan minska LD-dosen.

Huvudsyftet med den här avhandlingen är att studera LD hos patienter med PS; i blod och fettvävnad då LD ges i tablettform och se om det finns något samband med LD-upptag och hastigheten på magsäckstömningen (MT) och om kontinuerligt given LD påverkar LD-upptaget eller MT; i blod och i ryggmärgsvätska då enzymhämmarna entakapon och karbidopa tillsätts LD; i hjärna vid behandling med DBS och då LD ges både som tablett och som infusion i blodet.

Sammanfattningsvis kan vi se att LD-upptaget är mer gynnsamt hos patienter med PS i tidigare skede av sjukdomens komplikationsfas. MT är förlångsammad hos patienter med PS och det är inget tydligt samband mellan LD-upptag och MT eller mellan MT och sjukdomsgrad. Kontinuerligt given LD minskar LDnivåerna. Enzymhämmaren entakapon ökar den maximala koncentrationen av LD i blod och ryggmärgsvätska och effekten är mer tydlig vid tillägg av karbidopa vilket är viktigt att ta i beaktande vid behandling av PS för att undvika höga toppar av LD i hjärnan. LD ökar i hjärnan då man behandlar med LD i tablettform och som infusion i blodet och DA-nivåerna i hjärnan följer LD väl vilket visar på att patienter med PS fortfarande kan omvandla LD till DA trots trolig uttalad brist av de DA-producerande nervcellerna i hjärnan. DBS verkar öka DA i vissa områden i hjärnan och tillsammans med LD-infusion i blodet verkar det även öka LD i hjärnan och det kan förklara varför man kan sänka LDdosen efter DBS-operation.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 72 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1567
National Category
Neurology Anesthesiology and Intensive Care Gastroenterology and Hepatology Other Clinical Medicine Neurosciences
Identifiers
urn:nbn:se:liu:diva-136560 (URN)10.3384/diss.diva-136560 (DOI)9789176855577 (ISBN)
Public defence
2017-05-19, Berzeliussalen, Campus US, Linköping, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2017-04-20 Created: 2017-04-20 Last updated: 2017-08-14Bibliographically approved

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Nord, MariaZsigmond, PeterKullman, AnitaÅrstrand, KerstinDizdar, Nil

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