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Levodopa pharmacokinetics -from stomach to brain: A study on patients with Parkinson’s disease
Linköping University, Department of Clinical and Experimental Medicine, Divison of Neurobiology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Local Health Care Services in Central Östergötland, Department of Neurology.
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: urn:nbn:se:liu:diva-136560DOI: 10.3384/diss.diva-136560ISBN: 9789176855577 (print)OAI: oai:DiVA.org:liu-136560DiVA: diva2:1089533
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: 2017-04-20Bibliographically approved
List of papers
1. Is Levodopa Pharmacokinetics in Patients with Parkinson’s Disease Depending on Gastric Emptying?
Open this publication in new window or tab >>Is Levodopa Pharmacokinetics in Patients with Parkinson’s Disease Depending on Gastric Emptying?
2017 (English)In: Advances in Parkinsons Disease, ISSN 2169-9712, Vol. 06, no 01Article in journal (Refereed) Published
Abstract [en]

Levodopa uptake from the gastrointestinal tract in patients with Parkinson’s disease (PD) can be affected by delayed gastric emptying (GE). This might lead to fluctuating levodopa levels resulting in increased motor fluctuations. Continuous dopaminergic stimulation (CDS) improves motor fluctuations and could be a result of smoothening in levodopa uptake. In this study we wanted to study the levodopa pharmacokinetics peripherally in PD patients with motor fluctuations and investigate the relation between levodopa uptake and GE and the effect of CDS. PD patients with wearing off (group 1) and on-off syndrome (group 2) were included. Breath tests were performed to evaluate the half time (T1/2) of GE. Concomitantly 1 tablet of Madopark® was given and the levodopa concentrations in blood and subcutaneous (SC) tissue were analyzed for both groups. Group 2 was then given a 10-d continuous intravenous levodopa treatment and the tests were repeated. Higher levels of levodopa in group 1 compared to group 2 in blood (p = 0.014) were seen. The GE was delayed in both group 1 (p < 0.001) and group 2 (p < 0.05) compared to a reference group with healthy volunteers with T1/2 median values 105 and 78 min vs. 72 min. There was no difference in GE between the two PD groups (p = 0.220) or in group 2 before and after infusion period (p = 0.861). CDS resulted in lower levodopa levels in blood (p < 0.001) and SC tissue (p < 0.01). In conclusion, PD patients in early complication phase have a more favourable levodopa uptake than patients later in disease. We found delayed GE in PD patients with motor fluctuations but no obvious relation between GE and levodopa uptake or GE and PD stage. The effect of CDS indicates no effect of CDS on the mechanisms of GE but on the mechanisms of levodopa uptake.

Place, publisher, year, edition, pages
Scientific Research Publishing, 2017
National Category
Neurology Gastroenterology and Hepatology Anesthesiology and Intensive Care Surgery Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:liu:diva-136685 (URN)10.4236/apd.2017.61001 (DOI)
Available from: 2017-04-20 Created: 2017-04-20 Last updated: 2017-04-20
2. The Effect of Peripheral Enzyme Inhibitors on Levodopa Concentrations in Blood and CSF
Open this publication in new window or tab >>The Effect of Peripheral Enzyme Inhibitors on Levodopa Concentrations in Blood and CSF
Show others...
2010 (English)In: MOVEMENT DISORDERS, ISSN 0885-3185, 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 and Sons, Ltd, 2010
Keyword
Parkinsons Disease, levodopa, continuous infusion, COMT
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-54855 (URN)10.1002/mds.22613 (DOI)000276136900016 ()
Available from: 2010-04-16 Created: 2010-04-16 Last updated: 2017-04-20
3. Neurotransmitter levels in basal ganglia during levodopa and deep brain stimulation treatment in Parkinson’s disease
Open this publication in new window or tab >>Neurotransmitter levels in basal ganglia during levodopa and deep brain stimulation treatment in Parkinson’s disease
Show others...
2014 (English)In: Neurology and Clinical Neuroscience, ISSN 2049-4173, Vol. 2, no 5, 149-155 p.Article in journal (Refereed) Published
Abstract [en]

Background The mechanism by which deep brain stimulation of the nucleus subthalamicus improves Parkinson’s disease symptoms remains unclear. In a previous perioperative study, we showed that there might be alterations of neurotransmitter levels in the globus pallidum interna during deep brain stimulation of the nucleus subthalamicus. Aim In this study, we examined whether deep brain stimulation of the nucleus subthalamicus and levodopa infusion interact and affect the levels of neurotransmitters. Methods Five patients with advanced Parkinson’s disease took part in the study. During subthalamic nucleus surgery, microdialysis catheters were inserted bilaterally in the globus pallidum interna and unilaterally in the right putamen. A study protocol was set up and was followed for 3 days. Levodopa infusion with and without concomitant bilateral deep brain stimulation of the nucleus subthalamicus was also carried out. Results The putaminal dopamine levels increased during deep brain stimulation of the nucleus subthalamicus. In addition, an increase of gamma amino buturic acid concentrations in the globus pallidum interna during deep brain stimulation of the nucleus subthalamicus and during levodopa infusion was found. Conclusions These findings provide evidence that the subthalamic nucleus has a direct action on the substantia nigra pars compacta, and that deep brain stimulation of the nucleus subthalamicus might indirectly release putaminal dopamine. There is also evidence that deep brain stimulation of the nucleus subthalamicus interferes with levodopa therapy resulting in higher levels of levodopa in the brain, explaining why it is possible to decrease levodopa medication after deep brain stimulation surgery.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014
Keyword
deep brain stimulation, levodopa, microdialysis, neurotransmitters, Parkinson
National Category
Medical Bioscience Medical Biotechnology Basic Medicine
Identifiers
urn:nbn:se:liu:diva-113590 (URN)10.1111/ncn3.109 (DOI)
Available from: 2015-01-23 Created: 2015-01-23 Last updated: 2017-04-20Bibliographically approved

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