Influence of ageing on the pharmacokinetics of levodopa in elderly patients with Parkinson’s disease

Central Nervous System Medications: Pharmacokinetic and Pharmacodynamic Considerations for Older Adults

Most drugs have not been evaluated in the older population. Recognizing physiological alterations associated with changes in drug disposition and with the ultimate effect, especially in central nervous system-acting drugs, is fundamental. While considering pharmacokinetics, it should be noted that the absorption of most drugs from the gastrointestinal tract does not change in advanced age. There are only few data about the effect of age on the transdermal absorption of medications such as fentanyl. Absorption from an intramuscular injection may be similar in older adults as in younger patients. The distribution of lipophilic drugs (such as diazepam) is increased owing to a relative increase in the percentage of body fat, causing drug accumulation and prolonged drug elimination following cessation. Phase I drug biotransformation is variably decreased in aging, impacting elimination, and hepatic drug clearance has been shown to decrease in older individuals by 10-40% for most drugs studied. Lower doses of phenothiazines, butyrophenones, atypical antipsychotics, antidepressants (citalopram, mirtazapine, and tricyclic antidepressants), and benzodiazepines (such as diazepam) achieve the same extent of exposure. For renally cleared drugs with no prior metabolism (such as gabapentin), the glomerular filtration rate appropriately estimates drug clearance. Important pharmacodynamic changes in older adults include an increased sedative effect of benzodiazepines at a given drug exposure, and a higher sensitivity to mu opiate receptor agonists and to opioid adverse effects. Artificial intelligence, physiologically based pharmacokinetic modeling and simulation, and concentration-effect modeling enabling a differentiation between the pharmacokinetic and the pharmacodynamic effects of aging might help to close some of the gaps in knowledge.

Concomitant use of magnesium oxide significantly decreases absorption of levodopa preparations in patients with Parkinson's disease

Introduction

Constipation is one of the most frequent non-motor symptoms of Parkinson's disease (PD), and magnesium oxide (MgO) is a frequently used laxative. This study aimed to investigate the effect of concomitant use of MgO on the pharmacokinetics of levodopa preparations in patients with PD.

Methods

We prospectively enrolled 35 patients with PD and compared the pharmacokinetics of levodopa and carbidopa and motor symptoms with and without MgO. The impact of alterations in pH and the addition of MgO on the solubility of levodopa formulations were also evaluated under in vitro conditions.

Results

Concomitant use of MgO significantly reduced the maximum plasma concentration of levodopa (Cmax) (from 7.66 ± 3.74 μmol/L to 5.82 ± 3.69 μmol/L; p = 0.006) and area under the plasma concentration-time curve 3 h after drug administration (AUC3h, from 9.64 ± 3.23 μmol·h/L to 7.39 ± 3.15 μmol·h/L; p < 0.001), and further decreased carbidopa Cmax (from 64.02 ± 27.02 ng/mL to 38.83 ± 21.94 μmol/L; p < 0.001) and AUC3h (from 130.58 ± 65.64 ng/mL to 76.48 ± 52.24 ng·h/mL; p < 0.001). The Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale part III score also deteriorated significantly (from 30.71 ± 11.34 to 32.06 ± 11.22; p = 0.007). MgO significantly affected the pharmacokinetics of levodopa and carbidopa. This also applied when the findings were analyzed by sex and age. In vitro dissolution experiments revealed a decrease in the relative concentrations of levodopa, carbidopa, and benserazide as the pH increased and in the presence of MgO suspension, with the most prominent impact on benserazide.

Conclusions

Concomitant use of MgO and levodopa should be discouraged to improve levodopa absorption.

Associations between non-motor symptoms and patient characteristics in Parkinson's disease: a multicenter cross-sectional study

Objective

Parkinson's disease (PD) is characterized by various non-motor symptoms (NMS), such as constipation, olfactory disturbance, sleep disturbance, mental disorders, and motor symptoms. This study aimed to investigate factors associated with NMS in patients with PD.

Methods

Symptoms of PD were evaluated using the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS), Parts I-IV. NMS was assessed using the MDS-UPDRS Part I (self-assessment of NMS) and rapid eye movement sleep behavior disorder (RBD) questionnaires. Patients were categorized by age into <70 years and ≥ 70 years (older adults) groups, according to disease duration into early-stage and advanced-stage groups with a cut-off value of 5 years for motor symptoms, and by sex into male and female groups.

Results

A total of 431 patients with PD (202 males and 229 females) with a mean age of 67.7 years, a mean disease duration of 6.4 years, and a mean Part I total score of 9.9 participated in this study. The Part I total score was significantly positively correlated (p < 0.01) with disease duration and Part II, III, and IV scores. For Part I sub-item scores, the older group had significantly higher scores for cognitive impairment, hallucinations, sleep problems, urinary problems, and constipation than the <70 years group, whereas the advanced-stage group had significantly higher scores for hallucinations, sleep problems, daytime sleepiness, pain, urinary problems, and constipation (p < 0.05) than the early-stage group. Anxiety was higher in female patients than in male patients, whereas daytime sleepiness, urinary problems, and RBD were higher in male patients than in female patients (p < 0.05). Factors affecting Part I included disease duration, Part II total scores, Part IV total scores, and RBD.

Conclusion

According to the self-questionnaire assessment, NMS was highly severe in older adult patients, those with longer illness duration, subjective and objective motor function impairments, and RBD. Sex-based differences were also observed.

To restrict or not to restrict? Practical considerations for optimizing dietary protein interactions on levodopa absorption in Parkinson's disease

Administration of levodopa for Parkinson's disease (PD) has remained the most effective therapy for symptom management despite being in use for over 50 years. Advancing disease and age, changing tolerability and gastrointestinal (GI) dysfunction may result in change in dietary habits and body weight, as well as unpredictable motor fluctuations and dyskinesias. Dietary proteins which convert into amino acids after digestion are implicated as major factors that inhibit levodopa absorption. For people living with PD (PwP) who experience motor fluctuations, low protein diets (LPD) and protein redistribution diets (PRD) may be effective and are often recommended as a non-pharmacologic approach for improving levodopa bioavailability. However, there is a lack of consensus on a standard definition of these diets and appropriate treatment algorithms for usage. This may be due to the paucity of high-level evidence of LPD and PRD in PwP and whether all or specific subgroups of patients would benefit from these strategies. Managing diet and protein intake with proper education and monitoring may reduce complications associated with these diets such as dyskinesias and unintentional weight loss. Additionally, alterations to medications and GI function may alter levodopa pharmacokinetics. In this narrative review we focus on 1) mechanisms of dietary protein and levodopa absorption in the intestine and blood brain barrier, 2) dietetic approaches to manage protein and levodopa interactions and 3) practical issues for treating PwP as well as future directions to be considered.

Development and Validation of a New LC-MS/MS Bioanalytical Method for the Simultaneous Determination of Levodopa, Levodopa Methyl Ester, and Carbidopa in Human Plasma Samples

Levodopa (L-DOPA) treatment, combined with the administration of dopa-decarboxylase inhibitors (DDCIs), is still the most effective symptomatic treatment of Parkinson's disease (PD). Although its efficacy in the early stage of the disease has been confirmed, its complex pharmacokinetics (PK) increases the variability of the intra-individual motor response, thus amplifying the risk of motor/non-motor fluctuations and dyskinesia. Moreover, it has been demonstrated that L-DOPA PK is strongly influenced by several clinical, therapeutic, and lifestyle variables (e.g., dietary proteins). L-DOPA therapeutic monitoring is therefore crucial to provide personalized therapy, hence improving drug efficacy and safety. To this aim, we have developed and validated an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to quantify L-DOPA, levodopa methyl ester (LDME), and the DDCI carbidopa in human plasma. The compounds were extracted by protein precipitation and samples were analyzed with a triple quadrupole mass spectrometer. The method showed good selectivity and specificity for all compounds. No carryover was observed, and dilution integrity was demonstrated. No matrix effect could be retrieved; intra-day and inter-day precision and accuracy values met the acceptance criteria. Reinjection reproducibility was assessed. The described method was successfully applied to a 45-year-old male patient to compare the pharmacokinetic behavior of an L-DOPA-based medical treatment involving commercially available Mucuna pruriens extracts and an LDME/carbidopa (100/25 mg) formulation.

Sex Is the Main Determinant of Levodopa Clinical Pharmacokinetics: Evidence from a Large Series of Levodopa Therapeutic Monitoring

BACKGROUND

Different studies, mostly with limited cohorts, have suggested the effects of patients' characteristics on levodopa (LD) pharmacokinetics.

OBJECTIVE

We primarily aimed at investigating in a large population the relationship between patients' features and LD kinetic variables, to assess the main demographic and clinical predictors of LD clinical pharmacokinetics.

METHODS

The study was retrospective, based on data collected from subjects with parkinsonism on chronic LD undergoing LD therapeutic monitoring (TM). LD TM includes serial quantitative motor tests and blood samples to measure plasma drug concentrations after each subject's chronically taken first-morning LD dose intake.

RESULTS

Five hundred patients, 308 males (61.6%), mean (SD) age of 65 (10.1) years were included. Parkinsonian symptoms and LD therapy lasted 5.5 (4.5) and 3.4 (3.9) years, respectively. MDS-UPDRS part III "off" score was 28.8 (15.2). LD dose was 348.2 (187.1) mg/day. From multiple linear regression analysis, test dose, sex, type of LD decarboxylase inhibitor, weight and MDS-UPDRS part III score were linear predictors of both LD peak plasma concentration (Cmax) (R2 = 0.52) and area under the 3-h plasma concentration-time curve (AUC) (R2 = 0.71), while age was a further predictor only for AUC. Besides test dose, sex was the strongest independent contributing variable to LD AUC, which resulted 27% higher in females compared to males.

CONCLUSION

This is the largest collection of data on the relationship between demographic and clinical-therapeutic variables and LD kinetics in patients with parkinsonian symptoms. As a main clinically practical finding, women might require a 25% reduced weight-normalized LD dose compared with men to achieve the same LD bioavailability.

Drug safety profiles in geriatric patients with Parkinson's disease using the FORTA (Fit fOR The Aged) classification: results from a mono-centric retrospective analysis

To reduce potentially inappropriate medications, the FORTA (Fit fOR The Aged) concept classifies drugs in terms of their suitability for geriatric patients with different labels, namely A (indispensable), B (beneficial), C (questionable), and D (avoid). The aims of our study were to assess the medication appropriateness in PD inpatients applying the FORTA list and drug-drug interaction software, further to assess the adequacy of FORTA list for patients with PD. We retrospectively collected demographic data, comorbidities, laboratory values, and the medication from the discharge letters of 123 geriatric inpatients with PD at the university hospital of Hannover Medical School. Patients suffered on average from 8.2 comorbidities. The majority of the medication was labeled A (60.6% of PD-specific and 40.9% of other medication) or B (22.3% of PD-specific and 26.9% of other medication). Administered drugs labeled with D were amantadine, clozapine, oxazepam, lorazepam, amitriptyline, and clonidine. Overall, 545 interactions were identified, thereof 11.9% severe interactions, and 1.7% contraindicated combinations. 81.3% of patients had at least one moderate or severe interaction. The FORTA list gives rational recommendations for PD-specific and other medication, especially for general practitioners. Considering the demographic characteristics and the common multimorbidity of geriatric PD patients, this study underlines the importance of awareness, education, and preventive interventions to increase drug safety.

Female, aging, difference formulations of DCI, or lower body weight increases AUC4hr of levodopa in patients with Parkinson's disease

INTRODUCTION

There is considerable intra- and inter-individual variability in the pharmacokinetics (PK) of levodopa after oral administration. Inter-individual variability in levodopa PK has also been demonstrated in fasting single-dose studies. We examined the factors that affect levodopa PK in patients with Parkinson's disease (PD) and quantified the intensity of their respective effects.

METHODS

We studied 220 patients who underwent PK assessment after administration of 1 tablet of levodopa/DOPA decarboxylase inhibitor (DCI) combination, which contained 10 mg carbidopa/100 mg levodopa or 25 mg benserazide/100 mg levodopa. PK was evaluated using non-compartmental analysis.

RESULTS

In total, 220 PD patients (including 112 men) were studied. The mean age (±standard deviation) and mean disease duration was 68.1 ± 8.9 and 7.7 ± 5.8 years, respectively. The Cmax of levodopa was 9.0 ± 4.0 ng/mL, Tmax was 41.4 ± 40.2 min, and area under the blood concentration-time curve up to 4 h (AUC_4hr) was 12.3 ± 3.7 ng/mL*4hr. Factors affecting AUC_4hr were analyzed using multiple linear regression models. Age (1.1 ± 0.23 per +10 years, p = 3.1E-8), sex (2.2 ± 0.5 for female, p = 1.9E-5), DCI (1.4 ± 0.4 for benserazide, p = 0.0028), and body weight (-0.77 ± 0.22 per +10 kg, p = 5.4E-4) were significantly related to AUC_4hr, while disease duration, dyskinesia status, and eGFR were not related to AUC_4hr and Cmax.

CONCLUSION

Female, aging, difference formulations of DCI, or lower body weight independently contributes to increased AUC_4hr of levodopa in Japanese patients with PD in this study.

Population Pharmacokinetic Modeling and Pharmacodynamic Target Attainment Simulation of Piperacillin/Tazobactam for Dosing Optimization in Late Elderly Patients with Pneumonia

The aim of this study was to develop a population pharmacokinetic model for piperacillin (PIPC)/tazobactam (TAZ) in late elderly patients with pneumonia and to optimize the administration planning by applying pharmacokinetic/pharmacodynamic (PK/PD) criteria. PIPC/TAZ (total dose of 2.25 or 4.5 g) was infused intravenously three times daily to Japanese patients over 75 years old. The plasma concentrations of PIPC and TAZ were determined using high-performance liquid chromatography and modeled using the NONMEM program. PK/PD analysis with a random simulation was conducted using the final population PK model to estimate the probability of target attainment (PTA) profiles for various PIPC/TAZ-regimen–minimum-inhibitory-concentration (MIC) combinations. The PTAs for PIPC and TAZ were determined as the fraction that achieved at least 50% free time > MIC and area under the free-plasma-concentration–time curve over 24 h ≥ 96 μg h/mL, respectively. A total of 18 cases, the mean age of which was 86.5 ± 6.0 (75–101) years, were investigated. The plasma-concentration–time profiles of PIPC and TAZ were characterized by a two-compartment model. The parameter estimates for the final model, namely the total clearance, central distribution volume, peripheral distribution volume, and intercompartmental clearance, were 4.58 + 0.061 × (CL_cr − 37.4) L/h, 5.39 L, 6.96 L, and 20.7 L/h for PIPC, and 5.00 + 0.059 × (CL_cr − 37.4) L/h, 6.29 L, 7.73 L, and 24.0 L/h for TAZ, respectively, where CL_cr is the creatinine clearance. PK/PD analysis using the final model showed that in drug-resistant strains with a MIC > 8 μg/mL, 4.5 g of PIPC/TAZ every 6 h was required, even for the patients with a CL_cr of 50–60 mL/min. The population PK model developed in this study, together with MIC value, can be useful for optimizing the PIPC/TAZ dosage in the over-75-year-old patients, when they are administered PIPC/TAZ. Therefore, the findings of present study may contribute to improving the efficacy and safety of the administration of PIPC/TAZ therapy in late elderly patients with pneumonia.

Contributions of Gut Bacteria and Diet to Drug Pharmacokinetics in the Treatment of Parkinson's Disease

Parkinson's disease is the second-most common neurodegenerative disorder worldwide. Besides deciphering the mechanisms that underlie the etiology of the disease, it is important to elucidate the factors that influence the efficacy of the treatment therapeutics. Levodopa, which remains the golden treatment of the disease, is absorbed in the proximal small intestine. A reduction in levodopa absorption, leads to reduction in striatal dopamine levels and, in turn, an "off"-episode. In fact, motor fluctuations represent a major problem during the progression of the disease and alteration between "on" (mobility often with dyskinesia) and "off" (immobility, akinesia) episodes contribute to a decreased quality of life. Dietary amino acids can interfere with the absorption of levodopa from the gut lumen and its transport through the blood brain barrier. In addition, higher abundance of specific gut bacteria that restrict levodopa absorption plays a significant role in motor fluctuations in a subset of Parkinson's disease patients. Here, we review the impact of factors potentially interfering with levodopa absorption, focusing on levodopa transport, diet, and gut bacterial interference with the bioavailability of levodopa.

Benefits of subthalamic stimulation for elderly parkinsonian patients aged 70 years or older

OBJECTIVES

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an accepted treatment for advanced Parkinson disease (PD). However, there is general reluctance in considering this therapy for PD patients over age 70 years with limited supporting evidence. Present study investigates age impacts in STN-DBS outcomes, focusing particularly on the elderly patients.

PATIENTS AND METHODS

Seventy-two consecutive patients were divided into younger and elderly (n=16, cutoff age=70years) groups. Both groups were comparable in preoperative clinical severity, except the elderly exhibited a levodopa (LD) response (P<0.05) inferior to that of the younger. Improvements in drug-off/DBS-on Unified PD Rating Scale (UPDRS) scores and reduction in daily LD-equivalent dose (LED) after 6 months were evaluated relative to the presurgical drug-off baseline. Preoperative factors predictive of favorable surgical outcomes were analyzed using a multivariate linear regression model.

RESULTS

After DBS therapy, elderly patients exhibited clinical improvements particularly in the tremor (56%) and LD-induced dyskinesia (78%). Improvement of axial dysfunction (24%) and reduction of daily LED (24%) showed no intergroup difference. Adverse events, particularly dysarthria, occurred frequently in elderly group. The overall improvements in UPDRS scores were suboptimal in elderly group, correlating with their preoperative inferior LD responses. Elderly patients who presented predominantly with akinesia before surgery achieved superior surgical outcomes (adjusted R(2)=0.657, P<0.001).

CONCLUSION

STN-DBS therapy is beneficial to some elderly PD patients aged 70 years or older. Tremor, axial dysfunctions and drug-induced dyskinesia are the main indications for the elderly; however, their clinical benefits are inferior to those of younger patients.

[Geriatric particularities of Parkinson's disease: Clinical and therapeutic aspects]

Parkinson's disease (PD) is a frequent and complex progressive neurological disorder that increases in incidence with age. Although historically PD has been characterized by the presence of progressive dopaminergic neuronal loss of the substantia nigra, the disease process also involves neurotransmitters other that dopamine and regions of the nervous system outside the basal ganglia. Its clinical presentation in elderly subjects differs from that in younger subjects, with more rapid progression, less frequent tremor, more pronounced axial signs, more frequent non-motor signs linked to concomitant degeneration of non-dopaminergic systems, and more frequent associated lesions. Despite the high prevalence of PD in elderly subjects, few therapeutic trials have been conducted in geriatric patients. Nevertheless, to improve functional disability while ensuring drug tolerance, the principles of optimized and multidisciplinary clinical management have to be known. The aim of this review is to provide an update on clinical and therapeutic features of PD specifically observed in elderly subjects.

Pharmacokinetics of Levodopa before and after Gastrointestinal Resection in Parkinson's Disease

Introduction

Levodopa (LD) is important in the clinical treatment of Parkinson's disease (PD), and the changes of its pharmacokinetics may affect the clinical outcome. LD is mainly absorbed in the upper intestine; thus, the pharmacokinetics of LD may change after gastrointestinal operation. Here, we present the case of a patient who underwent resection of the intestine and compared his LD pharmacokinetics before and after resection.

Case Presentation

A 72-year-old Japanese male PD patient developed jaundice and was diagnosed with cholangiocarcinoma. Pancreaticoduodenectomy was performed and part of the stomach, total duodenum, and part of the jejunum were resected. The patient had been treated with LD, and his pharmacokinetics was checked twice at the age of 68 years. Because LD is absorbed in the duodenum and jejunum, we checked his pharmacokinetics again after the operation. The results before the operation were almost similar; however, in comparison, the area under the curve and peak drug concentration was reduced, and the time-to-peak drug concentration and elimination halftime were elongated after the operation.

Conclusion

Physicians must pay attention to the change of LD pharmacokinetics after gastrointestinal operation.

Simultaneous determination of levodopa, carbidopa, entacapone, tolcapone, 3-O-methyldopa and dopamine in human plasma by an HPLC-MS/MS method

BACKGROUND

In this study, we developed and validated a HPLC-MS/MS method capable of simultaneously determining levodopa, carbidopa, entacapone, tolcapone, 3-O-methyldopa and dopamine in human plasma. RESULTS & METHODOLOGY: Chromatographic separation was achieved using a C8 column with a mobile phase consisting of a gradient of water and acetonitrile:methanol (90:10 v/v), both containing 0.1% formic acid. The developed method was selective, sensitive (LD<7.0 ng ml(-1)), linear (r>0.99), precise (RSD<11.3%), accurate (RE<11.8%) and free of residual and matrix effects. The developed method was successfully applied in plasma patients with Parkinson's disease using Stalevo®.

CONCLUSION

The new method can be used for the clinical monitoring of these substances and applied to adjustments in drug dosages.

Differential effects of age on human striatal adenosine A₁ and A(2A) receptors

The aim of this study was to investigate the effect of age on the distribution of adenosine A₁ receptors (A₁Rs) and adenosine A(2A) receptors (A(2A)Rs) in the striatum of healthy subjects using PET imaging with 8-dicyclopropylmethyl-1-[¹¹C]methyl-3-propylxanthine ([¹¹C]MPDX) and [7-methyl-¹¹C]-(E)-8-(3,4,5-trimethoxystyryl)-1,3,7-trimethylxanthine ([¹¹C]TMSX), respectively. We recruited 8 young (22.0 ± 1.7 years) and 10 elderly (65.4 ± 7.6 years) volunteers to undergo [¹¹C]MPDX PET scanning, and 11 young (22.7 ± 2.7 years) and six elderly (60.7 ± 8.5 years) volunteers to undergo [¹¹C]TMSX PET scanning. A dynamic series of decay-corrected PET scans was performed for 60 min following injection of [¹¹C]MPDX or [¹¹C]TMSX. We calculated the binding potential (BP(ND) ) of [¹¹C]MPDX and distribution volume ratio (DVR) of [¹¹C]TMSX in the striatum. The BP(ND) of [¹¹C]MPDX was significantly lower in elderly than in young subjects, both in the putamen and head of the caudate nucleus. The BP(ND) was negatively correlated with age in both the putamen and the head of the caudate nucleus. However, no difference was found between the DVR of [¹¹C]TMSX in the striata of young and elderly subjects, nor was there a correlation between age and the DVR of [¹¹C]TMSX. The effect of age on the distribution of A₁Rs in the human striatum described herein is similar to previous reports of age-related decreases in dopamine D₁ and D₂ receptors. Unlike A₁Rs, however, this study suggests that the distribution of A(2A) Rs does not change with age.

The aging striatal dopamine function

Movement disorders are prevalent in the elderly and may have both central and peripheral origins. Age-related parkinsonism often results in movement disorders identical to some of the cardinal symptoms of typical Parkinson's disease (TPD). Nevertheless, there may be limited similarity in the underlying dysfunction of the sensory-motor circuitry since these two conditions exhibit different changes in the nigro-striatal pathway. In this short review, we highlight some of the key distinctions between aging and TPD regarding striatal dopaminergic activity and discuss them in the context of therapeutic strategies to alleviate motor decline in the elderly.