High levodopa plasma concentration after oral administration predicts levodopa-induced dyskinesia in Parkinson's disease

Classification of l-DOPA pharmacokinetics shapes and creating a predictive model

BACKGROUND

It is known that the pharmacokinetics (PK) of levodopa (LD) varies considerably. Difference in PK shapes is expected to affect drug efficacy and development of dyskinesia. In this study, the authors aimed to explore correlations between PK series data of LD and clinical characteristics and dyskinesia in patients with Parkinson's disease (PD).

METHODS

We studied 270 PD patients who underwent PK assessment after administration of LD/carbidopa (100/10 mg) in non-compartmental analysis. The patients were grouped according to similarities in time series data of blood LD concentration. Each group was analyzed with respect to clinical characteristics and PK parameters. We created a model to predict PK patterns based on these findings.

RESULTS

PD patients were divided into three groups by clustering analysis: blood LD concentration of the patients in Groups 1 (n = 129), 3 (n = 44) and 2 (n = 97) rose rapidly, relatively slowly and at an intermediate rate, respectively. There were no statistically significant differences in patient characteristics except age among the three groups (one-way ANOVA). Multivariate analysis showed that frequency of dyskinesias in Group 1 was significantly higher than that in Group 2. We successfully created a PK pattern prediction model based on body weight and blood LD concentration at 15 and 30 min after administration.

CONCLUSIONS

The PK series data of LD was classified into three patterns. The rapid absorption was associated with dyskinesias. Patients' PK patterns were successfully predicted based on their body weight and two-point LD concentration.

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.

The effect of visual cues on muscular activation in the lower limbs of Parkinson's disease patients with freezing of gait: a preliminary study

Freezing of gait (FOG) is a disabling symptom of Parkinson's disease (PD) patients, especially in advanced stages. Visual cues, such as the laser, have been confirmed to improve kinematic performance and alleviate FOG incidences. However, the muscular effect is unknown. In this study, we aim to investigate the effect of visual cues on muscular activity in the lower limbs of PD patients with FOG. Surface EMG signals of the tibialis anterior (TA), lateral gastrocnemius (GL), rectus femoris (RF), and biceps femoris (BF) muscles were collected from eight patients (FOGer) and eight healthy elderly (HC) in both normal walking and walking with laser cues. Results showed that visual cues improved FOGer's muscular activation pattern towards normal. The RMS of TA was significantly increased in the loading response phase (p=0.02) and decreased in the pre-swing phase for FOGer (p=0.005) under visual cue. The RMS of GL in FOGer was considerably reduced in the loading response phase (p<0.001) and increased in the pre-swing phase (p=0.008) of their gait cycle. A significant strong correlation was also observed between the decrement in GL RMS during the loading response phase and the increment in GL RMS during the pre-swing phase (R=-0.952, p<0.001) incurred by visual cue in FOGer. These results indicate that the visual cues can help FOGer to modulate their muscular activation of ankle muscles, especially to normalize GL's activation distribution during stance. For clinical purposes, future rehabilitative strategies aimed at the modulation of ankle muscles are suggested.