600mg/day works for me...as my only PD med.
Clinical Outcome
Levodopa, in a dose–response pattern, significantly (P<0.001) reduced the worsening of symptoms of Parkinson's disease as reflected in the change between the total score on the UPDRS at baseline and that at week 42 (i.e., two weeks after washout of the study medication), as compared with the change in the placebo group (Figure 2Figure 2
Changes in Total Scores on the Unified Parkinson's Disease Rating Scale (UPDRS) from Baseline through Evaluation at Week 42.
and Table 2Table 2
Changes in the Scores on the UPDRS between Baseline and Week 42.
). The subjects in the placebo group had mild improvement at the week 3 visit, but after that their symptoms worsened steadily throughout the balance of the study period, including the two-week washout phase. A strong dose–response benefit was detected during the period in which the medication was administered beginning at week 9, when the full dose of 600 mg daily was reached in the group receiving the highest dose of levodopa, and it persisted through week 40. The scores on the UPDRS in the three levodopa groups worsened during the two-week washout period, but these groups did not deteriorate to the level observed in the placebo group, and the group receiving the highest dose of levodopa had the best result (Figure 2 and Table 2). The adverse events that were significantly more common among those receiving levodopa at 600 mg daily than in the placebo group were dyskinesias, nausea, infection, hypertonia, and headache (Table 3Table 3
Adverse Events.
).
Peak doses of levodopa - how extreme are your symptoms? 
Is high dose thiamine therapy effective for people not taking levodopa?
levodopa or not levodopa 
Levodopa vs Other Parkinson medicines against Fatigue
Hot off the press. Randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson’s disease.
