Evidence
This page contains a snapshot of featured content which highlights evidence addressing key clinical questions including areas of uncertainty. Please see the main topic reference list for details of all sources underpinning this topic.
BMJ Best Practice evidence tables
Evidence tables provide easily navigated layers of evidence in the context of specific clinical questions, using GRADE and a BMJ Best Practice Effectiveness rating. Follow the links at the bottom of the table, which go to the related evidence score in the main topic text, providing additional context for the clinical question. Find out more about our evidence tables.
This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.
Confidence in the evidence is very low or low where GRADE has been performed and the intervention may be more effective/beneficial than the comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.
Population: People with early Parkinson disease (PD)
Intervention: Levodopa
Comparison: Dopamine agonists (with or without levodopa) or MAO-B inhibitors
| Outcome | Effectiveness (BMJ rating)? | Confidence in evidence (GRADE)? |
|---|---|---|
Levodopa versus dopamine agonists with or without levodopa | ||
Change in Unified Parkinson’s Disease Rating Scale (UPDRS) motor score from baseline to endpoint: at 6 months | No statistically significant difference | Low |
Change in UPDRS motor score from baseline to endpoint: at 1 year and at 4 years | Favors intervention | Low |
Change in UPDRS motor score from baseline to endpoint: at 2 years and at 5 years | Favors intervention | Moderate |
Change in UPDRS motor score from baseline to endpoint: at 3 years | Favors intervention | Very Low |
Change in UPDRS motor score from baseline to endpoint: at 6 years and 10 years | No statistically significant difference | Very Low |
Dyskinesia: at 2 years and at 4 years | Favors comparison | Moderate |
Dyskinesia: at 3 years, 5 years, 6 years, and 7 years | Favors comparison | Low to Very Low |
Dyskinesia: at 10 years and 14 years | No statistically significant difference | Very Low |
Hallucinations: at 2 years and at 3 years | Favors intervention | Low to Very Low |
Hallucinations: at 4 years and at 5 years | No statistically significant difference | Low |
Adverse event (AE)-related discontinuation of treatment: at 1 year and at 3 years | No statistically significant difference | Low to Very Low |
AE-related discontinuation of treatment: at 2 years | Occurs more commonly with dopamine agonists compared with levodopa (favours intervention) | Low |
AE-related discontinuation of treatment: at 4 years and 7 years | Occurs more commonly with dopamine agonists compared with levodopa (favours intervention) | Very Low |
AE-related discontinuation of treatment: at 5 years | No statistically significant difference | Moderate |
Levodopa versus MAO-B inhibitors | ||
PDQ-39 mobility score | Favors intervention ᵃ | GRADE assessment not performed for this outcome |
Mean difference on UPDRS motor score between baseline and 2-month follow-up visit | See note ᵇ | GRADE assessment not performed for this outcome |
Dyskinesia: at 3 years | No statistically significant difference | Very Low |
Dyskinesia: at 7 years | Favors comparison | Very Low |
AE-related discontinuation of treatment: at 3 years and at 7 years | Occurs more commonly with MAO-B inhibitors compared with levodopa (favours intervention) | Very Low |
Recommendations as stated in the source guideline Clinicians should counsel patients with early PD on the benefits and risks of initial therapy with levodopa, dopamine agonists, and MAO-B inhibitors based on the individual patient’s disease characteristics to inform treatment decisions (level B). In patients with early PD who seek treatment for motor symptoms, clinicians should recommend levodopa as the initial preferential dopaminergic therapy (level B). Clinicians may prescribe dopamine agonists as the initial dopaminergic therapy to improve motor symptoms in select early PD in patients <60 years who are at higher risk for the development of dyskinesia (level C). Clinicians should not prescribe dopamine agonists to patients with early-stage PD at higher risk of medication-related adverse effects, including individuals >70 years, patients with a history of ICDs, and patients with pre-existing cognitive impairment, excessive daytime sleepiness, or hallucinations (level B). Clinicians should counsel patients with early PD on the greater motor benefits of initial therapy with levodopa compared with MAO-B inhibitors to inform treatment decisions (level B). Clinicians may prescribe MAO-B inhibitors as the initial dopaminergic therapy for mild motor symptoms in patients with early PD (level C).
Note The guideline panel noted that initial treatment with levodopa is of greater benefit for motor symptoms in people with early PD than dopamine agonists and that while levodopa is more likely to induce dyskinesia for up to 5 years of follow-up, the likelihood of severe or disabling dyskinesia during this time is low. The guideline panel also noted that more than 60% of people randomized to MAO-B inhibitors will require additional therapy within 2 to 3 years. ᵃ The study compared levodopa with dopamine agonists and MAO-B inhibitors as initial treatment for PD. The guideline did not report PDQ-39 mobility results for levodopa versus MAO-B inhibitors, but stated that “the average score during the first 7 years of follow-up was 1.8 points (95% CI 0.5–3.0; p=0.005) better with levodopa than with levodopa-sparing therapy”. ᵇ The guideline only reported results for each drug separately (levodopa: mean difference [MD] -3.4, standard error [SE] 0.39; MAO-B inhibitor [deprenyl]: MD -2.4, SE 0.38).
This evidence table is related to the following section/s:
Cochrane Clinical Answers
Cochrane Clinical Answers (CCAs) provide a readable, digestible, clinically focused entry point to rigorous research from Cochrane systematic reviews. They are designed to be actionable and to inform decision making at the point of care and have been added to relevant sections of the main Best Practice text.
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