Objective: To retrospectively review the clinical utility of single dose levodopa challenges in the management of Parkinson in a tertiary movement disorder clinic.

Background: Acute levodopa challenges, also termed dose cycles, have been used by movement disorder specialists for many years. They are usually performed for one of two reasons: as a diagnostic tool to differentiate idiopathic Parkinson from atypical parkinsonism; and to assist the evaluation of fluctuating dose-response patterns in order to guide management [1]. However, a previous systematic review has criticised these challenges because of its inability to provide concrete results for the amount of expert time invested, significant burden to patients and failure to provide additional diagnostic value compared to chronic levodopa therapy [2]. However, a Movement Disorder Society consensus statement continues to recommend its use [1].

Method: We retrospectively reviewed the results of 115 dose cycles performed by two expert Parkinson Nurses in our Movement Disorders Unit between 2016 and 2019. We included consecutive cases that were referred for clinical purposes, but excluded cases which were performed for pre-treatment records or research. We reviewed the referral reason and determined whether the dose cycle result was able to definitively answer the main referral question. We also reviewed the number of cases where unexpected coincidental findings were discovered that helped diagnosis or management.

Results: The dose cycle was able to provide a definitive answer to the referral reason in 77% of cases. Dose cycles were particularly sensitive for investigating dyskinesias (100%) and freezing of gait (93%). In 42% of cases, we discovered unexpected coincidental findings that assisted with management, with orthostatic hypotension being the most common finding.

Conclusion: We conclude that a dose cycle is a useful investigative tool in the management of Parkinson, with a high chance of providing an answer to questions related to symptomatic response to levodopa. Acute levodopa challenges should not be regarded purely as a diagnostic tool for differentiating Parkinson and atypical Parkinsonism, but instead should be recognised for its capacity to guide management including both the assessment of levodopa-induced symptoms and discovery of unexpected symptoms. A prospective study is required to prove its efficacy.

References: [1] Albanese, A, Bonuccelli, U, Brefel, C, Chaudhuri, R, Colosimo, C, Eichhorn, T, Melamed, E, Pollak, P, Van Laar, T & Zappia, M 2001, ‘Consensus Statement on the Role of Acute Dopaminergic Challenge in Parkinson’s Disease’ Movement Disorders, Vol. 16, No. 2, pp. 197-201 [2] Clarke, C & Davies, P 2000, ‘Systematic review of acute levodopa and apomorphine challenge tests in the diagnosis of idiopathic Parkinson’s disease’ Journal of Neurology, Neurosurgery, and Psychiatry, Vol. 69, No. 5, pp. 590-594

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-utility-of-single-dose-levodopa-challenges-in-the-management-of-parkinsons-disease/