Research Article
Efficacy and safety of herbal medicines for idiopathic Parkinson's disease: A systematic review

Volume 21, Issue 10, Pages 1709-1715

Published Online: 7 Jul 2006

Copyright © 2006 Movement Disorders Society

http://www3.interscience.wiley.com/c...2921/HTMLSTART

Article Text

Parkinson's disease (PD) is the second most common manifestation under the umbrella of neurodegenerative disorder family in the United States, with a prevalence of 100 to 200 per 100,000 persons older than 40 years of age.[1] Various pharmacological and surgical approaches have been developed to manage this common disease, but some of these approaches carry significant adverse effects. For example, the most commonly prescribed drug, levodopa (LD), is associated with dose-limiting motor and psychiatric side effects in 100% of young-onset patients[2] and 50% of other patients after 6 years of therapy.[3] Due to these limitations of conventional medicine, patients resort to complementary and alternative medicine (CAM). In the United States, 40% of all PD patients reported the use of at least one form of CAM for their illness,[4] whereas in the United Kingdom, 38.7% of patients used it solely for the treatment of their Parkinsonism.[5]

One of the most popular CAM modalities used is herbal medicine (HM). Some basic research on their mechanisms of actions have been performed. For example, Mucuna pruriens (MP) originated from Indian Ayurvedic medicine[6] has been found to possess significantly higher antiparkinsonian activity compared with synthetic L-dopa in the 6-hydroxdopamine (6-OHDA)- lesioned rat model of PD.[7] This superiority is proposed to be exerted by the combined actions of intrinsic L-dopa and neuroprotective substances (nicotine adenine dinucleotide [NADH] and coenzyme Q-10) in the herb.[8] In traditional Chinese medicine (TCM), various combinations of herbs are used to treat PD.[9] Recent research suggests that certain Chinese herbal compounds show neuroprotective effects in 6-OHDA-treated PC 12 model, which indicates that TCM herbs may offer a potential therapeutic strategy for various neurodegenerative diseases.[10] In addition, the use of cannabis among long-term LD users is also mentioned in the literature for its antidyskinetic function.[11] It is postulated that cannabis achieved such action by augmenting -aminobutyric acid (GABA)ergic transmission by means of the inhibition of GABA reuptake in the lateral part of the globus pallidus.[12]

Anecdotal evidence shows that some of these herbs offer beneficial effects,[13-15] but their use has also raised much concern as to their safety.[16-18] We conducted this systematic review to shed light on their efficacy, safety, and clinical applicability.

Herbal Medicine as a Monotherapy

Katzenschlager reported that MP seed powder and LD coadministered with carbidopa caused a similar degree of dyskinesia, as measured by Abnormal Involuntary Movement Scale and Goetz scales, but MP exhibited a more rapid onset of action and longer on time when compared to LD plus carbidopa. However, the best UPDRS rating during the on state did not differ significantly among the two therapies.

Carroll reached a conclusion that cannabis has no therapeutic effect on L-dopa-induced dyskinesia, as measured by Question 32-24 of the UPDRS and by other relevant outcome measures. In addition, no statistically significant improvements on overall UPDRS and PDQ-39 were observed.

Compared to Madopar, Tang noted that zhiyinxifeng granules showed a similar efficacy; while Guo reported a relatively higher efficacy of kanli decoction, both measured in terms of the improvement in the overall Webster scale scoring. However, flaws in design and statistical analysis in these two studies limited the reliability of their conclusions.

Adverse Events and Withdrawals

As a monotherapy, the adverse events of herbal medicines were reported in three studies (Katzenschlager, Carroll, and Tang). Katzenschlager reported a case of dropout due to short-lasting vomiting after the ingestion of 30 g of MP. Other side effects included transient nausea and mild dizziness. No observations on clinically relevant abnormalities in hematology and biochemistry were made.

....Only Katzenschlager used a firm diagnostic criteria (Queen Square Brain Bank Criteria[48]) for enrollment. ....