Strong placebo responses in restless legs syndrome treatment trials

In the SP790 study, the slope for the placebo response in patients pre-treated with dopaminergic medications was -0.43, compared to 0.28 in drug-naïve patients.

• Patients pre-treated with dopaminergic medications showed reduced responses to placebo compared to those who were drug-naïve.
• The negative slope in the pre-treated group indicates that their response to placebo decreased as their baseline symptoms increased.
• In the SP792 study, the magnitude of the placebo response was significantly lower in the pre-treated group (6.31) compared to the drug-naïve group (10.49).
• Pre-treatment did not significantly alter the responses to rotigotine in either study.
• These findings suggest that dopaminergic pre-treatment may diminish the placebo effect in clinical trials for restless legs syndrome.

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