Objective: To evaluate the efficacy of the 5-HTP on RBD status in patients with Parkinson’s disease (PD).

Background: REM sleep behavior disorder (RBD) is reported in up to 50% of patients with PD. Serotonergic neurotransmission dysfunctions may have a pathological role in sleep disorders associated with PD[1]. The 5-Hydroxytryptophan (5-HTP) is the intermediate metabolite of L-tryptophan in the production of serotonin. Studies in other populations indicate that 5-HTP might be useful in the treatment of sleep disturbances[2]. To date, there have not been clinical trials on the use of 5-HTP for treating RBD in PD.

Method: A single-center, randomized, double-blind placebo-controlled cross-over trial was performed; 36 PD patients were subsequently enrolled into the study, 32 subjects completed the 16-week protocol. Patients received placebo and 50 mg of 5-HTP daily in a cross-over design over a period of 4 weeks. There were 4-weeks washouts between treatments. RBD diagnosis was made according to the International Classification of Sleep Disorders third edition (ICSD-3) including a full-night video-polysomnography (v-PSG). For the assessment of efficacy on the RBD status, home-based polysomnography was performed at weeks 4 and 12. In order to assess the RBD clinical status in-depth sleep, focus interview assessed patient’s subjective report of frequency and severity of dream-enactment motor behaviors, somniloquy and dreams recalled. For the assessment of efficacy on the overall functional status the UPDRS score (parts I, II, III,IV) was obtained at every timepoint. Primary efficacy outcomes were the effect of 5-HTP on the REM sleep without atonia (RSWA) measures and other polysomnographic sleep measures.

Results: Treatment with 5-HTP produced an increase in total percentage of REM sleep stage, as well as a marginal, non-significant reduction in arousal index and wake after sleep onset (WASO). Moreover, self-reported RBD frequency and severity were not increased at follow up. There were no other significant effects of 5-HTP on nighttime sleep parameters evaluated in our study.

Conclusion: This study provides preliminary evidence that 50 mg daily of 5-HTP is safe and effective in improving sleep stability in PD, contributing to ameliorate the global sleep quality. Larger studies with higher doses and longer treatment duration are needed to confirm these findings.

References: [1] Wilson H, Giordano B, Turkheimer FE, Chaudhuri KR, Politis M. Serotonergic dysregulation is linked to sleep problems in Parkinson’s disease. Neuroimage Clin. 2018 Mar 2;18:630-637. [2] Turner EH, Loftis JM, Blackwell AD. Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan. Pharmacol Ther. 2006 Mar;109(3):325-38.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/efficacy-and-safety-of-the-5-hydroxytryptophan-on-rem-sleep-behavior-disorder-in-parkinsons-disease/