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  • Melatonin analgesia is associated with improvement of the descending endogenous pain-modulating system in fibromyalgia: a phase II, randomized, double-dummy, controlled trial.

Melatonin analgesia is associated with improvement of the descending endogenous pain-modulating system in fibromyalgia: a phase II, randomized, double-dummy, controlled trial.

BMC pharmacology & toxicology (2014-07-24)
Simone Azevedo de Zanette, Rafael Vercelino, Gabriela Laste, Joanna Ripoll Rozisky, André Schwertner, Caroline Buzzatti Machado, Fernando Xavier, Izabel Cristina Custódio de Souza, Alicia Deitos, Iraci L S Torres, Wolnei Caumo
ABSTRACT

Central disinhibition is a mechanism involved in the physiopathology of fibromyalgia. Melatonin can improve sleep quality, pain and pain threshold. We hypothesized that treatment with melatonin alone or in combination with amitriptyline would be superior to amitriptyline alone in modifying the endogenous pain-modulating system (PMS) as quantified by conditional pain modulation (CPM), and this change in CPM could be associated with serum brain-derived neurotrophic factor (BDNF). We also tested whether melatonin improves the clinical symptoms of pain, pain threshold and sleep quality. Sixty-three females, aged 18 to 65, were randomized to receive bedtime amitriptyline (25 mg) (n = 21), melatonin (10 mg) (n = 21) or melatonin (10 mg) + amitriptyline (25 mg) (n = 21) for a period of six weeks. The descending PMS was assessed with the CPM-TASK. It was assessed the pain score on the Visual Analog Scale (VAS 0-100 mm), the score on Fibromyalgia Impact Questionnaire (FIQ), heat pain threshold (HPT), sleep quality and BDNF serum. Delta values (post- minus pre-treatment) were used to compare the treatment effect. The outcomes variables were collected before, one and six weeks after initiating treatment. Melatonin alone or in combination with amitriptyline reduced significantly pain on the VAS compared with amitriptyline alone (P < 0.01). The delta values on the VAS scores were-12.85 (19.93),-17.37 (18.69) and-20.93 (12.23) in the amitriptyline, melatonin and melatonin+amitriptyline groups, respectively. Melatonin alone and in combination increased the inhibitory PMS as assessed by the Numerical Pain Scale [NPS(0-10)] reduction during the CPM-TASK:-2.4 (2.04) melatonin + amitriptyline,-2.65 (1.68) melatonin, and-1.04 (2.06) amitriptyline, (P < 0.05). Melatonin + amitriptyline treated displayed better results than melatonin and amitriptyline alone in terms of FIQ and PPT improvement (P < 0.05, fort both). Melatonin increased the inhibitory endogenous pain-modulating system as assessed by the reduction on NPS(0-10) during the CPM-TASK. Melatonin alone or associated with amitriptyline was better than amitriptyline alone in improving pain on the VAS, whereas its association with amitriptyline produced only marginal additional clinical effects on FIQ and PPT. Current controlled trail is registered at clinical trials.gov upon under number NCT02041455. Registered January 16, 2014.

MATERIALS
Product Number
Brand
Product Description

Supelco
Melting point standard 235-237°C, analytical standard
Sigma-Aldrich
ChemiKine Brain Derived Neurotrophic Factor, Sandwich ELISA, This ChemiKine Brain Derived Neurotrophic Factor, Sandwich ELISA is used to measure & quantify BDNF levels in Neuroscience research.
Caffeine for system suitability, European Pharmacopoeia (EP) Reference Standard
USP
Caffeine melting point standard, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Caffeine, anhydrous, 99%, FCC, FG
Sigma-Aldrich
Melatonin, powder, ≥98% (TLC)
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Mettler-Toledo Calibration substance ME 18872, Caffeine, analytical standard, for the calibration of the thermosystem 900, traceable to primary standards (LGC)
Sigma-Aldrich
Caffeine, anhydrous, tested according to Ph. Eur.
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Caffeine, meets USP testing specifications, anhydrous
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Caffeine, powder, ReagentPlus®
Supelco
Caffeine Melting Point Standard, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Caffeine, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Caffeine, certified reference material, TraceCERT®
USP
Caffeine, United States Pharmacopeia (USP) Reference Standard
USP
Melatonin, United States Pharmacopeia (USP) Reference Standard
Caffeine, European Pharmacopoeia (EP) Reference Standard