A Clinical Trial with Brazilian Arnica (Solidago chilensis Meyen) Glycolic Extract in the Treatment of Tendonitis of Flexor and Extensor Tendons of Wrist and Hand Ary Gomes da Silva, 1 * Elbe Rodrigues Machado, 2 Leonardo Mendes de Almeida, 2 Ricardo Marcelo Menezes Nunes, 2 Patrícia Caldeira Pena Giesbrecht, 3 Regina Mamed Costa, 4 Helber B. Costa, 5 Wanderson Romão 5,6 and Ricardo Machado Kuster 7 1 Laboratory of Functional Ecology, University of Vila Velha—UVV, Brazil 2 Department of Pharmacy, University of Vila Velha—UVV-ES, Brazil 3 Department of Physiotherapy, University of Vila Velha—UVV-ES, Brazil 4 Doctoral Program in Biotechnology, Northeastern Web of Biotechnology—RENORBIO, Federal University of Espírito Santo—UFES, Brazil 5 Petroleomic and Forensic Laboratory, Department of Chemistry, Federal University of Espírito Santo—UFES, Brazil 6 Federal Institute of Espírito Santo, Vila Velha, IFES-ES, Brazil 7 Laboratory of Phytochemistry of Medicinal Plants, Institute of Natural Products Research, Federal University of Rio de Janeiro— IPPN-UFRJ, Brazil One of the Brazilian arnicas, Solidago chilensis Meyen, is a species of the Asteraceae family. This plant is known by this common name because it shares remarkably similar organoleptic properties with the genus Arnica L., also within the family Asteraceae. We examined the effectiveness of the S. chilensis fluid extract used externally for treating tendinitis of flexor and extensor tendons of wrist and hand in placebo-controlled double-blind clinical pharmacological studies. This study was approved by the Ethical Committee for Scientific Research in Human Beings at University Vila Velha-UVV. Two daily skin applications on the arm skin of a gel cream containing a 5% glycolic plant extract were administered to eight volunteers for 21 days. Among the volunteers, one of their arms was used as the placebo group, and the other one was used as a test group. Statistical data analyses demonstrated a significant reduction in the perception of pain in the arms in the test group, when it was compared to those receiving only the placebo. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: antiinflammatory; antinociception activity; repetitive strain injury; pain; phytotherapy; Asteraceae. INTRODUCTION Repetitive Strain Injuries (RSI), also found under the nomenclature ‘Work-Related Muscle-skeletal Disease (MSDs)’ can be defined as damage and/or a tissue suffer- ing because of physical trauma. These affect preferably upper limbs, including the neck, having necessarily occu- pational origin, deriving from abuse and misuse of muscle groups. In fact, RSI represent a heterogeneous group of disorders of the musculoskeletal system that are related to the job environment (Higgs and Mackinnon, 1995). Sociologists and psychologists believe that RSIs are somatic manifestations of distress of the current times, in people with susceptible emotional profile. This collec- tive hysteria can be unleashed by the organization of modern work (Henderson and Bass, 2006). On the other hand, anatomic and physiologic studies allow character- izing RSI as an inflammatory process originated from friction between bony structures, muscle, tendon, nerve, and connective tissue, because of excessive, cumulative, and repetitive movement of a body segment (Barbe and Barr, 2006). The repetitive stress has been associated with the in- stallation of tenosynovitis, a process in which there is an increase of synovial fluid, followed by inflammation of the sheath formed by the synovial membrane that covers and protects the tendon. As the initiator of this process is the fact that some tendons change the direc- tion on their way to perform a certain movement and, for that, should remain close to the bone through the fibrous structures called retinaculum. In these places, the tendon undergoes compression or friction, which is mitigated by the anatomical arrangement of the synovial membrane that forms a sheath, protecting the tendon slip. This sheath produces synovial fluid that lubricates the tendon, reducing friction. Although tendons have, in general, a robust vascular supply and nerve, tendon regions subjected to friction, compression, or torsion are avascular or hypovascularized, which contributes to aggravate the injury in these areas. Repeated and chronic inflammation leads to a hypertrophy of the retinaculum, which becomes more fibrocartilaginous, causing compression of the tendon beneath it, resulting in tenosynovitis (Kamienski, 2013). As the pain and inflammation are part of the tenosyno- vitis framework, plants with recognized antiinflammatory and analgesic properties have been popularly used to treat this type of disorder, as is the case of many Brazilian arnicas (Assini et al., 2013). However, little is known * Correspondence to: Ary Gomes da Silva, Laboratory of Functional Ecology, University of Vila Velha-UVV, Rua Comissário José Dantas de Melo, 21, Boa Vista, Espírito Santo, CEP 29102-770, Brazil. E-mail: arygomes@uvv.br PHYTOTHERAPY RESEARCH Phytother. Res. (2015) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ptr.5323 Copyright © 2015 John Wiley & Sons, Ltd. Received 06 July 2014 Revised 08 February 2015 Accepted 16 February 2015