B complex vitamins for analgesic therapy

ABSTRACT BACKGROUND AND OBJECTIVES: The B complex vitamins have been used as single therapy or combined to other drugs, such as anti-inflammatory drugs, in different clinical situations, such as degenerative spinal diseases, rheumatologic diseases, polyneuropathies and in different postoperative situations. This study aimed at identifying in the scientific literature most recent evidences of the use of B complex vitamins as analgesic therapy and at describing clinical situations where their analgesic action could be observed. CONTENTS: A search was carried out in Pubmed, Medline, LILACS, Cochrane Library and Scielo databases, contemplating the last 10 years and titles in Portuguese, Spanish and English. Keywords were: "pain", "B complex vitamins", "management", "vitamin B1", "vitamin B6", "vitamin B12", "thiamine", "pyridoxine" and "cyanocobalamin". Among 40 studies found, we have selected just musculoskeletal and neuropathic pain trials with humans, and where B complex vitamins were used as analgesic agents. From these, 13 studies were selected for meeting inclusion criteria. In all of them, B complex vitamins played roles in analgesia, even when in single therapy. B complex vitamins had also anti-inflammatory and anti-pruritus action, in addition to improving functionality. CONCLUSION: Existing studies, although scarce and heterogeneous, have shown that B complex vitamins have analgesic effect. They are considered safe and have low cost and have shown to be a good option as adjuvant analgesic therapy.