Appendix 1. MEDLINE (OvidSP) search strategy

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1 randomized controlled trial.pt. (469833)
2 controlled clinical trial.pt. (95075)
3 randomized.ab. (405922)
4 placebo.ab. (192462)
5 drug therapy.fs. (2035863)
6 randomly.ab. (286430)
7 trial.ab. (428193)
8 groups.ab. (1764339)
9 or/1‐8 (4191739)
10 exp animals/ not humans.sh. (4669484)
11 9 not 10 (3613342)
12 exp Diabetes Mellitus/ (386580)
13 diabet$.mp. (608134)
14 12 or 13 (609856)
15 exp Peripheral Nervous System Diseases/ (137699)
16 15 or (neuropath$ or polyneuropath$).mp. (222573)
17 14 and 16 (25606)
18 Diabetic Neuropathies/ (13937)
19 17 or 18 (25606)
20 Thioctic Acid/ (3831)
21 (lipoic acid or alpha lipoic or thioc*).mp. (25770)
22 20 or 21 (25770)
23 11 and 19 and 22 (189)
24 remove duplicates from 23 (168)