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. Author manuscript; available in PMC: 2020 Oct 1.
Published in final edited form as: J Pain. 2019 Apr 18;20(10):1218–1235. doi: 10.1016/j.jpain.2019.04.005

Figure 4.

Figure 4.

Mean steady-state plasma levels of (+)-M1 (A, E), (−)-M1 (B, F), (+)-tramadol (C, G), and (−)-tramadol (D, H) in trials A (n = 43) and B (n = 60). Bars are for SD and shown in 1 direction. Baseline points all below the quantitation limit.