NMDA-Receptor Antagonists and Opioid Receptor Interactions as Related to Analgesia and Tolerance Donald D Price, PhD, David J Mayer, PhD, Jianren Mao, PhD, Frank S Caruso, PhD Journal of Pain and Symptom Management Volume 19, Issue 1, Pages 7-11 (January 2000) DOI: 10.1016/S0885-3924(99)00121-9
Fig. 1 Oral administration of MS 32 mg/kg with DM 8 to 64 mg/kg twice daily for 8 days. Animals receiving MS alone showed development of tolerance (rapid decline in maximal analgesic effect after day 3), while animals receiving MS:DM in ratios of 2:1, 1:1, and 1:2 remained responsive. In particular, MS:DM 1:1 appeared to be the optimal ratio for prevention of tolerance. Reproduced from Mao et al. (10) with permission Journal of Pain and Symptom Management 2000 19, 7-11DOI: (10.1016/S0885-3924(99)00121-9)
Fig. 2 Potentation of MS analgesia by DM following a single dose of the combination. Maximal analgesia with the combination was significantly greater than MS alone during the first 90 minutes after administration (P < 0.05). Reproduced from Mao et al. (10) with permission Journal of Pain and Symptom Management 2000 19, 7-11DOI: (10.1016/S0885-3924(99)00121-9)