Table 2.

Summary of Opioid Agonist-mGluR5 Antagonist Interactions

Probe Drug, Intrathecal	Opioid Agonist ED50 value (C.I) nmol per 5 µL	mGluR5 antagonist ED50 value (C.I) nmol/ 5 µL	Interaction
Oxymorphone + MPEP 1:2 Dose Ratio
Single Drug	3.0 (1.8–4.1)	5.3 (3.0–7.6)
Observed Combination	0.36 (0.18–0.54)*	0.72 (0.37–1.1)*	Synergistic
Theoretical Additive	1.4 (0.99–1.8)	2.8 (2.0–3.6)
Oxymorphamine + MPEP 1:1 Dose Ratio
Single Drug	2.2 (1.4–3.0)	3.1 (2.2–4.0)
Observed Combination	0.43 (0.26–0.60)*	0.43 (0.26–0.60)*	Synergistic
Theoretical Additive	1.3 (1.0–1.6)	1.3 (1.0–1.6)

^*Significant difference from theoretical additive by Student t test, p < 0.05