Antinociceptive Effects and Interaction Mechanisms of Intrathecal Pentazocine and Neostigmine in Two Different Pain Models in Rats

Table 1

ED₅₀ and SEM for intrathecally administered pentazocine, neostigmine and in combination in a fixed-dose ratio.

Group	Drug	Pentazocine component		Neostigmine component		Sum of ED50 fractions
		Intrathecal dose (μg)	Fraction of ED50	Intrathecal dose (μg)	Fraction of ED50
Formalin test Phase I	PEN	91.1 ± 5.4	1.00	----	----
	NEO	----	----	8.93 ± 0.59	1.00	1.00
Formalin test Phase II	PEN	101.2 ± 6.2	1.00	----	---
	NEO	----	---	9.20 ± 0.55	1.00	1.00
Plantar incision model	PEN	98.0 ± 5.5	1.00	----	----
	NEO	----	----	10.2 ± 0.55	1.00	1.00
Interaction studies
Formalin test Phase I	PEO + NEO	30.3 ± 2.5	0.33	2.95 ± 0.30	0.33	0.66
Formalin test Phase II	PEO + NEO	34.4 ± 3.0	0.34	3.10 ± 0.24	0.34	0.68
Plantar incision model	PEO + NEO	34.0 ± 2.2	0.35	3.31 ± 0.27	0.32	0.67

PEN = Pentazocine; NEO = Neostigmine.