. 2018 Apr;365(1):37–47. doi: 10.1124/jpet.117.246439

TABLE 3.

Fentanyl ED₅₀ values and (95% confidence limits) administered alone or following a 15-minute pretreatment with naltrexone (0.0032–0.032 mg/kg), 10 mg/kg NAQ, or 0.032 mg/kg fentanyl/naltrexone (1:0.22) mixture in an assay of thermal nociception at 50 and 54°C

Data are presented as the mean value of three monkeys for the naltrexone pretreatment studies and mean value of four monkeys for the NAQ and fentanyl/naltrexone mixture pretreatment studies.

Treatment	ED₅₀ in mg/kg (95% CL)
Treatment	50°C	54°C
	mg/kg	mg/kg
Fentanyl alone	0.006 (0.006, 0.006)	0.018 (0.018, 0.018)
Fentanyl + 0.0032 mg/kg naltrexone	0.021 (0.016, 0.028)^a	0.035 (0.018, 0.069)
Fentanyl + 0.01 mg/kg naltrexone	0.018 (0.013, 0.05)^a	0.169 (0.057, 0.228)^a
Fentanyl + 0.032 mg/kg naltrexone	0.057 (0.043, 0.128)^a	0.257 (0.109, 0.608)^a
Fentanyl alone	0.006 (0.005, 0.006)	0.014 (0.012, 0.017)
Fentanyl + 10 mg/kg NAQ pretreatment	0.041 (0.014, 0.118)^a	0.155 (0.122, 0.197)^a
Fentanyl alone	0.006 (0.005, 0.006)	0.014 (0.012, 0.017)
Fentanyl + 0.032 mg/kg fentanyl/naltrexone (1:0.22) pretreatment	<0.017 (0.002, 0.18)^b	0.035 (0.015, 0.08)

CL, confidence limit.

^{^a}

Denotes nonoverlapping 95% CL.

^{^b}

The ED₅₀ value could only be determined in two out of four monkeys because no fentanyl dose produced <50%MPE.