TABLE 1.

Mean ED₅₀ values (with 95% CI) of four opioid agonists for producing antinociception, constipation, and respiratory depression in Sprague Dawley rats

Opioid	Antinociception	Constipation	Respiratory Depression
Morphine	52.2 (27.6-98.5)	111.5 (111.4-111.7)	88.5 (39.7-197.4)
Oxycodone	287.9 (199.2-416.2)	355.6 (335.4-377.1)a	ND
Fentanyl	4.9 (1.53-15.7)	9.9 (9.6-10.2)	13.9 (10.0-19.3)
Buprenorphine	∼20 (13.0-31.7)a	∼7.5b	12.3 (8.7-17.4)

ND, not determinable.

Table adapted from Kuo et al. (2015).

^aA ceiling effect and the ED₅₀ was estimated using doses up to that which produced the maximal effect.