TABLE 1

Predicted fold increase in the AUCs of codeine and morphine based on plasma ketamine concentrations reported following anesthetic and analgesic doses

Reference	KTM Dose	Total Plasma [KTM] (μM)^{^a}	Predicted Fold Increases in Codeine and Morphine AUC Ratios Based on Reported Total and Unbound In Vivo Ketamine Concentrations
Reference	KTM Dose	Total Plasma [KTM] (μM)^{^a}	Codeine ([KTM]_total)	Codeine ([KTM]_unbound)	Morphine^{^b} ([KTM]_total)	Morphine^{^b} ([KTM]_unbound)
Idvall et al. (1979)	2 mg + 41 μg · min⁻¹ · kg⁻¹ i.v.	9.3	2.39	2.12	1.61	1.50
Xie et al. (2003)	0.5 mg/kg epidurally	2.7	1.54	1.41	1.26	1.20
Clements and Nimmo (1981)	0.125–0.25 mg/kg i.v.	0.42^{^c}	1.09	1.07	1.04	1.03

↵a Unbound ketamine concentration calculated as fu × total plasma concentration.
↵b Morphine AUC ratios represent the sum of the separate ratios for the 3- and 6-glucuronidation pathways.
↵c Pain threshold increased >5 min when total plasma ketamine concentration was >100 μg/l.