Table 2.

Mean circulating concentrations (μM) of ketamine and its metabolites in 6 patients with refractory chronic migraine who underwent 5-day continuous infusion.

Racemic Molecule	Mean ± SD concentration (μM)*	Enantiomers	Mean ± SD concentration (μM)
(R,S)-ketamine
Baseline	0.0 ± 0.0
24 hours	2.0 ± 0.4	--	--
72 hours	2.6 ± 0.4
End of infusion	2.8 ± 0.4
		(R)-norketamine
		Baseline	0.0 ± 0.0
		24 hours	1.1 ± 0.5
(R,S)-norketamine		72 hours	1.0 ± 0.3
Baseline	0.0 ± 0.0	End of infusion	0.9 ± 0.2
24 hours	1.8 ± 0.9
72 hours	1.8 ± 0.4	(S)-norketamine
End of infusion	1.4 ± 0.4	Baseline	0.0 ± 0.0
		24 hours	0.8 ± 0.4
		72 hours	0.7 ± 0.2
		End of infusion	0.6 ± 0.2
		(2R,6R)-HNK
		Baseline	0.0 ± 0.0
		24 hours	1.8 ± 0.7
(RR,SS)-HNK		72 hours	3.6 ± 0.9
Baseline	0.0 ± 0.0	End of infusion	3.2 ± 0.8
24 hours	2.8 ± 1.1
72 hours	5.2 ± 1.3	(2S,6S)-HNK
End of infusion	4.4 ± 1.1	Baseline	0.0 ± 0.0
		24 hours	1.0 ± 0.5
		72 hours	1.5 ± 0.5
		End of infusion	1.1 ± 0.3
(R,S)-DHNK
Baseline	0.0 ± 0.0
24 hours	0.3 ± 0.1	--	--
72 hours	0.5 ± 0.1
End of infusion	0.5 ± 0.1

^*Racemic concentrations may differ slightly from the sum of the enantiomer concentrations because of rounding.

SD=standard deviation; HNK=hydroxynorketamine; DHNK=dehydronorketamine