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. Author manuscript; available in PMC: 2010 Dec 1.
Published in final edited form as: Neuropharmacology. 2009 Jul 22;57(7-8):687–693. doi: 10.1016/j.neuropharm.2009.07.025

Figure 4.

Figure 4

Comparison of the concentrations of D- and L-methylphenidate and D- and L-ritalinic acid in the plasma and brain. A and B show quantitative relationship (fold-increase) between plasma and brain concentrations (brain concentration ÷ plasma concentration) of the 4 compounds following 0.75 mg/kg (A) or 2 mg/kg (B) oral dose. Brain concentrations of D- and L-methylphenidate differ from the plasma concentrations (generally higher) as a function of dose and time. Brain concentrations of L-ritalinic acid are only about a tenth of its plasma concentration. D-ritalinic acid is not present in the brain.