Cerebrospinal fluid concentrations of caffeine following oral drug administration: correlation with salivary and plasma concentrations.

Twelve hospitalized adult patients received 300 mg of oral caffeine 1 h before a diagnostic lumbar puncture. Caffeine concentrations were determined simultaneously in saliva, plasma, and cerebrospinal fluid (CSF). Mean caffeine concentrations in plasma, saliva, and CSF were 5.9 +/- 2.1, 4.4 +/- 1.5, and 2.9 +/- 1.1 micrograms/ml, respectively, with coefficients of correlation plasma-saliva, saliva-CSF, and plasma-CSF of 0.89, 0.79, and 0.77, respectively, all statistically significant (p < 0.001).