Methotrexate serum and saliva concentrations in patients.

Serum and mixed saliva concentrations were determined in two patients upon i.v. injection of methotrexate. The concentration-time profiles were followed up for 100 h after dosing. Whereas no correlation was found between serum and saliva concentrations for the first 15 h, which corresponds with the distribution phase of methotrexate, a correlation was found for the terminal phase with a serum-saliva ratio of 3.8. The volume of distribution for the central compartment was approximately equal to the serum volume. The apparent volume of distribution was close to the total body fluid volume.