The pharmacokinetics of methyldopa after oral and intravenous administration was studied in hypertensive and normotensive patients. After intravenous administration methyldopa plasma concentrations decayed according to a two-compartment open model. 2. For intravenous administration the overall elimination constant Ke1 was 0.56 +/- 0.03 h-1, the volume of distribution of the central compartment 0.29 +/- 0.80 1 kg-1 and the plasma clearance rate 11.2 +/- 0.6 1 h-1. 3. Plasma half-times during the beta-phase of the methyldopa plasma decay curve following intravenous and oral administration were 2.8 +/- 1.3 and 2.1 +/- 0.7 h, respectively. 4. Maximal plasma levels in hypertensive out-patients show great variation and range from 0 to 1.9 microgram ml-1. 5. No relationships were found between maximal methyldopa plasma levels in patients under treatment and control of hypertension.
