Abstract
BACKGROUND: Droxidopa is an oral prodrug of norepinephrine approved for the treatment of symptomatic neurogenic orthostatic hypotension. This two-part, randomized, crossover study evaluated the 24-h pharmacokinetic profile of droxidopa in 24 healthy elderly subjects. METHODS: Noncompartmental analysis was used to calculate the area under the plasma concentration-time curve (AUC), maximum plasma concentration (C(max)), time of C(max) (t(max)), and elimination half-life (t(½e)) of droxidopa and metabolites. Droxidopa was administered in the fed (high-fat/high-calorie meal) or fasted state either as a single 300-mg dose (three 100-mg capsules) or 3 times/day (TID) (three 100-mg capsules) at 4-h intervals. RESULTS: Administration of a single droxidopa dose in the fed versus fasted state decreased mean C(max) (2057 vs 3160 ng/mL) and mean AUC (10,927 vs 13,857 h × ng/mL) and increased median t(max) twofold (4.00 vs 2.00 h). Differences between the fed and fasted state for mean t(½e) (2.58 vs 2.68 h) were not observed. Fed versus fasted geometric mean ratios for C(max) and AUC were 66% [90% confidence interval (CI) 60.7-71.7] and 80% (90% CI 72.6-88.1), respectively. With TID dosing, similar values for C(max) were observed after each dose (range 2789-3389 ng/mL) with no return to baseline between doses. Norepinephrine C(max) was 895 pg/mL following dose 1, with no further increases upon subsequent doses; norepinephrine levels remained above baseline for 12-16 h after dose 1. CONCLUSIONS: Absorption of a single dose of droxidopa is slowed after a high-fat/high-calorie meal; for consistent effect, administer droxidopa in the same manner (with or without food). Pharmacokinetic parameters of droxidopa are similar after single and TID dosing. ClinicalTrials.gov Identifier: NCT01149629.