This study will be an open-label, single-treatment, single-dose, parallel group study to evaluate the pharmacokinetics (PK) of droxidopa in subjects with mild, moderate, and severe renal dysfunction and End Stage Renal Disease (ESRD) after a single dose compared to matched healthy subjects with normal renal function.
A total of 48 male or female subjects, 16 subjects with normal renal function (eGFR greater than 90 mL/min/1.73m²) and eight each (8) with mild (60 less than eGFR less than 89 mL/min/1.73m²), moderate (30 less than eGFR less than 59 mL/min/1.73m²), or severe (15 less than eGFR less than 29 mL/min/1.73m²) renal impairment or ESRD (eGFR < 15 mL/min/1.73m² and requiring hemodialysis) will be selected according to the inclusion and exclusion criteria. The medical and laboratory examinations will take place within 28 days before dosing. A single dose of 600 mg of droxidopa as an investigational drug will be administered with 240 mL of water after an overnight fast (minimum 10 hours).
Blood samples for the measurement of plasma concentrations of droxidopa and metabolites including but not limited to 3-OM-DOPS, NE, vanillic acid, and protocatechuic acid will be collected before and 0, .5, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, 24, 30, 36 hours after dosing for healthy volunteers and subjects with mild, moderate, and severe renal impairment and those with ESRD. For the latter, samples will be collected on both a non-hemodialysis and a hemodialysis visit.
During dialysis, samples of dialysate, from the arterial and venous sides of the dialyzer will be collected at 30-minute intervals during the dialysis period. In addition, the entire dialysate will be collected, its volume recorded, and a sample retained for the measurement of droxidopa and metabolites including but not limited to 3-OM-DOPS, NE, vanillic acid, and protocatechuic acid concentrations.
Urine samples for the measurement of urinary excretion of droxidopa and metabolites including but not limited to 3-OM-DOPS, NE, vanillic acid, and protocatechuic acid will be collected before and over the following intervals after dosing: 0 2, 2-4, 4-6, 6-8, 8-12, 12-24, and 24-36 hours for healthy volunteers and subjects with mild, moderate, and severe renal impairment.
A post-study visit with physical examination and laboratory tests will take place within seven (7) days after the last PK blood sampling.