Double-blind, placebo-controlled, two-period, crossover trial to examine the pharmacokinetics of lisdexamfetamine dimesylate in healthy older adults

Background: Pharmacokinetic and safety data on stimulants in older adults are limited. The objective of this study was to characterize the pharmacokinetics of lisdexamfetamine dimesylate (LDX), a d-amphetamine prodrug, in older adults.

Methods: In this two-period crossover trial, healthy adults (n = 47) stratified by age (55-64, 65-74, and ≥ 75 years) and gender received randomized, double-blind, single doses of LDX 50 mg or placebo. Baseline creatinine clearance, d-amphetamine and intact LDX pharmacokinetics, and safety were assessed.

Results: Mean (±standard deviation) baseline creatinine clearance in participants aged 55-64, 65-74, and ≥ 75 years was 102.5 ± 26.1, 105.3 ± 23.1, and 94.9 ± 27.3 mL per minute, respectively. In the groups aged 55-64, 65-74, and ≥ 75 years, the mean maximum plasma d-amphetamine concentration in men was 44.2 ± 11.1, 47.7 ± 7.0, and 53.4 ± 19.4 ng/mL, respectively; area under the concentration time curve from time 0 extrapolated to infinity (AUC(0-inf)) was 915.0 ± 164.9, 1123.0 ± 227.0, and 1325.0 ± 464.4 nghour/mL; median time to reach peak plasma concentration was 4.5, 3.5, and 5.5 hours; in women, mean maximum plasma d-amphetamine concentration was 51.0 ± 6.7, 50.2 ± 6.8, and 64.3 ± 12.1 ng/mL, AUC(0-inf) was 1034.5 ± 154.6, 988.4 ± 80.5, and 1347.8 ± 198.9 ng hour/mL, and median time to reach peak plasma concentration was 3.5, 4.1, and 5.5 hours, respectively. d-Amphetamine clearance was unrelated to baseline creatinine clearance. Five participants aged 55-64 years reported treatment-emergent adverse events (versus one each aged 65-74 and ≥ 75 years), and as did six women (versus one man). No trends in blood pressure or pulse changes were seen with LDX according to age. In participants aged 55-64, 65-74, and ≥ 75 years, the mean change from time-matched baseline pulse ranged from -5.0 to 14.7, -4.3 to 9.5, and -3.0 to 14.7 beats per minute; for systolic blood pressure, from -3.9 to 18.5 mmHg, -2.1 to 14.5 mmHg, and -5.9 to 16.0 mmHg; for diastolic blood pressure from -2.5 to 8.3 mmHg, from -0.8 to 9.4 mmHg, and -0.6 to 9.5 mmHg. Vital sign changes were similar between men and women.

Conclusion: Clearance of d-amphetamine decreased with age and was unrelated to creatinine clearance. No trends in pulse or blood pressure changes with LDX were seen according to age. The safety profile of LDX was consistent with prior observations in younger adult study participants.