Urinary pH Dependence of Lisdexamfetamine Renal Excretion
Lisdexamfetamine (Elvanse) is a prodrug of dextroamphetamine, and urinary excretion of unchanged amphetamine is urinary pH dependent. [1]
Urine alkalinization is associated with lower amphetamine excretion, while urine acidification is associated with higher amphetamine excretion. [1]
Magnitude of Urinary pH Changes Needed to Alter Amphetamine Excretion
Amphetamine urinary excretion changes with urinary pH mainly when urinary pH is altered substantially. [2]
A mechanistic condition cited for pH-sensitive renal excretion is that urinary pH must differ from the drug’s pKa by roughly ~2 pH units to materially change the fraction of ionized vs unionized drug. [2]
Evidence Linking Caffeine/Coffee Intake to Urinary pH
Published evidence directly demonstrating that typical coffee/caffeine intake shifts urinary pH by ≥~2 units is not established in the medical literature available for review here. [2]
Coffee and caffeine effects on the kidney are more consistently characterized as affecting urine volume and fluid/electrolyte handling rather than producing large, sustained shifts in urinary pH. [3]
Clinical Implication for Elvanse Use
Because amphetamine urinary excretion is pH dependent, clinically meaningful effects on lisdexamfetamine exposure would be expected mainly when urinary pH is driven into a clearly more acidic or alkaline range (for example, via deliberate acidifying or alkalinizing interventions), rather than from typical dietary caffeine intake. [1]
Available literature supports pH as a determinant of renal amphetamine excretion, but it does not provide evidence that coffee-derived caffeine reliably alters urinary pH enough to produce a clinically important change in lisdexamfetamine/amphetamine renal clearance. [1]