Dexamfetamine Absorption and Disposition With Acidic Foods/Beverages
Oral dexamfetamine (Amfexa) is a weak base. Gastric/GI acidifying agents reduce gastrointestinal absorption, which lowers systemic (plasma) exposure and can reduce clinical efficacy. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Absorption: Impact of Acidic Foods or Beverages
GI acidifying agents (for example ascorbic acid and fruit juices) lower the absorption of amfetamine. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
The net effect is reduced oral bioavailability for dexamfetamine when meaningful GI acidification accompanies dosing. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Plasma Concentrations: Impact of Acidification
Because GI acidifying agents lower absorption, blood levels of amfetamines decrease. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Urinary acidifying agents increase the renal excretion of the ionized drug and decrease blood levels and efficacy. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Elimination Half-Life: Impact of Urine Acidification
Urine acidification decreases amphetamine elimination half-life by promoting retention of the ionized drug in renal tubules and increasing elimination. [1]
Controlled human studies under acidic versus alkaline urinary conditions have shown urine pH–dependent kinetics for amphetamine and altered half-life across acidification/alkalinization states. [2]
Clinical Efficacy: Impact of Reduced Exposure
Both GI acidifying agents (reduced absorption) and urinary acidifying agents (increased excretion) lower blood levels of amfetamines. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Reduced blood levels are associated with reduced efficacy of amfetamine therapy. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Practical Clinical Implications for Acidic Foods/Beverages
Acidic beverages with clinically meaningful GI acidifying potential (examples explicitly listed include ascorbic acid and fruit juices) can reduce dexamfetamine absorption when co-ingested with dosing. Dexamfetamine sulfate SmPC (Amfexa 5 mg)
Acidification strategies that meaningfully acidify urine can shorten apparent duration of drug exposure by increasing renal elimination and decreasing half-life. [1]
Urinary acidifying agents (examples include ammonium chloride and sodium acid phosphate) are expected to decrease systemic exposure and reduce efficacy based on the SmPC interaction mechanism. Dexamfetamine sulfate SmPC (Amfexa 5 mg)