Pharmacokinetics of reduced iso-α-acids in volunteers following clear bottled beer consumption

• Reduced iso-α-acids (IAA) are ingredient congeners found in clear, and in some green, bottled beer.
• We examine their presence in volunteers over 6 h given controlled doses of beer.
• Three varieties of clear bottled beer gave a blood alcohol concentration of near 0.05%.
• Reduced IAA were detected in all volunteers.
• These modified forms of IAA may be useful markers for detection of beer consumption.

Reduced iso-α-acids (reduced IAA) consisting of the rho-, tetrahydro- and hexahydro-IAA groups (RIAA, TIAA and HIAA, respectively) are ingredient congeners specific to beer and generally found in clear and also occasionally green bottled beer. Concentrations of reduced IAA were determined in the blood and urine of five volunteers over 6 h following the consumption of small volumes of beer containing each of the reduced IAA. The reduced IAA were absorbed and bioavailable with peak concentrations at 0.5 h followed by a drop of generally fivefold by 2 h. Preliminary pharmacokinetics of these compounds in humans shows relatively small inter-individual differences and an estimated short half-life varying between ∼38 and 46 min for the three groups. Comparison of RIAA analyte ratios within the group indicate that some analytes eliminate relatively faster than others and the formation of metabolite products was observed. Preliminary urine analysis showed only unmodified RIAA analytes were detectable throughout 6 h and suggests extensive phase I metabolism of TIAA and HIAA analytes. In authentic forensic casework where clear or green bottled beers are consumed, the identification of reduced IAA groups may provide a novel method to target ingredient congeners consistent with beer ingestion and suggest the type of beer consumed.