Kaempferia parviflora is widely used as a food supplement and a herbal medicine for vitalization. Previous study has shown that K. parviflora had CYP2E1 inducer activity. It is likely to affect the metabolism of CYP2E1 substrates such as acetaminophen which is a common household pain relief medicine. This study investigated the possible pharmacokinetic interaction between K. parviflora and acetaminophen in rats. Acetaminophen (100 mg/kg, p.o) was administered to rats for nine consecutive days. On days 4-9, K. parviflora extract (250 mg/kg, p.o) was given to the acetaminophen-treated rats. After co-administration with K. parviflora, the concentrations of acetaminophen during day 5-8 markedly decreased compared with acetaminophen-only group. At day 9, the pharmacokinetic parameters of acetaminophen in the presence of K. parviflora extract also decreased, including area under the concentration-time curve (from 1.68 ± 0.16 to 0.34 ± 0.04 mg.min/mL), the maximum concentration (from 19.10 ± 1.90 to 4.48 ± 0.56 µg/mL), and half-life (from 21.29 ± 1.36 to 10.81 ± 1.24 min). In addition, clearance and the elimination rate constant of acetaminophen were significantly increased (from 0.003 ± 0.000 to 0.006 ± 0.001 L/min and 0.03 ± 0.00 to 0.07 ± 0.01 min-1, respectively) in the presence of K. parviflora extract. These findings provide the data for in vivo herb-drug interaction between K. parviflora extract and acetaminophen. Therefore, the concomitant use of K. parviflora as a food supplement and acetaminophen should occasion therapeutic and safety concerns.
Keywords: Kaempferia parviflora; acetaminophen; herbal-drug interaction; pharmacokinetics; toxicity.