Association of antioxidant nutraceuticals and acetaminophen (paracetamol): Friend or foe?

Acetaminophen (paracetamol or APAP) is an analgesic and antipyretic drug that can induce oxidative stress-mediated hepatotoxicity at high doses. Several studies reported that antioxidant nutraceuticals, in particular phenolic phytochemicals from dietary food, spices, herbs and algae have hepatoprotective effects. Others, however, suggested that they may negatively impact the metabolism, efficacy and toxicity of APAP. The aim of this review is to discuss the pros and cons of the association of antioxidant nutraceuticals and APAP by reviewing the in vivo evidence, with particular reference to APAP pharmacokinetics and hepatotoxicity. Results from the murine models of APAP-induced hepatotoxicity showed amelioration of liver damage with nutraceuticals coadministration, as well as reductions in tissue markers of oxidative stress, and serum levels of hepatic enzymes, bilirubin, cholesterol, triglycerides and inflammatory cytokines. On the other hand, both increased and decreased APAP plasma levels have been reported, depending on the nutraceutical type and route of administration. For example, studies showed that repeated administration of flavonoids causes down-regulation of cytochrome P450 enzymes and up-regulation of uridine diphosphate glucuronosyltransferases (UGT). Moreover, nutraceuticals can alter the levels of APAP metabolites, such as mercapturate glucuronide, sulfate and cysteine conjugates. Overall, the reviewed in vivo studies indicate that interactions between APAP and nutraceuticals or plant foods exist. However, the majority of data come from animal models with doses of phytochemicals far from dietary ones. Human studies should investigate gene-diet interactions, as well as ethnic variability in order to clarify the pros and cons of co-administering antioxidant nutraceuticals and APAP.