Chapter twenty one - Pharmacokinetics and bioavailability of nutraceuticals

Abstract

The interplay between the pharmacodynamics (PDs) and pharmacokinetics (PKs) parameters is responsible for the bioavailability (BA) of any molecule. Drug efficacy depends on multiple factors, including PKs (absorption, distribution, metabolism, and excretion, ADME) and PDs. Different synergistic and detrimental interactions can cause a change in PD responses due to the presence of xenobiotics, a food, or an herbal remedy. We can alter the PD and PK properties by changing the ADME and physical properties of the active molecule on which the BA and bioaccessibility can be altered as required. Drugs can interact with nutrients by affecting the PK and PD parameters, which results in decreased therapeutic efficacy, increased nutritional risk, and greater pharmacological side effects. The BA and bioaccessibility of each molecule are determined by the interaction of PKs and PDs factors. PKs (ADME) and PDs are two aspects that influence the therapeutic efficacy of drugs. Structural and physicochemical modifications of drugs and formulations have a significant impact on BA and bioaccessibility and subsequently PK–PD aspects. Nutraceuticals are multicomponent, multiingredient complex systems and hence their disposition pattern is much more complicated than a routine synthetic drug molecule, which is generally, a single chemical entity. PK models are designed to understand the disposition pathway of therapeutic moiety after undergoing absorption. The compartment model is to provide a standardized and straightforward method for describing, analyzing, and interpreting data acquired during in vivo drug disposal research. Nutraceuticals, functional foods, and beverages containing specific combinations of bioactive agents are explored for a variety of applications. These products can be targeted at specific individuals, high-risk patients (such as depression, diabetes, cardiovascular disease, or hypertension), individuals of specific age groups (such as infants, adults, or the elderly), and people with specific nutritional requirements. Generally, a single or combination of two or more nutraceuticals is employed in clinical practice to have an effect on multiple molecular targets and increase the range of biochemical molecules that are targeted. Whether a single or combination, nutraceutical products comprise a plethora of bioactive markers with varied physicochemical properties and complex PK traits. Conventional synthetic drugs either follow one compartment model, that is, single central compartment (systemic circulation and extravascular tissues or organs grouped) or a two-compartment model comprising a central compartment (systemic circulation and highly perfused organs) and peripheral tissue compartment depending on their solubility and permeability characteristics. Nutraceuticals are assumed to follow multiexponential multicompartment models because of the diversity of active molecules present in the supplements, involvement, and significant effect of the food on the release, dissolution, and ADME (i.e., absorption, metabolism, distribution, and excretion) of the active components. This chapter discusses a comprehensive review of the PKs concepts along with the compartment model in detail.