Pharmacokinetics and Pharmacodynamics of Gastrointestinal Drugs

Pharmacokinetics (PK) refer to the process by which a drug is absorbed, distributed, metabolized, and excreted from the route of administration to the systemic circulation, and the process by which a drug that arrives at the site of action shows efficacy is called pharmacodynamics (PD). Various factors such as the patient’s age, weight, disease status, concomitant drugs, genotype, and sex can cause individual differences in PK and PD. Due to the structural, morphological, and physiological differences between men and women, the drug absorption, distribution, metabolism, and excretion (ADME) processes may also be different, resulting in different drug concentrations. In addition, drug effects can vary between sexes due to the differences in disease pathogenesis or drug receptors that the drug acts upon. Since the sex differences in PK and PD vary by drug, a drug-specific/disease-specific approach is required, and this chapter will illustrate these differences using gastrointestinal drugs such as proton pump inhibitors (PPIs) and antivirals as examples.