1. What are the four main processes of pharmacokinetics and how do they affect the drug concentration in the body? Explain with an example of a drug used in acute care settings. - The four main processes of pharmacokinetics are absorption, distribution, metabolism, and excretion. They affect the drug concentration in the body by determining how fast and how much of the drug enters the bloodstream, reaches the target tissues, is transformed by enzymes, and is eliminated from the body. For example, a drug that is poorly absorbed from the gastrointestinal tract will have a low bioavailability and a low plasma concentration, while a drug that is highly bound to plasma proteins will have a large volume of distribution and a long half-life. 2. What are the factors that influence the pharmacodynamics of a drug, i.e., the relationship between the drug concentration at the site of action and the resulting effect? Give an example of how each factor can modify the drug response in an older adult patient. - The factors that influence the pharmacodynamics of a drug are receptor affinity, intrinsic activity, receptor number and sensitivity, second messenger systems, and feedback mechanisms. For example, receptor affinity determines how strongly a drug binds to its receptor and influences its potency; intrinsic activity determines how well a drug activates its receptor and influences its efficacy; receptor number and sensitivity can change due to up-regulation or down-regulation in response to chronic exposure or withdrawal of a drug; second messenger systems mediate the intracellular effects of a drug and can be affected by other drugs or diseases; and feedback mechanisms regulate the homeostasis of the body and can counteract or enhance the drug effect. 3. What are the types and mechanisms of drug interactions and how can they affect the therapeutic outcome or cause adverse effects? Provide an example of each type of interaction and explain how it can be prevented or managed in acute care settings. - The types and mechanisms of drug interactions are pharmacokinetic interactions, pharmacodynamic interactions, and combined toxicity. Pharmacokinetic interactions occur when one drug alters the absorption, distribution, metabolism, or excretion of another drug, resulting in changes in plasma concentration or bioavailability. For example, antacids can reduce the absorption of some antibiotics by forming insoluble complexes in the stomach; enzyme inducers can increase the metabolism of some drugs by stimulating their breakdown in the liver; protein-binding displacers can increase the free fraction of some drugs by competing for binding sites on plasma proteins; and diuretics can increase the excretion of some drugs by increasing urine output. Pharmacokinetic interactions can be prevented or managed by adjusting the dose, timing, route, or formulation of the drugs involved; monitoring plasma levels; or avoiding concomitant use of incompatible drugs. Pharmacodynamic interactions occur when two drugs have additive, synergistic, or antagonistic effects on the same or different receptors or physiological systems. For example, opioids and benzodiazepines have additive effects on central nervous system depression and can cause respiratory depression; beta blockers and calcium channel blockers have synergistic effects on cardiac output and blood pressure reduction and can cause bradycardia or hypotension; and antihistamines and anticholinergics have