Reduced Fetal Drug Exposure

Chapter 6_ Drug Interactions Learning Objectives 1. Describe the consequences of drug–drug interactions, the basic mechanisms of drug– drug interactions, and the critical steps in minimizing adverse drug–drug interactions. ● Consequences of drug-drug interactions can include intensifying the effects of one drug, reducing the effects of another, or producing new and unpredictable responses. The basic mechanisms of drug-drug interactions include intensification of effects, reduction of effects, direct chemical or physical interactions, pharmacokinetic interactions (competition for protein binding, altered distribution, altered metabolism), pharmacodynamic interactions (producing new responses), and combined toxicity. To minimize adverse drug-drug interactions, it is important to consider drug-food interactions, the impact of food on drug absorption, metabolism, and toxicity, as well as the timing of drug administration with respect to meals. Drug-supplement interactions should also be taken into account. Additionally, monitoring for inhibitory interactions and taking steps to adjust dosages when necessary can help minimize the risk of adverse drug-drug interactions. 2. Explain the effect of food on drug absorption, on drug metabolism (e.g., grapefruit juice), and on drug toxicity and action, as well as the timing of drug administration with respect to meals. ● Food can have various effects on drug interactions. For drug absorption, some foods can impact the rate and extent of drug absorption, either by enhancing or reducing it. For drug metabolism, grapefruit juice can inhibit enzymes responsible for drug metabolism, leading to increased drug levels and potential toxicity. Food can also affect drug toxicity and action by interacting with drug targets or altering drug effects. Timing of drug administration with meals can be important, as some drugs may need to be taken with food to enhance absorption or reduce gastrointestinal side effects, while others should be taken on an empty stomach to avoid interactions with food components. Chapter 6 Readings Drug-drug interactions can lead to three possible outcomes: intensification of effects, reduction of effects, or the production of a new response. Intensification of effects can be beneficial or detrimental, while reduction of effects can be either beneficial or detrimental as well. It is important to minimize adverse drug-drug interactions to ensure optimal therapeutic outcomes. Bullet points Reduced drug absorption: ● Inhibition occurs when an antagonist drug blocks access of an agonist drug to its receptor ● Reduced absorption can increase drug export from cells of the intestinal epithelium into the intestinal lumen Reduced fetal drug exposure: ● Reduced fetal drug exposure can occur by increasing drug export from placental cells into the maternal blood Reduced brain drug exposure: ● Reduced brain drug exposure can occur by increasing drug export from cells of brain capillaries into the blood Minimizing adverse drug interactions: ● ● ● ● Minimize the number of drugs a patient uses Take a thorough drug history, including recreational drugs, OTC drugs, and herbal supplements Adjust the drug regimen accordingly based on the drug history Be aware that patients may not report illicit drug use Interactions resulting from actions at separate sites: ● ● If two drugs influence the same physiologic process, one drug can alter responses produced by the other Interactions can be potentiative or inhibitory Example of a potentiative interaction: ● The interaction between morphine and diazepam (Valium) ● Concurrent use of drugs that act at separate sites can reinforce the depressant effects of each drug Example of an interaction counteracting effects: ● ● ● The interaction between hydrochlorothiazide and spironolactone Hydrochlorothiazide increases excretion of potassium, while spironolactone decreases renal excretion of potassium The potassium-sparing effects of spironolactone balance the potassium-wasting effects of hydrochlorothiazide