1.14
Factors Affecting Drug Response: Overview
When it comes to infants and young children, they are typically administered smaller doses of medication in comparison to adults. This is primarily be…
Compared to adults, infants and young children are given smaller drug doses as their organ functions are not fully developed, and the drugs are not efficiently metabolized or eliminated.
Also, their blood-brain barrier is more permeable and high concentrations of drugs in the CNS can cause neurological damage.
Elderly patients are given smaller drug doses as aging influences drug disposition. If an elderly patient with several chronic diseases takes multiple drugs, it can lead to different adverse reactions.
In pregnant women, drugs can pass through the placenta, resulting in teratogenic effects in the developing fetus.
In patients with liver disease, lower doses of the drug over longer intervals are recommended because an impaired liver cannot metabolize or detoxify the drug efficiently.
Drugs given intravenously directly enter the bloodstream, bypassing the GI tract and hepatic metabolism, so the drug response is quick.
In contrast, drugs taken orally pass through the GI tract and undergo hepatic metabolism before entering the systemic circulation. Such drugs show a slow response.
View the full transcript and gain access to JoVE Core videos
Q1: Why do infants and young children receive smaller drug doses than adults?
Infants and young children have underdeveloped organ functions, making them less efficient at metabolizing and eliminating drugs. Additionally, their blood-brain barrier is more permeable, allowing high drug concentrations to penetrate the central nervous system and potentially cause neurological damage. Smaller doses protect developing systems from harm.
Q2: How does aging affect drug dosing in elderly patients?
Aging significantly influences drug disposition, requiring elderly patients to receive smaller doses. When elderly patients with multiple chronic diseases take numerous medications simultaneously, the risk of adverse reactions increases substantially. Dose adjustments account for reduced metabolic capacity and increased drug sensitivity.
Q3: What are the risks of drug exposure during pregnancy?
Drugs can cross the placenta and reach the developing fetus, potentially causing teratogenic effects that result in fetal developmental abnormalities. This placental transfer poses significant risks to fetal health and development. Pregnant women require careful medication selection and dosing to minimize fetal exposure.
Q4: Why do patients with liver disease need modified drug dosing?
A damaged liver cannot efficiently metabolize or detoxify drugs, so patients with liver disease require lower doses administered over longer intervals. This modification prevents drug accumulation and reduces the risk of toxicity. Hepatic impairment significantly slows drug elimination from the body.
Q5: How does the route of drug administration affect drug response speed?
Intravenous administration allows drugs to enter the bloodstream directly, bypassing the gastrointestinal tract and hepatic metabolism, resulting in a quick drug response. Oral drugs must pass through the GI tract and undergo hepatic metabolism before entering systemic circulation, producing a slower response. Routes of drug administration overview explains these differences in detail.
Q6: What happens to orally administered drugs before they reach the bloodstream?
Orally administered drugs pass through the gastrointestinal tract where they are absorbed, then undergo hepatic metabolism in the liver before entering the systemic circulation. This first-pass metabolism can reduce drug bioavailability and delay therapeutic effects. Understanding routes of drug administration enteral helps clarify this process.
Q7: How does drug metabolism differ between intravenous and oral administration?
Intravenous drugs bypass hepatic metabolism entirely by entering the bloodstream directly, avoiding first-pass metabolism. Oral drugs undergo hepatic metabolism before systemic circulation, which can significantly alter drug concentration and effectiveness. This metabolic difference explains why intravenous administration produces faster therapeutic responses than oral routes.