FB - Pharmacokinetics I Flashcards
What are the four fundamental principles of pharmacokinetics in medicines?
Absorption, Distribution, Metabolism, Excretion (ADME)
What does the absorption rate constant (Ka) indicate in pharmacokinetics?
The rate at which a drug is absorbed into the bloodstream
Define the ‘therapeutic window’ in pharmacology.
The range of drug concentrations in the body that is effective without being toxic
What are some common dosage regimens in pharmacotherapy?
Intermittent dosing, continuous infusion, slow release formulations
Why are slow release medications beneficial?
They help maintain drug concentrations within the therapeutic window for longer periods
What are the two types of intravenous dosing?
Intermittent injection and continuous infusion
What is the purpose of therapeutic drug monitoring (TDM)?
To optimize drug dosages for effective treatment, especially in patients with varying pathophysiological conditions
How are drug dosages adjusted?
Based on factors like patient’s age, weight, renal function, and the drug’s pharmacokinetic properties
How does the body’s absorption of a drug relate to its pharmacological effect?
Faster absorption generally leads to a quicker onset of the drug’s effect
What factors influence a drug’s distribution in the body?
Blood flow to tissues, tissue binding, and the drug’s lipid solubility
How does metabolism affect a drug’s activity in the body?
Metabolism can either activate a prodrug, inactivate an active drug or generate pharmacologically active metabolite(s)
What role does excretion play in pharmacokinetics?
It removes the drug or its metabolites from the body, ending its action
What is the significance of the half-life (t½) of a drug?
It indicates the time it takes for the drug’s plasma concentration to reduce by half
How does renal function affect drug excretion?
Impaired renal function can lead to reduced drug clearance and increased risk of toxicity
Why is patient compliance important in pharmacotherapy?
Non-compliance can lead to suboptimal therapeutic outcomes or increased risk of adverse effects
What are the challenges associated with high-frequency dosing regimens?
They can be inconvenient and increase the risk of non-compliance
What is the advantage of intermittent injection in IV dosing?
It allows control over drug concentrations and can prevent toxicity
How does continuous infusion benefit patients?
It maintains a constant drug concentration in the bloodstream
What is the importance of the loading dose in pharmacokinetics?
It rapidly achieves the desired therapeutic concentration of a drug in the body
How does the concept of a therapeutic window guide dosage adjustment?
It helps in maintaining drug concentrations within a safe and effective range
What factors are considered in therapeutic drug monitoring?
Drug levels, patient’s clinical response, potential side effects, drug-drug interactions
Why is monitoring renal function important in drug dosing?
To adjust dosages in patients with renal impairment and avoid toxicity
How can drug interactions influence pharmacokinetics?
They can alter absorption, metabolism, and excretion, affecting drug efficacy and safety
What is the impact of liver function on drug metabolism?
Impaired liver function can reduce drug clearance and increase the risk of adverse effects
How do age and weight influence drug dosing?
They affect drug distribution, metabolism, and clearance, requiring dosage adjustments
Why is understanding pharmacokinetics crucial in clinical practice?
It helps in optimizing drug therapy for efficacy and safety in individual patients
What is the significance of drug solubility in absorption?
Solubility affects the rate and extent of a drug’s absorption into the bloodstream
How does blood-brain barrier affect drug distribution?
It restricts the entry of many drugs into the central nervous system
What is the role of protein binding in drug distribution?
It affects the drug’s free concentration in the plasma, influencing its pharmacological action
How can genetic factors influence drug metabolism?
Genetic variations can lead to differences in drug-metabolizing enzymes, affecting drug response
What is the concept of ‘bioavailability’ in pharmacokinetics?
The proportion of a drug that enters the circulation when introduced into the body and so is able to have a pharmacological effect
How does the first-pass effect influence drug bioavailability?
It refers to the reduction in concentration of a drug before it reaches systemic circulation
What is the significance of volume of distribution (Vd) in pharmacokinetics?
It represents the degree to which a drug is distributed in body tissues compared to the bloodstream
Why is the clearance (Cl) of a drug important in pharmacokinetics?
It indicates the body’s efficiency in eliminating the drug, impacting dosing and potential toxicity
How do protein-drug interactions affect drug efficacy?
They can influence the drug’s free concentration, distribution, and elimination, affecting its therapeutic effect
What does ‘pharmacokinetics’ refer to in medicine?
How the body absorbs, distributes, metabolizes, and excretes drugs
What is the significance of the absorption rate constant (Ka) in pharmacokinetics?
Indicates the speed at which a drug is absorbed into systemic circulation
Define ‘bioavailability’ in the context of drug absorption.
The proportion of a drug that enters systemic circulation intact and is available for therapeutic action
How does the first-pass effect impact drug bioavailability?
It reduces the concentration of a drug before it reaches systemic circulation, particularly for orally administered drugs
What is the ‘volume of distribution’ (Vd) and why is it important?
A theoretical volume that indicates how extensively a drug distributes into body tissues compared to the bloodstream
Explain the concept of drug ‘clearance’ in pharmacokinetics.
The rate at which a drug is removed from the body, indicating the efficiency of elimination processes
How do protein-drug interactions influence pharmacokinetics?
They affect the drugâs distribution and availability, as drugs can bind to plasma or tissue proteins
What is the significance of the half-life (T1/2) of a drug?
The time required for the plasma concentration of a drug to reduce by half, important for determining dosing intervals
Describe the role of metabolism in drug processing by the body.
Converts drugs into more water-soluble forms for excretion and can activate or deactivate the drug
Where is the primary site for drug metabolism?
Liver
Explain the role of excretion in pharmacokinetics.
The process of eliminating the drug or its metabolites from the body, primarily through the kidneys
How does renal function affect drug excretion?
Impaired renal function can decrease drug clearance, necessitating dosage adjustments
What factors can influence a drug’s pharmacokinetic profile?
Age, weight, genetic factors, liver and kidney function, and drug interactions
Why is understanding pharmacokinetics important in clinical practice?
To optimize drug dosing for efficacy and safety based on individual patient characteristics
How do drugs reach their target sites in the body?
Via systemic circulation after absorption, influenced by their pharmacokinetic properties like solubility and protein binding
What is the formula for calculating the half-life (T1/2) of a drug?
T1/2 = In 2 / k or 0.693 / k, where k is the elimination rate constant
How is drug clearance (Cl) calculated?
Cl = Rate of elimination / Plasma drug concentration
What are the two key parameters governs Bioavailability (F)?
Rate and Extent of unchanged drug absorbed into the systemic circulation from a particular dosage form.
