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Questions and Answers
How long will it take for the theophylline intravenous infusion to reach 93.75% of its final steady-state concentration?
How long will it take for the theophylline intravenous infusion to reach 93.75% of its final steady-state concentration?
- 7.4 h
- 32 h
- 24 h
- 48 min (correct)
In the context of the pharmacokinetics discussed, what does the term 'half-life' represent?
In the context of the pharmacokinetics discussed, what does the term 'half-life' represent?
- The time required for the drug concentration to decrease by half (correct)
- The time taken for the drug to reach steady state
- The total time for drug elimination
- The time taken for the drug concentration to double
What would be the elimination constant (Ke) of drug X given its half-life of 3 hours?
What would be the elimination constant (Ke) of drug X given its half-life of 3 hours?
- 0.231 (correct)
- 0.173
- 0.346
- 0.693
What is the elimination type for drug X based on the information given?
What is the elimination type for drug X based on the information given?
What is the initial plasma level (C0) if the plasma level at 6 hours is 5 mg/L?
What is the initial plasma level (C0) if the plasma level at 6 hours is 5 mg/L?
How is the half-life of drug X calculated based on the data provided?
How is the half-life of drug X calculated based on the data provided?
What is the correct formula to calculate the maintenance dose for tobramycin?
What is the correct formula to calculate the maintenance dose for tobramycin?
What is the amount of drug eliminated after 5 hours as per the provided data?
What is the amount of drug eliminated after 5 hours as per the provided data?
How much tobramycin should be administered every 6 hours to maintain a plasma concentration of 8 mg/L?
How much tobramycin should be administered every 6 hours to maintain a plasma concentration of 8 mg/L?
What is the concentration of drug X at 2 hours after administration?
What is the concentration of drug X at 2 hours after administration?
What loading dose of tobramycin is required to achieve a therapeutic plasma concentration of 8 mg/L?
What loading dose of tobramycin is required to achieve a therapeutic plasma concentration of 8 mg/L?
What is the remaining amount of drug X in the body after 4 hours as per the provided data?
What is the remaining amount of drug X in the body after 4 hours as per the provided data?
Which of the following represents the steady-state plasma concentration equation for a continuously administered drug?
Which of the following represents the steady-state plasma concentration equation for a continuously administered drug?
Given a continuously administered infusion of lidocaine at 2.9 mg/min, what is the expected steady-state plasma concentration?
Given a continuously administered infusion of lidocaine at 2.9 mg/min, what is the expected steady-state plasma concentration?
If the clearance and volume of distribution for theophylline are 48 mL/min and 35 L respectively, what pharmacokinetic property does this relate to?
If the clearance and volume of distribution for theophylline are 48 mL/min and 35 L respectively, what pharmacokinetic property does this relate to?
What is the relationship between half-life and plasma concentration over time?
What is the relationship between half-life and plasma concentration over time?
What is the amount of filtered drug that must be reabsorbed in the renal tubules if the renal clearance of inulin is 120 ml/min and the clearance of the drug is 18 ml/min, given that the drug is 40% protein bound?
What is the amount of filtered drug that must be reabsorbed in the renal tubules if the renal clearance of inulin is 120 ml/min and the clearance of the drug is 18 ml/min, given that the drug is 40% protein bound?
If a drug is eliminated by first-order kinetics and 100 mg is eliminated from a 200 mg dose in the first two hours, how much drug remains after 6 hours?
If a drug is eliminated by first-order kinetics and 100 mg is eliminated from a 200 mg dose in the first two hours, how much drug remains after 6 hours?
What is the loading dose required to obtain an initial plasma level of 5 mg/L in a patient weighing 70 kg?
What is the loading dose required to obtain an initial plasma level of 5 mg/L in a patient weighing 70 kg?
A 500 mg dose of a drug has therapeutic efficacy for 6 hours. Given the drug's half-life is 8 hours, how long would a 1-gram dose remain effective?
A 500 mg dose of a drug has therapeutic efficacy for 6 hours. Given the drug's half-life is 8 hours, how long would a 1-gram dose remain effective?
What is the steady-state level in plasma equivalent to if the pharmacokinetic characteristics of propranolol include Vd = 300 L/70 kg and the target plasma level is 20 μg/L?
What is the steady-state level in plasma equivalent to if the pharmacokinetic characteristics of propranolol include Vd = 300 L/70 kg and the target plasma level is 20 μg/L?
How much drug is eliminated after one half-life if the total dose is 200 mg?
How much drug is eliminated after one half-life if the total dose is 200 mg?
If a drug has a clearance of 18 ml/min and is 40% protein bound, what is the free fraction of the drug available for clearance?
If a drug has a clearance of 18 ml/min and is 40% protein bound, what is the free fraction of the drug available for clearance?
What is the calculated plasma level of a drug 6 hours after an intravenous bolus dose if the plasma level at 6 hours is noted to be 5 mg/L?
What is the calculated plasma level of a drug 6 hours after an intravenous bolus dose if the plasma level at 6 hours is noted to be 5 mg/L?
Flashcards
Renal Clearance
Renal Clearance
The volume of drug that is removed from the body per unit time. It is a measure of how quickly the body eliminates a drug.
Free Fraction (ff)
Free Fraction (ff)
The fraction of a drug that is not bound to plasma proteins. This free fraction is the only part of the drug that can be filtered by the kidneys and eliminated from the body.
Tubular Reabsorption
Tubular Reabsorption
The process where a drug is removed from the plasma and transported back into the bloodstream. It occurs in the renal tubules, reducing the amount of drug eliminated in urine.
Elimination Half-Life
Elimination Half-Life
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Loading Dose
Loading Dose
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Volume of Distribution (Vd)
Volume of Distribution (Vd)
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Oral Bioavailability (f)
Oral Bioavailability (f)
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Steady-State Level
Steady-State Level
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Maintenance Dose
Maintenance Dose
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Steady-State Plasma Concentration (Css) Continuous Infusion Equation
Steady-State Plasma Concentration (Css) Continuous Infusion Equation
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Drug Clearance
Drug Clearance
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Bioavailability
Bioavailability
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Initial Plasma Concentration (Co)
Initial Plasma Concentration (Co)
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Half-life
Half-life
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Drug Elimination
Drug Elimination
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Elimination Rate Constant (Ke)
Elimination Rate Constant (Ke)
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First Order Kinetics
First Order Kinetics
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Initial Redistribution Phase
Initial Redistribution Phase
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Steady State Concentration
Steady State Concentration
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Time to Reach Steady State
Time to Reach Steady State
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Study Notes
Practical 2 - Pharmacokinetic Problems
- Renal Clearance: A subject with a renal clearance of inulin at 120 ml/min is given a drug. The drug's clearance is measured at 18 ml/min. If the drug is 40% plasma protein bound, the amount of filtered drug reabsorbed in the renal tubules is 54 ml/min.
First-Order Elimination Kinetics
- Drug Dose and Elimination: A patient receives a 200 mg IV dose of a drug. 100 mg is eliminated in the first two hours. Assuming first-order elimination kinetics, 25 mg of the drug will remain after 6 hours.
- Half-Life: The elimination half-life is two hours. Each half-life reduces the amount in the body by 50%. At 6 hours, three half-lives have passed (200 mg to 100 mg, then 100 mg to 50 mg, and finally 50 mg to 25 mg).
Volume of Distribution and Loading Dose
- Total Body Water: If a drug distributes into total body water, and a patient weighs 70 kg (and 60% of body weight is water), the volume of distribution is 42 liters. A loading dose of 210 mg is needed to achieve an initial plasma level of 5 mg/L.
- Loading Dose Formula: Loading dose (LD) = Volume of Distribution (Vd) x plasma concentration (CP).
Therapeutic Efficacy and Half-Life
- Drug Efficacy Duration: A 500 mg dose of a drug has therapeutic efficacy for 6 hours. The drug's half-life is 8 hours. A 1 gram dose will be effective for 14 hours (8 hours + 6 hours). Duration of effectiveness is not directly related to half-life. it's about drug concentration remaining above the minimum effective concentration in the body.
Propranolol Pharmacokinetics
- Pharmacokinetic Parameters: Propranolol has a volume of distribution (Vd) of 300 L/70 kg, a clearance (Cl) of 700 ml/min, and an oral bioavailability (f) of 0.25.
- Loading Dose Calculation: A loading dose of 24 mg is needed to achieve a steady-state plasma level of 20 µg/L. (Using the formula: LD = Vd x CP / f)
Bolus Dose and Half-Life
- Initial Plasma Level: A drug is administered as a bolus dose IV. At 6 hours post-injection, the plasma level is 5 mg/L. The volume of distribution (Vd) is 10 L, and the elimination half-life is 3 hours. The dose administered was 200 mg..
Tobramycin Maintenance Dose
- Pharmacokinetic Data: The patient's tobramycin clearance is 0.16 L/min and the volume of distribution (Vd) is 40 L.
- Calculating the Maintenance Dose: A maintenance dose of 460.8 mg is delivered intravenously every six hours to achieve a steady-state plasma concentration of 8 mg/L. (using formula: Maintenance dose = Clearance X Desired concentration / Bioavailability)
Aminoglycoside Pharmacokinetics
- Half-Life: A single intravenous bolus of an aminoglycoside administered to a 70 kg man. The elimination half-life of the drug can be calculated from the graph/data displayed.
- Elimination Constant: The elimination constant (Ke) of drug X is 0.231.
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