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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?
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?
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?
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?
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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?
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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?
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What is the correct formula to calculate the maintenance dose for tobramycin?
What is the correct formula to calculate the maintenance dose for tobramycin?
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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?
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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?
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What is the concentration of drug X at 2 hours after administration?
What is the concentration of drug X at 2 hours after administration?
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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?
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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?
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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?
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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?
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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?
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What is the relationship between half-life and plasma concentration over time?
What is the relationship between half-life and plasma concentration over time?
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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?
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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?
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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?
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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?
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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?
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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?
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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?
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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?
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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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Description
Test your knowledge on pharmacokinetic concepts including renal clearance, drug dose elimination, and volume of distribution. This quiz covers practical scenarios that apply first-order elimination kinetics and the calculations of loading doses. Perfect for students in pharmacology or healthcare fields.
