Welcome, PharmD students, to this MCQ quiz focusing on Intravenous (IV) Infusion! Unlike rapid IV bolus injections, IV infusions involve administering drugs at a constant rate over a period, allowing for more controlled plasma concentrations. This method is crucial for drugs with narrow therapeutic windows or those requiring sustained levels for efficacy. This quiz will test your understanding of the pharmacokinetics of continuous and intermittent IV infusions, including concepts like steady-state concentration, infusion rates, loading doses, and factors influencing drug levels. Let’s explore the dynamics of controlled drug delivery!
1. Continuous intravenous (IV) infusion is characterized by:
- a) Rapid injection of a drug in a small volume.
- b) Administration of a drug at a constant rate (zero-order input) over an extended period.
- c) Oral administration of a liquid formulation.
- d) A single, large dose given subcutaneously.
Answer: b) Administration of a drug at a constant rate (zero-order input) over an extended period.
2. During a continuous IV infusion, the plasma drug concentration:
- a) Reaches its peak immediately and then declines.
- b) Gradually increases until it reaches a plateau, known as steady state.
- c) Fluctuates widely between doses.
- d) Remains at zero until the infusion is stopped.
Answer: b) Gradually increases until it reaches a plateau, known as steady state.
3. The steady-state plasma concentration (Css) during a continuous IV infusion is achieved when:
- a) The rate of drug infusion is zero.
- b) The rate of drug absorption equals the rate of distribution.
- c) The rate of drug infusion equals the rate of drug elimination.
- d) The drug is completely eliminated from the body.
Answer: c) The rate of drug infusion equals the rate of drug elimination.
4. The steady-state plasma concentration (Css) during a continuous IV infusion can be calculated as:
- a) Infusion rate (R0) × Clearance (CL)
- b) Infusion rate (R0) / Clearance (CL)
- c) Clearance (CL) / Infusion rate (R0)
- d) Infusion rate (R0) × Volume of distribution (Vd)
Answer: b) Infusion rate (R0) / Clearance (CL) (Css = R0 / CL, also Css = R0 / (k * Vd))
5. If the infusion rate (R0) of a drug is doubled, and its clearance remains constant, the new steady-state plasma concentration (Css) will:
- a) Halve
- b) Remain the same
- c) Double
- d) Increase four-fold
Answer: c) Double
6. The time required to reach approximately 94-97% of the steady-state concentration during a continuous IV infusion is primarily determined by the drug’s:
- a) Infusion rate
- b) Volume of distribution
- c) Elimination half-life (approximately 4-5 half-lives)
- d) Bioavailability
Answer: c) Elimination half-life (approximately 4-5 half-lives)
7. The equation describing the plasma drug concentration (Ct) at any time (t) during a continuous IV infusion (before steady state, assuming a one-compartment model) is:
- a) Ct = Css × e^(-kt)
- b) Ct = Css × (1 – e^(-kt))
- c) Ct = R0 / (k × Vd × t)
- d) Ct = R0 × t
Answer: b) Ct = Css × (1 – e^(-kt)) (where Css = R0/CL or R0/(k*Vd))
8. If a drug has an elimination half-life of 6 hours, approximately how long will it take to reach steady state during a continuous IV infusion?
- a) 6 hours
- b) 12 hours
- c) 24-30 hours
- d) 48 hours
Answer: c) 24-30 hours (4-5 × 6 hours)
9. A loading dose (LD) may be administered at the beginning of a continuous IV infusion primarily to:
- a) Decrease the drug’s half-life.
- b) Reduce the drug’s clearance.
- c) Achieve the desired therapeutic steady-state concentration more rapidly.
- d) Increase the drug’s bioavailability.
Answer: c) Achieve the desired therapeutic steady-state concentration more rapidly.
10. The appropriate loading dose (LD) to achieve a target steady-state concentration (Css,target) can be calculated as:
- a) Css,target / Vd
- b) Css,target × Vd
- c) Css,target × CL
- d) Css,target / CL
Answer: b) Css,target × Vd
11. After a continuous IV infusion is stopped (assuming steady state had been reached), the plasma drug concentration declines:
- a) Linearly over time.
- b) In a zero-order fashion.
- c) Exponentially, following first-order elimination kinetics, similar to an IV bolus from Css.
- d) Remains at the steady-state level indefinitely.
Answer: c) Exponentially, following first-order elimination kinetics, similar to an IV bolus from Css.
12. If a patient’s drug clearance (CL) decreases (e.g., due to renal impairment) while the IV infusion rate (R0) is maintained, the resulting steady-state concentration (Css) will:
- a) Decrease
- b) Increase
- c) Remain unchanged
- d) Fluctuate more
Answer: b) Increase
13. One of the main advantages of administering a drug by continuous IV infusion is:
- a) Rapid achievement of peak concentration similar to an IV bolus.
- b) Avoidance of first-pass metabolism and ability to maintain a relatively constant plasma drug concentration.
- c) Suitability for all drugs, regardless of solubility.
- d) Reduced need for patient monitoring.
Answer: b) Avoidance of first-pass metabolism and ability to maintain a relatively constant plasma drug concentration.
14. A potential disadvantage of continuous IV infusion is:
- a) Increased fluctuation in plasma drug concentrations.
- b) Requirement for IV access, risk of infection, and potential for extravasation.
- c) Poor bioavailability.
- d) Significant first-pass effect.
Answer: b) Requirement for IV access, risk of infection, and potential for extravasation.
15. If the infusion of a drug is stopped after 2 half-lives, the plasma concentration will be approximately what percentage of the steady-state concentration?
- a) 25%
- b) 50%
- c) 75%
- d) 87.5%
Answer: c) 75% (After 1 t½ = 50% of Css; After 2 t½ = 50% + 25% = 75% of Css)
16. The rate of drug input during a continuous IV infusion is a _________ process.
- a) First-order
- b) Zero-order
- c) Second-order
- d) Variable-order
Answer: b) Zero-order
17. For a drug given by continuous IV infusion, if the desired Css is 10 mg/L and the drug’s clearance is 5 L/hr, what infusion rate (R0) is required?
- a) 2 mg/hr
- b) 0.5 mg/hr
- c) 50 mg/hr
- d) 10 mg/hr
Answer: c) 50 mg/hr (R0 = Css × CL = 10 mg/L × 5 L/hr)
18. Intermittent IV infusions differ from continuous IV infusions in that they:
- a) Provide a constant plasma concentration without any fluctuation.
- b) Involve administering the drug over short periods at regular intervals, leading to peaks and troughs in concentration.
- c) Are only used for drugs with very long half-lives.
- d) Do not require IV access.
Answer: b) Involve administering the drug over short periods at regular intervals, leading to peaks and troughs in concentration.
19. The elimination of most drugs from the body during and after an IV infusion follows ________ kinetics.
- a) Zero-order
- b) First-order
- c) Second-order
- d) Capacity-limited
Answer: b) First-order
20. If a loading dose is administered along with a continuous IV infusion, the goal is for the decline in concentration from the loading dose to be offset by:
- a) The drug’s metabolism.
- b) The increase in concentration from the infusion, ideally maintaining a level near Css.
- c) The drug’s distribution phase.
- d) The patient’s renal function.
Answer: b) The increase in concentration from the infusion, ideally maintaining a level near Css.
21. If the volume of distribution (Vd) of a drug increases, but the clearance (CL) and infusion rate (R0) remain the same, the steady-state concentration (Css) will:
- a) Increase
- b) Decrease
- c) Remain unchanged
- d) Become unpredictable
Answer: c) Remain unchanged (Css = R0 / CL; Vd does not directly determine Css, but affects time to Css and LD)
22. However, if Vd increases, the time to reach steady state during a continuous IV infusion will:
- a) Decrease (if half-life decreases)
- b) Increase (if half-life increases, as t½ is proportional to Vd/CL)
- c) Remain unchanged
- d) Be independent of Vd
Answer: b) Increase (if half-life increases, as t½ is proportional to Vd/CL)
23. Which factor does NOT directly influence the steady-state concentration (Css) achieved during a continuous IV infusion?
- a) Infusion rate (R0)
- b) Drug clearance (CL)
- c) Drug’s elimination half-life (t½) (It determines time to Css, not Css itself)
- d) Drug bioavailability (F, which is 1 for IV)
Answer: c) Drug’s elimination half-life (t½) (It determines time to Css, not Css itself)
24. The concentration of a drug in plasma (Ct) just before stopping a continuous infusion that has reached steady state is:
- a) C0
- b) Cmin,ss
- c) Css
- d) Half of Css
Answer: c) Css
25. If an infusion is run for a very long time (e.g., 10 half-lives), the plasma concentration will be:
- a) Still rising significantly.
- b) At approximately 100% of the steady-state concentration.
- c) Declining rapidly.
- d) Equal to the loading dose concentration.
Answer: b) At approximately 100% of the steady-state concentration.
26. If a drug has a clearance of 2 L/hr and a Vd of 20 L, what is its elimination rate constant (k)?
- a) 0.1 hr⁻¹
- b) 10 hr⁻¹
- c) 0.05 hr⁻¹
- d) 40 hr⁻¹
Answer: a) 0.1 hr⁻¹ (k = CL / Vd = 2 L/hr / 20 L)
27. Using the information from Q26 (k=0.1 hr⁻¹), what is the drug’s half-life?
- a) 1.44 hr
- b) 6.93 hr
- c) 10 hr
- d) 20 hr
Answer: b) 6.93 hr (t½ = 0.693 / k = 0.693 / 0.1 hr⁻¹)
28. If an infusion is started at 10 mg/hr for the drug in Q26 & Q27 (CL=2 L/hr), what will be the Css?
- a) 2 mg/L
- b) 5 mg/L
- c) 10 mg/L
- d) 20 mg/L
Answer: b) 5 mg/L (Css = R0 / CL = 10 mg/hr / 2 L/hr)
29. To achieve the Css of 5 mg/L (from Q28) immediately for the drug in Q26 (Vd=20L), what loading dose would be needed?
- a) 10 mg
- b) 20 mg
- c) 50 mg
- d) 100 mg
Answer: d) 100 mg (LD = Css × Vd = 5 mg/L × 20 L)
30. For intermittent IV infusions, the peak concentration (Cmax,ss) is achieved:
- a) Just before the next infusion starts.
- b) At the midpoint of the dosing interval.
- c) At the end of the short infusion period.
- d) It remains constant.
Answer: c) At the end of the short infusion period.
31. For intermittent IV infusions, the trough concentration (Cmin,ss) is achieved:
- a) Immediately after the infusion ends.
- b) At the midpoint of the dosing interval.
- c) Just before the next infusion period begins.
- d) It is always zero.
Answer: c) Just before the next infusion period begins.
32. One reason to choose intermittent IV infusion over continuous IV infusion might be:
- a) To achieve more constant plasma levels.
- b) For drugs that are unstable in solution over long periods or to reduce certain concentration-dependent toxicities.
- c) To ensure the drug is eliminated more slowly.
- d) Because it requires less frequent IV access.
Answer: b) For drugs that are unstable in solution over long periods or to reduce certain concentration-dependent toxicities.
33. The degree of fluctuation between peak and trough concentrations during intermittent IV infusion is influenced by:
- a) Only the infusion duration.
- b) The dosing interval, infusion duration, and drug’s half-life.
- c) Only the drug’s clearance.
- d) Only the drug’s Vd.
Answer: b) The dosing interval, infusion duration, and drug’s half-life.
34. The principle of superposition can be applied to predict drug concentrations during:
- a) Only single IV bolus administration.
- b) Only continuous IV infusion.
- c) Both multiple IV bolus dosing and intermittent IV infusions.
- d) Only oral administration.
Answer: c) Both multiple IV bolus dosing and intermittent IV infusions.
35. If a drug is administered as a short IV infusion (e.g., over 30 minutes) repeatedly, the pharmacokinetic profile during the infusion period resembles:
- a) A zero-order elimination process.
- b) A continuous IV infusion approaching steady state (if the infusion is long enough relative to half-life).
- c) An oral absorption phase.
- d) A purely distribution phase.
Answer: b) A continuous IV infusion approaching steady state (if the infusion is long enough relative to half-life).
36. After the short infusion period ends in an intermittent regimen, the drug concentration declines following:
- a) Zero-order kinetics.
- b) First-order kinetics, as if an IV bolus was given (starting from the concentration at the end of infusion).
- c) Michaelis-Menten kinetics.
- d) No decline occurs until the next infusion.
Answer: b) First-order kinetics, as if an IV bolus was given (starting from the concentration at the end of infusion).
37. The main purpose of calculating Css or target concentrations for IV infusions is to:
- a) Maximize drug cost.
- b) Ensure drug concentrations are within the therapeutic range to optimize efficacy and minimize toxicity.
- c) Standardize all infusion rates.
- d) Only to determine the duration of therapy.
Answer: b) Ensure drug concentrations are within the therapeutic range to optimize efficacy and minimize toxicity.
38. If a patient receives a loading dose that is too high relative to their Vd for the target Css, they may experience:
- a) Delayed onset of action.
- b) Initial subtherapeutic concentrations.
- c) Initial supratherapeutic concentrations and potential toxicity.
- d) No effect on initial concentrations.
Answer: c) Initial supratherapeutic concentrations and potential toxicity.
39. If a maintenance infusion rate is set too low for a patient’s clearance, the achieved Css will be:
- a) Higher than desired.
- b) Lower than desired.
- c) Exactly as desired.
- d) Unpredictable.
Answer: b) Lower than desired.
40. A drug administered by IV infusion bypasses which pharmacokinetic process?
- a) Distribution
- b) Metabolism
- c) Absorption (from site of administration into systemic circulation)
- d) Excretion
Answer: c) Absorption (from site of administration into systemic circulation)
41. If a continuous IV infusion is maintained for 3 half-lives, the plasma drug concentration will be approximately what percentage of Css?
- a) 50%
- b) 75%
- c) 87.5%
- d) 93.75%
Answer: c) 87.5% (1 t½ = 50%; 2 t½ = 75%; 3 t½ = 87.5%)
42. For drugs with very short half-lives (e.g., minutes), which method of IV administration is often preferred to maintain therapeutic levels?
- a) Infrequent IV bolus injections
- b) Continuous IV infusion
- c) Oral administration
- d) Intramuscular injection
Answer: b) Continuous IV infusion
43. Stopping an IV infusion and observing the rate of decline in plasma concentration can be used to estimate the patient’s:
- a) Absorption rate constant.
- b) Elimination half-life and clearance (if infusion rate and Css were known).
- c) Bioavailability.
- d) First-pass metabolism.
Answer: b) Elimination half-life and clearance (if infusion rate and Css were known).
44. The choice between continuous vs. intermittent IV infusion for a drug often depends on:
- a) The color of the drug solution.
- b) The drug’s stability, desired concentration profile (e.g., need for constant levels vs. peaks/troughs), and clinical convenience.
- c) The patient’s preferred route.
- d) The cost of IV bags only.
Answer: b) The drug’s stability, desired concentration profile (e.g., need for constant levels vs. peaks/troughs), and clinical convenience.
45. When an IV infusion is started, the rate of change of drug in the body is equal to:
- a) Rate of elimination only.
- b) Rate of infusion minus rate of elimination.
- c) Rate of infusion plus rate of elimination.
- d) Rate of distribution only.
Answer: b) Rate of infusion minus rate of elimination.
46. If the target Css for a drug is 20 mg/L and its Vd is 10 L, an ideal IV loading dose would be:
- a) 2 mg
- b) 20 mg
- c) 100 mg
- d) 200 mg
Answer: d) 200 mg (LD = Css × Vd = 20 mg/L × 10 L)
47. Drugs that exhibit concentration-dependent killing (e.g., aminoglycosides) are often administered via:
- a) Slow continuous IV infusion to maintain low constant levels.
- b) Intermittent IV infusions to achieve high peak concentrations.
- c) Oral route only.
- d) IV bolus only once a week.
Answer: b) Intermittent IV infusions to achieve high peak concentrations.
48. The primary determinant of how quickly steady state is approached during IV infusion is the drug’s half-life, not the infusion rate. Changing the infusion rate will change:
- a) The time to reach steady state.
- b) The value of the steady-state concentration (Css).
- c) The drug’s volume of distribution.
- d) The drug’s bioavailability.
Answer: b) The value of the steady-state concentration (Css).
49. A practical reason for administering a loading dose when starting an IV infusion for a drug with a long half-life is to:
- a) Reduce the total amount of drug given.
- b) Avoid the delay in achieving therapeutic concentrations that would occur if only a maintenance infusion was started.
- c) Decrease the risk of side effects.
- d) Make the infusion process shorter.
Answer: b) Avoid the delay in achieving therapeutic concentrations that would occur if only a maintenance infusion was started.
50. Understanding the pharmacokinetics of IV infusions allows pharmacists to:
- a) Only prepare the IV admixture.
- b) Design and adjust infusion regimens, calculate loading doses, and predict patient-specific concentrations to optimize therapy.
- c) Administer anesthesia.
- d) Prescribe all IV medications.
Answer: b) Design and adjust infusion regimens, calculate loading doses, and predict patient-specific concentrations to optimize therapy.