Conversion from intravenous to oral dosing MCQs With Answer

Introduction: This quiz set focuses on conversion from intravenous (IV) to oral dosing — a key topic in Clinical Pharmacokinetics and Therapeutic Drug Monitoring for M.Pharm students. It covers the principles that determine oral bioavailability, equations for dose equivalence, the impact of first‑pass metabolism, nonlinear kinetics, enterohepatic recycling, formulation differences, and special populations (renal/hepatic impairment). Emphasis is placed on calculations used in practice, practical decision points when conversion is or is not appropriate, and the role of therapeutic drug monitoring to confirm exposure. These MCQs will help you apply quantitative and conceptual knowledge for safe and effective IV→oral transitions.

Q1. When converting an intravenous single dose to an oral single dose to achieve the same systemic exposure (AUC), which formula is correct?

• Oral dose = IV dose × F
• Oral dose = IV dose / F
• Oral dose = IV dose × Cl
• Oral dose = IV dose × Vd

Correct Answer: Oral dose = IV dose / F

Q2. You are converting a continuous IV infusion (steady state) to intermittent oral dosing with dosing interval τ. Which expression gives the oral dose per administration to maintain the same Css, assuming complete compliance and constant F?

• Oral dose = (Infusion rate × τ) × F
• Oral dose = (Infusion rate × τ) / F
• Oral dose = Css × Vd × F
• Oral dose = Css × Cl × Vd

Correct Answer: Oral dose = (Infusion rate × τ) / F

Q3. A drug shows high hepatic first‑pass extraction. What is the most important consequence when converting from IV to oral dosing?

• Oral bioavailability is high, so oral dose needs to be reduced
• Oral bioavailability is low, so oral dose will often need to be increased
• Clearance increases after oral dosing
• Volume of distribution changes with oral dosing

Correct Answer: Oral bioavailability is low, so oral dose will often need to be increased

Q4. In which clinical situation is automatic IV-to-oral conversion generally NOT recommended?

• Patient stabilized on IV therapy but able to tolerate oral intake
• Drug with narrow therapeutic index and highly variable oral bioavailability
• Drug with well-characterized, consistent oral F near 100%
• Chronic stable therapy with existing oral equivalent dosage forms

Correct Answer: Drug with narrow therapeutic index and highly variable oral bioavailability

Q5. Why must conversion from IV to oral be cautious for drugs that display nonlinear (saturable) pharmacokinetics like phenytoin?

• Because bioavailability always increases with dose for nonlinear drugs
• Because changes in dose can produce disproportionate changes in clearance and plasma concentrations
• Because Vd becomes dose‑dependent and unpredictable
• Because first‑pass metabolism is abolished in nonlinear kinetics

Correct Answer: Because changes in dose can produce disproportionate changes in clearance and plasma concentrations

Q6. A patient receives a continuous IV infusion at 24 mg/hr. You will switch to oral dosing every 12 hours; oral bioavailability is 60%. What oral dose per administration is required to maintain equivalent exposure?

• 240 mg
• 360 mg
• 480 mg
• 576 mg

Correct Answer: 480 mg

Q7. A single IV bolus of 100 mg produced a reference AUC. If a drug’s oral bioavailability is 25%, what oral single dose would be expected to give the same AUC (ignoring absorption rate differences)?

• 25 mg
• 250 mg
• 400 mg
• 500 mg

Correct Answer: 400 mg

Q8. What is the primary role of therapeutic drug monitoring (TDM) when converting a patient from IV to oral therapy?

• To measure the oral bioavailability directly
• To ensure that measured plasma concentrations reach and remain within the target therapeutic range after conversion
• To determine Vd for dose calculation
• To estimate hepatic blood flow in the patient

Correct Answer: To ensure that measured plasma concentrations reach and remain within the target therapeutic range after conversion

Q9. How does enterohepatic recirculation (EHR) typically affect oral exposure compared with IV dosing, and what implication does that have for IV→oral conversion?

• EHR reduces oral exposure and shortens half‑life, making oral doses larger
• EHR increases and prolongs oral exposure unpredictably, complicating conversion and possibly requiring dose adjustments
• EHR affects only IV dosing, not oral dosing
• EHR always doubles oral bioavailability so IV doses should be halved

Correct Answer: EHR increases and prolongs oral exposure unpredictably, complicating conversion and possibly requiring dose adjustments

Q10. Which of the following conversion scenarios is likely to be most problematic because of differences in active form after oral administration?

• Switching from IV active metabolite to oral prodrug that requires first‑pass activation
• Switching from IV to oral when both forms are identical active drug
• Switching between IV and oral formulations with identical excipients
• Switching when oral F is 100%

Correct Answer: Switching from IV active metabolite to oral prodrug that requires first‑pass activation

Q11. Which pharmacokinetic parameter is generally independent of route of administration and therefore unchanged when switching between IV and oral routes (assuming no route‑dependent changes in clearance)?

• Oral bioavailability (F)
• Absorption rate constant (ka)
• Clearance (Cl)
• First‑pass extraction ratio

Correct Answer: Clearance (Cl)

Q12. If a drug shows dose‑dependent (saturable) absorption at higher oral doses, what effect does this have when increasing oral dose to match IV exposure?

• Absorption becomes more efficient so less oral dose is needed
• Proportional increase in exposure is guaranteed
• Further increases in oral dose may yield smaller than expected increases in exposure, undermining simple dose scaling by 1/F
• Oral bioavailability becomes 100% at high doses

Correct Answer: Further increases in oral dose may yield smaller than expected increases in exposure, undermining simple dose scaling by 1/F

Q13. For a drug with a high hepatic extraction ratio, oral bioavailability (F) is most sensitive to changes in which physiological factor?

• Plasma protein binding only
• Renal blood flow
• Hepatic blood flow
• Gastric pH

Correct Answer: Hepatic blood flow

Q14. When switching from IV to oral dosing for a drug with a long half‑life where immediate therapeutic concentration is required, what dosing strategy is most appropriate?

• Use only maintenance oral dose and wait several half‑lives to reach Css
• Administer an appropriate loading dose (IV or oral) followed by maintenance oral dosing
• Reduce the maintenance dose to half when switching
• Avoid any loading dose because it increases toxicity

Correct Answer: Administer an appropriate loading dose (IV or oral) followed by maintenance oral dosing

Q15. Which oral formulation is generally preferred when converting from continuous IV infusion to oral dosing to reduce peak‑to‑trough fluctuations for a drug with a short half‑life?

• Immediate‑release (IR) tablets
• Sustained‑release (SR) or controlled‑release (CR) formulations
• Intramuscular depot injection
• Intravenous bolus equivalent

Correct Answer: Sustained‑release (SR) or controlled‑release (CR) formulations

Q16. Steady‑state plasma concentration is 10 mg/L and total clearance is 2 L/hr during IV infusion. Oral bioavailability is 50%. What oral dose (mg) every 8 hours will maintain the same average concentration?

• 160 mg every 8 hours
• 320 mg every 8 hours
• 480 mg every 8 hours
• 640 mg every 8 hours

Correct Answer: 320 mg every 8 hours

Q17. After converting from IV to oral, which pharmacokinetic metric is most informative to confirm equivalent systemic exposure over the dosing interval?

• Maximum concentration (Cmax) only
• Trough concentration only (Ctrough)
• Area under the concentration‑time curve (AUC) over the dosing interval
• Volume of distribution (Vd)

Correct Answer: Area under the concentration‑time curve (AUC) over the dosing interval

Q18. In a patient with severe renal impairment switching from IV to oral for a renally‑cleared drug, what is the primary consideration?

• Increase oral dose because F is decreased in renal failure
• No dose adjustments are needed for either route
• Reduce maintenance dose based on reduced clearance; oral bioavailability is usually unchanged
• Switching to oral always avoids accumulation in renal failure

Correct Answer: Reduce maintenance dose based on reduced clearance; oral bioavailability is usually unchanged

Q19. A drug given IV as 50 mg every 8 hours is being converted to oral dosing. Oral bioavailability is 70%. What approximate oral dose should be given every 8 hours to maintain equivalent exposure?

• 35 mg every 8 hours
• 50 mg every 8 hours
• 71 mg every 8 hours
• 100 mg every 8 hours

Correct Answer: 71 mg every 8 hours

Q20. Which of the following statements about IV→oral conversion is FALSE?

• Oral doses are often higher than IV doses when F < 1
• Therapeutic drug monitoring can help confirm equivalent exposure after conversion
• Oral bioavailability is always predictable and constant among all patients
• Special populations (hepatic/renal disease, GI dysfunction) may require individualized conversion strategies

Correct Answer: Oral bioavailability is always predictable and constant among all patients

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