Question

Which of the following combination of properties in a drug makes it suitable for once a day sustained release tablet?

• A. Absorbed from the stomach, plasma half-life is 8 hours
• B. Administered thrice a day, plasma half-life is 6 hours
• C. Dose – 400 mg, administered thrice a day
• D. Dose 500 mg, shows extensive first pass metabolism

Hint:

Ideal sustained-release candidates have an intermediate half-life ($2 \text{ to } 8 \text{ hours}$). Drugs already administered multiple times a day benefit most from being converted into once-daily formulations.

Answer 1

The Correct Option is B

Concept: Sustained-release (SR) drug delivery systems are designed to maintain therapeutic blood levels over an extended period. Candidate drugs must possess specific biopharmaceutic and pharmacokinetic properties to be suitable for these formulations. Pharmacokinetic Evaluation Criteria:
• Elimination Half-life ($t_{1/2}$): Drugs with an intermediate half-life between 2 to 6 or 8 hours are ideal candidates for sustained release.
• If a drug's half-life is very short (less than 2 hours), a once-a-day formulation requires an excessively large dose to maintain therapeutic levels, increasing tablet size beyond acceptable limits.
• If the half-life is already long (greater than 12 hours), the drug naturally maintains therapeutic levels over 24 hours, making a sustained-release formulation unnecessary.
• Dosing Frequency: A drug that requires standard administration thrice daily with a half-life of 6 hours is an ideal candidate for conversion into a once-daily extended-release system, improving patient compliance.
• Deconstruction of other choices: Extensive first-pass metabolism or absorption limited strictly to a narrow stomach window make reliable sustained release throughout the intestinal tract difficult to achieve. Therefore, option (B) represents the most suitable pharmacokinetic profile for a sustained-release formulation.