Question:
The rate limiting step for the absorption of controlled release tablet is the:
The rate limiting step for the absorption of controlled release tablet is the:
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In controlled release formulations, the dissolution of the drug is often the slowest step, determining the overall release and absorption rate.
Updated On: Jul 14, 2026
- Metabolism of the drug
- Excretion of the drug
- Dissolution of the drug
- Distribution of the drug
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The Correct Option is C
Approach Solution - 1
For controlled release tablets, the rate limiting step for absorption is typically the dissolution of the drug. This is because the drug needs to dissolve in the gastrointestinal tract before it can be absorbed into the bloodstream. The controlled release mechanism is designed to slow down the dissolution rate for prolonged therapeutic effect.
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Approach Solution -2
Drug absorption from a tablet follows a set order of events, and the rate limiting step is whichever one takes the longest and controls how fast the rest can proceed. Checking each proposed step against a controlled-release tablet:
- Metabolism of the drug: Metabolism happens after the drug has already entered the bloodstream and reached the liver or other tissues. It is a downstream event that follows absorption, so it cannot be the step limiting how fast absorption itself occurs.
- Excretion of the drug: Excretion, the removal of the drug or its metabolites from the body, happens even later in the drug's journey, well after absorption and distribution are complete. It plays no role in controlling the speed of absorption.
- Dissolution of the drug: Before a drug can cross the intestinal wall and enter the bloodstream, it must first dissolve into solution within the gastrointestinal fluids. A controlled-release tablet is deliberately engineered with a slow-releasing matrix or coating that makes dissolution happen gradually, and since the drug cannot be absorbed any faster than it dissolves, dissolution becomes the step that sets the pace for the entire absorption process.
- Distribution of the drug: Distribution is the movement of already-absorbed drug from the bloodstream into various tissues, which by definition happens only after absorption has taken place. It cannot be the limiting factor for a step that comes before it.
Since metabolism, excretion, and distribution all occur after a drug has already been absorbed, none of them can control how quickly absorption itself proceeds. Only dissolution happens before absorption and is deliberately slowed in a controlled-release design, making it the true rate-limiting step.
So the correct answer is Dissolution of the drug.
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