Question

For solid oral drug products, a change in the concentration of which of the following excipients is more likely to influence the bioavailability of a drug.

• A. Starch
• B. Magnesium stearate
• C. Microcrystalline cellulose
• D. Lactose

Answer 1

The Correct Option is B

To determine which excipient is more likely to influence the bioavailability of a drug in solid oral drug products, it's crucial to understand the role each excipient plays in the formulation.

1. Starch: Starch is commonly used as a disintegrant in oral tablets. It facilitates the disintegration of the tablet upon ingestion, which helps in releasing the active ingredient. Although it plays a role in the release, its impact on the direct bioavailability is lesser compared to lubricants.
2. Magnesium Stearate: Magnesium stearate is a commonly used lubricant in tablet formulations. It prevents ingredients from sticking to manufacturing equipment but is known to form hydrophobic films around particles. This can retard the dissolution rate of tablets, significantly influencing the bioavailability of the drug. Therefore, changes in the concentration of magnesium stearate can have a pronounced effect on drug bioavailability.
3. Microcrystalline Cellulose: This is primarily used as a binder and filler in tablet production. It provides hardness to tablets and aids in their disintegration, but like starch, its direct impact on bioavailability is less pronounced.
4. Lactose: Lactose acts mainly as a filler or diluent. Its primary role is to provide bulk to the formulation, and while it may impact the tablet's properties, its effect on bioavailability is limited compared to lubricants.

Considering these roles, Magnesium stearate is the excipient most likely to influence the bioavailability of a drug in solid oral drug products due to its role in modifying the dissolution and subsequent absorption of the active drug.