Classification systems Flashcards
What is the Biopharmaceutical Classification System (BCS)?
A scientific framework for classifying drugs into four classes based on dose, solubility, and permeability for oral administration.
What are the criteria used in the BCS?
Maximum dosage required, aqueous solubility across the GI pH range, and permeability across the GI mucosa.
What defines high solubility in the BCS?
If the highest dose strength dissolves in 250 mL or less of water at pH 1–7.5 at 37 °C.
What defines high permeability in the BCS?
If absorption in humans exceeds 90% of the administered dose.
What defines a rapidly dissolving drug product?
85% or more of the labeled amount dissolves within 30 minutes using USP Apparatus 1 or 2 in 900 mL or less of buffer.
Describe BCS Class I drugs.
High solubility and high permeability; good bioavailability.
Describe BCS Class II drugs.
Low solubility and high permeability; bioavailability affected by dissolution.
Describe BCS Class III drugs.
High solubility and low permeability; bioavailability affected by permeability.
Describe BCS Class IV drugs.
Low solubility and low permeability; poor oral bioavailability.
Why is 250 mL used as the standard volume in solubility testing?
It approximates a glass of water that patients typically take with a tablet.
Why is the pH range 1–7.5 used in BCS solubility tests?
It reflects the expected pH range of the gastrointestinal tract.
What apparatus are used to test if a drug is rapidly dissolving?
USP Apparatus 1 (basket) or 2 (paddle).
How is permeability assessed in the BCS?
Based on extent of absorption in humans; must exceed 90% of dose using mass balance or comparison with IV dose.
Why is permeability the hardest BCS criterion to determine?
It requires human mass balance or absolute bioavailability studies, or validated in vitro systems.
Name three methods used to assess drug permeability.
Computational/in silico (e.g., log P), physicochemical (e.g., partition coefficient), biological methods (e.g., in vitro, in vivo).
Describe the in vitro cell culture technique for permeability testing.
Epithelial cells are grown on a filter membrane to mimic intestinal cells; well correlated with human data.
What is the formulation approach for BCS Class I drugs?
Simple solid oral dosage forms; good bioavailability expected.
What is the formulation strategy for BCS Class II drugs?
Improve dissolution through particle size reduction or solid dispersions.
What is the formulation strategy for BCS Class III drugs?
Use early release dosage forms and permeation enhancers.
What is the formulation strategy for BCS Class IV drugs?
Use alternative routes, lipid-based vehicles, or prodrugs.
Why is the BCS important?
Helps in drug candidate selection, formulation design, and can reduce need for human studies.
What does the BCS classification inform?
Best formulation strategies based on dose, solubility, and permeability.
