Biopharmaceutics Classification System

The Biopharmaceutics Classification System is a scientific framework for classifying drug substances based on their Aqueous Solubility and Intestinal Permeability.

When combined with the dissolution of the drug product, the BCS takes into account three major factors that govern the rate and extent of drug adsorption from IR solid oral dosage forms. These factors are Dissolution, Solubility, and Intestinal Permeability.

The BCS aims to provide a regulatory tool for the replacement of certain BE studies by conducting accurate in-vitro dissolution tests.

Biopharmaceutics Classification System

According to the Biopharmaceutics Classification System, Drug substances are classified as follows:

  • Class I – High Permeability, High Solubility
  • Class II – High Permeability, Low Solubility
  • Class III – Low Permeability, High Solubility
  • Class IV – Low Permeability, Low Solubility

Class I – High Permeability, High Solubility

  • Drugs dissolved rapidly.
  • Drugs are absorbed rapidly.
  • Rapid therapeutic action.
  • Excellent property.
  • Ideal for oral route.
  • e.g. Metoprolol, Diltiazem, Verapamil, Propranolol.

Class II – High Permeability, Low Solubility

  • Drugs dissolved slowly.
  • Drugs are absorbed rapidly.
  • Controlled released drugs.
  • Oral / IV route for administration.
  • e.g. Glibenclamide, Ezetimibe, Phenytoin, Nifedipine.

Class III – Low Permeability, High Solubility

  • Dissolved rapidly
  • Absorbance is limited
  • Incomplete bioavailability
  • Oral / IV route for administration
  • e.g. Cimetidine, Acyclovir, Captopril

Class IV – Low Permeability, Low Solubility

  • Low dissolution rate
  • Low permeability property
  • Slow or low therapeutic action
  • IV or other routes are required
  • e.g. Hydrochlorothiazide

Significance of Biopharmaceutics Classification System

  • The regulatory toll for replacement of certain BE studies.
  • It can save both time and money – if the immediate – release, orally administered drug meets specific criteria, and the FDA will grant a waiver for expensive and time-consuming bio-equivalence studies.
  • A valuable tool for formulation scientists for the selection of the design of formulated drug substances.
  • When integrated with other information provides a tremendous tool for efficient drug development.
  • Reduces cost and time of approving scale-up and post-approval challenges.
  • Applicable in both pre-clinical and clinical drug development processes.
  • Works as a guiding tool in the development of various oral drug delivery systems.
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