The Biopharmaceutics Classification System is a system to differentiate the drugs on the basis of their solubility and permeability.^[1]

Jump to BCS classes. Biopharmaceutical Classification System (BCS) drug substances are classified to four. Class II - high permeability, low solubility. According to the Biopharmaceutics Classification System, MLT is a class II drug exhibiting a very short half-life and minimal and variable bioavailability.

This system restricts the prediction using the parameters solubility and intestinal permeability. The solubility classification is based on a United States Pharmacopoeia (USP) aperture. The intestinal permeability classification is based on a comparison to the intravenous injection. All those factors are highly important because 85% of the most sold drugs in the United States and Europe are orally administered^{[citation needed]}.

BCS classes[edit]

According to the Biopharmaceutical Classification System (BCS) drug substances are classified to four classes upon their solubility and permeability:^[1]

• Class I - high permeability, high solubility
  • Example: metoprolol, paracetamol^[2]
  • Those compounds are well absorbed and their absorption rate is usually higher than excretion.
• Class II - high permeability, low solubility
  • Example: glibenclamide, bicalutamide, ezetimibe, aceclofenac
  • The bioavailability of those products is limited by their solvation rate. A correlation between the in vivo bioavailability and the in vitro solvation can be found.
• Class III - low permeability, high solubility
  • Example: cimetidine
  • The absorption is limited by the permeation rate but the drug is solvated very fast. If the formulation does not change the permeability or gastro-intestinal duration time, then class I criteria can be applied.
• Class IV - low permeability, low solubility
  • Example: Bifonazole
  • Those compounds have a poor bioavailability. Usually they are not well absorbed over the intestinal mucosa and a high variability is expected.

Definitions[edit]

The drugs are classified in BCS on the basis of solubility, permeability, and dissolution.

Solubility class boundaries are based on the highest dose strength of an immediate release product. A drug is considered highly soluble when the highest dose strength is soluble in 250 ml or less of aqueous media over the pH range of 1 to 7.5. The volume estimate of 250 ml is derived from typical bioequivalence study protocols that prescribe administration of a drug product to fasting human volunteers with a glass of water.

Permeability class boundaries are based indirectly on the extent of absorption of a drug substance in humans and directly on the measurement of rates of mass transfer across human intestinal membrane. Alternatively non-human systems capable of predicting drug absorption in humans can be used (such as in-vitro culture methods). A drug substance is considered highly permeable when the extent of absorption in humans is determined to be 90% or more of the administered dose based on a mass-balance determination or in comparison to an intravenous dose.

For dissolution class boundaries, an immediate release product is considered rapidly dissolving when no less than 85% of the labeled amount of the drug substance dissolves within 15 minutes using USP Dissolution Apparatus 1 at 100 RPM or Apparatus 2 at 50 RPM in a volume of 900 ml or less in the following media: 0.1 N HCl or simulated gastric fluid or pH 4.5 buffer and pH 6.8 buffer or simulated intestinal fluid.

See also[edit]

• ADME

References[edit]

1. ^ ^abMehta M (2016). Biopharmaceutics Classification System (BCS): Development, Implementation, and Growth. Wiley. ISBN978-1-118-47661-1.
2. ^'Draft agreement'(PDF). www.ema.europa.eu. 22 June 2017. Retrieved 2019-07-03.

Further reading[edit]

• Folkers G, van de Waterbeemd H, Lennernäs H, Artursson P, Mannhold R, Kubinyi H (2003). Drug Bioavailability: Estimation of Solubility, Permeability, Absorption and Bioavailability (Methods and Principles in Medicinal Chemistry). Weinheim: Wiley-VCH. ISBN3-527-30438-X.
• Amidon GL, Lennernäs H, Shah VP, Crison JR (March 1995). 'A theoretical basis for a biopharmaceutic drug classification: the correlation of in vitro drug product dissolution and in vivo bioavailability'. Pharm. Res. 12 (3): 413–20. PMID7617530.

External links[edit]

• BCS guidance of the U.S. Food and Drug Administration

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