What is BCS classification?

According to the BCS classification system, drugs are classified based on their solubility and intestinal permeability. The full form of BCS is the Biopharmaceutics Classification System. Drugs are classified by considering their solubility, dissolution, and intestinal permeability. It is the most accepted classification system of drugs based on scientific framework.

As Per BCS, drugs are classified into the following classes based on solubility and permeability

Class 1: high solubility–high permeability
Class 2: low solubility–high permeability
Class 3: high solubility–low permeability
Class 4: low solubility–low permeability

Solubility – A drug is considered highly soluble when its highest dose is soluble in 250 ml water or less in the pH range of 1-8. From this, we can gain knowledge that a drug is classified based on volume sufficient to dissolve the highest dose. And a drug is considered to be having good dissolution rates when not less than 85 percent of label amount of drug dissolves in USP Apparatus 1 at 100 rpm. Permeability of drug is based on studies like in vivo intestinal perfusion studies that we are going to discuss in coming articles.

1. Class 1 drugs are highly soluble and well absorbed and show good bioavailability
2. Class -2 drugs have good absorption rate and have low solubility rates which impacts the dissolution rate of the drug
3. Class-3 drugs have poor permeability characteristics and have good solubility
4. Class -4 drugs possess significant challenges to the formulators as they have very low solubility and very low permeability.

Examples of class-1 drugs

• Metoprolol
• Propranolol
• Verapamil
• Lisinopril

Examples of Class-2 drugs

• Ketoconazole
• Carbamazepine

Examples of Class -3 drugs

• Acyclovir
• Atenolol

Examples of Class – 4 drugs

• Hydrochlorothiazide
• Furosemide