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BENEFITS OF ENTERIC COATED CAPSULES

A QUAY PHARMA EXPERIMENT COMPARING ENTERIC CAPSULE SHELL VS. ENTERIC COATED CAPSULES

Introduction Disintegration Test Analysis

One of the questions we are asked most by our clients is which capsule technology we would recommend they use. The two main capsule technologies available, which offer enteric protection, are enteric capsule shells and enteric-coated capsules.

Both enteric capsules and enteric-coated capsules are commercially available and both claim to deliver drug substances into the small intestine unharmed by the harsh acidic conditions of the human stomach. The main issue with the enteric protection of capsules is the lack of clarity with respect to in vivo performance: in vitro capsule performance; can be interpreted several ways at face value and shown to perform adequately, however, in vivo, this might not be true.

What are ‘Enteric Shell Capsules’
What are ‘Enteric Coated Capsules’

Disintegration Test

To gain full insight, a disintegration test was performed and capsules were removed at 30-minute intervals to have the contents examined. Alongside this, active capsules were tested against a GMP compliant Viable Cell Count (VCC) method from the same time intervals. All analysis was compliant with the European Pharmacopoeia and was designed to provide more in-depth and detailed data over standard disintegration testing. As can be seen from the images, both the enteric-coated and enteric shell capsules contain white, free-flowing powder.

Enteric Shell Capsule

Enteric Coated Capsule

After only 30 minutes of exposure to 0.1M HCl, which mimics the acidic conditions of the human stomach, there are clear signs of acid ingress into the enteric shell capsule, as evident by:
1. The deep blue colour and agglomeration of the powder.
2. A partial reduction in the viability of the drug substance by VCC analysis*.

In contrast, the contents of the enterically coated capsules remain as a white, free-flowing powder with no reduction in VCC*.

Enteric Shell Capsule (clear signs of acid ingress)

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30 Minutes

Enteric Coated Capsule

At 120-minute exposure time, there is now a profound difference between the two enteric protection technologies. The appearance and VCC* of the contents of the enterically coated capsules remain the same as before the test. However, the following suggests catastrophic penetration of acid into the enteric shell capsule:
1. The contents have agglomerated severely and are stained heavily by the blue dye.
2. Most of the viability has been lost according to VCC measurements* described below

Enteric Shell Capsule (progressive signs of acid ingress)

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120 Minutes

Enteric Coated Capsule

Viable Cell Count Analysis

In addition to disintegration testing, capsules containing living bacteria were also sampled at the same intervals. These were then analysed for cell viability (VCC = Viable Cell Count), the results of which can be seen in the graph below The two capsule types perform very differently across the disintegration test:

(a) Enteric-Coated Capsules (Blue line): VCC values remain consistent across the disintegration test i.e. essentially no change in cell viability.

(b) Enteric Shell Capsules (Red line): A 50% decrease in viability is seen within 30 minutes which continues to decrease.

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