The lower gastro-intestinal tract plays an important role in optimizing bio-availability and drug absorption – and therefore the effectiveness of many therapies. But delivering sensitive APIs to the right location is a challenge. In a series of ‘real world’ questions, we explore the options and solutions when it comes to the targeted delivery of acid-sensitive APIs.
Question: Which dosage form – enteric-coated or prolonged/delayed-release capsules – stays longest in the intestine?
Answer: Two principal factors affect the intestinal residency of dosage forms: the gastro-intestinal transit rate and the formulation of the dosage form itself. Enteric coating of a drug formulation or dosage form is one means of delaying release of active pharmaceutical ingredients (APIs).1 The primary purpose of enteric coating is to protect the active drug compound from degradation as a result of dissolution of the capsule by the acidic environment in the stomach.1 At the same time, the enteric coating protects the stomach from an API that might be harmful to the gastric mucosa. Upon entering the small intestine (duodenum), the enteric-coated dosage form initially encounters an ambient pH of typically around 6.1. The pH is not consistent throughout the small intestine, with a pH of around 7.4 in the terminal ileum.2 Dissolution of the protective enteric coating can occur at any stage throughout the small intestine, depending on the pH at which it has been designed to release its drug payload.
Gastro-intestinal transit rates have a significant influence on drug absorption and vary both between individuals and as a result of their fed or fasted state. Since it potentially determines the physical residence time of the capsule in the absorption site, rapid pH-dependent dissolution is critical to payload delivery.3
Delayed- or extended-release dosage forms may also contain an API, which is concentrated in a matrix (e.g. an “XL” tablet) that enables gradual and controlled release of the drug. So, ultimately, intestinal residency is a function of transit rate and capsule formulation. If the API is acid sensitive, enteric protection is essential, and if targeted or controlled release is required at a specific site, then a bespoke capsule providing both properties – such as Lonza’s Capsugel® Enprotect® capsule – may enable you to achieve the dissolution and release profile that is optimal for your API.
Learn more about Capsugel® Enprotect® capsule and how it could help solve your oral-dosage challenge.
1. Trenfield SJ, Basit AW. Modified drug release: Current strategies and novel technologies for oral drug delivery. Nanotechnology or Oral Drug Delivery. 2020
2. Fallingborg J. Dan Med Bull. Intraluminal pH of the human gastrointestinal tract. PMID: 10421978 Review https://pubmed.ncbi.nlm.nih.gov/
3. Kimura T, Higaki K. Biol & Pharm Bull. 2002;25(2):149–164.
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