Modified release oral solid dosage form can be achieved by either incorporating matrix polymers (both hydrophilic or hydrophobic) in the batch formula to be compressed as a tablet or into a hard gelatin capsule shell to deliver the API over up to a period of 24 hours for a longer-lasting therapeutic effect. This is achieved by laying a film of diffusion-controlled membrane.
Modified-release solid dosage drug product can be classified into two major groups:
- Extended Release
- Delayed Release
Polymers for Modified Release Dosage Form
- Ethyl cellulose, Methyl Cellulose, Methacrylic acid pH independent polymers; Eudragit® RL and RS or NE/NM systems.
- Ethocel with a pore former has been widely used in the Pharmaceutical industry for extended-release coating.
- Many ready mixed aqueous dispersion are also available, e.g. Surelease® from Colorcon.
Pore former for Modified Release Dosage Form
- Various soluble ingredients; e.g., micronized lactose, mannitol, NaCl or hydrophilic ingredients; e.g, Natural gum, PVP, Na-CMC, HPMC, HPC, pH independent methacrylate, etc.
Delayed Release Dosage Form
The intention for a delayed release drug
product is to prevent the release of the API
mostly in the stomach; due to various
reasons:
- To protect drug unstable in acidic pH
- To protect esophagus or stomach from irritation: e.g., doxycycline hyclate, acetylsalicylic acid, iron compounds, etc.
- Delaying drug release due to food effect
- GI targeting at different sections of the small intestine or the colon.
Way to Control Delayed Release
- The pH-dependent polymer is the key element in controlling the dissolution of coated membrane.
- Drug can be released in a precise manner in specific sections of the GI tract or specific time after intake (specifically for food affect).
- Among the pH dependent polymers, Polyvinyl Acetate Phthalate and Methacrylate Eudragit® L and Eudragit® S are used.
- Sodium Alginate, from natural source due to its unique property of congealing in acidic media is also used alone as a clear suspension or with opacifier for enteric coating.
