Functional Film Coating by BIOGRUND

Controlling the drug release with functional film coating?

Why not!

Functional Film Coatings

Definition of “Functional Film Coating”:

A functional film coating has an influence on the drug release and is used to modify the release of API and achieve the desired tablet performance. As well as for other solid dosage forms like capsules, granules or pellets.
Therefore non-functional film coating is not related to the API. It is more for aesthetic, mechanical stability, marketing reasons (color) or easier intake (swallowability).

Why use functional film coating?

The tablet core is coated with a functional coating, e.g. to achieve an odor or taste masking of APIs that are bitter or bad of smell. Furthermore, it is possible to protect the API against environmental influences such as oxidation, UV radiation and moisture. Other functions include the targeted or delayed release of the active ingredient, protection against stomach acid or protection of mucous membrane and reduction of side effects.

Reasons for functional coating

1. Moisture Protection & Stabilization of the drug

Especially drugs susceptible to hydrolysis, require good moisture protection. This is mainly achieved by packaging and the use of desiccants. However, special moisture protection film coating systems such as AquaPolish® MS, AquaPolish® PRO, etc. can be very useful to protect the solid oral dosage form. The film coating provides moisture protection and can help increase stability of the tablet core. It also protects the dosage form during further processing (packaging/transport) by stabilizing a moisture-sensitive active ingredient and at the same time reducing possible incompatibilities with a second active ingredient in a fixed-dose combined pill (FDC). A coating with special moisture protection thus ensures that the active ingredient remains permanently isolated in the tablet core, especially in environments with high humidity

2. Taste & Odor masking

Masking bitter tasting and bad smelling API’s is necessary to make the intake of tablets as pleasant as possible for the patient and thus to increase patient compliance. The aim is to mask the taste for the time it takes to swallow the medication. An important intention is therefore to delay dissolution in the oral cavity without affecting rapid dissolution in the stomach. The bioavailability should not be affected.
Patients with dysphagia hold the tablet/granule/pellet significantly longer in their mouth. (“Pill swallowing by Adults with dysphagia” by Giselle Carnaby-Mann, 2005)
In addition, Dr. Mahmud Yunis (Technical Director, BIOGRUND) said that elderly people or people with problems when swallowing oral dosage forms sometimes have them in their mouth for up to 10 minutes before they have swallowed everything.
Coating systems formulated with synthetic polymers like AquaPolish® TC, AquaPolish® OM, Eudragit® E PO Ready-Mix are suitable to mask bad odor and taste of solid oral dosage forms.

3. Enteric Protection – modified / delayed release

Traditionally, enteric coatings with pH-sensitive polymers were used to delay the release of certain active ingredients. This is done either to protect the product from the acidic stomach environment or to protect the stomach from gastric irritation caused by the API.

GI Tract (pH Values/Retention time)

Basically it can be distinguished between a fast and a modified-release formulation.
In order to prevent that the dosage form disintegrates already in the mouth or esophagus, a water-soluble coating is sufficient, since the retention times could be low.
To perform drug release only upon entry into the small intestine, polymers must be used, which are dissolved only above the pH value of 5.5.

Polymer requirements

Enteric-coated drugs do not dissolve in the acidic condition of the stomach. While they readily dissolve in the alkaline pH of the small intestine.
Important: An enteric coating is only effective as long as the tablet is not crushed or cut/tilled before taking it.

  • Stability in gastric fluid: pH 1.0 – 1.5 (fasted), pH 3.0 – 5.0 (fed)
  • Quick dissolution & drug release in the duodenum: pH > 6.0

For example: Polymer with a defined number of functional acidic groups.

NameAvailabilitySolubilityRelease site
L 30 D-55
L 100-55
Aqueous Dispersion, Powder≥ pH 5.5Duodenum
Dispersion 30%≥ pH 5.5Duodenum
MAE 100-55
Non-neutralized Powder≥ pH 5.5Duodenum
MAE 100 P
Pre-neutralized Powder≥ pH 5.5Duodenum
L 100
L 12,5
Powder, Organic Solution ≥ pH 6.0Jejunum
S 100
S 12,5
Powder, Organic Solution ≥ pH 7.0Ileum/colon
AquaPolish® ECustomized formulated film coating powder premixCustomizedCustomized

BIOGRUND formulates due to customized formulation independent of polymers. Even existing formulations can be reformulated & unwanted polymers replaced.

4. Product / Tablet design

The appearance of the product is defined by tablet shape, size and of course the film coating (functional and non-functional).
Important aspects of a tablet’s brand image are determined above all by distinctive colors and shapes. The color of a tablet helps the patient to distinguish between different medicines. The color also affects patient compliance and taste perception (e.g. pink = sweet).
Dysphagia – difficulty in swallowing solid oral dosage forms in elderly patients. This can be alleviated by the design and shape of the tablet (capsule, pellet, oblong, small), as well as by a film coating.


Film coating is often used in tablet development to overcome various universal challenges. While dysphagia, poor palatability and brand image can be addressed with non-functional film coating. In addition, functional film coating can handle the following challenges: control of the drug release, (delayed/modified release) taste/odor masking and moisture protection.
The stability of a tablet, capsule and co. can often be improved by the judicious selection of a film coating with reduced moisture permeability. PH sensitive film coatings are typically used to delay and modify drug release to achieve better patient outcomes.

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