A film coated tablet is a type of oral medication where the tablet's surface is covered with a thin layer of a polymer or similar material. This coating serves several purposes, including masking the taste of the medication, protecting the tablet from moisture, and making it easier to swallow.

1. Film Coated Tablet
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2. Introduction
A film coated tablet is a type of oral medication where the tablet's surface
is covered with a thin layer of a polymer or similar material. This coating
serves several purposes, including masking the taste of the medication,
protecting the tablet from moisture, and making it easier to swallow.

3. Types of film coating
● The common way to classify the film coating is by the effect of the applied
coating on drug release characteristics. The film coating can be:
a. Immediate release film coating(nonfunctional coatings): These coatings are typically
readily soluble in water, so they do not significantly affect the biopharmaceutical
properties of the drug.
b. Modified release film coatings (functional coatings): These may be categorised as
extended-release coatings or delayed-release coatings.
● Delayed release coatings, also known as gastro-resistant coatings, are designed to be
soluble in high pH values, typically above 5-6. This value exists in the intestine and is
intended to either protect the drug from the stomach or prevent the release of the drug in the
stomach.

4. Description of the film-coating process
Film coating involves the application of a liquid, polymer-based
formulation to the surface of the tablets. Additionally, specialized
equipment is typically used to take advantage of the fast coating and high
degree of automation. Moreover, it is possible to use conventional
panning equipment.

5. The coating liquid, whether a solution or
suspension, contains a polymer along
with other ingredients such as pigments
and plasticizers, all in a suitable liquid
medium. This solution is sprayed onto a
rotating or fluidized mass of tablets.
Drying conditions are employed in the
process to remove the solvent, leaving
a thin coating around each tablet core
(Fig. 1). Fig. 1: illustration of the production of
film-coating tablets. (It takes from Remington
Essentials of Pharmaceutics)

6. Film Coating raw materials
The major components in any film coating formulation consist essentially of a
polymer, plasticizer, colorant, and solvent.
Types of film-coating polymers:
Polymers for immediate-release coatings:
1. Hydroxypropyl methylcellulose (HPMC)
2. Vinyl derivatives
3. Aminoalkyl methacrylate copolymers

7. Hydroxypropyl methylcellulose (HPMC)
Is the most widely used of cellulosic polymers. The polymer is
prepared by reacting alkali-treated cellulose first with methyl chloride
to introduce methoxy groups and then with propylene oxide to
introduce propylene glycol ether groups. It is readily soluble in
aqueous media and coatings that are relatively easy to apply.

8. Vinyl derivatives
Polyvinylpyrrolidone is the most commonly used vinyl polymer in
pharmaceutical applications, but its tackiness limits its use in film-coating
formulations. Copovidone, a copolymer of vinylpyrrolidone and vinyl
acetate, is preferred for its better film-forming properties. Another valuable
vinyl polymer is poly(vinyl alcohol) (PVA), derived from poly(vinyl acetate)
hydrolysis, which can produce film coatings with appropriate mechanical
properties and strong adherence to pharmaceutical tablets.

9. Aminoalkyl methacrylate copolymers
These acrylic copolymers dissolve easily in aqueous solutions with low
pH, making them crucial for coating dosage forms where effective taste
masking is essential. Typically, these polymers are applied as solutions in
organic solvents, although special forms can also be used to create
aqueous polymer dispersions.

10. Plasticizer
● Plasticizer is added to the formulation to enhance the flexibility of the coating,
reduce the risk of film cracking, and potentially enhance adhesion to the
substrate. The plasticizer must be highly compatible with the polymer and
remain in the film permanently to maintain consistent coating properties
during storage.
● Examples of typical plasticizers include glycerin, propylene glycol,
polyethylene glycols, triacetin, acetylated monoglycerides, citrate esters (e.g.,
triethyl citrate), or phthalate esters (e.g., diethyl phthalate).

11. Colorants
● Colorants are typically added to enhance product appearance, aid in product
identification, and improve the stability of coated products. They can be categorized
as water-soluble dyes or insoluble pigments. Water-soluble dyes are not suitable for
organic solvent-based film coating due to their lack of solubility in the solvent
system. Therefore, pigments, particularly aluminum lakes and inorganic pigments
like titanium dioxide and iron oxides, are preferred for coloring film-coating systems.
Using insoluble pigments in aqueous formulations is preferred because they:
a. Act as bulking agents to increase the solids content in the coating dispersion without significantly
increasing viscosity.
b. Are more light stable.
c. Are generally opaque, aiding in the stability of photolabile APls like nifedipine.
d. Additionally, decreasing coating permeability to moisture can potentially improve product stability.

12. Solvent
Film coating relies on various types of solvents, including alcohols (like methanol,
ethanol, and isopropyl alcohol), ketones (such as acetone), esters (like ethyl acetate),
chlorinated hydrocarbons (such as dichloromethane), and water.These solvents are
crucial for applying the coating to the substrate's surface. Additionally, effective
interaction between the solvent and polymer is essential for achieving optimal film
properties as the polymer solution dries and forms a solid film coating. The initial
interaction between solvent and polymer leads to maximum polymer chain extension,
resulting in films with high cohesive strength and excellent mechanical properties.
Moreover, film-coating formulations vary widely based on the materials used. They
typically consist of 5-25% (w/w) coating solids in the vehicle, with higher concentrations
preferred for aqueous formulations. These formulations usually contain 60-70% polymer,
6-7% plasticizer, and 20-30% pigment.

13. Reference
Aulton, M. (2018). Aulton’s pharmaceutics, the design and manufacture of
medicines. Edinburgh. : Elsevier
Felton. L. (2013). Remington Essentials of Pharmaceutics. London. UK:
Pharmaceutical Press.
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