Ultimate Guide to Evaluating and Purchasing Pharmaceutical Tablet Film Coatings

Changes in technology or a desire to achieve efficiencies may prompt pharmaceutical manufacturers to look at new suppliers. In this Technical Note we provide a defined approach for selecting and evaluating suppliers and their offerings. The process is split into three stages: Supplier Evaluation, Quality/Regulatory Compliance & Technical Evaluation, and Product Evaluation.


Supplier Evaluation

New supplier evaluation should involve verifying the ability to meet your requirements. This is an important step since supplier non-performance, even the most basic or for the simplest items, can have serious consequences for your company. Some of the important parameters to consider are:

  • Capacity (equipment scale, batch size, minimum order quantity)
  • Safety/Health/Environmental risk
  • Financial solvency/business stability
  • REACh compliance
  • Delivery performance(distribution footprint & lead time)
  • Supply chain management


For a long time, the film coatings supplier base was limited to two or three, mainly European and American companies. With the on-boarding of several small to medium suppliers, the situation is changing, bringing with it choice, innovation and flexibility for customers.


Regulatory Compliance and Technical Evaluation

The next consideration should be the supplier’s quality and regulatory track record. We suggest buyers evaluate suppliers on the basis of the following criteria:

  • cGMP compliance & other quality management systems
  • Recalls and complaints policies
  • Change management policies
  • Material management controls
  • Quality agreement
  • Production facilities
  • Documentation standards
  • Technical capabilities


Supplier technical capabilities assessment should look at their laboratory capabilities, technical skill/staff qualifications, new product development capabilities and process development/understanding capabilities. We suggest obtaining feedback from previous customers and asking about the supplier’s delivery performance, adherence to contract terms and ability to resolve issues.

Although film coatings are simple physical blends, their application is highly challenging and the availability of technical support is crucial to project success. Suppliers’ technical support is critical to timely and successful resolution of technical issues that may arise from time to time.


Product Evaluation

The final consideration is product assessment. The table below summarises some of the tests that can be performed on products to assess and compare their suitability.


Tests for powders/formulations Purpose Test
Odour Odours can inform about the presence of volatile ingredients, impurities or signs of degradation.

Caution: Some formulations may contain ammonia or solvents. Take extra care with such systems.

Record any distinctive odours and note if there are differences with existing product
Description Colour, texture & other observable characteristics are an indication of the quality of the powder Physical description, particle size, colour distribution/homogeneity, presence of fibres & other extraneous matter
Dry Draw Down Also known as Doctor Blade. It is a very simple and effective way to measure appearance and colour homogeneity of a film coating formulation Observe and make a note of any differences in appearance between samples
Sieve analysis Used to determine the particle size distribution of powdered coating formulation. Record the percentage of different grain sizes contained within samples.
Bulk and tapped density To assess the bulking properties (flowability, packing, handling, intermolecular interactions, etc) of the powders Record the sample Unsettled apparent volume, Final tapped volume and Hausner Ratio.
Tests for suspensions/dispersions Purpose Test
pH pH (and ionic content) provide valuable information about the chemical properties of the formulation and how it interacts with substrates Record the pH of the dispersion. How does it compare with other materials?
Viscosity Viscosity is an important parameter during the application stage. It gives an indication on


Use a rotational viscometer to record viscosity as a function of % solids content. Also, make a record of the time taken to hydrate the sample
Wet Draw Down Same as the Dry Draw Down Note the colour, presence of insoluble materials or contaminants
Wet sieve test Used to measure levels of insoluble or poorly dispersed material owing to its effectiveness at separating granular material from finer fractions Observe and record the amount of insoluble or poorly dispersed material
Suspension characteristics Suspension characteristics provide an indication on how well individual formulation ingredients are held in suspension Note and record the sedimentation rate, level of foaming, ease of dispersion of the sample
Minimum Film Forming Temperature (MFFT) This is a simple test that is used to determine the lowest temperature at which the coating will uniformly coalesce into a film. The MFFT gives an indication on how well a product is developed Make a record of the MFFT for each formulation
Tests for cast films Purpose Test
Adhesion In order to perform well as coatings, adhesion to the substrate is critical. This test allows you to assess this parameter There are several ways that can be used to measure adhesion (Scrape Adhesion, Pull-off or Instron). Make the appropriate observations
Tensile strength Mechanical strength is directly correlated with film aesthetics such as bridging, peeling and cracking. Record the film’s elongation and tensile strength and compare between samples
Water vapour transmission rate (MVTR) For moisture barrier coatings, this parameter describes how effective the film is at performing as a barrier to moisture Record the MVTR
Tests for coating process & coated substrates Purpose Test
Coating parameters Coating parameters (bed temperature, spray rate, atomization pressure & spray gun nozzle size) determine how operationally efficient a given coating system is Compare and contrast recommended parameters, throughput and weight gains achieved for similar equipment loads
Film colour/whiteness For white or pigmented systems, a uniform coloration communicates to the consumer that the product is of high integrity Use an appropriate colour measuring tool (e.g Pantone® CAPSURE™ to measure colour differences in matched systems. Other measures such as the Berger Whiteness and CIE 82 can be used to assess whiteness
Friability, disintegration & dissolution rate Friability gives an indication about film coating mechanical properties while disintegration and dissolution rate provide an indication on how the coating system performs in-vivo Make a record of the friability, the disintegration time and dissolution time



Having undertaken the technical assessment, the final aspect of the product evaluation step is to look at the comparative price of the material, in particular, the full cost of use. For film coatings, it is especially useful to examine the material’s recommended weight gain as this single factor will influence the material needed for a comparable equipment load.