Coating of tablets
Understanding the different methods and their benefits
Table of Contents
Coating of tablets is a crucial step in the production of pharmaceuticals, improving drug stability, efficiency and patient compliance. In the coating process, a layer is applied to the tablet core. Such a thin coating layer may seem insignificant, but its impact is significant. The right coating technique can improve medication effectiveness, facilitate easier administration, and ensure regulatory compliance.
Understanding the different benefits and types of coating of tablets is therefore critical to optimizing drug performance and ensuring a positive patient experience. Learn more about the benefits of coating tablets and the different forms in our blog article.
Why coating of tablets is essential?
Tablets may appear complete once the active ingredients are pressed into a solid form, but the coating plays a crucial role in improving their quality and functionality. Beyond pure aesthetics, coatings serve multiple purposes, from protecting the tablet core to improving performance and patient acceptance. Below we outline the specific reasons of tablet coating.
Protection layer
Pharmaceutical tablets contain active ingredients that can degrade when exposed to moisture, light, or oxygen. Coatings act as a barrier against these environmental factors, preserving the medication’s stability and extending its shelf life.
Coatings also protect the tablet against mechanical stress during packaging and avoids potentially hazardous during the handling.
Barrier layer
Coating of tablets can be used to avoid reactions between the API and some additional functional coating. Where either the API or the functionality of the coating could suffer in a direct interaction.
Improved Patient Compliance
Many drugs have a bitter taste or an unpleasant odor, which can make them difficult for patients to take. Coatings help mask these undesirable properties and provide a smooth finish, making tablets easier to swallow.
Coatings in different colours play also a vital role for drug safety by allowing the patient or the medical staff to distinguish between different formulations or different dosages.
Controlled drug release
Some medications require a controlled drug release to optimize therapeutic efficacy and minimize side effects. Coating of tablets can be formulated to modify drug release, ensuring the medication is delivered at the right time and location in the body.
A special type of controlled drug release is the active coating of pharmaceutical dosage forms. This method can apply a certain API directly after the tablet is taken where the main ingredient might be different or release differently.
As you can see, the coating of tablets is more than just an extra layer. It is a critical component that improves the stability and efficacy of medicines and the patient experience. Whether for protection, controlled release or improved delivery, coating plays a key role in pharmaceutical production. Now that we’ve learned about the essential functions of coating, let’s take a closer look at the different types of tablet coating and how each method serves a specific purpose.
Different types of coating of tablets
When it comes to tablet coating, there is no one-size-fits-all solution. Different types of coating of tablets are used to achieve different goals explained above, such as improving stability, controlling the release of active ingredients or improving patient compliance. In this section, we look at two of the most common types of tablet coating: Film coating and sugar coating, exploring how they differ, how the process works and what specific benefits they offer.
1. Film coating of tablets
Film coating of tablets involves the application of a thin, polymer-based layer to tablets, capsules, or pellets. It is the most widely used coating technique in modern pharmaceutical manufacturing due to its efficiency and versatility.
Film coatings typically consist of the following components:
- Film-forming polymers (e.g., hydroxypropyl methylcellulose, ethylcellulose, polyvinyl alcohol, methacrylates)
- Plasticizers (e.g., polyethylene glycol, triacetin) to improve flexibility
- Colorants (e.g., titanium dioxide, iron oxides) for aesthetics or light protection
- Anti tacking agents (e.g., Talkum, glycerol monostearate, magnesium stearate) to avoid sticking tendencies during the coating process and storage
- Solvents (e.g., water, organic solvents) to dissolve the coating materials
The process of film coating
When film coating of tablets, the coating solution is sprayed onto tablets inside a rotating coating pan or fluidized bed system. Simultaneously, warm air is applied to evaporate the solvent, leaving a uniform and dry film on the tablet surface.
What are the benefits of film coating?
- Efficient and fast process: Total process times of 1h possible with modern equipment
- Various functions of the film properties can be selected by choosing the different ingredients
Typically, a film coating of tablets is used when a protection or barrier layer is required or when a controlled release of the active ingredient is necessary. Film coating is the new standard today, so there are not really any disadvantages at all.
2. Sugar coating of tablets
Sugar coating of tablets is a traditional technique primarily used to mask the unpleasant taste and odor of tablets. But it creates also very nice dragee shaped tablets with an unique appearance. It involves multiple layers of sugar-based solutions, resulting in a thick, glossy and smooth outer shell.
The composition of the sugar coating of tablets consists of:
- Sugar syrup (typically sucrose) as the main ingredient
- Anti tacking agents (typically Talcum)
- Colorants for aesthetic appeal
- Polishing agents (e.g., wax) to give a shiny finish
The process of sugar coating
The sugar-coating solution is applied to the tablets in a cyclic process (via a rake) consisting of three key steps:
- Application – The coating solution is applied onto the tablets without airflow. Once the set spray duration or amount is reached, the process moves to the next step.
- Distribution – The system ensures even distribution of the coating solution across the tablets for a specific duration. (without airflow)
- Drying – Airflow is activated to dry the applied coating layer, ensuring proper adhesion.
These steps are repeated in multiple cycles until the desired coating thickness and formulation are achieved. Finally, a cooling and polishing step is performed to give the tablets a smooth, glossy finish.
What are the benefits and disadvantages of sugar coating?
- Effectively masks unpleasant tastes
- Improves tablet aesthetics
- Provides mechanical protection
However, sugar coating also has a few drawbacks:
- Increases tablet size and weight significantly
- Time-consuming and labor-intensive
- Less commonly used in modern pharmaceutical production
Conclusion – the right coating of tablets makes the difference
As we have seen, a simple coating can have a significant impact on tablet effectiveness, stability, and patient compliance. Choosing the right method for coating of tablets is therefore crucial for pharmaceutical manufacturers.
Due to its efficiency and flexibility, film coating is the most widely used method. Understanding these coating techniques enables pharmacists to optimize production and deliver high quality medicines to patients.
By continuously improving coating processes and materials, the pharmaceutical industry ensures that drugs are safe, effective and easy to administer, ultimately benefiting both manufacturers and patients. Want to learn more about coating and gain hands-on experience? We regularly offer workshops on coating topics.
Sources:
(1) Introduction to pharmaceutical film coatings – Pharma Excipients – https://www.pharmaexcipients.com/introduction-to-pharmaceutical-film-coatings/
(2) A Comprehensive Review on Pharmaceutical Film Coating: Past, Present, and Future –
https://www.dovepress.com/a-comprehensive-review-on-pharmaceutical-film-coating-past-present-and-peer-reviewed-fulltext-article-DDDT
(3) Pharmaceutical Coating and Its Different Approaches, a Review,
https://www.mdpi.com/2073-4360/14/16/3318
(4) Webcast – Functional Film Coating –
https://www.biogrund.com/webcast-functional-film-coating/?lang=en