Rotronic highlights importance of humidity control in tablet coating

Bassersdorf, Switzerland: – Rotronic AG, the world’s leading measurement solutions specialist, has identified control of humidity and other environmental variables as key success factors in high quality pharmaceutical tablet coatings.

Effective coatings are a huge issue in an industry that depends on tablets for delivery of the bulk of its medicines. Aspirin alone accounts for some 35,000 tonnes of annual production; more than 100 billion tablets.

Environmental factors

In a newly-posted website article, senior scientist Dr. Jeremy Wingate of Rotronic UK, points out that many of the most commonly encountered problems in tablet coating, such as contamination, impurity, color variations, surface pitting from over-wetting, and ‘twinning’ due to spray drying, cracking or peeling, can be overcome by better control of the environment within the process.

“Over-wetting, for example, occurs when the coating hits the still wet tablet surface and the surrounding air does not dry it quickly enough. Another example involves spray drying, when the coating hits the tablet surface after the moisture has been removed resulting in poor adhesion of the coating,” says Dr. Wingate.

Importance of coatings

The tablet coating is key to the patient experience, covering unpleasant taste, improving appearance and ‘swallow’ characteristics, aiding identification providing physical and chemical protection for the medicine from light, moisture and air.

Most important of all from the medical viewpoint, the coating directly controls release properties and absorption.

Several different types of coating are typically used, including:

• Sugar-coated tablets: a colored or uncolored sugar layer that is water-soluble and quickly dissolves after swallowing.
• Film-coated tablets: a thin layer of a polymer, usually colored, that forms a skin-like film that it is more durable than sugar coating, less bulky and allows the tablet to work faster in the gastrointestinal tract.
• Enteric-coated tablets: A delayed release coating resistant to gastric acid that designed to allow tablet to pass unchanged through the stomach to the intestines, where the tablets disintegrate and allow the drug to dissolve and start its effect.

Temperature and humidity

In all cases, the required environment for a perfect coating strongly depends on the precise composition of the tablets, which are affected by variables of temperature and humidity.

“A very common issue is incorrect cooling and drying of the sugar solution, producing a rough, translucent and uneven coating,” observes Dr. Wingate.

Pharmaceutical tablet coating involves applying a coating composition to a moving bed of tablets, using heated air to accelerate evaporation of the solvent.

Environmental controls

“Many pharmaceutical manufacturers have scientists who perform experiments to determine the ideal coating procedure including temperature and humidity levels. Once these specific requirements are determined, the set-points can be configured at the controller to enable the precision tablet-coating machines to work at optimal performance,” Dr. Wingate points out.

Environmental control is the practice of managing the temperature, humidity, air circulation, ventilation and air pressure of a given space.

“Within certain types of pharmaceutical manufacturing processes, precise environmental control can help limit inefficiencies and potential problems and this is an area where Rotronic measuring and monitoring technologies can make important contributions,” said Dr. Wingate.

About Rotronic

Founded in 1965, Rotronic AG has become one of the world’s leading names in humidity and temperature measurement and is renowned for the high quality of its Swiss-made meters, instrumentation, sensors, data loggers and other measuring equipment.

Its specialist measuring solutions are in daily use worldwide in pharmaceutical, chemical, foodstuffs and many other industrial sectors.

Rotronic’s lines of business include products for measuring humidity, temperature, CO2 and differential pressure. As a leader in the field of humidity and temperature measurement, Rotronic is also increasingly making a name for itself as a world leader in the measurement of other parameters including low dew point, CO2, differential pressure, process pressure and airflow.

With more than 180 employees, 42 sales outlets and 8 subsidiaries worldwide, Rotronic Group is becoming an increasingly international company, realizing some 60 per cent of its turnover in export sales. The company’s eight subsidiaries are located in main global markets, such as the USA, China, the UK, France, Italy, Germany, Singapore and, most recently, Canada where a branch office opened in 2015.