Either on the external surface of tablets, or on materials dispensed within gelatine capsules. Coating serves a number of purposes:
Ideally, the tablet should release the material gradually and the drug should be available for digestion beyond the stomach. The coating can be specially formulated to regulate how fast the tablet dissolves and where the active drugs are to be absorbed into the body after ingestion.
Many factors can affect the end-use properties of pharmaceutical tablets:
Tablet coating takes place in a controlled atmosphere inside a perforated rotating drum. Angled baffles fitted into the drum and air flow inside the drum provide means of mixing the tablet bed. As a result, the tablets are lifted and turned from the sides into the centre of the drum, exposing each tablet surface to an even amount of deposited/sprayed coating.
The liquid spray coating is then dried onto the tablets by heated air drawn through the tablet bed from an inlet fan. The air flow is regulated for temperature and volume to provide controlled drying and extracting rates, and at the same time, maintaining the drum pressure slightly negative relative to the room in order to provide a completely isolated process atmosphere for the operator.
Tablet coating equipment may include spray guns, coating pan, polishing pans, solution tanks, blenders and mixers, homogenizers, mills, peristaltic pumps, fans, steam jackets, exhaust and heating pipes, scales and filters. Tablet coating processes may include sugar coating (any mixtures of purified water, cellulose derivatives, polyvinyl, gums and sugar) or film coating (purified water, cellulose derivatives).
The coating process is usually a batch driven task consisting of the following phases:
A control system must therefore provide flexibility in the way in which accurate and repeatable control of the coating environment is achieved and will include the following features:
The EyconTM Visual Supervisor is an ideal solution for the tablet coating process.