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The Tablet Coating process
Application Note
Many solid pharmaceutical dosage mediums are produced with coatings,either on the external surface of tablets, or on materials dispensed withingelatine capsules. Coating serves a number of purposes: Protects the tablet (or the capsule contents) from stomach acids Protects the stomach lining from aggressive drugs such as enteric-coated aspirin Provides a delayed release of the medication Ideally, the tablet should release the material gradually and the drug shouldbe available for digestion beyond the stomach. The coating can be speciallyformulated to regulate how fast the tablet dissolves and where the activedrugs are to be absorbed into the body after ingestion.
Many factors can affect the end-use properties of pharmaceutical tablets: Control and sequencing
Batch control &
reporting
Coating Process Design & Control
Setpoint programming
Tablet coating takes place in a controlled atmosphere inside a perforated Bespoke displays
rotating drum. Angled baffles fitted into the drum and air flow inside thedrum provide means of mixing the tablet bed. As a result, the tablets are Alarm management
lifted and turned from the sides into the centre of the drum, exposing eachtablet surface to an even amount of deposited/sprayed coating.
21 CFR Part 11
The liquid spray coating is then dried onto the tablets by heated air drawnthrough the tablet bed from an inlet fan. The air flow is regulated fortemperature and volume to provide controlled drying and extracting rates,and at the same time, maintaining the drum pressure slightly negativerelative to the room in order to provide a completely isolated processatmosphere for the operator. Tablet coating equipment may include spray guns, coating pan, polishingpans, solution tanks, blenders and mixers, homogenisers, mills, peristalticpumps, fans, steam jackets, exhaust and heating pipes, scales and filters.
Tablet coating processes may include sugar coating (any mixtures ofpurified water, cellulose derivatives, polyvinyl, gums and sugar) or filmcoating (purified water, cellulose derivatives).
• DATA MANAGEMENT • CONTROLS • PROCESS AUTOMATION• The coating process is usually a batch driven task consisting of the The Auditor feature on the Visual Supervisor has been specifically designed to meet the requirement of the FDA’s 21 CFR Part 11including: Batch identification and Recipe selection (film or sugar coating) Loading/Dispensing (accurate dosing of all required raw Secure Data logging in tamperproof format Audit trail recording user actions and changes to process Spraying (application and rolling are carried out With the Auditor feature, Electronic signature is configurable for all actions which may be performed form the Visual Supervisor display including the customised display and standard features such asbatch, recipe changes, access control changes, etc.
A control system must therefore provide flexibility in the way inwhich accurate and repeatable control of the coating environmentis achieved and will include the following features: Precise loop control with setpoint profile programming Recipe Management System for easy parameterisation Sequential control for complex control strategies Secure collection of on-line data from the coating system foranalysis and evidence 21 CFR Part 11
Local operator display with clear graphics and controlled accessto parameters Eurotherm T800 Visual Supervisor
The Eurotherm Visual Supervisor is ideal for coating applicationsbecause it combines all these key features into a single compactunit: Powerful Loop & Sequence Control
Flexible Graphics
Setpoint Programmer
Scalable Architecture
A complete system can be created in combination with the 2500
Batch Control & Reporting
DIN rail I/O bases. Connection is via a Profibus-DP link and I/O isscalable by adding 4, 8 or 16 slot bases as required. A range of I/O Audit Trail
modules caters for the various interfaces required: SVGA Touchscreen Display to IP65
Temperatures (Inlet and Outlet Air), Air Flow, Secure Data Logging and Trending
Differential Pressure (Pan), Pressure (Atomising Recipe Management
Control valves, Air Flow/Pressure regulators, Alarm Management
Access Control & Electronic Signatures
Coating solution low level switch, Fans and Pumps statuses, etc.
Valve control solenoids, Pump control etc.
21 CFR Part 11 Ready
Tablet coating machines are in industries likely to require validation System Building Blocks:
to the requirements of the FDA, EMEA or other applicable regulatory body. The Visual Supervisor has been widely used invalidated processes including freeze dryers, autoclaves, reactors, Multiple Units with Supervisory Workstation(s) fermenters, purified water systems, etc.
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Eurotherm Limited pursues a policy of continuous development and product improvement. The specifications in this document may therefore be changed without notice. The information in this document isgiven in good faith, but is intended for guidance only. Eurotherm Limited will accept no responsibility for any losses arising from errors in this document.

Source: http://www.eurotherm-danmark.dk/medic/pharma_doc/applications/an_coating_process.pdf