TABLETCOATING Presented By: G.Monica, I/II M.Pharmacy(pharmaceutics) HINDU COLLEGE OF PHARMACY Under the GUIDANCE: Dr.A.SEETHADEVI Ph.D HEAD OF PHARMACEUTICS HINDU COLLEGE OF PHARMACY

 DEFINITION  OBJECTIVES OF TABLET COATING  COATING PROCESS  EQUIPMENT DESIGN  EQUIPMENTS FOR COATINGOF TABLETS  TYPES OF TABLET COATING  SUGAR COATING  FILMCOATING  FILM COATING MATERIALS  ENTERIC COATING  FILM DEFECTS

Tablet coating is the process of evenly covering particles with a substance by applying a series of thin layers. These coaters differ in their function and application.

COATING PROCESS DESIGN AND CONTROL: 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. The coating process is usually a batch driven task consisting of the following phases: Batch identification and Recipe selection (film or sugar coating) Loading/Dispensing (accurate dosing of all required raw materials) Warming Spraying (application and rolling are carried out simultaneously) Drying Cooling Unloading

EQUIPMENT DESIGN Four systems make up a pan coater: the drum, the spray system, the charging mechanism, and the control system. The Drum The three key elements of a drum are its size, perforations, and baffles. Research-size drums hold about 10 liters of material while industrial-scale drums can hold more than 2,000 liters, or about 2 tons of material. Some pan- coating machines will accept various drum sizes The size of the perforations restricts the size of tablets the drum is capable of processing. As the drum rotates, the baffles churn the tablets to prevent sticking and to ensure that they all receive an equal coatingperforationsbaffles.

The Spray System The core of the pan-coater, and most other coating machines, is the spray system. The more effectively the spray system atomizes the coating suspension, the more evenly the tablets get coated. Batch-to-batch consistency is a consideration in the pharmaceutical industry. Shown below are examples of spray systems. atomizes To achieve this optimal spraying, the nozzle is selected to suit the type of suspension being applied. Sugar coating machines conventionally use a rake, while aqueous and organic suspensions use binary nozzles

Charging and Discharging Systems To charge the pan, tablets are typically poured down a chute that empties into the drum. However, some applications require closed charging. In these cases, the tablets enter the machine through a pipe in the front or on top of the pan. In open discharging a scoop is attached to the machine. The tablets are lifted out of the drum as it spins and are sent down a chute into a barrel or hopper, as shown below. Closed discharging requires a fixed discharge scoop that sends the tablets through a pipe and into a closed containerhopper.

Control Systems The machine must be monitored to ensure batch-to-batch consistency and quality. Modern coaters use computer software, such as the program pictured below, to achieve this. The computer can monitor a number of parameters, such as: the temperature of the incoming air, the humidity, the drum spin-rate, and the spray-rate. Computers are also capable of fully automating the process, from charging to discharging. The computer can store process instructions, or recipes, that yield specific results.

EQUIPMENT DESIGN A fluidized bed is composed of four systems: Air Handling, Spraying, Cleaning, and Control. Air Handling The air handling system removes any entrained product from the air before it leaves the system. By reducing the amount of product wasted, this system helps save money and avoid air pollution issues. The two most prevalent devices used are bags, shown at the top, and cartridge filters, shown below. Usually the cartridges or bags are installed in pairs, so that one can process air while the other is cleaned, thereby enabling continuous production. Spraying The core of the fluidized bed coater is the spray system. The more effectively the spray system atomizes the coating suspension, the more evenly the tablets get coated. The spray can reach the particles from the top, the bottom or the side.atomizes In top spraying, the coating solution is applied counter-currently to the tablets' motion, as seen on the right. After they are sprayed, the tablets fall back down in the bed. The fluidizing air evaporates the solvent, leaving behind a layer of coating. Once the tablets are dry, the process is repeated to achieve the desired thickness. This configuration generally allows for the highest throughput.

USAGE EXAMPLES Manufacturers primarily market fluidized bed coaters to the food and pharmaceutical industries. Drug manufacturers may apply active ingredients as a thin coating onto tablets. They may also coat the active ingredient with a film to modify its release- time in the body. The food industry uses the tablet coaters for taste masking and coloring as well. Fluidized beds offer a high degree of control over the thickness of these layers.

ADVANTAGESDISADVANTAGES Can coat smaller diameter tablets than a horizontal pan. Coats more uniformily than horizontal pan. Relatively inexpensive to modify the spray configuration. Bed itself can also be used for granulation, spraying, drying, etc. Totally closed design meets CGMPstandards.CGMP About 1 mm maximum particle diameter. Volatile fluidized particles and solvents pose risk of explosion. Not suitable for sugar-coating. Cannot process batches as large as a horizontal pan.

3.ENTERIC COATING

 Modern approach to coating tablets, capsules, or pellets by surrounding them with a thin layer of polymeric material.

 Picking and sticking This is when the coating removes a piece of the tablet from the core. Overwetting or examples or excessive film tackiness causes tablets to stick to each other or to the coating pan. On drying, at the point of contact, a piece of the film may remain adhered to the pan or to another tablet, giving a “picked” appearance to the tablet surface and resulting in a small exposed area of the core. It is caused by over-wetting the tablets, by under-drying, or by poor tablet quality. REMEDY: A reduction in the liquid application rate or increase in the drying air temperature and air volume usually solves this problem. Excessive tackiness may be an indication of a poor formulation.

Roughness A rough or gritty surface is a defect often observed when coating is applied by a spray. Some of the droplets may dry too rapidly before reaching the tablet bed, resulting in the deposits on the tablet surface of “spray dried” particles instead of finely divided droplets of coating solution. Surface roughness also increases with pigment concentration and polymer concentration in the coating solution. REMEDY: Moving the nozzle closer to the tablet bed and reducing the degree of atomization can decrease the roughness due to “spray drying

 Orange Peel This refers to a coating texture that resembles the surface of an orange. Inadequate spreading of the coating solution before drying causes a bumpy or “orange- peel” effect on the coating. It is usually the result of high atomization pressure in combination with spray rates that are too high. This also indicates that spreading is impeded by too rapid drying or by high solution viscosity. REMEDY: Thinning the solution with additional solvent may correct this problem.

 Twinning This is the term for two tablets that stick together, and it’s a common problem with capsule shaped tablets. REMEDY : Assuming you don’t wish to change the tablet shape, you can solve this problem by balancing the pan speed and spray rate. Try reducing the spray rate or increasing the pan speed. In some cases, it is necessary to modify the design of the tooling by very slightly changing the radius. The change is almost impossible to see, but it prevents the twinning problem.

 Erosion This can be the result of soft or friable tablets (and the pan turning too fast), an over-wetted tablet surface, inadequate drying, or lack of tablet surface strength

 Bridging This occurs when the coating fills in the lettering or logo on the tablet and is typically caused by improper application of the solution, poor design of the tablet embossing, high coating viscosity, high percentage of solids in the solution, or improper atomization pressure. During drying, the film may shrink and pull away from the sharp corners of an intagliation or bisect, resulting in a “bridging” of the surface. This defect can be so severe that the monogram or bisect is completely obscured. REMEDY: Increasing the plasticizer content or changing the plasticizer can decrease the incidence of bridging.

 Color Variation This problem can be caused by processing conditions or the formulation. Improper mixing, uneven spray pattern and insufficient coating may result in color variation. The migration of soluble dyes, plasticizers and other additives during drying may give the coating a mottled or spotted appearance. REMEDY: 1. The use of lake dyes eliminates dye migration. 2. A reformulation with different plasticizers and additives is the best way to solve film instabilities caused by the ingredients.

Mottled color This can happen when the coating solution is improperly prepared, the actual spray rate differs from the target rate, the tablet cores are cold, or the drying rate is out of specification. Hazing / Dull Film This is sometimes called Bloom. It can occur when too high a processing temperature is used for a particular formulation. Dulling is particularly evident when cellulosic polymers are applied out of aqueous media at high processing temperatures. It can also occur if the coated tablets are exposed to high humidity conditions and partial salvation of film results. Filling Filling is caused by applying too much solution, resulting in a thick film that fills and narrows the monogram or bisect. In addition, if the solution is applied too fast, Overwetting may cause the liquid to quickly fill and be retained in the monogram. REMEDY: Judicious monitoring of the fluid application rate and thorough mixing of the tablets in the pan can prevent filling.

Net source THE THEORY AND PRACTICE OF INDUSTRIAL PHARMACY :LEON LACHMAN