Podcast
Questions and Answers
What is the primary function of a plasticizer in a polymer coating?
What is the primary function of a plasticizer in a polymer coating?
Which of the following is NOT a recommended component of aqueous coating?
Which of the following is NOT a recommended component of aqueous coating?
What concentration range of plasticizers is commonly recommended for film formers?
What concentration range of plasticizers is commonly recommended for film formers?
Lakes pigments are preferred colorants for sugar or film coating systems because they:
Lakes pigments are preferred colorants for sugar or film coating systems because they:
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Opaquants are primarily used in coating solutions to:
Opaquants are primarily used in coating solutions to:
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Which plasticizer is primarily water-soluble and commonly used in aqueous coating?
Which plasticizer is primarily water-soluble and commonly used in aqueous coating?
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What impact do plasticizers have on the molecular structure of polymers?
What impact do plasticizers have on the molecular structure of polymers?
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Which of the following statements about opaquants is true?
Which of the following statements about opaquants is true?
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Which factor does NOT influence the concentration of plasticizers used?
Which factor does NOT influence the concentration of plasticizers used?
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Which of the following best describes the interaction of plasticizers with polymers?
Which of the following best describes the interaction of plasticizers with polymers?
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What is the primary reason for not adding color to tablets until they are quite smooth?
What is the primary reason for not adding color to tablets until they are quite smooth?
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In the context of polishing tablets, which wax is commonly used to achieve luster?
In the context of polishing tablets, which wax is commonly used to achieve luster?
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Which of the following is NOT a reason film coating is preferred over sugar coating?
Which of the following is NOT a reason film coating is preferred over sugar coating?
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What is a potential consequence of using a spraying speed that is too high during the pan spray method?
What is a potential consequence of using a spraying speed that is too high during the pan spray method?
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During the sugar coating process, what is the critical aspect that should be controlled to ensure uniform coating?
During the sugar coating process, what is the critical aspect that should be controlled to ensure uniform coating?
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What is a crucial characteristic of tablets for coating to resist abrasion during the coating process?
What is a crucial characteristic of tablets for coating to resist abrasion during the coating process?
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Which of the following tablet shapes is preferred for coating?
Which of the following tablet shapes is preferred for coating?
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Which type of coating material is NOT preferred when tablets have surfaces that are affected by coating compositions?
Which type of coating material is NOT preferred when tablets have surfaces that are affected by coating compositions?
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In the tablet coating process, what happens to tablet surfaces that are brittle?
In the tablet coating process, what happens to tablet surfaces that are brittle?
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Which of the following is NOT a primary component in studying tablet coating?
Which of the following is NOT a primary component in studying tablet coating?
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What is one of the effects of using coating compositions on tablet surfaces?
What is one of the effects of using coating compositions on tablet surfaces?
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Why must tablets be able to resist chipping during the coating process?
Why must tablets be able to resist chipping during the coating process?
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What is the ideal shape for tablets during the coating process to prevent agglomeration?
What is the ideal shape for tablets during the coating process to prevent agglomeration?
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What happens if a square flat-faced tablet is used during the coating process?
What happens if a square flat-faced tablet is used during the coating process?
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Which property is NOT essential for coating materials used on tablets?
Which property is NOT essential for coating materials used on tablets?
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What is the purpose of adding surfactants to the coating solution?
What is the purpose of adding surfactants to the coating solution?
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Which of the following statements about the properties of coating materials is true?
Which of the following statements about the properties of coating materials is true?
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What characterizes the non-enteric materials used for tablet coating?
What characterizes the non-enteric materials used for tablet coating?
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What property should coating materials have regarding their interaction with common additives?
What property should coating materials have regarding their interaction with common additives?
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Which of the following coating characteristics is most critical for ensuring the coating adheres properly?
Which of the following coating characteristics is most critical for ensuring the coating adheres properly?
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Why is it important to ensure that coating materials do not bridge or fill the debossed tablet surfaces?
Why is it important to ensure that coating materials do not bridge or fill the debossed tablet surfaces?
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What is the main advantage of using Hydroxypropyl Methylcellulose (HPMC) in tablet coating?
What is the main advantage of using Hydroxypropyl Methylcellulose (HPMC) in tablet coating?
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Which statement best describes the non-ideal property of Hydroxypropyl Methylcellulose (HPMC)?
Which statement best describes the non-ideal property of Hydroxypropyl Methylcellulose (HPMC)?
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Why is Ethyl Cellulose (EC) not suitable for use alone in tablet coating?
Why is Ethyl Cellulose (EC) not suitable for use alone in tablet coating?
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Which of the following characteristics is NOT true for Ethyl Cellulose (EC)?
Which of the following characteristics is NOT true for Ethyl Cellulose (EC)?
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What is the primary reason for applying enteric coating to tablets?
What is the primary reason for applying enteric coating to tablets?
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Which of the following is NOT a benefit of using Hydroxypropyl Methylcellulose (HPMC) in film coating?
Which of the following is NOT a benefit of using Hydroxypropyl Methylcellulose (HPMC) in film coating?
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What problem is typically encountered when using Hydroxypropyl Methylcellulose (HPMC) alone as a coating agent?
What problem is typically encountered when using Hydroxypropyl Methylcellulose (HPMC) alone as a coating agent?
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Which enteric material is known to solubilize based on pH changes in the gastrointestinal tract?
Which enteric material is known to solubilize based on pH changes in the gastrointestinal tract?
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Among the following, which property of HPMC contributes to its effectiveness as a coating agent?
Among the following, which property of HPMC contributes to its effectiveness as a coating agent?
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Study Notes
Tablet Coating
- Tablet coating is adapted from food preservation processes.
- The first air suspension coater was created by Dr. Dale Wurster in 1950.
- Wurster introduced airflow and perforated coating pans into the tablet coating machine.
- His work led to the first reproducible and uniform tablet coating.
Tablet Coating Principles
- Tablet coating increases cost, so decisions are based on multiple factors.
- Minimizing undesirable taste, odor, or color of the drug.
- Providing physical and chemical protection for the drug.
- Controlling the drug's release from the tablet.
- Protecting the drug from the stomach's acidic environment (enteric coating).
- Improving the pharmaceutical's appearance through colors and printing.
- Assisting tablet movement and mobility, particularly for those with dysphagia.
Tablet Coating Process
- The process involves the tablet substrate, coating quality, and coating formulation.
- Each part influences the successful coating of a tablet.
Tablet Coating: Three Main Parts
- Tablet Properties: Ideal tablet shape for coating, and tablet physical properties.
- Coating Compositions: Non-enteric coating materials, enteric coating materials, solvents, plasticizers, colorants, and opaquants.
- Coating Process: Coating equipment, coating processes (sugar coating, film coating), and evaluation of film and film defects.
Preferred Tablet Properties for Coating
- Tablets must withstand intense mechanical stress, and possess an intact shape free of imperfections.
- Brittle tablet surfaces that soften with heat should not be used for film coating.
- The ideal tablet shape for coating is a sphere that allows for free rolling in the coating pan, and minimizes tablet-to-table contact.
- The worst shape is a square flat-faced tablet.
- Tablet surface hydrophobicity/hydrophilicity should match the coating materials.
Coating Compositions
- Coating materials can form a physical deposition on the tablet surface (sugar and wax coatings).
- Coating materials need to be soluble in the solvent for preparation, produce elegant-looking products, remain stable in the presence of heat, light, moisture, air, and aging.
- Coating materials should be essentially tasteless, odorless, and colorless.
- Compatibility with common coating solution additives.
- Nontoxic and pharmacologically inert.
- Resistance to cracking.
Coating Compositions: Film Forming Materials
- Polymers are used to form the film around tablets.
- Polymers can be classified as non-enteric and enteric.
- Non-enteric materials: Tend to solubilize inside the GI tract and release the drug (e.g., Hydroxypropyl methylcellulose (HPMC), Ethyl Cellulose (EC)).
- Enteric materials: Tend to solubilize depending on the pH of the GI tract (e.g., Hydroxypropyl Methyl Cellulose Phthalate (HPMCP), Cellulose Acetate Phthalate, Acrylate Polymers).
Non-enteric Materials (Non-Functional FC)
- Hydroxypropyl methylcellulose (HPMC): Available in different viscosity grades, close to ideal coating polymer for film coating, soluble in organic and aqueous solvents, and flexible and stable. However, when used alone can tend to bridge and fill debossed tablet surfaces.
- Ethyl Cellulose (EC): Insoluble in water and gastrointestinal fluids, but combined with water-soluble polymers to reduce water solubility, and nontoxic, colorless, odorless, tasteless, quite stable. However, without plasticizers, it can be brittle.
Enteric Materials
- The most important reasons for using enteric coating include protecting the drug from the stomach's enzymes, protecting the stomach from the drug, delivering drugs optimally absorbed in the small intestine, and providing a delayed-release component for repeat-action tablets.
- Ideal enteric coating materials should resist gastric fluids, be permeable to intestinal fluids, and compatible with coating solution components and drug substrates, be stable both alone and in solutions, form a continuous film, be nontoxic, be reasonably priced, and be easy to apply without special equipment.
- Stomach pH varies from 1-5, enteric materials either resist or are pH sensitive to allow the drug to dissolve and be absorbed in the small intestine.
Challenges for Enteric Coated Tablets
- Tablets must pass the USP disintegration test.
- The pH of the stomach varies from 1 to 5 and varies between individuals.
Coating Compositions: Specific Materials
- Cellulose Acetate Phthalate (CAP): Widely used, dissolving above pH 6, but can delay absorption and be hygroscopic.
- Acrylate polymers (Eudragit): Resistant to gastric fluid, soluble at higher pH levels in the GI tract.
- Hydroxy Propyl Methyl Cellulose Phthalate (HPMCP): Dissolves at lower pH levels(pH 5-5.5), resulting in higher bioavailability for some drugs.
Coating Compositions: Solvents
- Solvents are needed to dissolve or disperse polymers and additives.
- Ideal solvents should dissolve the polymer system, easily disperse coating components, have low concentrations of polymers without creating excessive viscosity, be colorless, tasteless, odorless, inexpensive, non-toxic, inert, have rapid drying rate, and no environmental impact.
- Common choices include water, ethanol, chloroform, and acetone but water is preferred due to environmental and economic reasons.
Coating Compositions: Plasticizers
- Plasticizers are non-volatile materials that improve flexibility and adhesion properties when incorporated into the film.
- They can help maintain the flexibility of coated tablets.
- Common plasticizers include castor oil, glycerin, low-molecular-weight polyethylene glycol (PEG), Tweens, and Spans.
Coating Compositions: Colorants
- Colorants can be soluble or insoluble powders.
- Lakes pigments are a common choice for even color distribution in sugar or film coatings.
Coating Compositions: Opaquants
- Fine inorganic powders that increase film coverage and mask the tablet core color.
- Titanium dioxide is the most commonly used opaquant.
Coating Process
- Application of coating materials to moving tablets while simultaneously evaporating the solvent
- Distribution is done by continuous movement of the tablets through the coating pan.
- Tablets pass through an application zone where they receive coating materials.
- Recycled through the application zone until coat is achieved by hot air.
Coating Equipment: Conventional Pan System
- A spherical pan mounted angularly and rotate by a motor.
- Heated air is directed into the tablet bed and exhausted through ducts.
Coating Equipment: Perforated Pan System
- A perforated drum that rotates inside a closed chamber.
- Drying air passes through tablets via the drum's perforations.
- High coating capacity, and can be automated for sugar and film coating.
- Coating solution applied through spraying nozzles inside the drum.
Sugar Coating
- Frequently used in the past, but a time-consuming process (hours to several days).
- Excellent appearance.
- Success strongly relies on the operator's skill, especially with the pan-ladling method.
- Steps include sealing, subcoating, syruping, finishing, and polishing.
- Sealing prevents moisture from penetrating the tablet core.
Film Coating Process
- Faster and more economic than sugar coating.
- More versatile film coating polymers that can be used.
- Slightly increases tablet weight (2-5%).
- Same equipment as sugar coating can be used.
Pan Spray Method for Film Coating
- Introduction of spraying equipment in the film coating process.
- Automatic control of liquid application.
Pan Spray Method: Control Variables
- Variables that depend on the pan shape, load, and speed (e.g., pan variables).
- Variables concerning speed can result in sticking due to slow speeds or roughness due to high-speed drying issues.
- The rate of liquid application, degree of atomization, and nozzle-to-bed distance (e.g., spray variables).
- The Drying Air that needs to be controlled in temperature, volume, and rate.
Evaluations of Coated Tablets
- Evaluation of general appearance (color, continuity, size, physical defects).
- Evaluation of tablet performance (drug release characteristics and stability).
- Visual inspection is often sufficient for quality assessment.
- Resistance test is done by rubbing coated tablets on white paper.
Film Defects
- Sticking/picking: Overwetting/tackiness causes tablets to stick together or to the pan; poor drying results in stuck films.
- Roughness: Rough or gritty surfaces from improper spray application; some may dry too rapidly before reaching sufficient mixing.
- Orange peel effects: Inadequate spreading of the coating solution before drying, appearing bumpy or like an orange peel; too rapid drying and/or excessive viscosity.
- Bridging/filling: Film may shrink and pull away during the drying stage; due to inadequate plasticizers.
- Blistering: Rapid solvent evaporation at high temperatures causes inner core issues that are more noticeable during drying in ovens. Milder drying may help.
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