5 - Coating

What are the important polymer characteristics (in film coating)? →Why?

-Solubility → determines behavior of coating in GIT, determine solubility -Viscosity → limiting factor regarding the easy a coating can be applied (spraying etc) -Permeability → responsible to mask the taste (prevents water-vapor to interrogate), shields the internal material from the outside world -Mechanical properties → strength

Fundamentals of film formation: How exactly is the polymeric dispersion applied, what gives the film? →What is the crucial parameter?

→ Film coating involves the deposition of a thin film of polymer formulation to the surface of a tablet, capsule, or multiparticulate core →Crucial: temperature If its higher than the temperature the film can handle, the film will deform and the film collapses

What makes the enteric coating possible? -When are thy administered? -For what kind of drugs are they made?

→ play with the chemistry of the plasticizers: insoluble to low pH and soluble at higher pH →at least 30min prior to food intake → unhindered passage trough the stomach For: -acid labile drugs -drugs that could harm the stomach -higher [drug] in the lower part of GI -drug could have an impact on digestion

Sugar coating: Stages of the coating process:

-Sealing -Subcoating -Coating -Coloring -Smoothing -Polishing

Coating material for: Modified release coatings

- Ethyl cellulose - Cellulose acetate - Methacrylic acid copolymers - Phthalate esters →looking for cellular derivatives with more substituents (= less soluble in water)

Film coating: -Process: -the equipment:

-Adequate means of atomizing spray liquid -Adequate mixing and agitation of the tablet bed -Sufficient energy input to evaporate the solvent (heated drying air) -Good exhaust facilities to remove dust- and solvent-laden air →Coating are organic solvents and polymers that can be sprayed most of the time -Side-vented pan -Fluidized-bed coaters (much more appealing in industrial level)

Compression coating: →difference to sugar/ film coating → Process?

-Compression coating differs radically from film coating and sugar coating -The process involves the compaction of granular material around preformed tablet cores -Compression coating is based on a modification of the traditional tableting process: first tablet cores, then compaction of coating in a die filled with coating powder -Compression coating is a mechanically complex process that requires careful formulation and processing of the coating layer.

Coating material for: Immediate release coatings

-Hydroxypropyl methylcellulose -Polyvinyl alcohol -Aminoalkyl methacrylate copolymers →looking for cellulose derivatives with less number of substituents (= higher water solubility!)

How do you expect the solubility of the different film coatings to be? (Immediate-, Extended release, Gastro resistant coatings)

-Immediate-release coating → usually soluble in water -Gastro-resistant coatings → only soluble in water at pH values > 5-6 -Extended-release coating → insoluble in water (release over 6-12h)

4 main ingredients of film coating material:

-Polymers -Plasticizers (e.g. PEG, triacetin, castor oil) -Colorants (e.g. Sunset Yellow, TiO2, riboflavine) -Solvent/vehicle (e.g. water, alcohols)

Sugar coating defects: → difficult or easy process? → What are the possible defects?

-Sugar coating technically and practically difficult process → great deal of skill and experience -Most defects are visual in nature Tablets may show: -Rough in appearance (marbled appearance possible) -Smooth but dull in appearance -Pieces of debris (usually from broken tablets from the same batch) stuck to the surface -Poor color uniformity -Split on storage as a result of inadequate drying (causing the tablets to swell)

Evaluation of polymeric films: What properties are testet? →How are they tested? (+ what can be interpreted)

-Water vapor permeability -Thermal analysis -Mechanical properties -Polymer adhesion → Water-vapor transmission cell (with a saturated salt solution to get a specific pressure), linear weight gain is expected → Stress-strain on isolated free film (film starts to be stretched, a strain is applied and the stress is measured → the grater the slope of the line, the greater the youngs's modulus, the greater the stiffness! →Plateau area = more streching applied but no increasing stress because we reached the phase of elongational break! =Ultimate stress! → AUC= work → toughness of the polymer!

Motion and localization of added syrup in the pan coater: -Zone I -Zone II -Zone III →Where to add the coating syrup?

-Zone I: whirling zone (almost circular rotation of the tablets) -Zone II: motion patterns + energetic considerations -Zone III: most suitable position to add the coating syrup →has a high E(kin) = minimal risk of aggregation!

Quality tests: -Film coating defects:

-defects in the film → twinning, orange peel (not dried properly), capping an lamination (in-proper tablet compression), roughness, bridging -characteristics of the substrates -Physical aging → erosion (inadequate drying)

Film coating: -Different types:

-immediate release film coatings -modified release film coatings

Pan coater: →What is this used for?

-large pot of zB copper -rolling metal container Typically sugar coating is performed by a panning technique → traditional rotating sugar-coating pan with a supply of drying air → extraction system to remove dust- and moisture-laden air

Quality control: What is the most performed? -What are the others?

most → Visual examination -Light section microscopy -Surface profilimetry -Scanning electron microscopy: Dissolution, Adhesion measurements, Permeability measurements →Mainly made with human evaluation!

Coating: -Definition and reason →What should it mask? →What should it improve?

process by which an essentially dry, outer layer of coating material is applied to the surface of a dosage form in order to confer specific benefits that broadly range from facilitating product identification to modifying drug release from the dosage form →Mask: Taste, Appearance →Improving: -Swallowing -Product appearance -Identification -Product flow and mechanical strength -Product stability (moisture/light) →Additionally: drug release characteristics can be modified

Enteric coating: -What kind of release? -Goal of the formulation? -Typical enteric film polymers?

→Specific delayed release Goal: Enteric-coated solid dosage forms are intended to pass through the stomach intact to disintegrate and release their content for absorption along the intestine Typical polymers: -Phtalat esters -Acrylate polymers

Types of coating: →Where applied

→applied to a wide range of oral dosage forms (tablets, capsules, drug crystals) -Sugar coating -Film coating (most popular nowadays) -Compression coating (less popular compared to the other two)

Sugar coating: -Time consuming? -Release profile of dragées?

→time consuming process! it takes weeks to produce a batch of dragées -mostly immediate release, because the sugar coating watersoluble!