Micro-encapsulation (Pharmaceutical Technology), Slides of Pharmacy

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Definition of Microcapsules: Microcapsules are particles or droplets of liquid material coated with a continuous film of polymeric material (the shell). Definition of Microcapsulation: It is the process by which individual particles or droplets of solid or liquid material (the core) are surrounded or coated with a continuous film of polymeric material (the shell) to produce capsules in the micrometer to millimeter range.

1- Mononuclear (core-shell) microcapsules contain the shell around the core. 2- Polynuclear capsules have many cores enclosed within the shell. 3- Matrix encapsulation in which the core material is distributed homogeneously into the shell material.

• In addition to these three basic morphologies, microcapsules can also be mononuclear with multiple shells, or they may form clusters of microcapsules.

Solid or liquid materials that are surrounded or coated with a continuous film of polymeric material are known as core material. Examples of Core Materials:  Acetaminophen For taste masking  Aspirin For Taste masking Sustain release Reduction of gastric irritation Separation to avoid incompatibility  Vitamin A Prevention of oxidation Composition of Core: Core material may contain the following additional materials with API:  Stabilizers, Antioxidants, Butylated Hydroxy Toluene  Diluents, Starch  Release rate retardants, MC  Release rate accelerators, Sodium Starch Glycolate Examples:-

• Vitamin A 10 Kg
• Butylated Hydroxy Toluene 0.1 Kg
• Avicel pH 101 3.00 kg
• Ethyl Cellulose 0.5 Kg Examples:-
• Paracetamol 10 Kg
• Butylated Hydroxy Toluene 0.1 Kg
• Avicel pH 101 3.00 kg
• Sodium Starch Glycolate 0.2 Kg

Composition of core materials

Example -

• Vitamin A 10 Kg
• Butylated Hydroxy Toluene 0.1 Kg
• Avicel pH 101 3.00 kg
• Ethyl Cellulose 0.5 Kg Example 2
• Mefenamic Acid 10 Kg
• Butylated Hydroxy Toluene 0.1 Kg
• Avicel pH 101 3.00 kg
• Sodium Starch Glycolate 0.2 Kg Coating Materials- Composition
• HPMC 1.00 Kg
• Ethanol 15 L
• PEG-6000 0.100 Kg
• Titanium Dioxide 0.050 Kg
• Tween-80 0.070 L

Methods of microencapsulation: 1- Fluidized-Bed Technology 2- Pan coating 3- Solvent Evaporation 4- Spray Drying 5- Coacervation 6- Supercritical fluids Technology

Solvent Evaporation Method for

Microencapsulation

Formulation: Mefenamic Acid 200 gm Light liquid paraffin (L.L.P) 1 L Span 80 10 ml HPMC 100 gm Ethanol 200 ml PEG-6000 1 ml Titanium Dioxide 5 mg Tween-80 0.2 ml It is the most extensively used method of microencapsulation. Step 1: Dispersion of drug in liquid paraffin: The preparation of microspheres by solvent evaporation method is initiated by dispersion of drug in light liquid paraffin (L.L.P) using span 80. At first, L.L.P is emulsified in a plastic beaker with span 80 for few minutes with the help of stirrer at 1500-2000 rpm and then drug is dispersed in the mixture slowly and stirred for 5-10 minutes. Step 2: Preparation of polymer solution: Polymer solution is prepared by dissolving the polymer in ethanol or acetone or combination of ethanol and acetone with the help of vortex mixer.

Step 7: Storage: The prepared microcapsules are then sieved and weighed and transferred to glass vials and stored in desiccators.

Fluidized-Bed Technology for Microencapsulation

Formulation: Mefenamic Acid 10 Kg HPMC 1.00 Kg Ethanol 15 L PEG-6000 0.100 Kg Titanium Dioxide 0.050 Kg Tween-80 0.070 L Step-1: Preparation of polymer suspension: Solvent (Ethanol) is mixed with surface active agent (Tween 80) and plasticizer (PEG 6000). Polymer is then dispersed in the mixture to prepare Polymer Suspension. Step-2: Heating of core material: Core particles are loaded in fluid bed chamber and hot air is passed through the material to increase the temperature. Different types of fluid-bed coaters include top spray, bottom spray, and tangential sprays are used for encapsulating solid or liquids absorbed into porous particles. Step-3: Spraying of polymer solution suspension in core material: Then polymer suspension is sprayed into a hot chamber. Step-4: Evaporation of solvent and formation of microcapsules: The shell material solidifies onto the core particles as the solvent evaporates. The rapid evaporation of the solvent helps in the formation of an outer layer on the particles. This process is continued until the desired thickness and weight is obtained. The microcapsules obtained are of poly nuclear or matrix type. Schematics of a fluid-bed coater

1. Taste masking
2. To produce free flowing powder
3. Conversion of liquid to solid
4. Reduction of volatility
5. Taste Masking Some drugs are highly bitter such as ciprofloxacin, metronidazole, flucloxacillin, erythromycin etc. These drugs can be coated to make them bitter less. Some drugs having unpleasant taste may me coated before manufacturing of final dosage form. Such as chewable tablets, powders for suspension, suspension etc. Core Material Purpose of Encapsulation Final Product Form Ciprofloxacin Taste-masking Tablet Flucloxacillin Taste-masking Powder for syrup
6. To produce free flowing powder Adhesive materials may be encapsulated to produce free flowing powder.

3. Conversion of liquid to solid Complex coacervation technique is used to produce solid microcapsules containing different liquid. Such as vitamin A, fragrant oils, liquid crystals, flavors, dyes or inks as the core material
4. Reduction of volatility Microencapsulation technique is used to produce solid microcapsules containing different volatile liquid to reduce their volatility which makes them more stable. Example: Menthol Core Material Polymer Purpose of Encapsulation Menthol/methyl salicylate camphor mixture Chitosan^ Reduction of volatility;

Hydrolysis of Aspirin into salicylic acid and acetic acid can be prevented by microencapsulation.

7. Prevention of Drug-Drug Interaction Aspirin in the presence of Chlorpheniramine maleate is hydrolyzed into salicylic acid and acetic acid which is known as drug-drug interaction. About 2% salicylic acid is produced from uncoated aspirin in the presence of chlorpheniramine maleate within 200 days. On the other hand only 0.2% salicylic acid is produced from coated aspirin.
8. Prevention of Drug-Excipients Interaction Excipients may react with drugs. For examples drugs congaing amine group react with lactose. This Drug-Excipients Interaction can be prevented by microencapsulation of drug.

Stability of Aspirin in Presence of CP MAleate

Time (Days)

S al i c y l i c A ci d

Aspirin-CP maleate

Mixture

Microencapsulated

Mixture

Only Aspirin

9. Prevention of Drug-gastric Fluid interaction Some drugs are unstable in the gastric fluid. Omeprazole is break down in the acidic environment of gastric fluid. On the other hand insulin is hydrolyzed in presence of proteolytic enzyme. This instability can be prevented by microencapsulation technique. Category Drug Polymer PPI Omeprazole Eudragit Antidiabiatic agent Insulin Chitosan
10. Reduce gastric Irritation Acidic drug produces irritation in stomach such as diclofenac sodium, aspirin etc. Irritation can be minimized by encapsulation by enteric coating. Cellulose acetate phthalate is an enteric polymer. Highly soluble chemicals may also produce irritation. Category Drug Polymer Result NASID Aceclofenac Eudragit minimize local side effect Highly water soluble solid Potassium chloride Eudragit Reduced gastric irritation
    11. Immediate Release
    12. Sustained release
    13. Delayed release
11. Immediate Release