Capsules, Coatings, Crystals Flashcards
Differentiate between atoms, molecules, crystals, and particles.
• Atoms: The smallest unit of an element, consisting of protons, neutrons, and electrons.
• Molecules: Groups of two or more atoms bonded together (e.g., H2, C2H5OH).
• Crystals: Solids with molecules arranged in a regular, repeating pattern over long distances.
• Particles: Aggregates of crystals or molecules, often observed microscopically.
Define the term “crystalline material.”
Crystalline materials are solids characterized by long-range order, where molecules are arranged in a regular pattern in three dimensions.
Define the term “amorphous material.”
Amorphous materials lack long-range order. Their molecules are arranged randomly, similar to a liquid, but the material is solid (e.g., glass).
Discuss the importance of the crystalline state in pharmacy.
• Crystalline structures influence the solubility, dissolution rate, and bioavailability of drugs.
• Understanding the crystalline state helps control the physicochemical properties of pharmaceutical powders, improving drug formulation and efficacy.
What is polymorphism in the context of crystalline materials?
Polymorphism refers to the ability of a substance to exist in multiple crystalline forms with different three-dimensional arrangements of the same compound.
Describe the basic steps of crystallization.
- Nucleation: Formation of small clusters of molecules.
- Growth: Expansion of these clusters into larger, defined crystals.
- Maturation: Crystals reach their final size and shape.
How does the solid state influence drug solubility and dissolution?
• Solubility depends on the crystal structure (Cs).
• Dissolution rate affects bioavailability, as only dissolved drugs are absorbed.
• Crystal size and shape can impact these properties.
What is a crystal unit cell?
The smallest repeating structure of a crystal, defined by its dimensions (a, b, c) and angles (α, β, γ), that replicates throughout the crystal.
How can we differentiate between crystalline and amorphous materials?
Crystalline materials scatter X-rays in a regular pattern, while amorphous materials do not show such order when exposed to X-ray radiation.
What holds crystalline solids together?
Crystalline solids are held together by non-covalent intermolecular forces, such as:
• Electrostatic interactions (e.g., NH3+…Cl-)
• Hydrogen bonds (e.g., δ+C=O…δ+H-O)
• Dipole-dipole interactions
• Dispersion forces (van der Waals forces).
How does polymorphism affect solubility and bioavailability?
Different polymorphs have varying solubility due to differences in crystal packing. Solubility impacts the dissolution rate, which in turn affects bioavailability.
Describe the steps in crystallization from a solution.
- Dissolve solid in a solvent to saturation.
- Remove excess solid to form a saturated solution.
- Cool or evaporate solvent to reach supersaturation.
- Nucleation and crystal growth occur.
What is the difference between solvates, hydrates, and co-crystals?
• Solvates: Crystals containing solvent molecules in their structure.
• Hydrates: Solvates with water as the solvent.
• Co-crystals: Crystals composed of the API and a neutral compound, not a solvate or salt.
How can the solubility of a poorly soluble API be improved?
- Use a different polymorph.
- Create a salt form.
- Form a co-crystal with another molecule.
What are the main types of capsules?
- Hard Capsules: Two-piece shells filled with dry solids or liquids.
- Soft Capsules (Softgels): One-piece shells filled with liquids or pastes.
Why are capsules used in pharmaceuticals?
Capsules protect the API, mask unpleasant tastes, and allow for precise dosing and controlled drug release.
What materials are used to manufacture capsules?
• Gelatin or hydroxypropylmethylcellulose (HPMC)
• Water
• Plasticizers (for soft capsules)
• Colourants and preservatives
What are the quality tests for capsules?
Capsules must pass tests for weight uniformity, API content, disintegration, and dissolution time.
How is gelatin produced for capsule manufacturing?
• Acid Process: Collagen treated with acid, heated, filtered, and dried.
• Alkali Process: Collagen treated with NaOH, demineralized, filtered, and dried.
What are the advantages and disadvantages of gelatin in capsules?
• Advantages: Non-toxic, soluble at body temperature, and good film-forming properties.
• Disadvantages: Unsuitable for vegetarians as it is derived from animal by-products.
What are common excipients in powder-filled capsules?
• Diluents: Improve plug formation.
• Lubricants: Reduce adhesion.
• Glidants: Enhance flow properties.
• Disintegrants: Help break down the capsule.
What are the main reasons for coating pharmaceutical dosage forms?
• Protecting the API from light and moisture.
• Masking the taste of the drug.
• Improving ease of swallowing.
• Enhancing product appearance and brand identification.
• Facilitating identification by manufacturers, pharmacists, and patients.
• Improving handling during manufacturing (e.g., flow, strength, reducing cross-contamination).
• Imparting modified-release characteristics.
What are the three main types of coating processes?
- Film Coating: Thin polymer-based coating applied to tablets, capsules, or multiparticulates.
- Sugar Coating: Sucrose-based coating for tablets, providing a glossy finish and taste masking.
- Compression Coating: Compacting granular material around a tablet core, often used to separate incompatible materials.
What are the two types of film coatings and their purposes?
- Immediate-release film coatings: Non-functional, water-soluble, used for appearance and identification.
- Modified-release film coatings: Include gastro-resistant coatings (soluble at pH >5-6) and extended-release coatings (consistent release over 6-12 hours).
What is the film-coating process?
• Spraying a liquid polymer-based formulation onto rotating or fluidized dosage forms.
• Removing solvent through drying, leaving a thin polymer film.
What are the components of a film-coating formulation?
• Polymer
• Plasticiser
• Colourants
• Solvent/vehicle
What are the requirements for film-coating polymers?
• Solubility (in GI tract and solvents).
• Viscosity (low for ease of transfer).
• Permeability (important for taste masking and stability).
• Mechanical properties (strength, flexibility, adhesion).
Name some polymers used in immediate-release coatings.
• Cellulose ethers: Hydroxypropylmethylcellulose (HPMC), Methylcellulose (MC).
• Synthetic polymers: Polyvinyl alcohol (PVA), Poly(N-vinylpyrrolidone) (PVP).
Which polymers are used for modified-release coatings?
• Cellulose derivatives: Ethylcellulose (e.g., ETHOCEL™).
• Methacrylic acid copolymers (e.g., Eudragit®).
What are the steps in the sugar-coating process?
- Sealing (waterproofing the core).
- Subcoating (applying bulking agents, antiadherents, binders).
- Smoothing (sucrose to even the surface).
- Colouring (using dyes or pigments).
- Polishing (adding wax for a glossy finish).
- Printing (logos, names, dosage).
What are the benefits of sugar coating?
• Low cost and simple equipment required.
• Glossy, attractive finish.
• Taste masking, improving swallowability.
Why are plasticisers used in coatings?
To improve film flexibility and reduce residual stresses during drying.
What are examples of plasticisers?
Propylene glycol, oligomeric PEG, diethyl phthalate (DEP), triethyl citrate.
What types of colourants are used in coatings?
• Water-soluble dyes (e.g., Quinoline Yellow).
• Water-insoluble pigments (e.g., Titanium Dioxide, Iron Oxides).
What is compression coating, and what is its primary use?
Compaction of granular material around a tablet core, mainly to separate incompatible materials.
