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Making drugs into medicines ☆ > Formulations to improve bioavailability > Flashcards

Formulations to improve bioavailability Flashcards

1
Q

What is the importance of particle size in pharmaceutical dosage forms (6)

A

Influences:

  1. Physical properties of the dosage form
  2. Powder flow
  3. Powder mixing (drug & excipients)
  4. Solubility & stability (suspensions, solutions)
  5. Dissolution
  6. Aerosol deposition
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2
Q

What is the importance of free-flowing powders (4)

A
  1. Important when preparing solid dosage forms (tablets, capsules)

Promotes:

  1. Uniformity of feed
  2. Uniformity of dose
  3. Reproducibility of the finished product
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3
Q

How does the particle side influence dissolution (5)

A
  1. Small particles dissolve more rapidly than larger ones.
  2. The drug in solid dosage form disintegrates into drug crystals exposed to GI fluids.
  3. The drug crystals are then dissolved in GI fluids (dissolution) to then be absorbed in the blood.
  4. Smaller particle size = larger specific surface area.
  5. Specific surface area = surface area/volume
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4
Q

Where do inhaled particles deposit (3)

A
  1. > 5 microns in the mouth and trachea (impaction)
  2. 1-5 microns in the bronchi and bronchioles (sedimendation)
  3. <1 microns in the terminal bronchioles and alveoli (diffusion)
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5
Q

What methods are used for particle size reduction (5)

A
  1. Cutting methods - cutter mill
  2. Compression methods - mortar and pestle
  3. Impact methods - hammer mill
  4. Attrition methods - roller mills
  5. Combined impact and attrition methods - fluid energy mill
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6
Q

How do fluid energy mills work (5)

A
  1. Air is injected as a high-pressure jet through nozzles at the bottom of the loop.
  2. The high velocity of the air gives rise to zones of turbulence into which solid particles are fed.
  3. The high kinetic energy of the air causes the particles to impact with each other with sufficient momentum for fracture to occur.
  4. Particle size reduction is achieved by impact and attrition.
  5. Fine particles are exhausted from the mill, and the remaining coarser particles are retained within the mill for further milling.
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7
Q

What are the mixing processes (3)

A
  1. Complete segregation-A
  2. Ideal or perfect mix-B
  3. Random mix-C
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8
Q

How is segregation overcome (5)

A
  1. Sieving
  2. Milling of components (size reduction)
  3. Reduce the extent to which the powder mass is subjected to vibration or movement after mixing.
  4. Use equipment where several operations can be carried out without transferring the mix.
  5. Production of an ‘ordered mix’
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9
Q

What are the criteria that divide particle-size analysis methods into different categories (5)

A
  1. Size range of analysis
  2. Wet or dry methods
  3. Manual or automatic methods
  4. Speed of analysis
  5. The sample size
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10
Q

What is sieving (6)

A
  1. Sieves stacked in order of ascending aperture size
  2. The powder is placed on the top sieve and agitated (manual or mechanical).
  3. the powder is classified into fractions
  4. A closed pan, a receiver, is placed at the bottom of the stack to collect the fines and a lid is placed on top to prevent loss of powder.
  5. The results are expressed in the form of a cumulative undersize percentage distribution.
  6. Range of analysis = 45-1000um
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11
Q

What are the two microscopy techniques (2)

A
  1. Scanning electron microscopy (SEM)
  2. Transmission electron microscopy (TEM)
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12
Q

How does SEM work (5)

A
  1. 3D image
  2. Greater depth of field
  3. Able to capture the image
  4. Able to measure to nm range
  5. Range of analysis = 0.05-1000um
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13
Q

How does TEM work (5)

A
  1. 2D image
  2. Able to capture the image
  3. Able to measure to nm range
  4. Greater than SEM
  5. Range of analysis - 0.001-0.05um
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14
Q

What are the principles of laser light scattering measurements (3)

A
  1. Based on the interaction of laser light with particles (measure the size of diameter at 1 um-1mm).
  2. Fraunhofer diffraction: With particles that are much larger than the wavelength of light, any interaction with particles causes light to be scattered in a forward direction.
  3. This produces light intensity patterns that occur at regular angular intervals and are proportional to the particle diameter producing the scatter.
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15
Q

What are the different types of solutions (3)

A
  1. Solid solute dissolved in a liquid solvent.
  2. Solid solute - Drug and excipients
  3. Liquid - Aqueous or a combination of Aqueous / Non-aqueous
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16
Q

What are aqueous solvents (3)

A
  1. Potable water
  2. Purified water
  3. Water for injections
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17
Q

What are non-aqueous solvents?

A

Used as co-solvents with water to enhance solubility/stability of drugs

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18
Q

What are the issues surrounding non-aqueous solvents (4)

A
  1. Toxicity
  2. irritancy
  3. Drug solubility
  4. Glycerol, ethanol, poly(ethylene glycol) -Low concentrations
19
Q

Why is drug concentration below its saturation point solubility?

A

prevents precipitation

20
Q

What are the properties of excipients (3)

A
  1. Non-toxic
  2. Non-irritating
  3. Biocompatible
21
Q

What are the functions of excipients (5)

A
  1. Product stability
  2. Bioavailability
  3. Patient acceptability
  4. Manufacture
  5. Route of administration can influence excipients.
22
Q

What is important for solutions by different routes (4)

A
  1. Parenteral & Ocular - Sterile
  2. Oral - Palatable
  3. Solutions contact body fluids - Isotonic and at physiological pH.
  4. Multidose products - Preservatives and prevent microbial growth
23
Q

How must solution stability be kept stable for the duration of shelf life (4)

A
  1. Physical (colour, viscosity, taste)
  2. Efficacy
  3. Remain sterile
  4. The chemical nature of the drug must not change.
24
Q

How is the chemical degradation of solutions prevented (3)

A
  1. Formulate at pH, favouring drug stability.
  2. Add antioxidants and/or metal chelators.
  3. Remove oxygen by purging it with nitrogen.
25
Q

What are the advantages of solutions (4)

A
  1. Rapid drug action as the drug is dissolved
  2. A range of doses can be administered.
  3. Patient acceptability
  4. Ease of manufacture
26
Q

What are the disadvantages of solutions (3)

A
  1. Many drugs are unstable and poorly soluble.
  2. Liquids are bulky
  3. Packaging and transport costs are high.
27
Q

Why administer drugs via the parenteral route (4)

A
  1. Some drugs are broken in GIT and are inactivated.
  2. Provide a highly localised effect.
  3. Rapid distribution and onset of action
  4. Patient is unconscious
28
Q

How are drugs absorbed from the injection site (5)

A
  1. Drugs administered by intradermal, subcutaneous and intramuscular undergo absorption to enter the systemic circulation.
  2. Diffusion through tissues followed by penetration through walls of capillaries of lymph vessels
  3. As solutions absorption is comparable to oral delivery ~30 min
  4. lipophilic drugs can delay absorption as has a higher affinity to fat tissues
  5. Large molecules, i.e. proteins (Insulin) and peptides, are absorbed by lymph vessels.
29
Q

What are the formulation factors for suspensions (2)

A
  1. The drug must dissolve from a solid state before absorption.
  2. It can be used to reduce dose frequency.
30
Q

What is the formulation factor for intramuscular injection solutions?

A

Drugs with low aqueous solubility to provide prolonged effect

31
Q

What are the formulation factors for the release of a drug (3)

A
  1. Solubility of drug in tissue
  2. Surface area of drug
  3. Particle size and crystal structure
32
Q

What are the formulation factors for oily intramuscular injections (3)

A
  1. Non-solutions or suspensions
  2. Steroids, hormones or fat-soluble vitamins
  3. Oil vehicle, i.e. arachis or sesame
33
Q

What are the formulation factors for water-insoluble drugs (2)

A
  1. Chemically modified drugs to produce water-insoluble
  2. More viscous than aqueous solutions and thus does not spread along muscle fibres.
34
Q

What is the formulation factor for Depot?

A

Very slow release as the drug must partition from oil into an aqueous muscle environment

35
Q

What are the excipients for water for injection as solvent (3)

A
  1. Co-solvent for water-insoluble drugs - Ethanol, glycerol,
  2. Solubilising agents to aid the dissolution of hydrophobic drugs
  3. Oil-in-water emulsion - Droplet size < 3 µm to prevent oil embolism in the bloodstream
36
Q

What are the antioxidant excipients (7)

A
  1. Drug substance degrades via oxidation - Nitrogen purged through solution during manufacturing and added during sealing.
  2. Vitamin C (ascorbic acid) - water-soluble – 0.01 – 0.1 % w/v also can adjust pH
  3. Vitamin E (alpha-tocopherol) - oil-based products – 0.001 – 0.05 % w/v
  4. Sodium metabisulphite - used for acid parenteral products
  5. Sodium bisulphite - used for neutral products
  6. Sodium sulphite - used in alkali products
  7. Chelating agents - remove metal elements that can act as catalysts in oxidation (copper, iron, manganese)
    EDTA 0.0005 – 0.01 % w/v
37
Q

What is the importance of buffer excipients (5)

A
  1. The physiological pH of plasma and extracellular fluid is 7.4. However, drugs may be soluble at different pHs, and stability may also be at different pHs, so we have to compromise
  2. pH must be 3 – 9 Above or below can cause tissue damage at the injection site
  3. Can adjust using acidifying or alkalising agents
  4. Buffer was added to maintain pH at the optimum value regarding solubility and stability.
  5. Citric acid, sodium acetate, sodium lactate, mono and dibasic sodium phosphate
38
Q

What is the danger of a hypotonic solution, and how can this be solved (4)

A
  1. Lower osmotic pressure than plasma - If mixed with blood, causing blood cells to swell and burst as water enters via osmosis.
    Made isotonic with:
  2. Sodium chloride
  3. dextrose
  4. mannitol
39
Q

What is the danger of hypertonic solutions, and how can this be solved (4)

A
  1. Higher osmotic pressure than plasma - If mixed with blood, causes cells to shrink as cells lose water via osmosis
    Made isotonic by:
  2. dilution prior to use according to pharmacopoeia
  3. Subcutaneous, intradermal, intramuscular not pharmacopoeia requirement but desirable
  4. Intrathecal & intraocular should be isotonic to avoid changes in pressure in cerebrospinal fluid and the eye
40
Q

What are the properties of pressurised metered-dose inhaler delivery (3)

A
  1. Propellant
  2. Solution or suspension
  3. Excipients
41
Q

What are the properties of dry powder inhaler delivery (5)

A
  1. Drug alone
  2. Carrier – Drug
  3. Carrier is sugar-based, lactose, trehalose and mannitol.
  4. 50 – 150 µm
  5. Flow aid
42
Q

What are the types of nasal drug delivery (2)

A
  1. Mucoadhesive polymers - Adhere to epithelial surface and nasal mucus and increase residence time
  2. Cellulose derivatives
43
Q

What are the properties of solid dosage forms (4)

A
  1. Contain more than one ingredient.
  2. Active drug
  3. Other excipients
  4. Diluents, binders, disintegrants and lubricants

Making drugs into medicines ☆ (13 decks)

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