Oral Solution Dosage Forms I Flashcards

1
Q

Properties

Pharmacutical solutions

A
  • Rate of absorption can be limited by precipitation
  • Chemical stability is lowest in solutions
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2
Q

Definition

Pharmacutical solutions

A
  • liquid preparations in which the therapeutic agent and the various excipients are dissolved in the chosen solvent system
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3
Q

Solution

A
  • Easily administered for individuals who have difficulty in swallowing
  • The therapeutic agent is dissolved in the formulation and is therefore immediately available for absorption
  • Reduces the chance of forming a precipitate
  • Taste-masking of bitter therapeutic agents
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4
Q

Disadvantages

A
  • Unsuitable for therapeutic agents that are chemically unstable in the presence of water
  • The poor solubility of certain therapeutic agents may prohibit their formulation as pharmaceutical solutions
  • Expensive to ship and are bulky for the patient to carry (packaging might break)
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5
Q

Co-solvents

A
  • Ethanol
  • Glycerol
  • Proylene glycerol
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6
Q

Examples of Excipients

A
  • Anti oxidents
  • Antimicrobial preservatives
  • pH adjuster
  • Viscosity enhancer
  • Sweetners
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7
Q

Water for non-parental

A

Purified by distilation, ion exchange reverse osmosis

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8
Q

Water for injections

A

Futher purified to remove pyrogens

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9
Q

Drug solubility

A
  • Both the therapeutic agent and the excipients are required to be present in solution over the shelf-life of the formulated product
  • Needs to be homogeneous
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10
Q

High solubility

A

Readily incorporated into the vehicle and formulated as an oral solution

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11
Q

Moderate solubility

A
  • Solubility enhanced using co-solvents or by related methods (changing pH, salt conversion)
  • Aqueous solubility is less than the requested concentration of therapeutic agent
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12
Q

Low solubility

A

Formulated as an alternative-dosage form, e.g. a suspension

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13
Q

Drug dissolution

A
  • Removal of a molecule of the drug from the solid state
  • Formation of a cavity within the solvent
  • Accommodation of the drug molecule into the formed cavity
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14
Q

Propeties that effect solubility

A
  • Molecular weight - less soluble
  • Particle size
  • Solubility ∝ “1” /”melting point”
  • Number of hydrogen bonds
  • Hydrophilic groups (OH-, COO-, NH4+) >
  • lipophilic - groups (methyl, ethyl)
  • Crystalline/amorphous properties
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15
Q

Factors effecting theraputic agents

A
  • Vast majority of drugs are either weak acids or bases and therefore solubility are pH-dependent
  • The solubility of acids and bases increases as the degree of ionisation increases
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16
Q

Weak acidic drugs and solubility

A

pH > pKa solubility increases
less ionised when pH is lower (mainly ionised)

17
Q

Weak basic drugs solubility

A
  • pH < pKa solubility increases
  • Mainly ionised at lower pH (less ionised at high pH)
18
Q

Optimisation of formulation pH

A
  • Adding buffer in the range of pH 5 to 8 suitable to be consumed orally
19
Q

Weak acid into a salt

A
  • The dissolution rate of a weakly acidic drug in gastric fluid is low
  • ↑ pH in the diffusion layer, ↑ dissolution rate, ↑ saturation solubility
  • ↑ pH of the diffusion layer by changing weakly acidic drug from free acid to basic salt
20
Q

Conversion of weak acid to salt benifits

A
  • The sodium salt (naproxen sodium) is absorbed faster and is more effective in indications, such as mild to moderate pain
21
Q

Disadvantage of converting some weak acid to salt

A
  • The sodium salt of aspirin, sodium acetylsalicylate, is much more prone to hydrolysis (phenolicesterbond) than aspirin
  • difficult for manufacuring
22
Q

Co-solvent

A
  • Water used to make it more soluble
  • liquid components (miscible in both phases) incorporated into a formulation to enhance the solubility of poorly soluble drugs
23
Q

Micellular solublisation

A
  • Incorporating drugs into or onto micelles
  • Micellar solubilisation can also increase the solubility of drugs in the GI tract
24
Q

Cyclodextrin complexation

A
  • Aids with solublisation due to outside being hydrophilic
  • Place the hydrophobic solvent into the cyclodectrin
  • Enzymatically modified starches composed of glucopyranose units beta-cyclodextrin
25
Q

Excipients

A
  • To facilitate the administration of the dosage form, e.g. pourability, palatability
  • To protect the formulation from issues regarding physical and chemical stability and to enhance the solubility of the therapeutic agent
26
Q

Buffers

A
  • To maintain the solubility of the therapeutic agent in the formulated product
  • To enhance the stability of products in which the chemical stability of the active agent is pH-dependent
  • Acetates, Citrates and Phosphates
27
Q

Sweeting agent

A
  • To increase the palatability of the therapeutic agent
  • Avoid in oral formulations for children and patients with diabetes mellitus
28
Q

Flavours

A
  • Flavour adjuncts (e.g. menthol, chloroform) that add flavour and desensitise the taste receptors
  • To mask the taste of the drug substance
29
Q

Colourants

A
  • To impart the preferred colour to the formulation
  • The selected colour should ‘match’ the flavour
30
Q

Viscosity enhancing agent

A
  • To ensure the accurate measurement of the volume to be dispensed
  • Admistration via Syringe, Small-metered cup and Traditional 5-ml spoon
  • Syrups, due to the inherent viscosity, do not require the specific addition of viscosity-enhancing agents
  • Increased (and controlled) by the addition of non-ionic or ionic hydrophilic polymers
31
Q

Antioxidants

A
  • Molecules that exhibit higher oxidative potential than the therapeutic agent, to inhibit free radical-induced drug decomposition
  • enhance the stability of therapeutic agents that are susceptible to chemical degradation by oxidation
  • Aqueous soluion and oil based solution
32
Q

Chelating agents

A

To form complexes with heavy-metal ions involved in oxidative degradation of therapeutic agents with antioxidants e.g. Citric acid & EDTA

33
Q

Preservatives

A
  • To control the microbial bioburden of the formulation
  • Broad antimicrobial spectrum
  • Chemically and physically stable over the shelf-life of the product
  • Low toxicity
  • A combination of two members enhances the antimicrobial spectrum