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Pharm304 > Parenteral Drug Delivery > Flashcards

Parenteral Drug Delivery Flashcards

0
Q

Why do we need modified release injectables?

A
  • short acting injections have limitations for chronic care products
  • improved safety and/or efficacy with modified release formulations
  • improved patient compliance as you reduce the injection frequency
  • cost reduction
  • allows bolus delivery for some drugs that would otherwise require slow iV infusion
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1
Q

Why do we use injectables?

A

~15% of current drug delivery market are injectable prodcuts

-there is increasing potential requirements due to the rapid biotechnology revolution

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2
Q

What is drug release?

A

-process by which a drug leaves a drug product and is subjected to ADME, eventually becoming available for pharmacologic action

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3
Q

What is drug release related to?

A

First step: Dissolution

Diffusion

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4
Q

What is diffusion in terms of drug release?

A

Transport of drugs from the dosage form matrices into the absorption site

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5
Q

What is drug release controlled by?

A

Physicochemical properties of the drug and delivery system

It is also controlled by the biological system

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6
Q

What are the fundamental parameters governing the diffusion process?

A

The variables in fick’s law:
Temperature, viscosity of medium, radius of molecule, distance to absorption site, concentration of the drug, diffusion coefficient

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7
Q

What parameters affect the dissolution rate?

A

The variables in the Noyes whitney equation:
Diffusion coefficient
Surface area of solid
Solubility of solid
Concentration of solute in the bulk at time t
Thickness of the diffusion layer

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8
Q

How can parenteral modified release delivery systems be achieved?

A
  • dissolution controlled depot
  • adsorption type depot
  • partition controlled depot
  • esterification type depot
  • encapsulation type
  • insitu solidifying depots
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9
Q

What is dissolution controlled release?

A

Form of MR Pareneteral preparation that is

  • aqueous based
  • can also be oil based, but will mean slower release due to dissolution and partitioning differences
  • Decreases the release/absorption rate by reducing the drug dissolution rate of the tissue fluid E.g. Suspensions of macrocrystals or micronised particles such as long acting penicillin and insulin
  • dissolution and hence absorption can be controlled to produce long acting products like depot antipsychotics (Depixol), depot hormones (Depo-Provera), depot anticancer agents (Elingard)
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10
Q

What are adsorption type depot formulations?

A
  • a from of MR parenteral preparation which forms a depot in the muscle mass from which the drug is slowly absorbed
  • C Max is usually seen within 1-2hours
  • only free rug is available for absorption
  • e.g. Diptheria vaccine containing antigens bound to Al(OH)3 gel
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12
Q

What are esterification type depot formulations?

A

-A form of MR parenteral drug formulation where bioerodable esters of drugs are formulated within an oily vehicle which forms a reservoir at the injection site.

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13
Q

What are encapsulation type depot preparations?

A
  • A form of modified release parenteral drug formulation
  • the drug is encapsulated or dispersed in biodegradable/bioadsorbable polymers or macromolecules. It forms colloidal particle spheres, capsules and ‘somes’
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14
Q

What are examples of biodegradable or bioabsorbable polymers or macromolecules used in encapsulation type depot preparations?

A
  • gelatin
  • dextran
  • lactide/glycolide copolymers
  • phospholipids,
  • long chain fatty acids
  • glycerides
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15
Q

What are examples of the particle spheres, capules or ‘-somes’ that encapsulation type depot preparations use?

A
  • solid lipid nanospheres
  • niosomes
  • liposomes

These are considered as carriers

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16
Q

What are in-situ solidifying depots?

A
  • e.g. gels
  • these stay as a free flowing liquids at ambient conditions and solidify in the body as a result of potential triggers such as pH, temperature, ions or hydration
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17
Q

Where are in-situ solidfying depots injected?

A

-either Subcutaneously or intramuscularly

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18
Q

What is the process of drug release for a esterification type depot formulation?

A
  • the drug ester partitions from the reservoir to the tissues
  • the ester bioerodes to release the drug which prolongs the drug action
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19
Q

What is an example of an esterification type depot formulated drug?

A
  • Fluphenthixol deconate is formulated in oil.
  • It is given as a single 10mg/kg IM injection which lasts 10 days. -Onset of action occurs within 24-40 hours
  • the depot is administered every 2-4 weeks
20
Q

What are examples of advanced carrier-based parenteral products?

A
  • microspheres
  • microcapsules
  • polymeric or solid lipid nanoparticles
  • liposomes/PEGylated liposomes,
  • drug polymer conjugates
  • dendrimers
21
Q

What are dendrimers?

A

-highly branched, star shaped macromolecules

22
Q

What are co-polymer based gels?

A
  • These ABA or ABC co-polymers are also called triblock polymers and have properties where they are micelles at room temperature but form a gel when heat is applied.
  • This occurs due to the restructuring of molecules to become a micellular network which can form a gel.
  • not all micelles can do this.
23
Q

What is an example of an ABA triblock copolymer?

A

poloaxmers

24
Q

What are Carrageenan based thermal gels?

A
  • a family of linear sulfated polysaccharides extracted from red edible seaweeds
  • these form a gel when temperature is lowered
  • like starch, which becomes a thicker solution when dispersed in cool water and chilled, when these polysaccharides are dissolved and cooled down in the presence of salt, a gel is formed.
25
Q

Why is choosing a gel base important?

A

the formulation of the gel depends on the nature of the polymer we are using.

26
Q

What process must drug particles in an oil based solution and suspension require?

A

dissolution followed by partition

27
Q

What process must carrier systems undergo?

A

erosion

28
Q

What process must gel systems undergo?

A

erosion of the base before absorption

29
Q

What process must complex/conjugated drugs undergo?

A

drug complex dissociation

30
Q

What is the engineering approach?

A

when a pharmaceutical agent is encapsulated within or attached to a polymer or lipid, drug safety and efficacy can be greatly improved and new therapies are available

31
Q

What is the engineering approach used to treat?

A

cancers.

-parenteral routes of delivery are essential to maintain the ‘engineered’ features of the delivery systems

32
Q

What are the advanced features of the engineering approach compared to conventional dosage forms?

A
  • improves therapeutic effectiveness
  • lowers systemic toxicity of the drug
  • potentially reduces irritancy at active site
33
Q

What are the reasons behind the advantages of the engineering approach compared to conventional dosage forms?

A
  • more consistent drug concentrations in blood
  • site specific drug delivery
  • long circulating (favourable distribution)
34
Q

What are the different types of targeted drug delivery?

A
  • passive targeting
  • active targeting
  • other targeting mechanisms
35
Q

When is passive targeting used?

A
  • for small molecules e.g. nanosized drug particles for tumours
  • results in an enhanced permeability and retention effect in tumours
36
Q

What are the features of tumours which allow us to passively target them?

A
  • leakage of vasculature

- relatively suppressed lymphatic system.

37
Q

When is active targeting used?

A
  • when a carrier molecule is required.

- these can be recognised by a specific cell type such as a tumour

38
Q

What does active targeting invovle?

A
  • surface modification to incorporate an antigen or specific antibodies
  • attachment of cell receptor specific ligands such as folic acid.
39
Q

What are other targeting mechanisms?

A
  • mechanisms which only release the drug when exposed to specific microenvironments like changes in temperature.
    e. g. therma; sensitive liposomes
40
Q

What are examples of advanced drug delivery systems in the market?

A
  1. CALEYX which are sterically stabilised liposomes of doxorubicin. They have a long plasma half life and reduced toxicity
  2. MYOCET which are liposomes containing doxorubicine citrate. It is a small sized liposome with reduced toxicity
  3. ABRAXANE which is a protein bound paclitaxel nanoparticle formulation.
41
Q

What is Abraxane?

A
  • the first albumin bound taxane particle of ~130nm that takes advantage of albumin.
  • albumin is an insoluble protein and acts as the body’s key transporter of nutrients and other water-insoluble molecules
  • albumin selectively accumulates in tumour tissues
42
Q

What is long circulation?

A

-where there is a circulating reservoir containing the drug in the blood compartment by essentially reducing the drug’s body distribution

43
Q

How is long circulation achieved?

A
  • the carrier surface has to be altered to optimise drug targeting and to achieve prolonged circulation times
  • often done with PEGylation
  • this also avoids rapid rclearance by the reticuloendothelial system
44
Q

What is PEGylation?

A

the covalent coupling of non toxic, hydrophilic polyethylene glycol to pharmaceutical ingredients of the carriers.

45
Q

What is the result of lon-circulation and passive targeting using PEGylated liposomes of doxorubicin?

A

an overall increased efficacy and reduced toxicity.

Pharm304 (21 decks)

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