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B33 CAN > B33 CAN Pharmaceutics > Flashcards

B33 CAN Pharmaceutics Flashcards

1
Q

Formulation of cancer drugs depends upon

A

The Physiochemical & Biopharmaceutical properties of the patient

Intended dose & route of administration

Disease Factors (types of cancer & location)

The patient (ADME)

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2
Q

How does therapeutic window guide formulation

A

Cancer drug formulations by simplest pharmaceutics profile route

Narrow therapeutic window

Variation in patients

Dosing close to MTD

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3
Q

Routes of Administration for cancer drugs

A

Oral

Parentarel formulations
- I.V. , I.M. , S.c.

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4
Q

Oral route of administration cancer drugs

A 
Drugs has to be absored via gut
Stays in Stomach
Proteases break down protein drugs (E.g Mabs)
Subject to first pass metabolism
Fed & fasted effects
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5
Q

Parenteral formulations in cancer drugs

A

Avoids N&V and first pass

  • Accurate dosing
  • Flexibility of dose & schedule
  • Rapid onset of action
  • Rapid withdrawal of drug
  • No fed/fasted effect
  • Avoids first pass metabolism
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6
Q

Requirments for IV formulation

A
  • Sterile production

-Formulation stability
Particle size
Solubility
Clearance time

No preservatives

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7
Q

Sub-cutaneous (e.g I.M.) affects

A

Local or systemic affect needed
Rapid absorption for drugs with good solubility
High collagen content in muscle (can bind charged drugs)
Muscles highly vascularised

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8
Q

Topical effects

A

Formulations needed to retain drug at/in skin

Shouldnt penetrate into deep tissue and enter circulationq

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9
Q

How do the constrains placed on the use of I.V. route affect the form of drug used?

A

1) Sterility and size play a factor

2) No precipitation can occur in blood stream

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10
Q

How can chemistry solve formulation problems (Etoposide & doxorubicin)

A

Eptoposide is in solution containign sodium salicylate

Parabens used in lyophilised formulation

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11
Q

Etoposide (Topoisomerase II inhibotor) & sodium salicylate

A

Before

  • Low solubility in water
  • Tendecy to precipitate or crystallise
  • Binds strong to plasma proteins

After Sodium salicylate

  • Improved aq. solubility
  • Reduced precipitaton
  • Reduced protein binding
  • Enhanced F
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12
Q

Doxorubicin and Parabens

A

Before

  • Dox forms stacked dimers and self aggregates
  • Pi-Pi interactions strong between aromatic rings

After additon Parabens

  • Disrupts the self assembly and dimerisation of drug
  • Enabiling rapid dissolution from lyophilised formulation
  • Enhanced F
  • More predictable dosing
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13
Q

Reduced protein binding (Etopside)

A
  • Congregation of lots of charges prevents protein binding
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14
Q

Albumin

A

Albumin binds hydrophobic drugs

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15
Q

Epimerization

A

Chemical process when an epimer is made to transform into its chiral counterpart

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16
Q

Doxorubicin Amino group allows for…?

A

The Amino group in Dox allows for doxorubicin to be formulated as a salt (powder for reconsitiation)

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17
Q

Formulation problems for proteins

A

Proteins are amphiphilic

  • Contain charged amino acids & hydrophoic regions
  • If the protein is denatured or assembled at an interface associaton & aggregation can occur
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18
Q

Protein aggregation at intersurface interfaces

A
  • Protein hydrophobic region comes into contact with vial
  • Hydrophobic region adsorbs to vial surface
  • Other part of protein ‘wobbels about’
  • Another protein can bind to the hydrophillic region and form OLIGOMERS (Aggregates and coalescense)
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19
Q

Hydrophobic & hydrophillic parts of protein forming Particles in bulk solution

A

Hydrophobic region of protein adsorbs to interface
Hydrophillic region is exposed in solution
Shedding of protein due to binding leads to;
Visible & sub-visible particles detected in bulk

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20
Q

When formulating for proteins what should you be wary of

A

Not possible to deliver by oral route (proteins degraded by proteases in stomach)

Charge
Solubility
Stability
Size

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21
Q

What is Enhanced Permeabiility and Retention

A

EPR is Enhanced permeation and retention effect
- In arease around solid tumours or inflammation, the integrity of blood vessels changes -> materials transported also effected
Allowing for increased permeation and reteniton of materials

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22
Q

How do we avoid systemic toxicity (doxorubicin is a potent small cytotoxic agent)

A
  • Enhanced Permeation and Retention effect

- Encapsulate doxorubicin into virus-sized carrier

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23
Q

Factors affecting the EPR effect

A

Vehicle related

  • Particle size
  • Carrier vehicle

Tumour related

  • Tumour Type
  • Microenvironment

External mediators

  • Radiation
  • COX inhibitor
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24
Q

Other factors defining passive targeting

A
  • Prolonged blood circulation of drug carries important
  • Extravasation is slow
  • Reticuloendothelial system (RES) in liver,spleen and lung removes small molecules

Size matters

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25
Q

Liposomal Doxorubicin - Parts and what they do

A

PEG outer finders (Shield)
(Highly hydrated so for protein to adsorb to it must displace H20)

Liposomal phospholipid bilayer - (encapsulates drug)
(

Doxorubicin HCL - Loaded inside by pH gradient
(precipitates and aggregates inside increasing drug load)

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26
Q

Liposomal delivery and EPR effect

A

Small molecules diffuse IN *& OUT easily
Individual cancer cells within tumour pump out small molecules via Efflux transporters

Release of Doxorubicin intracellulary avoids efflux pumps

No efflux pumps for large liposomes so retention

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27
Q

Palmar-plantat syndrome is due to?

A

Palmar-plantar syndrome is damage to peripheral sites due to unwated accumulation of Liposomal doxorubicin at sites with POOR CIRCULATION

28
Q

Albumin in blood transports HYDROPHOBIC molecules this allows it too act as…

A

Albumin binds to hydrophobic molecules in circulation, can be used as a drug carrier e.g Paclitaxel
Exploits albumin receptor (gp-60) mediated transport across EC

29
Q

Mode of action : Potent & water insoluble drug

A

1) Administration followed by rapid dissolution
2) Binding to albumin

3) binding to albumin-specific receptors on EC leads to activation of TRANSCYTOSIS
(albumin & drug carried in via vesicles)

4) Release drug into tumour interstitum
5) Tumour uptake -> tumour cell death

30
Q

What can happen to a poorly soluble drug when injected

A 
Reduced uptake into target cell
Protein binding will occur
Stays in body for a long time (long clearance time(
Dosing can be unpredictable
F is low
31
Q

What are the adv. to a patient using liposomal formulation of anti-cancer drug

A

Can have drug precipitate within liposome -> high drug loading
Less protein binding so drug is cleared from circulation quicker
PEG -> longer circulation of free drug
Can exploit natural mechanisms (Albumin gp60 transport across ECs)

32
Q

What are the disadv. to a drug manufactoror in development liposmal formulation

A

Limiting factor for drug loading
Liposomes highly diluted on injection
- Drug leakage
- Balance of stability liposome and drug release

33
Q

Methotrexate use

A

Management of acute lymphoblastic leukamie

34
Q

Methotrexate MOA:

antimetabolite

A

Antagonist of folic acid
Immunosuppresant properties
Inhibits DHFR -> preventing formation of THF from DHF which is necessary for DNA, RNA and protein synthesis
Cell cycle-specific

35
Q

PK (Pharmacokinetics of MTX)
MTX needed for parentaral for cancer due to Long circulation and residence time needed (Only kills actively rapidly divinding cells)

A

Low dose rapidly absored from GI tract , High doses less well absorbed (Only a finite number of influx carriers of RFC)
I.M. MTX rapidly and COMPLETELY absorbed
Explains why oral MTX dosing isn’t suitable for Cancer

36
Q

MTX toxicity is due to..

A

The penetration of Ascitic fluids

- Acts as depot and enhances toxicity even after serum concentrations fall

37
Q

MTX PK - Active transport mechanism -> TRAPPING

A

MTX enters cell by active trasnport
-> converted into cojugate drug that is NOT ACTIVELY exported
MTX can remainin body several months

38
Q

Consequence of MTX conjugate drug trapping

A

Can lead to development of resistance

  • > Decrease influx and increased efflux
  • > Impaired polyglutamylation (needed for active conjugate drug)
39
Q

Practical issues with MTX treatment

A

MTX pharmacokinetics highly variable

  • Affected by AGE, RENAL & HEPATIC function
  • Does not diffuse across lipi membranes

Main route of Elim

  • Glomerular filtration
  • Active tubular secretion
  • Toxicity dependent on duration
40
Q

Practical issues with MTX treatment

A

MTX can bind to plasma proteins

Negative effects of aspirin and other NSAIDs
- Displace MTX from protein - increased serum levels of free MTX
Inhibit MTX secretion in proximal tubule reducing RENAL clearance
- Increase duration of MTX exposure hence INCREASE toxicity

41
Q

High dose MTX can result in…?

A

High dose MTX can result in SUPERSATURATION of the urin with MTX and metabolites
Crystals cause intrarenal obstruction (acute renal failure)

Crystal formation;
Acid urine

Crossing the blood-brain barrier

42
Q

MTX development of resistance

A

Intervention in DNA and RNA sythesis can form resistant phenotypes

43
Q

MTX overdose

A

Antidote folinic acid is given I.V.
- Maintains high hydration avoiding acidic urine

Single acute oral ingestions rarely cause ADE: (Absorption of MTX is active, easily saturated, F decrease high doses)

44
Q

What problems arise due to protein binding in MTX (comapre with ABRAXANE)

A

The volume of distribution of MTX is 0.6L/KG. It is poorly lipid soluble.
Protein binding also leads to MTX being excreted slower. and a variation that leads to toxicity threapetuic windows

45
Q

What are the adv. and disadv. of drugs which exploit active transport processes

A

Adv
- Allow MTX to be taken up by active process by receptors

Disadv.

  • Development of resistant at cell membrane level
  • Can decrease influx with changes in RFC and with increased efflux of MTX
46
Q

Treatment of prostate cancer requires….?

A

Treatment of prostate cancer requires sustained release of PEPTIDE THERAPEUTIC

47
Q

Goserelin is a…?

A

Goserilin is a DECAPEPTIDE AGONIST of Lutenising hormone releasing hormone LHRH
SHORT HALF LIFE - CONSTANT INJ

48
Q

How to get slow sustained release for LHRH?

A

Polymer material that dissolves slowly and reveals new drug reservers continually

49
Q

Achieving Slow Dissolution: Option 1

A

HMW water-soluble polyemer that disentagles over time

50
Q

Achieving slow Dissolution:

Option 2

A

Polymer that chemically breaks down

51
Q

Achieving slow dissolution O1: Problems

A

Unreliable as dependent on entalngment
Most polymers dissolve to quick
How is polymer excreted after?

52
Q

Designing polymers that slowly break down in the body needs…?

A

A chemical group that hydrolyses

53
Q

General rule on rate of hydrolysis & Polymer

A

Anhydrides > Orthoesters > Esters > Amides(peptides)

Polymer must be water-insoluble but LMW degradation products must be water soluble

54
Q

Degradation is…?

Erosion is…?

A

Degradation is the chemical breakage of bonds

Erosion only starts when the polyer chains have decreased in MW enough to drive WATER solubilty

55
Q

Poly(lactid acid) polyermised from….

A

Polylactic acid polyermised from DIMER called LACTIDE

56
Q

The effect of stereochemistry on PLA degradation…?

& explained?

A

DL-Lactic acid takes 1 year
L-Lactic acid takes 2 years to degrade fully

Explained by CRYSTALLINITY, L-Lactic acid is semi-crystalline and DL-Lactic acid is amorphous

(DENSER, LESS WATER PEN, SLOW HYDROLYSIS)

57
Q

PLA undergoes BULK EROSION

A

Water penetration and chain scission is FASTER than erosion (SOME drug escapes with these)

58
Q

PLA + Glycolic acid

A

Adding Glycolic acid, GA is more susceptible to hydroylsis (DUE to lack hydrophoic Methyl group)

59
Q

Increasing GA in PLGA …..?

A

Incrreasing GA in PLGA should INCREASE degradation rate in patient

60
Q

The effect of AUTOCATALYSIS

A

Autocatalyic degradation is in rod systems
(dosing more rapid than predicted)

Hydration and fragmentation of the rod allows drug release by diffsuion

LMW chains increase early erosion
+ Increase LOCAL acidity as PLGA cannot escape rod

61
Q

What parameters can be varied in polymer formations to control the release of drug

A

Amount of LMW and HMW polyermers added
The ratio between the sterochemistry ( DL vs L-lactic avid)
Ratio between polymer and GA added

62
Q

Adeno virions drug delivery

A

1) Adenovirus virions bind to CAR and intergrins on plasma membrane
2) Virions enter cell by receptor-medidated endocytosis
3) Endosome acidifies and capsid breaks down releaseing viral contents

63
Q

siRNA MOA:

A

After internilization into cell, siRNA duplex Recongnizd and unfolded by RNA inducing silecning complex (RISC)
RISC catalyses cleavge of mRNA of specific sequence and PREVENTS it from being transcribed into protein

Endonuclease occurs

64
Q

Biological barriers & Delivery challengs of siRNA

A

Rapidly degrades by nucleases
Size allows glomerular filtration (ELIMINATED With URINE)
Hydrophlic

Toxicity or Off target effects

65
Q

Cancer cells have efflux transporters for small molecule drugs but not for liposomes

A

TRUE

B33 CAN (5 decks)

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