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Biopharmaceutics > other types of delivery- peptides/proteins > Flashcards

other types of delivery- peptides/proteins Flashcards

1
Q

what is the problem with delivering protein

A

large hydrophilic molecules, extravascular access is hard, poor stability, hard to absorb, complex pharmacological action

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2
Q

size and shape of macromolecules and proteins

A

macromolecules have limited size, molecular weight and size relationship depends on shape, proteins usually globular and tightly packed

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3
Q

the amount of macromolecules reaching tissues are affected by

A

rate of elimination by kidneys and metabolism

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4
Q

how are macromolecules eliminated

A

kidney filtration

small proteins are eliminated from kidney by glomerular filtration, larger molecules are not

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5
Q

how are small proteins eliminated from the kidney

A

glomerular filtration

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6
Q

what are macromolecules

A

molecule containing lots of atoms eg. protein

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7
Q

why are proteins needed as drugs/medicine

A

to meet unmet conditions idk

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8
Q

properties of protein and peptide drugs

A

large hydrophilic molecule (0.5-100kDa), not well transported across biological membrane, <2% bioavailability, instabilities

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9
Q

describe the physical instability of protein/peptide drugs

A

proteins can easily lose their 3d structure (secondary, tertiary, quaternary denaturation)

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10
Q

what causes physical instability of protein/peptide drugs

A

hydrophobic conditions, surfactants, pH, solvent, temperature, dehydration, lyophilisation

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11
Q

results of physical instability in protein/peptide drugs

A

adsorption- at interfaces
aggregation/precipitation- denatured unfolded proteins interact

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12
Q

main processes of chemical instability in protein/peptide drugs

A

deamidation- asparagine and glutamine residues hydrolysed to form a carboxylic acid

oxidation- methionine, cysteine, oxygen in air, oxygen radical, catalysed by transition metal, peroxide formation

photo-oxidation

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13
Q

comment on the biological stability of protein/peptide drugs

A

hydrolysed into amino acids and small peptides by GI tract, very few are stable to biodegradation

gastric acid causes denaturation

small intestine

colon- less digestive enzymes, substantial microbial enzymes

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14
Q

roles of additives in preformulation of protein/peptide drugs

A

salts- decrease denaturation by binding to protein

polyalcohol- stabilise by selective solvation

surfactants- prevent adsorption of proteins at surfaces and aggregation

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15
Q

chemical modifications of proteins

A

synthetic polymers or lipids covalently bound to proteins

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16
Q

primary sequence alterations of proteins

A

specific amino acid can be changed, improves physical and chemical stability

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17
Q

why chemically modify proteins

A

control pharmacokinetics and pharmacodynamics through the formulation

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18
Q

describe the routes of administration of protein/peptide drugs

A

parenteral- only practical method for most, intravenous/subcutaneous/intramuscular

non parenteral- highly desirable, oral is best, low absorption

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19
Q

advantages and disadvantages of parenteral delivery in protein/peptide drugs

A

advantages- controlled drug release, improves therapeutic index, protects from unwanted drug disposition, extravascular access

disadvantages- particulate system but particles cant cross vascular endothelium, soluble carrier systems have transport/stability problems

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20
Q

types of implantables

A

polymer gel matrix, polymer fibre system, osmotic mini pump, tablet type implants, automatic feedback system

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21
Q

how do implantables work

A

delivered through intramuscular or subcutaneous route

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22
Q

chronobiological effects of protein/peptide drugs

A

zero order controlled released may not be optimal, pulsatile or complex delivery kinetics is beneficial sometimes, optimal pattern for delivery unknown, non zero order delivery difficult to produce

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23
Q

oral delivery of proteins

A

avoids acidic pH and proteolysis

24
Q

problems with using protein/peptide drugs

A

physiological barriers and stability is big issue

25
Q

what is topical delivery

A

delivery of drugs on surface of skin, local action, skin diseases

26
Q

what is transdermal delivery

A

delivery of drugs across/through skin, maximises systemic absorption, drug target in body

27
Q

describe skin structure and function

A

subcutaneous tissue- adipose tissue, fat insulates and prevents mechanical shock, rich blood supply, nerves

dermis- collagen/elastin in mucopolysaccharide gel, nerve endings, sweat and sebaceous glands, low drug conc drugs due to rich blood supply, conc gradient drives drug penetration, drug taken away quickly, lots of water, high aqueous environment

epidermis- keratinocytes differentiates to form corneocytes, Langerhans cells, melanocytes

28
Q

what do melanocytes do

A

produce melanin

29
Q

different routes drugs get transported into skin

A

intracellular route- stratum corneum
intercellular route- main route
shunt route- minor route

30
Q

drug properties that affect permeation

A

drug conc in vehicle

partition coefficient- must be soluble in both oil and water to pass through layers

lipophilic drugs more likely to pass through than hydrophilic- if too lipophilic slow permeation

molecular weight- small penetrate faster

drug structure- hydrogen bonding to skin constituents, pKa causes drug to diffuse into unionised form, unionised is better

31
Q

ideal drug properties for a transdermal drug

A

Log P between 1-4
max molecular weight <500 (low dose is ok)
daily dose 10-20mg, flux 1mg/cm^2 per day, patch size 20cm^2
unionised at pH of skin

32
Q

why is it better for transdermal drugs to be unionised at pH of skin

A

ionised/charged+ more polar so the intercellular route is less of an option

33
Q

adhesive patches for transdermal delivery

A

designed for constant controlled release over an extended period of time, avoids first pass metabolism, liner adhesive and backing layer, low delivery efficiency

34
Q

biological factors of transdermal delivery

A

specify where to apply patch, skin age affects permeability, skin conditions (injury, solvents, disease, hydration), site of application (variation of stratum corneum thickness), skin metabolism, penetration enhancers

35
Q

common targets of topical delivery

A

surface microorganisms, nail, hair, stratum corneum, viable epidermis and dermis

36
Q

functions of a good topical formulation

A

cleansing, lubricant, emollient action

37
Q

formulations of topical delivery

A

complex multicomponent base needed- aqueous bas, thickening/emulsifying agents
vehicle cosolvents enhance permeability and partition into skin
buffer/antioxidant/preservatives

38
Q

formulation designs of topical delivery

A

thin film, open to atmosphere changes in use, short acting, variable delivery rate, low delivery efficiency

39
Q

factors that affect topical delivery

A

application of film, diffusion of drug through vehicle, partitioning of drug from vehicle into skin, partitioning of drug from stratum corneum into viable epidermis, diffusion of drug across skin membrane

40
Q

what is the main barrier of permeation of drugs on skin

A

stratum corneum

41
Q

use of topical delivery

A

skin disease

42
Q

use of transdermal delivery

A

systemic delivery

43
Q

formulation types of transdermal/topical

A

transdermal patches, creams, ointments, gels

44
Q

what does gingival mean

A

on gums

45
Q

what does sublingual mean

A

under tongue

46
Q

what does buccal mean

A

mucosa of mouth, often inside cheek or behind lips

47
Q

issues with buccal and sublingual

A

wet layer with mucin on surface. structure of mucosa shows epithelial tissue like skin, some keratinised epithelium but thickness and keratinisation varies

48
Q

common targets of buccal and sublingual conditions

A

mouth ulcers, sore throat, gum disease, breath freshening, infections, dry mouth, angina, analgesia

49
Q

benefits of buccal and sublingual delivery

A

easy/convenient to administer, easy removal if theres side effects, direct route to systemic circulation avoids first pass metabolism in liver and enzymatic degradation in GI tract, fast action

50
Q

how is drug absorbed by in buccal and sublingual delivery

A

passive diffusion

51
Q

relative permeability for buccal and sublingual delivery

A

sublingual>buccal>external skin

52
Q

sublingual mucosa structure

A

thin membrane, large veins, rapid absorption and good bioavailability

53
Q

what type of drugs has the best absorption and bioavailability and why

A

lipid soluble drugs with small dose, avoids large 1st pass effect, better predictability of dose

54
Q

formulation designs of buccal and sublingual delivery

A

palatable- taste masking, flavouring for patient compliance

buccal dose form- formulated to stick ot mucosa otherwise it might be swallowed, viscous polymer, bioadhesive polymer, design to erode slowly

sublingual tablet- designed to dissolve rapidly for fast and rapid absorption/effect

55
Q

types of buccal and sublingual delivery designs

A

lozenges- sugar/sorbitol glass/compressed tablets, suck to release active agent (like strepsils)

gels-polymers

mouthwash- solution/suspension to rise in mouth

polymer patches- adhesive hydrogel disc

56
Q
A

Biopharmaceutics (11 decks)

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