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Respiratory Diseases & Dermatology > P11, P12 & P13: Topical Drug Delivery > Flashcards

P11, P12 & P13: Topical Drug Delivery Flashcards

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Dermatology Board Prep flashcards
1
Q

what is the structure of the stratum corneum

A

bricks= dead keratin-filled cells
mortar= complex lipid mixture
has rivets holding corneocytes together are specialised protein structures called corneodesomes

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2
Q

what are corneodesomes

A

major structures to be degraded for desquamation of the skin

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3
Q

what are the pathways through the stratum corneum

A

transcellular

intercellular

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4
Q

via which pathway does H2O cross the stratum cornea

A

intercellular

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5
Q

what is the drug/delivery system supposed to do

A

modulate barrier function, treat disease states in the epidermis an dermis, alleviate local pain/inflammation in subcutaneous tissues, elicit systemic pharmacological effect

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6
Q

where is the therapeutic target and how accessible is it

A

surface, stratum corneum, viable epidermis/dermis, skin appendages, suncutaneous tissue, systemic circulation

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7
Q

what happens during percutaneous absorption

A

absorption of drugs from the skin surface into the body

drug penetrates into skin and is taken up by microcirculation

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8
Q

what does percutaneous absorption depend on

A

physiochemical properties of a drug, interactions of drug with vehicle or delivery system and with the skin, condition of the skin

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9
Q

how are topical formulations optimised

A

many are lipophilic with very low aqueous solubility

introduction of co-solvent into a formulation can increase Csat but this has the opposite effect on Ksc/v

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10
Q

how does pH of vehicle influence absorption

A

skin surface pH is acidic
unionised drugs best absorbed
extreme pH values damaging to skin, formulations mostly neutral

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11
Q

how does skin permeation affect absorption

A

some excipients, when incorporated in wehicle, can improve drug flux, but correlation between enhancement efficacy and skin irritation produced

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12
Q

what is the ideal vehicle in drug formulation

A

elicits no pharmacological effects, solubilises the drug, releases the drug with appropriate kinetics, is chemically and physically stable, is cosmetically appealing, is non-allergenic and non-irritating

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13
Q

what are the issues during drug formulation

A

interaction of vehicle with skin, interaction between drug and vehicle, no ‘rules’ for matching a formulation to a particular drug, enhancing delivery without irritating the skin

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14
Q

what physiochemical considerations need to be made during drug formulation

A

MW, lipophilicity, H-bonding, solubility in different solvents

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15
Q

how are formulations selected

A

type of emulsion, lipid content and occlusivity

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16
Q

what type of formulation is preferred for chronic skin disease

A

hydrocarbon-based formulations

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17
Q

how can drug solubility be enhanced

A

by formulation with hydrocarbon-miscible solvents like isopropyl myristate or propylene glycol

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18
Q

what is the water-free PEG-gel formulation

A

polar, 1-phase, semi-solid system, based on polyethylene glycols

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19
Q

what is the water-free lipogel formulation

A

polar, 1-phase, semi-solid system, principally based on triglyceride derivatives

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20
Q

what is the water-free oleogel formulation

A

polar, 1-phase, semi-solid system compromising triglycerides and/or hydrocarbon/ silicon oils and inorganic filter

21
Q

what is the water-free fatty ointment formulation

A

apolar, 1-phase, semi-solid system, based on hydrocarbon materials

22
Q

what are water-free formulations used to treat

A

psoriasis, chronic eczema, mycosis

small area of application to very dry skin

23
Q

what is the base for polar gel formulations

A

water and/or alcohol-based with low lipid content or even lipid free
variety of gelling agents for thickening solutions and suspensions, allowing creatino of diverse formulations

24
Q

what is an emulsion gel

A

hydrogel containing a dispersed lipid phase

25
Q

what are suspension gels

A

suspensions of water-insoluble drugs in hydrogels

26
Q

what is hydrogel

A

semi-solid system, typically compromising large organic molecules inter-penetrated by water

27
Q

what is emugel

A

2-phase system, consisting of large organic molecules inter-penetrated by water and small fraction of emulsified lipids

28
Q

what are gel formulations used to treat

A

acne, acute eczema, allergic skin conditions

small application areas to normal-to-oily and inflamed skin, transparent to opaque semi-solid gels, rapidly absorbed

29
Q

what are emulsions

A

creams, disperse systems and the majority of aqueous formulations
readily adjustable properties, require emulsifiers

30
Q

what are the features of w/o emulsions

A

blend easily with SC lipids, improving bioavailability of lipid-soluble drugs and moisturising skin via slight occlusive effect

31
Q

what are the features of o/w emulsions

A

more cosmetically appealing as lipids therein are finely dispersed
can withdraw moisture from the skin due to surfactant-like emulsifiers

32
Q

what is w/o lotion

A

hydrophobic, semi-liquid, 2-phase system, compromising water and a continuous lipid phase

33
Q

what is w/o cream

A

hydrophobic, semi-solid, 2-phase system, compromising water and a continuous lipid phase

34
Q

what are w/o creams used to treat

A

psoriasis, chronic eczema, mycosis

broad areas of application to normal to dry skin

35
Q

what is o/w cream

A

hydrophilic, semi-liquid, 2-phase system, compromising lipids and a continuous aqueous phase

36
Q

what is o/w cream

A

hydrophilic, semi-solid, 2-phase system, compromising lipids and a continuous aqueous phase

37
Q

what are o/w creams used to treat

A

acne and acute and sub-acute eczema

broad areas of application to normal to slightly dry skin and to inflamed areas

38
Q

what is the absorption base of dermatological formulations

A

apolar, 1-phase, semi-solid system compromising mainly hydrocarbon structures

39
Q

what is the liposome formulation

A

bi- or multi-lamellar phospholipid structure entrapping a hydrophilic core

40
Q

what are nanoemulsions

A

vesicles of phospholipids, surfactant and other lipid dispersed un water

41
Q

what are microemulsions

A

transparent o/w or w/o colloidal emulsions compromising lipophilic and hydrophilic surfactants and water

42
Q

what are emulsifier-free systems

A

2-phase, semi-solid and hydrophilic, comprising various lipids, a continuous aqueous phase and polymers/co-polymers

43
Q

what are multiple emulsions

A

3-phase, semi-solid, hydrophilic (w/o/w) or hydrophobic (o/w/o) systems

44
Q

what are spray emulsions

A

stable, sprayable, 2-phase, semi-liquid emulsions

45
Q

what are foam/mousse formulations

A

gas dispersions in liquids containing lipids and water stabalised with surfactants

46
Q

what are water-free 2-phase systems

A

physical mixture of 2 non-miscible organic phases forming semi-solid stabalised with polymers/co-polymers

47
Q

what are lacquers

A

polymeric film-builders in volatile solvents and plasticiser leaving transparent, elastic and adhesive film on skin/nail

48
Q

what happens to formulations when they are applied to skin

A

structural matrix of formulation may change due to rubbing or loss of volatile excipients leading to increased viscosity
rubbing may cause emulsifying effects

Respiratory Diseases & Dermatology (34 decks)

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