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Dermatology > Topical pharmacology > Flashcards

Topical pharmacology Flashcards

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Dermatology Board Prep flashcards
1
Q

What are the 3 main routes of absorption through the skin?

A
  • Intercellular - Between cells
  • Intracellular - Through cells
  • Transappenageal - Through glands
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2
Q

What makes it hard for drugs to pass through the skin?

A

It is hard to navigate the stratum corneum due to its insoluble keratin matrix and intracellular lipid layers

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3
Q

What are some factors that affect absorption through the skin?

A
  • Water solubility (More WS = More absorption)
  • Molecular weight (Perfect = 100-500Da)
  • Oil/water partition coefficient (LogP = 2 is perfect)
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4
Q

What is meant by topical drug delivery?

A

This is a method of delivery that involves applying the drug formulation directly onto intact and healthy skin

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5
Q

What are some skin conditions that can be treated topically?

A
  • Psoriasis
  • Eczema
  • Skin infection
  • Itching
  • Dry skin
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6
Q

What are some advantages of topical drug absorption?

A

Advantages of topical drug administration are that the drugs can be applied directly to the affected tissue and reduce risk of systemic effects, especially in glucocorticoids

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7
Q

What are some disadvantages of topical drug absorption?

A

They can be messy and time consuming, however, and it is hard to ensure the correct dose

It can have systemic effects, moving through the dermis and subdermis and into systemic circulation

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8
Q

What are some formulations of topical drugs?

A

Ointments
Pastes
Creams
Topical solutions
Topical suspensions
Lotions
Gels
Foams
Sprays
Emollients

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9
Q

What are ointments?

A

Ointments are suspensions or emulsions containing <20% water and volatiles, and >50% hydrocarbons, waxes or polyethylene glycol

They may contain ethanol to disrupt the structure of the stratum corneum and increase permeability

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10
Q

What are some advantages of ointments?

A

They help to form an occlusive layer over the skin, preventing loss of heat and water, while also enhancing percutaneous absorption

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11
Q

What are some disadvantages of ointments?

A

They do have a greasy texture however, and are hard to wash off and spread

They can also be easily contaminated

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12
Q

Where are ointments most commonly used?

A

This is most commonly used in glabrous areas (Skin with sparse or short hair, dry areas such as trunk and extremities)

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13
Q

What are the 2 main types of ointments?

A
  • Lipophilic ointments (Base of paraffins, vegetable oils, animal fats, synthetic glycerides or waxes)
  • Water-soluble ointments (Base of polyethylene glycol)
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14
Q

What are pastes?

A

Pastes are stiff ointments which can be used as vehicles for insoluble powders

They contain a large proportion of solid component (>25%)

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15
Q

What are some advantages of pastes?

A

They can be used to restrict the active ingredient to the affected area without spread to the surrounding skin

The powder also acts as an absorbent for discharge

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16
Q

What is a disadvantage of pastes?

A

They are thicker and stiffer than other formulations, however, and so are hard to spread

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17
Q

What are creams?

A

Creams are emulsions containing >20% water and volatiles, and <50% hydrocarbons, waxes or polyethylene glycol

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18
Q

What are the advantages of creams?

A

They are useful in moisturising and have emoilient properties

They are also more spreadable than ointments and can be used on all areas of the body

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19
Q

What is a disadvantage of creams?

A

They are less hydrating that ointments

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20
Q

What are the 2 types of cream?

A
  • W/O emulsions
  • O/W emulsions
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21
Q

What are W/O emulsion creams?

A

W/O emulsions are oily creams (e.g. zinc oxide cream, sunscreens), with a lipophilic continuous phase

They contain W/O emulsifiers such as lanolin,, glyceryly stereate and lecithin

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22
Q

What are the O/W emulsion creams?

A

O/W emulsions are vanishing creams (e.g. topical steroid cream), with a hydrophilic continuous phase

They contain emulsifiers such as polysorbate, sorbitan laurate and cetearyl alcohol

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23
Q

What are topical solutions?

A

Topical solutions are a clear, homogeneous liquid dosage form for external application to the skin, composed of one or more solutes dissolved in aqueous, non-aqueous, or hydroalcoholic solvents

They can contain gelling agents to thicken

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24
Q

What are some advantages of topical solutions?

A

They are more spreadable than ointments and creams and can be used on all areas of the body, whilst also being very simple to make

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25
Q

What are some disadvantages of topical solutions?

A

They can be messy, however, and do not provide any protection or moisturisation to the skin

Alcohol-based solutions can cause stinging, dryness and irritation

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26
Q

What are topical suspensions?

A

Topical suspensions are a liquid dosage form that consists of a solid suspended in a liquid vehicles in a 2-phase system, containing up to 2-% of a finely divided, insoluble drug dispersed in an aqueous or alcoholic vehicle

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27
Q

What are some advantages of topical suspensions?

A

They are easy to apply and so are popular in children, providing a cooling and soothing after effect

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28
Q

What are some disadvantages of topical suspensions?

A

They do require shaking beforehand and require more drying than other formulations

Alcohol-based suspensions can cause stinging, dryness and irritation

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29
Q

What are lotions?

A

Lotions are an emulsion liquid dosage form, containing usually >50% water and volatiles, in which a finely dispersed drug is suspended or dispersed

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30
Q

What are some advantages of lotions?

A

They have moistening and emollient properties and ae more spreadable than ointments

They can be used on all areas of the body

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31
Q

What are some disadvantages of lotions?

A

They are less hydrating than ointments

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32
Q

Where are lotions usually used?

A

They are usually used in dry and exudative skin conditions and are commonly used on flexural or genital areas

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33
Q

What are gels?

A

Gels are transparent semi-solid emulsions that liquefy on contact with warm skin and dry to form a non-occlusive film

They contain water, volatile components (acetone or alcohol) and a gelling agent (Cellulose) to provide stiffness

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34
Q

What are some advantages of gels?

A

They are easy to apply and wash off and are non-greasy, which also providing a cooling sensation

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35
Q

What are some disadvantages of gels?

A

They can be removed by perspiration, however, and provide very little hydration

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36
Q

What are foams?

A

Foams are pressurised liquids added to a hydrocarbon propellant

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37
Q

What are some advantages of foams?

A

They do not contain fragrances or preservatives and are easy to apply

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38
Q

What are some disadvantages of foams?

A

They do not leave a residue

They may result in stinging or burning to excoriated skin and provide very little hydration

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39
Q

What are sprays?

A

Sprays are aerosols consisting of a solution (or suspension) of the drug in the pure propellant, or the propellant plus a suitable solvent

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40
Q

What are some advantages of sprays?

A

They can treat large areas of skin and are easy to app

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41
Q

Where are sprays usually used?

A

They should be used carefully in skin folds, where absorption can be higher

42
Q

What are emollients?

A

Emollients are topic formulations used to enhance rehydration of the epidermis

43
Q

What conditions are emollients used in?

A

They are used in all dry or scaly conditions, especially eczema

Patients are usually perscribed 300-500g in a patient with active eczema, which needs frequent application

44
Q

What are some application tips for emollients?

A
  • Apply immediately after bathing
  • Apply in direction of hair growth
  • Be careful of slippery skin and surfaces
  • Use a clean spoon or spatula to remove from the tub
  • Fire risk if paraffin-based
45
Q

What is involved in wet wrap therapy?

A

They involve layering the body with topical drugs, and then placing cotton wool wraps over the top to keep the drug against the skin for longer periods of time

46
Q

What conditions is wet wrap therapy used in?

A

Very dry (xerotic) skin

47
Q

What are transdermal patches?

A

Transdermal patches are patches placed on the skin surface, allowing movement of a drug into the skin and then blood at a controlled rate

48
Q

What are some transdermal patches used for analgesia?

A

Buprenorphine
Fentanyl

49
Q

What is an example of a transdermal patch used for HRT?

A

Estradiol

50
Q

What is an example of a transdermal patch used for contraception?

A

Ethinyloestradiol with norgelstromin

51
Q

What is an example of a transdermal patch used for urinary incontinance?

A

Oxybutynin

52
Q

What is an example of a transdermal patch used for angina?

A

Glyceryl nitrate

53
Q

What is an example of a transdermal patch used for motion sickness?

A

Hyoscine

54
Q

What is an example of a transdermal patch used for nausea and vomiting in chemotherapy?

A

Granisetron

55
Q

What is an example of a transdermal patch used for Parkinson’s disease and restless leg syndrome?

A

Rotigotine

56
Q

What is an example of a transdermal patch used for Alzheimer’s disease?

A

Rivastigmine

57
Q

What is an example of a transdermal patch used for smoking cessation?

A

Nicotine

58
Q

What is an example of a transdermal patch used for neuropathic pain?

A

Capsaicin

59
Q

What are some advantages of transdermal patches?

A

Transdermal patches are simple, conveniant and painless, allowing for steady and prolonged administration of a drug overtime

There is also no 1st pass metabolism in the liver, unlike with oral administration

60
Q

What are some disadvantages of transdermal patches?

A

Disadvantages include possible local irritation, slow delivery to site of action and they are only useful in lipophilic drugs with high skin permeability and low required dose

61
Q

What are some chemical strategies to enhance transdermal absorption?

A
  • Penetration enhancers:
    • Water
    • Alcohols
  • Prodrugs
  • Novel formulations containing nanoparticles and liposomes
62
Q

How can water increase transdermal absorption?

A

Water in liquid preparations can accumulate in the stratum corneum, resulting in swelling of the corneocytes and the formation of pares that increase permeability

63
Q

How can alcohol increase transdermal absorption?

A

Alcohols disrupt the lipid bilayer in the stratum corneum and increase flux

64
Q

What are some physical strategies of increasing transdermal absorption?

A
  • Electroporation - Use of electric pulses to create new pores and pathways in the skin
  • Iontophoresis - Use of low voltage electric field to drive ionised drugs through the skin
  • Sonophoresis - Use of ultrasound
65
Q

What is a possible consequence of twice daily 40% salicylic acid ointment?

A

Salicylism
Death

66
Q

What are some consequences of vitamin D analogue treatment?

A

Hypercalcaemia
Hypercalcuria

67
Q

What are some consequences of topical steroid use?

A

Adrenal crisis and cushingoid features if stopped abruptly

68
Q

What are some of the actions of glucocorticoids?

A

They suppress lymphocyte proliferation, collagen synthesis, fibroblast proliferation (Scar tissue formation) and release of chemical mediators of inflammation

They can also cause vasoconstriction

69
Q

What skin conditions can glucocorticoids be used in?

A

Immune suppression is useful in allergic responses and eczema

Fibroblast and lymphocyte suppression is useful in psoriasis

70
Q

Describe the movement of glucocorticoids into the cells?

A

Glucocorticoids bind to intracellular receptors (GCRs), belonging to the nuclear receptor family

GCRs are protein monomers containing DNA-binding domains that, in the absence of a ligand, reside in the cytoplasm

71
Q

What are the 2 mechanisms of glucocorticoid pharmacodynamics?

A

Transactivation mechanism
Transrepression mechanism

72
Q

Describe the transactivation mechanism of glucocorticoids

A

Upon binding with their glucocorticoid ligand, GCRs dimerise and translocate inside the nucleus, where they bind to specific DNA responsive elements (GREs) and up-regulate the transcription of genes encoding for regulatory proteins responsible for metabolic, anti-inflammatory, and immunosuppressive effects

73
Q

Describe the transrepression mechanism of glucocorticoids?

A

GCRs can repress gene expression (e.g. genes encoding for pro-inflammatory proteins) by binding negative DNA responsive elements (nGREs) or transcription factors that constitutively drive the expression of these genes

74
Q

How is glucocorticoid potency classified?

A

Glucocorticoids are classified in seven classes of potency (I-VII), with class I being the most potent and class VII the least potent

75
Q

How much ointment could cover the whole body?

A

20-30 grams

76
Q

How much body area can be covered by 1 fingertip unit of ointment (0.5g)?

A

2 hand areas

77
Q

What are some possible side effects of topical glucocorticoids?

A
  • Thinning of the skin
  • Purpura
  • Stretch marks
  • Steroid rosacea
  • Fixed telangectasia
  • Perioral dermatitis
78
Q

What is the action of calcineurin inhibitors?

A

Suppresses lymphocyte activation

79
Q

What are some examples of calcineurin inhibitors?

A
  • Tacrolimus
  • Pimecrolimus
80
Q

What are the uses of calcineurin inhibitors?

A

Topical treatment of atopic eczema, especially on the face and in children

81
Q

What are some possible side effects of calcineurin inhibitors?

A

There is no risk of cutaneous atrophy, but may cause burning sensation of application

There is a risk of cutaneous infections and possible skin cancer risk

82
Q

What is the action of anti-septics?

A

Bacteriostatic or bacteriocidal effects

83
Q

What are some examples of anti-septics?

A
  • Povidone iodine
  • Chlorhexidine
  • Triclosan
  • Hydrogen peroxide
84
Q

What are some uses of anti-septics?

A

Used in recurrent infection (Broad spectrum), skin cleansing and wound irrigation

For example, potassium permanganate is used to acute exudate eczema

85
Q

What are some uses of antibiotics in dermatology?

A
  • Treatment of acne and rosacea
  • Treatment of skin infection (e.g. impetigo)
  • Treatment of infected eczematous process (e.g. otitis externa)
86
Q

What are some dermatological uses of anti-virals?

A
  • Herpes simplex virus (Cold sore)
  • Eczema herpeticum
  • Herpes zoster (Shingles)
87
Q

What are some examples of anti-fungals?

A
  • Nystatin
  • Clotrimazole
  • Terbinafine
  • Ketoconazole
88
Q

What are some dermatological uses of anti-fungals?

A
  • Candida (Thrush) - Nystatin or clotrimazole
  • Dermatophytes (Ringworm) - Clotrimazole or terbinafine
  • Pityriasis versicolor - Ketoconazole
89
Q

What is the action of anti-pruritics?

A

Used to prevent itching

Capsaicin depletes substance P at nerve endings and reduces neurotransmission, building its affect

90
Q

What are some examples of anti-pruritics?

A
  • Menthol
  • Capsaicin
  • Camphor/phenol
  • Crotamiton (E.g. eurax cream)
91
Q

What are the uses of anti-pruritics?

A

Menthol is added to calamine and other lotions and creams to impart a cooling sensation

Camphor or phenol is used for pruritis ani

Crotamiton is used after treament of scabies to relieve residual itch

92
Q

What is the action of keratolytics?

A

Used to soften keratin

93
Q

What is an example of a keratolytic?

A

Salicylic acid ointment

94
Q

What are some dermatological uses of keratolytics?

A
  • Viral warts
  • Hyperkeratotic eczema and psoriasis
  • Corns and calluses
  • Remove keratin plaques in the scalp
95
Q

What is a possible side effect of dithranol?

A

Dithranol is effective, but difficult to use and can only be used on plaques as it can cause burning, irritation and stains on normal skin

96
Q

How are warts treated?

A

Treatment of warts require mechanical pairing, alongside:

  • Keratolytics (E.g. salicyclic acid)
  • Formaldehyde
  • Glutaraldehyde
  • Silver nitrate
  • Cryotherapy (Usually liquid nitrogen)
  • Podophyllin (Genital warts)
97
Q

What are some medications that can be used in psoriasis treatment?

A
  • Coal tar
  • Vitamin D analogue
  • Keratolyics
  • Topical steroids
  • Dithranol
    + Emolient
98
Q

How is stable chronic plaque psoriasis usually treated?

A

Coal tar, vitamin D analogues or dithranol

99
Q

How is scalp psoriasis usually treated?

A

Greasy ointments, tar shampoo, steroid shampoo or vitamin D analogues

100
Q
A

Dermatology (38 decks)

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