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Dermatology Lectures > Pharmacology and Skin > Flashcards

Pharmacology and Skin Flashcards

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Dermatology Board Prep flashcards
1
Q

Major routes of drug administration through skin?

A

Topical
Transdermal
Subcutaneous

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2
Q

Single most important barrier to drug penetration?

A

Stratum Corneum

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3
Q

What does the stratum corneum consist of?

A

Corneocytes (hardened dead keratinocytes)

Surrounded by intercellular lipids

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4
Q

Brick and Mortar model of the stratum corneum?

A

Bricks: corneocytes embedded in a filaggrin matrix
Surrounded by cornified cell envelope

Mortar: Multiple lamellar structure of intercellular lipids, cholesterol, free fatty acids

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5
Q

How do corneocytes have tensile strength?

A

Highly cross-linked by protein rivets

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6
Q

Drug delivery into stratum corneum process when applied topically?

A

Passive process

Mediated by diffusion when a drug is applied topically

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7
Q

When is topical application most commonly used?

A
  • Superficial skin disorders (eczema, psoriasis)
  • Skin infections
  • Itching
  • Dry skin
  • Warts
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8
Q

Choices of type of topical treatment are decided by?

A

Physiochemical properties of drug

Clinical condition

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9
Q

What law does the rate of absorption of topical creams follow?

A

Fick’s law of diffusion

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10
Q

Kp=?

A

Permeability coefficient

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11
Q

Cv=?

A

Concentration of a drug in the vehicle

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12
Q

What are Cv and Kp highly dependent on?

A

The vehicle of transmission (ointment, paste, cream)

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13
Q

Important factors of the vehicle that can affect extent of absorption of drug and rate of absorption?

A

Dissolved concentration of drug in vehicle

Movement of the drug from vehicle into stratum corneum and deeper

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14
Q

What is the driving force for skin penetration in topical drugs?

A

The fraction within the vehicle that is solubilized

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15
Q

What factors can improve topical drug absorption?

A
  • Hydration of the skin
  • Site of application
  • Integrity of the epidermis
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16
Q

Side effects of long term use of higher potency steroids?

A
  • Steroid rebound
  • Skin atrophy
  • Systemic effects
  • Steroid rosacea
  • Production of stretch marks
17
Q

How do glucocorticoids signal?

A

Via nuclear receptors specifically GRa

18
Q

How do glucocorticoids enter cells?

A

By diffusion across plasma membrane

19
Q

Journey of glucocorticoids?

A
  • Diffuse across plasma membrane
  • -Within cytoplasm they combine with GRa, producing dissociation of inhibitory heat shock proteins
  • Within the nucleus activated receptor monomers assemble into homodimers and bind to glucocorticoid response elements
  • Transcription of specific genes either switched on or switched off to alter mRNA levels
20
Q

How are drugs delivered sub cutaneously?

A

Needle inserted into fatty tissue

21
Q

How does a subcutaneous drug reach systemic circulation?

A

Diffusion into either capillaries or lymphatic vessels

22
Q

Advantages of subcutaneous administration?

A
  • Absorption is relatively slow due to poor vascular supply (pro & con)
  • Can be used to introduce a depot of drug or drug under the skin that is very slowly released into circulation
  • Relatively simple, not very painful
23
Q

Disadvantages of sub cutaneous administration?

A

Injection volume is limited

24
Q

Why the skin is an attractive route for a lack of systemic side effect?

A

Avoids first pass metabolism - to liver and intestine and potential toxicity to those organs
-Potentially allows for steady state plasma concentration of drug to be achieved over prolonged period of time

25
Q

What is transdermal drug delivery?

A

Drug is usually incorporated into an adhesive patch applied to the epidermis

26
Q

What type of drugs is TDD most suitable for?

A
  • Low molecular weight
  • Moderately lipophilic
  • Potent
  • Relatively brief half-life
27
Q

Advantages of Transdermal drug delivery?

A
  • Steady rate of drug delivery
  • Decreased dosing frequency
  • Avoidance of first pass metabolism
  • Rapid termination of action if t1/2 is short
28
Q

Disadvantages of TTD?

A

Relatively few drugs suitable for it, allergies, cost

29
Q

Examples of TDD drugs?

A
  • Scopolamine
  • Nicotine
  • GTN
  • Fentanyl
  • Buprenorphine
  • Estradiol
30
Q

Agents of enhancing TDDs?

A

Water

Variety of solvents

Dermatology Lectures (19 decks)

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