Topical formulations

Question 1

what is the role of the skin?

Answer 1

• protect us against contaminated atmosphere

- performs protective sensory and homeostatic functions

Question 2

what specific purpose does the skin have?

Answer 2

•Protect the internal body structures by merging
with respiratory, genitourinary and digestive
tracts
•Limit entry into the body of noxious chemicals,
allergens etc
•Stabilise body temperature, BP
•Act as sensory organ (heat, cold, touch, pain)

Question 3

what is the stratum corneum?

Answer 3

• hydrophobic barrier and prevent toxins from entering the skin
• top layer dead skin

Question 4

what brings about the skin pigment?

Answer 4

the melanocytes which is taken up by the kertainocytes

Question 5

what layer in the skin has metabolic enzyme ?

Answer 5

viable epidermis

Question 6

what is 70% of the dermis made from?

Answer 6

collagen

Question 7

what glands within the skin create sweat?

Answer 7

eccrine and apocrine sweat glands

Question 8

what is does the eccrine sweat gland control?

Answer 8

• body temperature homeostasis and emotional
response
• Sympathetic cholinergic innervation – controlled by
central nervous system
• Different sweats for emotion, spice, body
temperature

Question 9

what is the role of the apocrine sweat gland?

Answer 9

Thought to serve as emulsifier of sweat to
stop dripping (forms sheet of sweat), pheromone.

Question 10

what does the sebaceous gland and Together with the hair follicle forms?

Answer 10

pilosebaceous unit

Question 11

when does overactivity of the sebaceous gland do?

Answer 11

causes acne vulgaris normally during puberty

Question 12

whats the main 3 functions of the subcutaneous fat?

Answer 12

• Mechanical protector
• Thermal insulator
• Energy store

Question 13

what are the two reasons for topical delivery?

Answer 13

-local and systemic treatment

Question 14

what affects the rate of drug absorption across the skin?

Answer 14

-concentration of drug applied to the skin
-diffusion coefficient of drug in stratum corneum
-Solute partition coefficient between formulation
and skin
-

Question 15

how to increase the rate of drug across the skin?

Answer 15

• increase conc diff between formulation and skin, by using supersaturated drug formulation
• increasing the drug coefficient by making the drug more lipophilic

Question 16

how do we measure the rate of drug transport across the skin?

Answer 16

-using franz diffusion cell
• Place skin tissue between two glass pieces
• Apply drug solution or formulation
• Take sample through side arm
• Measure drug levels with sensitive analytical technique

Question 17

what types of drug transport across the SC faster?

Answer 17

hydrophobic

Question 18

what is the process of the drug diffusion in skin delivery?

Answer 18

• Partitioning from formulation into SC
•Diffusion of drug across SC
• Partitioning of drug from SC into lower epidermis
and dermis (if drug is highly lipophilic (high logP
this may be low)

Question 19

what are some factors that affect candidates for transdermal delivery?

Answer 19

Physicochemical nature of the drug (above) 
• Potency of the drug
• Timescale of drug exposure
• Site and condition of skin
• Formulation
• Alteration of skin barrier by formulation
• Skin hydration
• Potency of drug

Question 20

what affects the rate of transdermal drug transport?

Answer 20

• timescale of drug exposure
• site and condition of skin
• ointment, cream, lotion, gel
• alteration of skin barrier by formulation

Question 21

what are the advantages of using transdermal skin patches?

Answer 21

•Avoids first-pass metabolism of drug in liver
•Consistent site of absorption i.e. no missing gut
absorption window, food effects etc
•Can give constant drug input rate
•Can stop dosing by removing patch

Question 22

what are the 2 main categories of transdermal skin patches?

Answer 22

• Monolith (matrix) system

* Rate-limiting membrane system

Question 23

what kind of molecules cant diffuse through the skin?

Answer 23

• Large drug molecules like
peptides/proteins are too large
and hydrophilic

Question 24

why cant peptides/proteins be diffused through the skin?

Answer 24

• Peptides/protein rapidly
degraded in GI tract. Skin has
much lower enzymatic activity

Question 25

how are large drugs and peptides diffused through the skin?

Answer 25

-using microneedles

Question 26

what will make it harder for a drug to partition from formulation into the SC?

Answer 26

low Log K