Pharmacology

Question 1

What are the common routes of admission ?

Answer 1

Topical — for local effect
Transdermal
Subcutaneous

Question 2

In the bricks and mortar model of the stratum corneum what are the bricks?

Answer 2

Corneocytes.

Adjacent corneocytes are held together by corneodesmosomes.

Question 3

What is the mortar in this model?

Answer 3

Intercellular lipids.

Very hydrophobic so acts as a resevoir for lipid soluble drugs.

Question 4

True or False

Only local effects require penetration of the stratum corneum

Answer 4

False.

Systemic effects still require it.

Question 5

When are topical treatments most often used?

Answer 5

Local effects.
Especially in the treatment of:
psoriasis, eczema, skin infections, pruritus, xerosis and warts.

Question 6

Give an example of an antihistamine used to treat pruritus

Answer 6

Loratidine

Question 7

What is Ficks Law?

Answer 7

Rate of absorption= permeability X concentration of drug
J=KpCv

Kp encapsules the partition coefficient, the diffusion coefficient and the length of the diffusion pathway

Question 8

What is Km?

Answer 8

The solubility of the drug in the stratum corneum relative to its solubility in the vehicle

Question 9

What is an excipient?

Answer 9

Increases the solubility of the drug in the vehicle e.g. propylene glycol

Question 10

What happens when excess non-dissolved drug is included in transdermal patches?

Answer 10

Increase duration, effectiveness and a better constant

Question 11

Why are topically applied drugs poorly absorbed?

Answer 11

only a small fraction actually goes into the stratum corneum

Question 12

How can the uptake of topical drugs be improved?

Answer 12

Hydrating the skin
Inclusion of excipients which increase the solubility of hydrophobic drugs
Thinner skin areas- scrotum better than nail.

Question 13

When are steroids used?

Answer 13

Topically in eczema

Question 14

What factors effect the potency of the steroids?

Answer 14

body site and thickness of stratum corneum
state of skin
vehicle (ointment>cream/lotion)
Concentration of drug
Hydrocortisone butyrate is more potent than hydrocortisone acetate

Question 15

What is the mechanism of action of steroids?

Answer 15

The lipophilic molecules enter by diffusion across the membrane.
Combine with GRalpha which produces inhibitory heat shock proteins which translocates to the nucleus and assembles into homodimers and bind to GRE in specific genes.
This changes transcription and alters mRNA and therefore the synthesis and levels of mediator proteins.

Question 16

What are the advantages of subcutaneous administration?

Answer 16

Relatively slow since the drug goes through the capillaries which there are few of.
Many protein based drugs are administered this way.
Also many contraceptives.

Question 17

The skin avoids first pass metabolism. Why is this a good thing?

Answer 17

Absorbed and acts quicker.

Isn’t filtered by the liver.

Question 18

What is transdermal drug delivery?

Answer 18

Patches , like nicotine, controlled by diffusion across a cutaneous barrier

Question 19

What qualities do transdermally applied drugs have?

Answer 19

Low molecular weight
Lipophilic
potent
brief half life

Question 20

What kind of product would be wise to use on a wet and weeping skin?

Answer 20

A powder.

Non-oily and will dry it up.

Question 21

What kind of product would be wise to use on a hairy part of the body?

Answer 21

A lotion.

Less oily and will absorb better.