Principles of topical therapy

Question 1

What is an ointment?

Answer 1

Water in oil emulsion

Question 2

What is a cream?

Answer 2

Oil in a water emulsion

Question 3

What is a gel?

Answer 3

Cellulose cut with alcohol or acetone

Question 4

What is a lotoin?

Answer 4

Oil in water

Question 5

What is a solution?

Answer 5

An alcohol base

Question 6

What factors affect percutaneous absorption of topical therapy?

Answer 6

Patient factors:
* Patient age - suboptimal skin barrier in neonates / prems
* Diseases, physical injuries etc that affect skin barrier (e.g Nethertons)
* skin hydration / occlusion
–> intrigenous zone

Properties of the medicaiton / applicaiton
* Drug / prodrug properties that increase absorption
–> smaller, molecular size
–> increased lipophilicity
–> increased concentration and/ or solubility
* Vehicle compostion
* applicaiton under occlusion increases absorption

Question 7

How do you explain topical steroid dosing to adults?

Answer 7

Best to do in fingertip units (FTUs)
- amount applied from the distal creas to the tip of the index finger from a 5mm nozle

Face - 2.5 FTU
Trunk (front OR back) - 7 FTU
One arm - 3 FTU
One hand, both sides - 1 FTU
One leg - 6 FTU
One foot - 2 FTU

That is based on 1 gram of cream covering a 10 x 10 cm area of skin