Formulation of Topical Preparations

What are the 3 layers of the skin?

• epidermis

• dermis

• subcutaneous

What is the largest barrier to drug diffusion via skin?

What routes pass across this barrier?

• stratum corneum

• transcellular and intercellular

Why does dermis have a large blood supply?

• a metabolically active area

• regulates body temp among other stuff

How are corticosteroid and their metabolites excreted?

• mainly kidneys but also bile

Is oil-in-water, or water-in-oil emulsions more common?

• oil in water more common

What corticosteroids were developed from hydrocortisone?

• prednisolone, betamethasone, clobetasone

Why does it matter that drug metabolising enzymes are expressed in the skin?

• means topical preparations also need to resist metabolism (unless they’re pro-drugs)

What is the FTU method?

• fingertip unit method

• 1 FTU = 1/2g of cream or ointment

• 1 FTU is enough to treat an area of skin tice the size of the adults palm and fingers together

What are counselling points for applying topical formulations?

• clean affected area well with warm water and soap, pat dry with soft cloth, before applying product

• used clean hands to apply (according to FTU)

• avoid touching eyes, mouth when applying topical product

• wash hands with soap and warm water after each application (reduces contamination and systemic absorption)