Observations on the Role of Vehicles in Percutaneous Penetration

Biopharmaceutics: Absorption Aspects

“…Hydrophilic ointment contains 37% w/w water and one would expect the thermodynamic activity of salicylic acid in this vehicle to be quite high. This would be also true for the watercontaining emulsions used by Shelmire (177). The rate of penetration of salicylic acid from these vehicles was reported to be very rapid (175,177).…”

“…This would be also true for the watercontaining emulsions used by Shelmire (177). The rate of penetration of salicylic acid from these vehicles was reported to be very rapid (175,177). The thermodynamic activities of salicylic acid at a given concentration in hydrophilic petrolatum and petrolatum would be expected to be intermediate between those in hydrophilic ointment and polyethylene glycol ointment on the basis of solubilities and the anhydrous nature of the former two ointments.…”

Percutaneous Absorption, Vehicles and Dermatological Prescribing

“…and 9 mg per 100 ml when in Hydrated Petrolatum U.S.P. Comparing the effect of different vehicles on the rate of penetration of salicylic acid, Shelmire (1958) found that the threshold concentration was 2-5 per cent and tliat penetration was higliest from oil-in-water emulsions. Profuse erythema was produced after three hours unoccluded contact.…”

“…Total penetration appears to be proportional to the time of ap])lication as long as a concentration gradient exists between the vehicle and the skin (Shelmire 1958).…”

“…Such is probably the case when absorption occurs througli injured skin, at least until the " barrier " reforms. Shelmire (1956Shelmire ( , 1958 showed that both diffusion to the skin surface and percutaneous penetration of highly water soluble drugs are greatest from vehicles having an aqueous external phase. If the vehicle is occluded, the aqueous external phase is conserved and so the amount of drug delivered to the skin surface is increased.…”