Systemic absorption of topical salicylic acid

Area of Science:

• Dermatology
• Pharmacokinetics
• Toxicology

Background:

• Salicylic acid is commonly used topically.
• Understanding its systemic absorption is crucial for safe and effective use.
• Vehicle formulation can influence drug penetration.

Purpose of the Study:

• To investigate the systemic absorption of salicylic acid after topical application in humans.
• To evaluate the impact of different vehicles (hydrophilic ointment, polyethylene glycol 400) on absorption.
• To assess the potential for systemic toxicity with repeated topical application.

Main Methods:

• Subjects received topical salicylic acid in hydrophilic ointment or polyethylene glycol 400.
• Skin integrity (stratum corneum removal) was varied.
• Plasma salicylate concentrations were measured over time.
• A one-compartment pharmacokinetic model was applied.

Main Results:

• Systemic absorption was minimal on intact skin.
• Measurable plasma salicylate levels (8 mg/dl) were achieved after stratum corneum removal with hydrophilic ointment.
• Pharmacokinetic modeling indicated potential for toxicity with repetitive application.

Conclusions:

• Stratum corneum integrity significantly impacts topical salicylic acid absorption.
• Hydrophilic ointment vehicle can facilitate systemic absorption, potentially leading to toxicity.
• Caution is advised with repeated topical salicylic acid application, particularly on compromised skin.