Eva Benfeldt, Jørgen Serup, Torkil Menné
DOI: 10.1080/000155599750010210

Our aim was to simultaneously investigate 2 techniques for in vivo sampling of peripheral compartment pharmacokinetics after systemic administration of acetylsalicylic acid. Ten volunteers were given 2 g acetylsalicylic acid orally. Blood samples and dialysates from 4 microdialysis probes inserted in the dermis of the forearm were collected for 5 h and suction blisters were raised 1-3 h after dosing. In microdialysates, both acetylsalicylic acid and the metabolite salicylic acid were measurable in the absence of hydrolysing enzymes. The mean C max (maximum concentration) of total, unbound salicylic acid was 9.5 μg/ml in microdialysates, 13.2 μg/ml in suction blister fluid and 56.5 μg/ml in plasma. Mean T max (time to C max ) for salicylic acid was 188 and 161 min in plasma and microdialysates, respectively. The dermis-to-plasma C max ratio was 0.16±0.04 (mean±SD) by microdialysis sampling and 0.25±0.09 by the suction blister fluid method. Close correlations (p<0.01) were found between C max of salicylic acid in microdialysates and plasma, and between C max of salicylic acid in suction blister fluid and plasma. The 2 techniques were in excellent accordance with even closer correlation between maximum concentrations obtained by microdialysis and suction blister fluid sampling (p<0.001). However, comparing the tolerability of the sampling procedure, ease of analysis, and detail in chronology, microdialysis is superior for sampling in vivo pharmacokinetics in the dermis.