Microdialysis vs. suction blister technique for in vivo sampling of pharmacokinetics in the human dermis

Our aim was to simultaneously investigate 2 techniques for bl vivo sampling of peripheral compartment pharmacokinetics after systemic administration o f acetylsalicylic acid. Ten volunteers were given 2 g acetylsalicylic acid orally. Blood samples and dialysates from 4 microdialysis probes inserted i n the dermis of the forearm were collected for 5 h and suction blisters wer e raised 1-3 h after dosing. In microdialysates, both acetylsalicylic acid and the metabolite salicylic acid mere measurable in the absence of hydroly sing enzymes, The mean C-max (maximum concentration) of total, unbound sali cylic acid was 9.5 mu g/ml in microdialysates, 13.2 mu g/ml in suction blis ter fluid and 56.5 mu g/ml in plasma. Mean T-max (time to C-max) for salicy lic acid was 188 and 161 min in plasma and microdialysates, respectively. T he dermis-to-plasma C-max ratio was 0.16 +/- 0.04 (mean +/- SD) by microdia lysis 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 micr odialysates and plasma, and between C-max of salicylic acid in suction blis ter fluid and plasma, The 2 techniques were in excellent accordance with ev en closer correlation between maximum concentrations obtained by microdialy sis and suction blister fluid sampling (p < 0.001). However, comparing the tolerability of the sampling procedure, ease of analysis, and detail in chr onology, microdialysis is superior for sampling in vivo pharmacokinetics in the dermis.