Peak blistering point: influence on fluid levels of 5-MOP in human skin in vivo after systemic administration.

The concentration of 5-methoxypsoralen (5-MOP) in suction blister fluid (SBF) after oral intake was determined in relation to the peak blistering point. Interstitial fluid was obtained from nine healthy male volunteers by applying mild suction (300-350 mmHg) to the skin of the volar aspect of the forearm. Blisters were raised at three different times: 18 h prior to drug administration (group I); 2 h prior to drug administration (group II); and during drug ingestion (group III). SBF levels of 5-MOP were determined in each group of blisters 2 h after oral administration of 1.2 mg/kg micronized 5-MOP. The results showed a statistically significant difference in the concentrations of 5-MOP between each group of blisters. The highest concentration of 5-MOP in the SBF was found in group III and the lowest in group II blisters. These findings suggest that the point of peak blistering in relation to drug administration needs to be known in each pharmacological study using suction blisters.