Pilocarpine iontophoresis test: an index of physiological sweat secretion?

Abstract

Pilocarpine iontophoresis test: an index of physiological sweat secretion? Summary. The pilocarpine iontophoresis test (P‐test) is used as a predictor of the capacity to produce sweat. Therefore, we studied the reproducibility of this test in 12 normal subjects on 10 consecutive days. Furthermore, we determined whether the P‐test reflects whole‐body and regional sweat secretion during exercise in the heat. Finally, we determined whether the P‐test stimulates the eccrine sweat glands to maximal sweat secretion. Six growth hormone‐deficient (GHD) patients who are known to have decreased sweating, and 11 healthy control subjects were studied. To induce maximal sweat secretion, the patients exercised on a bicycle ergometer at a workload corresponding to 40% of their maximal aerobic power (VO 2 max). The 11 healthy subjects exercised at a workload of 150 W. All subjects exercised for 60 min in ambient air at 35°C, with 50% relative humidity. The P‐test showed a mean day‐to‐day variation of 20‐8% between individual subjects. There was a significant positive correlation between the P‐test and regional sweat secretion (r 2 =0.74). The correlation coefficient (r 2 ) was 0.50 for the correlation between the P‐test and whole‐body sweat secretion, and 0.52 for the correlation between regional sweat secretion and whole‐body sweat secretion. We conclude that the pilocarpine iontophoresis test reflects heat‐ and exercise‐induced sweating capacity. However, this test does not induce maximal sweating, and it cannot be used as a single reliable predictor of whole‐body sweating, due to considerable day‐to‐day variation.