Nedocromil sodium inhibits histamine-induced itch and flare in human skin

Abstract

This study was designed to test the hypothesis that nedocromil sodium inhibits sensory nerve function to reduce flare and itch in human skin. Nedocromil sodium (2%) or water (control) was introduced into the volar forearm skin of eight non-atopic volunteers by iontophoresis (8 mC) and histamine (20 microl of 1 microM and 300 nM) injected intradermally 10 min later at the same site. Itch was assessed on a visual analogue scale every 20 s for 5 min. Weal and flare areas and mean blood flux within the flare were assessed by scanning laser Doppler imaging at 10 min. The results showed that nedocromil sodium reduced itch scores, totalled over 5 min, by approximately 74.0% (P<0.005) and flare areas by approximately 65% (P<0.03). Neither weal areas nor blood flux within were reduced. These data demonstrate that nedocromil sodium is effective in reducing neurogenic itch and flare in the skin. We suggest that its mechanism of action is modulation of sensory neurone activation or conduction in the skin.

Figure 1

Histamine-induced itch in the presence and absence of nedocromil sodium. Itch was recorded on a 100 mm VAS every 20 s for 5 min in eight subjects. Water (control) and nedocromil sodium were introduced into the skin by iontophoresis. Histamine (20 μl) at (A) 1 μM and (B) 300 nM was injected 10 min later.

Figure 2

Histamine-induced itch and flare in the presence and absence of nedocromil sodium. (A) Itch is presented as the total VAS score summed over 5 min and (B) the flare area assessed by scanning laser Doppler imaging in eight subjects. Water (control, open bars) and nedocromil sodium (closed bars) were introduced into the skin by iontophoresis. Histamine (20 μl) was injected 10 min later. Reductions in both itch and flare in the nedocromil treated sites were statistically (P<0.05) significant with both concentrations of histamine.