Reduced skin hyperemia during tap water iontophoresis after intake of acetylsalicylic acid

Skin microcirculation and skin temperature of 10 healthy subjects (6 men and 4 women, 20-44 yr of age) without any vascular diseases were registered when a thermoindifferent tap water iontophoresis was applied. The aim of this controlled study was to evaluate the development of skin hyperemia after the intake of 500 mg of acetylsalicylic acid (ASA). The measurement was conducted by laser-Doppler flowmetry on the proximal forearm. The skin temperature was measured before and after the treatment by an infrared thermometer. In all persons there was an intense erythema on the side of the cathode and only a modest one on the side of the anode. Without ASA preliminary treatment, the cutaneous flow showed an increase of 106% at the anodal side and that of 834% at the cathodal side (P < 0.001). After ending tap water iontophoresis, the skin temperature increased more on the cathode side than on the anode side (P < 0.001). After the intake of 500 mg ASA, the increase of the flow was 78% at the anode and 88% at the cathode. The comparison of the skin microcirculation did not show any differences at the anodal side when acetylsalicylic acid was taken before, but a strong suppression of the galvanic erythema at the cathodal side was observed after the intake of ASA. There is a direct influence of acetylsalicylic acid on the induction of the neurogenic inflammation caused by a galvanic erythema. The intensity of the induced erythema correlates with the analgesic effects of constant current treatment. An attenuation of the electrotherapeutic analgesia is possible.