A randomized parallel trial of topical aspirin-moisturizer solution vs. oral aspirin for acute herpetic neuralgia

Background In this study, the efficacy of oral aspirin vs. topical aspirin in moisturizer (Vaseline Intensive Care Lotion) was studied in an open, randomized, parallel trial in patients with acute herpetic neuralgia. Methods Thirty patients were evaluated in the trial, with 15 in each group. The patients were randomized to receive either oral aspirin, 375-750 mg three times a day, or 75 mg topical aspirin/mL of moisturizer (5-10 mL, depending on the extent of involvement), three times a day, for 21 days. Pain was assessed daily by means of a self-rating visual analog scale and physician assessment. In addition, the skin and plasma levels of aspirin were measured in both groups. Results The mean time to onset of pain relief was 44 min with topical aspirin and 110 min with oral aspirin. The mean duration of pain relief after a single application of topical aspirin was 5.4 h, whereas it was 3.5 h with oral aspirin. The mean visual analog scale scores for pain with oral aspirin decreased from 68.2 +/-6.1 on day zero to 43.1 +/-8.7 on day 21, which was not significant compared with the baseline score. With topical aspirin, the baseline pain score was 77.5 +/-3.7 and decreased to 6.8 +/-3 on day 21 (P<0.001 compared to the baseline score and compared to oral aspirin). The mean plasma and skin levels of aspirin following oral administration were 16.21<plus/minus>1.1 gg/mL and 1.97 +/-0.3 mug/mm(2), respectively. After topical administration, the mean plasma level of aspirin was 2.29 +/-0.5 mug/mL (P<0.01 vs. oral aspirin) and the skin level was 5.96<plus/minus>0.4 mug/mm(2) (P<0.05 vs. oral aspirin). Treatment tolerance was excellent in both groups. Conclusions This trial has demonstrated that topical aspirin in moisturizer is clearly superior to oral aspirin in relieving the pain of acute herpetic neuralgia, and that the analgesic activity of aspirin is largely due to its local effect.