European journal of clinical pharmacology
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Eur. J. Clin. Pharmacol. · May 1998
Randomized Controlled Trial Comparative Study Clinical TrialSkin and plasma levels of acetylsalicylic acid: a comparison between topical aspirin/diethyl ether mixture and oral aspirin in acute herpes zoster and postherpetic neuralgia.
The aim of this investigation was to elucidate whether the analgesic effect was due to the local aspirin or to the systemic drug. This was done by comparing skin and plasma levels of acetylsalicylic acid (ASA) and salicylic acid (SA) after topically administered ASA/diethyl ether (ADE) mixture in acute herpetic neuralgia (AHN) and postherpetic neuralgia (PHN). The analgesia and the plasma and skin levels of ASA were also determined after oral administration of aspirin. ⋯ The analgesic effect can be obtained only after topical administration, because by this route the skin levels of ASA are much higher than after oral administration. The mechanism is exclusively local; there are no active drugs in plasma after topical administration.