Objective: Postherpetic neuralgia (PHN) is one of the most painful neuropathic conditions, the mechanism of which remains unclear. There is no universally accepted treatment. The pain in PHN is often relieved by bathing, heating, or sympathetic blockade, suggesting a circulation-dependent property of the pain. Therefore, we examined the effectiveness of prostaglandin E(1) (PGE(1)), which has an analgesic effect via improvement of peripheral blood circulation, for patients with PHN.
Design: A total of 27 patients with PHN underwent intravenous administration of 60 microg of PGE(1) dissolved in 100 mL of physiological saline and 5 mL of 8.4% sodium bicarbonate solution at an infusion rate of 0.02 microg/kg/min. Oral administration of PGE(1), limaprost alfadex, was followed at doses of 30 microg/day for 2 weeks. Pain at rest and tactile allodynia before and after the treatment was evaluated with visual analog scale (VAS).
Results: Intravenous PGE(1) significantly decreased VAS in rest pain and tactile allodynia without severe adverse effects. The analgesic effect of PGE(1) continued during the 2 weeks of oral administration of PGE(1). Oral PGE(1) caused nausea in seven cases, diarrhea in three, and abdominal distention in one subject. All subjects, except for two cases of nausea, continued the treatment until the end of the study, although some required a decrease in the dose to 15 microg/day. During the 2-week oral administration, the VAS did not change remarkably in the three patients whose VAS were not decreased by at least 80% during the initial infusion.
Conclusions: The results of the present study indicate that oral PGE(1) following the intravenous administration produces prompt and continuous analgesia in patients with PHN. Moreover, the intravenous treatment using PGE(1) appears useful for predicting the analgesic effect of PGE(1) in the patients.