Anti-asthma effect of an antiviral drug, acyclovir: A clinical case and experimental study

Background Although acyclovir (9-(2-hydroxyethoxymethyl) guanine) is an antiviral drug that inhibits DNA polymerase of herpes virus, we have had the experience of an asthmatic patient's peak flow rate being improved by oral administration of acyclovir. Objective The aim of this experiment is whether acyclovir has anti-asthma effects using an asthma model in guinea-pigs. Methods The airway response was induced by a single inhalation of calcium ionophore A23187 (2 mg/mL). The airway obstruction was estimated by the ratio of expiration to inspiration time (E/I). The peribronchial eosinophil infiltration and eosinophil influx into bronchoalveolar lavage (BAL) fluid 7 h after the inhalation were also examined. To assess the effects of acyclovir (1, 10, and 100 mg/kg), aminophylline (20 mg/kg) and pemirolast potassium (TBX, 20 mg/kg) on A23187-induced asthmatic response, the drugs were intraperitoneally administered before the inhalation. Results The immediate airway obstruction was significantly suppressed by acyclovir (10 mg/kg) and aminophylline, whereas different doses of acyclovir (1 and 100 mg/kg) and TBX showed only a small inhibitory effect on the airway obstruction. On the other hand, the peribronchial eosinophilia was most successfully inhibited by TBX. Acyclovir (10 mg/kg) and aminophylline also suppressed the eosinophilia significantly. Furthermore, acyclovir significantly suppressed eosinophil influx into BAL fluid, whereas aminophylline and TBX weakly suppressed the influx. Conclusion These results suggest that acyclovir exhibits not only antiviral but also antiasthma activity.