“Drugs applied locally 30 min after prostaglandin E2 induced the following effects: fentanyl (0.…) caused a dose-dependent inhibition of the antihyperalgesic effect of fentanyl, co-administration of L-arginine (0.5 mol) with NOARG (0.2 mol) plus ….5-2.0 mol) potentiated a subeffective dose of fentanyl (….”