Remifentanil inhibits muscular more than cutaneous pain in humans

In experimental studies, drug-induced analgesia is usually assessed by cuta neous stimulation. If analgesics act differently on cutaneous and deep noci ception, the results of these studies may not be entirely applicable to cli nical pain involving deep structures. We tested the hypothesis that opioids have different abilities to inhibit cutaneous and muscular pain. Either th e opioid remifentanil or placebo was infused in 12 healthy volunteers in a cross-over fashion. Repeated electrical stimulation (five impulses at 2 Hz) was applied to both skin and muscle. Pain thresholds were recorded. Remife ntanil caused a higher increase in the muscular pain thresholds than in the cutaneous pain thresholds (P=0.035). We conclude that opioids inhibit musc ular pain more strongly than cutaneous pain in humans.