Effects of D-Met2, Pro5-enkephalinamide on pain tolerance and some cognitive functions in man

The effects ofd-Met², Pro⁵-enkephalinamide (EA) on pain tolerance and some cognitive functions have been examined in healthy male volunteers. Dihydrocodeine (DC) was used as reference substance. Applying the submaximum effort tourniquet technique EA (10 mg SC) was found to elevate the pain threshold similarly to DC (20 mg SC). Neither DC nor EA impaired the performance in the symbol cancellation test, which quantitates the intensity of attention. In this assay rather a slight improvement was detected. In addition the short-term memory performance (Wechsler test) was also improved by EA and DC. No alteration was seen in the word fluency test, an indicator of long-term (semantic) memory. The data show that EA not only improves pain tolerance but some of its mental effects are similar to those of a classical morphine congener DC.