The interaction between Ukrain and Naltrexone, a nonselective opioid recept
or antagonist, was studied in the 'writhing syndrome' test in mice. Naltrex
one (1 mg/kg s.c.) was administered i.p. 30 min before Ukrain (2.375, 4.75,
9.5 and 19 mg/kg). In addition, the antinociceptive properties of Ukrain a
nd Naltrexone in 10-day treatment in mice were studied. The results show th
at the antinociceptive effect of both single dose and prolonged administrat
ion of Ukrain is completely antagonized by Naltrexone.