Synthesis of N,N-dialkyl(dialkenyl)amides of 7-methyl-3-phenyl-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-5-carboxylic acid (5–9) and their 1-[2-hydroxy-3-(4-phenyl-1-piperazinyl)propyl] derivatives (10–14) is described. Compounds 10–14 were tested for analgesic and sedative activities as well as for μ-opioid receptors binding affinities. All the amides, being the object of investigation, displayed an interesting analgesic action, which in case of the compounds 10–12 and 14 was superior to that of acetylsalicylic acid in two different tests. Furthermore all the amides (10–14) significantly suppressed the spontaneous locomotor activity, prolonged barbiturate sleep in mice and showed a weak affinity to μ-opioid receptors. [Copyright &y& Elsevier]