Giuseppe Petrone

4,5-Functionalized 6-phenyl-3(2H)-pyridazinones : synthesis and evaluation of antinociceptive activity

Abstract A series of 2-substituted 4,5-functionalized 6-phenyl-3(2 H )-pyridazinones were synthesized and their antinociceptive activities were evaluated in the mouse abdominal constriction model. Single dose studies showed that compounds 11, 18a and 23 were more active than the reference drug, Emorfazone, in inhibiting the effects of the noxious chemical stimulus, p -phenylquinone. Subsequent dose—response studies revealed 18a to be almost seven-fold more potent than Emorfazone.

4-Amino-3(2H)-pyridazinones bearing arylpiperazinylalkyl groups and related compounds: synthesis and antinociceptive activity

A series of 4-amino-3(2H)-pyridazinones substituted at position 2 with arylpiperazinylalkyl groups and analogues were synthesized and their antinociceptive effect was evaluated in the mouse abdominal constriction model. Preliminary SARs studies were performed. Several of the novel compounds dosed at 100 mg/kg s.c. significantly reduced the number of writhes induced by the noxious stimulus. Compound 12e showed 100% inhibition of writhes and was able to protect all the treated animals from the effect of the chemical stimulus. Subsequent dose-response studies revealed 12e to be almost 40-fold more potent than the structurally related Emorfazone.

Antinociceptive effects of non-steroidal anti-inflammatory drugs in a rat model of unilateral hindpaw inflammation.

The antinociceptive activity of intramuscular 6-methoxy-2-naphthylacetic acid (6-MNA), the active metabolite of nabumetone, was examined in a rat model of unilateral hindpaw inflammation/hyperalgesia and compared with that of three other non-steroidal anti-inflammatory drugs (NSAIDs)--diclofenac, naproxen and piroxicam. Over a dose range of 10-100 mg/kg i.m., 6-MNA produced a dose-dependent increase in the withdrawal threshold to a noxious mechanical stimulus applied to the inflamed paw; however, a higher dose (300 mg/kg) produced no further increase in antinociceptive activity. Peak effects occurred 30 min after intramuscular injection. Diclofenac, naproxen and piroxicam produced antinociceptive effects that were qualitatively similar to those of 6-MNA. There was an indication of quantitative differences between the four NSAIDs in terms of potency and efficacy although this was not statistically significant. The rapid onset of effect and the lack of correlation between the relative antinociceptive effects of the four NSAIDs and the anti-inflammatory activities (assayed as inhibition of carrageenan-induced rat paw oedema) suggest that their pain relieving properties may not be entirely the result of their anti-inflammatory effects. These experimental data support the therapeutic value of 6-MNA as an analgesic in conditions of inflammatory pain.