Antiallergic activity profiles in vitro of RHC 3164 and related compounds. II. Comparison of RHC 3164 with disodium cromoglycate

Antinociceptive effect from Ipomoea cairica extract

Ipomoea cairica L. Sweet (Convolvulaceae) is used in Brazilian folk medicine for the treatment of rheumatism and inflammations. Ipomoea cairica ethanolic extract (100, 300, 1000 and 3000 mg/kg; per os) induced dose-dependent reduction of response in the formalin test inflammatory phase in mice. The same dose range did not modify neurogenic pain in formalin test, tail-flick reflex latency, carrageenan-induced paw edema, and Rota-Rod test motor performance. From the bio-active fraction 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid were obtained. These compounds have been previously reported to have analgesic and antioxidative effects. A possible explanation for the antinociception is that somehow the compounds present in the extract reduced the release of pro-nociceptive mediators unrelated to carrageenan-induced edema, such as histamine. Interestingly, caffeoylquinic acid derivatives have been reported to inhibit histamine release on in vitro models. The isolated caffeoylquinic acids could explain, at least in part, the antinociceptive effect of Ipomoea cairica polar extract.

Common ion effect on solubility and dissolution rate of the sodium salt of an organic acid

The solubility and the dissolution rate of the sodium salt of an acidic drug (REV 3164; 7-chloro-5-propyl-1H,4H-[1,2,4]triazolo[4,3-alpha]quinoxaline-1,4-dione) decreased by the effect of common ion present in aqueous media. The solubility of the sodium salt of REV 3164 in a buffered medium was much lower than that in an unbuffered medium. Also, the presence of NaCl decreased its solubility in water. The apparent solubility product (K'sp) of the salt, however, did not remain constant when the concentration of NaCl was changed. A decrease in K'sp value with the increase in NaCl concentration was observed; for example, the K'sp values at 0 and 1 M NaCl were 7.84 X 10(-4) and 3.94 X 10(-4) M2, respectively. Even when corrected for the effect of ionic strength, the solubility product decreased. This decrease in the solubility product in the presence of NaCl indicated a decrease in the degree of self-association (increase in activity coefficient) of the drug in aqueous media.

REV 2871 (CHBZ): a potent antiallergic agent with a novel mechanism of action. I. Activity profile as an inhibitor of mediator release

REV 2871 (CHBZ) and its putative metabolite REV 3579-Z (also designated in the literature as RHC 3579-Z) were shown to be potent and orally effective inhibitors of passive cutaneous anaphylaxis (PCA) in the rat (ED50 = 12 mg/kg). The activity profiles of CHBZ, REV 3579-Z and disodium cromoglycate (DSCG) were compared as inhibitors of histamine release (HR) in vitro from rat mast cells, human basophils, and guinea pig lung slices. CHBZ was a potent inhibitor of both immunologic and non-immunologic HR (I50 2-20 microM from rat mast cells). The activity profile of CHBZ as an inhibitor of HR from rat mast cells differed from that of DSCG and REV 3579-Z in the following respects: increasing inhibition of HR with increasing preincubation time; irreversibility of the inhibition; lack of tachyphylaxis and cross-tachyphylaxis to DSCG; potentiation of the inhibition of antigen-induced release of histamine (AIR) by DSCG; and inhibition of HR induced by dextran + phosphatidyl serine, compound 48/80, ionophore A23187 and platelet activating factor (PAF). In the human basophil model, CHBZ was: a potent inhibitor (I50 = 25 microM) of anti-IgE-induced release (AbIR), whereas DSCG and REV 3579-Z had no effect on AbIR; more potent as an inhibitor of AbIR than ionophore-induced release, whereas the reverse was true for proxicromil; an inhibitor of PAF-induced release, whereas proximcromil stimulated it; and potentiative with proxicromil for inhibition of AbIR. In the guinea pig lung slice model, CHBZ inhibited AIR (I50 = 800 microM) whereas DSCG and REV 3579-Z did not (I50 greater than 300 microM). We conclude that CHBZ is an orally effective antiallergic agent whose mechanism of action as an inhibitor of mediator release is different from DSCG and proxicromil.