Niridazole biodegradable inserts for local long-term treatment of periodontitis: possible new life for an orphan drug

Periodontal pocket inserts of niridazole (NZ) made with Resomer(R) (grades RG 503H and RG858, designated as RH and RG, respectively) were studied. Various formulation variables were evaluated to obtain a biodegradable delivery systems showing device degradation and drug depletion parallel to each other in vitro. Drug release from the prepared inserts was evaluated using a static dissolution setup (for 1 month). Incorporation of 3 parts of RG in 1 part of RH inserts caused a 50% decrease in the initial release rate. The RH-NZ inserts showed a spurt in release around the 10th day of the study, which coincided with the decrease in device weight, suggesting onset of device degradation. Pilot-scale clinical trials in 12 patients indicated improvements in clinical indices from the baseline values. The average pocket depth was reduced significantly (alpha = 0.05) from 6.34 +/- 1.86 mm at baseline to 5.94 +/- 0.28 mm after 28 days of treatment.

Concentration-time course of niridazole and six metabolites in the serum of four Filipinos with Schistosoma japonicum infection

Niridazole and six of its metabolites have been quantitated by high-pressure liquid chromatography in sera of four male Filipino patients with mild Schistosoma japonicum infections given single oral doses of niridazole (15 mg/kg) on two occasions 10 days apart. Of the five oxidative metabolites measured, 4-hydroxyniridazole and 4-ketoniridazole achieved the highest concentrations, reaching peak values of 0.9 +/- 0.3 microgram/ml of serum (mean +/- S.D., n = 4) and 0.7 +/- 0.1 microgram/ml of serum within 1 to 4 hr. 4-Ketoniridazole achieved peak serum levels 1 hr after the other oxidative metabolites in three of four patients and was the predominant metabolite in the serum of all patients 6 to 10 hr after dosing. By 24 hr, both 4-ketoniridazole and 4-hydroxyniridazole had largely disappeared from the serum. Niridazole and three other oxidative metabolites, 4,5-dihydroxyniridazole, 5-hydroxyniridazole and 4,5-dehydroniridazole, appeared within 1 hr in serum but failed to exceed 0.4 microgram/ml; none of these compounds were detected in the 24-hr serum samples. The pharmacokinetic pattern of niridazole and the oxidative metabolites showed marked interindividual variation but was quite reproducible in the same individual studied 10 days later. 1-Thiocarbamoyl-2-imidazolidinone was analyzed in serum samples by a different high-pressure liquid chromatographic procedure. This reductive metabolite attained maximal levels of 50 to 150 ng/ml of serum 6 to 12 hr after drug administration and remained at 40% or more of its peak concentration even after 24 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicogenetics of niridazole in inbred mice

The lethal potency of the antischistosomal agent niridazole (NDZ) was compared in C57BL/6J (B6) and DBA/2J (D2) mice and in their F1 hybrid, backcross and F2 progeny. A daily i.p. dosage range was chosen so that the lethal effect, ascribed to central nervous system toxicity, did not occur before 4 to 5 days. Death was always preceded by a generalized tonic-clonic seizure which terminated in respiratory arrest. In B6 mice the LD50 was 202 mg kg-1 day-1 while in D2 mice the LD50 was 146 mg kg-1 day-1; the LD50 for NDZ in similarly treated F1 hybrid mice was found to be the arithmetic mean of the LD50 values for the parental strains (172 mg kg-1 day-1). Determination of the level of NDZ in the plasma and brains of B6 and D2 mice treated subacutely with the same daily dose of NDZ failed to reveal any strain differences. Moreover, there was no evidence of in vivo accumulation of NDZ with subacute treatment which suggests that a NDZ metabolite is responsible for the observed toxicity. An association between susceptibility to the lethal effects of NDZ and the Ah locus is suggested by experiments in backcross and F2 mice. The incidence of death observed after subacute treatment with 162 mg/kg-1 day-1 of NDZ matched that predicted on the basis of genotype, i.e., it was lethal to 72% of nonresponsive and 38% of aromatic hydrocarbon responsive mice.

Studies on the mechanism of suppression of delayed hypersensitivity by the antischistosomal compund niridazole

Niridazole given in a single oral dose of 100 mg/kg to guinea pigs sensitized to ortho-chlorobenzoyl chloride-bovine gamma-globulin (OCB-BGG) regularly abolished delayed cutaneous reactivity. Little effect was observed, however, when cells from these animals were tested in vitro with either direct or indirect assays for migration inhibitory factor (MIF). On the other hand, sera taken from nonsensitized guinea pigs after they had received 100 mg/kg of niridazole markedly diminished antigen-induced inhibition of migration of sensitized peritoneal exudate cells in vitro. The immunosuppressive effects of such sera could not be produced by niridazole itself, thereby suggesting an effect of niridazole metabolites. This suppressive activity was readily removed from the serum by dialysis. The active serum blocked the production of MIF by sensitized lymph node cells but did not affect the action of preformed MIF on macrophages. The effect of this serum was reversible; lymph node cells incubated for 24 hr with active serum, then washed and reincubated with antigen in normal serum, produced normal amounts of MIF. These studies suggest that metabolites of niridazole, but not the parent compound itslef, suppress delayed hypersensitivity in guinea pigs and prevent MIF production by lymphocytes without affecting the macrophage response to MIF.