Niridazole metabolism by rat embryos in vitro

We report the results of studies on the reductive activation of the schistosomicidal agent, niridazole (NDZ). Intact rat embryos in vitro reduced this compound, generating a stable metabolite in the presence of 5% O2. By contrast, embryo and yolk sac homogenates or liver microsomes appeared to require anaerobiasis. Malformation incidence--specifically, axial asymmetry--showed a strong correlation with nitroreductase activity rates when the latter were modulated by oxygen tension. Data presented here suggest that when embryos are exposed to NDZ under conditions of low oxygen in vitro, redox cycling ensues with molecular oxygen serving to oxidize early reduction products. This process continues, regenerating the parent compound until oxygen is depleted locally. The basis of this localized depletion is unknown, but inability of the immature supply system to replete oxygen or demand by precociously aerobic tissues may be involved. Once local anaerobiasis is attained, further reduction could generate toxic metabolites capable of covalently binding cellular macromolecules. Localized hypoxia represents another potential mechanism of dysmorphogenesis.

Comparative trials of regimes for the treatment of urinary schistosomiasis in The Gambia

Alternative regimes for the treatment of Schistosoma haematobium infection were compared in two trials. Praziquantel at a dose of 40 mg kg-1 appeared to cure 63% of a random sample of heavily infected subjects; significantly more than the 18% cured by three fortnightly doses of metrifonate at 10 mg kg-1. However, praziquantel led to a greater incidence of mild, transient side-effects. A single dose of metrifonate was found to be an inadequate treatment in the same group of subjects as it left 53% with an egg count of at least 100 ova/10 ml. A combination of 10 mg kg-1 of metrifonate and 25 mg kg-1 of niridazole had a similar effect to that of a single dose of metrifonate alone and it had more side-effects. Reduced doses of praziquantel had less effect on egg counts than the standard regime, but the difference was not significant in the case of 20 mg kg-1. Although a combination of metrifonate and praziquantel, each at 10 mg kg-1, had a greater effect than either constituent alone, the difference was not significant. Factors affecting the choice of drug for use in mass treatment of urinary schistosomiasis in The Gambia are discussed. The present findings suggest that the standard regime of praziquantel should be used or, if this is not possible, a three-dose metrifonate regime.

Influence of dosing interval and in-patient versus out-patient status on incidence of side-effects of niridazole

The side-effects of niridazole used for urinary schistosomiasis were studied prospectively over a 3-month period in male patients receiving the standard dose of 25 mg day-1 kg-1 for 7 days. Side-effects were detected in 80% of in-patients but only in 33% of out-patients. The range of side-effects was greater in in-patients taking their daily doses in two portions than in those taking theirs in three. Cure rates and degree of schistosoma egg suppression were significantly lower in out-patients suggesting that compliance with treatment was poorer.

Niridazole-induced red/brown urine pigment is associated with increased urinary beta-glucuronidase excretion and a bladder site of formation

Niridazole caused red/brown urine pigment in a man during treatment for Schistosoma mansoni infection. The urine pigment has been observed during niridazole treatment of schistosomiasis, but has not been documented during treatment of other diseases. Urinary beta-glucuronidase (EC 3.2.1.31) concentration increased proportionately to the amount of red/brown pigment in the urine. Concurrently, sterile pyuria developed. The duration of the time urine was in the bladder was directly related to the concentration of beta-glucuronidase and to the intensity of the red/brown urine color, there being much more in infrequently than in frequently voided urine specimens. Pigment development appears to occur in the bladder. The associated and possibly contributing components appear to be niridazole or one of its metabolites, beta-glucuronidase from the kidneys or from urinary granulocytes, and possibly a schistosomal factor. Given time, this combination generated the red/brown pigment.

A comparative trial of praziquantel, metrifonate and niridazole against Schistosoma haematobium

Praziquantel administered in a single oral dose of 30 mg kg-1 to subjects infected with Schistosoma haematobium produced minimal side effects and was more effective than established regimes of niridazole and metrifonate. Praziquantel should prove a major tool in schistosomiasis control programmes.

Oxamniquine versus niridazole for treatment of uncomplicated Schistosoma mansoni infection

One hundred sixteen male patients with uncomplicated Schistosoma mansoni infection were randomized to treatment with oxamniquine (20 mg/kg a day for 3 days) or niridazole (15 mg/kg a day for 8 days) in an in-hospital study. Fifty-four patients were treated with oxamniquine; no serious drug side effects were noted. Twenty-six percent of children 16 years old and younger were cured, while 85% of adults were cured. Egg reduction was 89%. Sixty-two patients were treated with niridazole; four patients (one child and three adults) had serious side effects which necessitated discontinuing the drug. Seventy-one percent of children and 84% of adults were cured. Egg reduction was 84%. Minor clinical side effects occurred during therapy with both drugs (26% with oxamniquine, 48% with niridazole) but cleared after completion of therapy. Niridazole is the more effective drug for the child with uncomplicated Schistosomiasis mansoni, but oxamniquine is advised for the adult with this disease.

Carcinogenic effects of niridazole on rodents infected with Schistosoma mansoni

The carcinogenicity of 1-(5-nitro-2-thiazolyl)-2-imidazolidinone (niridazole), a widely used schistosomicide, was examined in Swiss mice and Syrian golden hamsters. Schistosoma mansoni infection was evaluated as a cofactor. High incidences of drug-related neoplasms of the forestomach, lungs, mammary glands, urinary tract, and ovaries were found in mice, and tumors of the forestomach and urinary tract were found in hamsters. Infection with schistosomes had no apparent influence on tumor incidence. The results indicated a need for reevaluation of the possible carcinogenicity of this drug in man and suggested that care should be taken during its clinical use.

Ambilhar in the treatment of Schistosoma japonicum infection and as an egg suppressant for mass treatment

Ambilhar or niridazole at a dose of 25 mg per kg body weight for 7 days was found ineffective against Sl japonicum infection. Longer period of treatment for 10 to 14 days gave impressive stool negative conversion and egg reduction rates but with moderately severe reactions, the most alarming of which was hallucination. To minimize toxicity, the daily dose was reduced but given for a longer duration so that the total amount of the drug given per kilogram body weight was approximately the same as the 25 mg pre kg per day for 10 to 14 days. Of the two treatment schedules tried, the 15 mg per kg per day for 24 days was found relatively effective. Although the drug with this treatment regimen was well tolerated, a drop-out of 50.8% was observed. Ambilhar was therefore tried as an egg suppressant. With a 10-day treatment, all patients were again positive after 6 months. Egg reduction rates during the 6 months stool follow-up ranged from 69.8 to 93.5%. Further trials using this dose to be repeated every 3 to 6 months is contemplated.

Drug trial of Schistosoma japonicum enfection in Indonesia

A limited drug trial was carried out on 42 cases with schistosomiasis japonica from an endemic area of Central Sulawesi. The drugs used were niridazole and stibophen. The effects of treatment were reported and discussed. The results of this study offer promise for treating S. japonicum infection in Central Sulawesi on a larger scale.

Clinical evaluation of niridazole and hycanthone in schistosomiasis mansoni endemic areas

One hundred patients with active schistosomiasis mansoni were treated with niridazole (25 mg/kg/day po for 7 days). The most serious side effects were those connected with the neuropsychic area (convulsion, hallucination, etc.). Therapeutic activity, based on repeated stool examinations, was about 90% in adults and 60% in children. Because of the side effects, as well as the long-term schedule of treatment, niridazole is not recommended for use under field conditions. Seven hundred and forty-five patients were treated with hycanthone (2.5 mg/kg im) after clinical examination. The side effects observed were mild and of short duration (24-48 hr). The therapeutic activity was very high (about 95% cure). So far we have treated more than 9,000 infected patients without severe complications, including hepatic failure and death, which have been reported by some authors. A hycanthone-resistant strain has been isolated from two patients unsuccessfully treated twice with hycanthone and once with niridazole. Considering that an important aspect of the control of schistosomiasis is mass treatment, further studies regarding mutagenicity, teratogenicity, resistance, and toxicological effects of hycanthone are still required before this drug can be recommended for wide use.

Detection of mutagenic activity of metronidazole and niridazole in body fluids of humans and mice

After humans were treated at therapeutic doses with the trichomonacide metronidazole (Flagyl) and the antischistosomal agent niridazole mutagenic activity was demonstrable in their urines when tested with the histidine auxotroph of Salmonella typhimurium. Both compounds were active in the host-mediated assay in mice, and evidence of activity was found in the blood and urine of mice treated with niridazole but not with metronidazole.

Schistosomiasis mansoni in Yemeni in California: duration of infection, presence of disease, therapeutic management

Investigations of schistosomiasis mansoni in 218 Yemeni agricultural workers in the San Joaquin Valley of California revealed a prevalence of 56%. In those infected, quantitative egg counts performed by the Kato thick smear method revealed that 57% had light infections (1-100 eggs/g), 27% moderate infections (101-400 eggs/g), and 16% heavy infections (greater than 400 eggs/g; mean--918 eggs/g). The Yemeni had been migrating to the USA for the past 20 years, a period in which the prevalence of schistosomiasis had remained constant in the Yemen. The prevalence of schistosomiasis in those who had been away from Yemen for less than 5 years was 59% with a mean egg output of 236 eggs/g, but in those away for more than 5 years (up to 20 years) it was 32% with a mean egg output of 75% eggs/g. This is in spite of the fact that 75% of the latter had returned to Yemen for short visits. Statistical analysis by the Fisher's exact probability test revealed a significantly lower egg output in those away from Yemen more than 5 years. On the basis of these findings the mean life span of the Yemen strain of Schistosoma mansoni in man was estimated to be between 5 and 10 years. The presence of disease was assessed in this population by traditional medical means without prior knowledge of the status of the infection in the individuals examined. Under these circumstances, there were no differences in symptoms such as weakness, diarrhea and abdominal pain among the uninfected proportion of the population, total infected group and a small subgroup of those most heavily infected. None of the patients had hepatomegaly and only two had splenomegaly--one lightly and the other heavily infected. Because of the toxicity of antischistosomal drugs and the lack of treatment facilities only the 22 most heavily infected (greater than 200 eggs/g) of the 122 individuals with schistosomiasis mansoni were treated with niridazole. In addition the two individuals with splenomegaly were treated with antimony dimercaptosuccinate. Side effects, though common, were not severe. Although follow-up in this migrant population was poor the nine patients examined 3 to 7 months after treatment showed a mean decrease in egg output of 97%.

Drug-induced respiratory disorders

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