Academic journal article Bulletin of the World Health Organization

Efficacy of Oxamniquine and Praziquantel in the Treatment of Schistosoma Mansoni Infection: A Controlled Trial. (Research)

Academic journal article Bulletin of the World Health Organization

Efficacy of Oxamniquine and Praziquantel in the Treatment of Schistosoma Mansoni Infection: A Controlled Trial. (Research)

Article excerpt

Introduction

Schistosomiasis mansoni infection, an endemic disease of worldwide importance in terms of public health, affects large geographical areas in several countries. In Brazil, its prevalence is estimated to be 8-10 million infected people, and about 30 million people living in areas of S. mansoni transmission are currently at risk of the disease (1).

Approximately 4% of untreated parasitized people develop severe forms of S. mansoni--hepatosplenic schistosomiasis. In areas in which the disease is endemic, a marked correlation between worm burden and disease severity has been reported. Chemotherapy plays a very important role in reducing morbidity in those areas; it is also valuable for resolving the disease in individual cases (1).

Oxamniquine and praziquantel are the only drugs used to treat schistosomiasis in Africa and the Americas. Oxamniquine, a 2-aminomethyltetrahydroquinoline derivative, is produced by biological synthesis and is one of the most promising schistosomicides. It has an anticholinergic effect, which increases the parasite's motility (2) and inhibits nucleic acid synthesis (3). It is more effective against male than female parasites and has no notable effect on other Schistosoma spp. that parasitize humans. In Brazil, oxamniquine was shown to be well tolerated--a single oral dose of 15 mg/kg for adults and two daily doses of 10 mg/kg for children showed cure rates of over 83%, when its efficacy was evaluated by means of stool examinations (6-10 examinations) (4-6). However, when rectal biopsy (quantitative oogram) was used to evaluate cure after treatment with oxamniquine (15-18 mg/kg), the cure rate was only 38.3% (7).

Praziquantel, a pyrazinoisoquinoline derivative with low toxicity, has proved to be effective against S. mansoni and other species of the genus Schistosoma that parasitize humans. It affects mainly the female parasite, and causes tegument changes (8) and a reduction in the glutathione concentration (9) in the worm. A single dose of 40-60 mg/kg was shown to give a cure rate of 80% (10), when the cure was evaluated by the Kato & Katz (KK) method of stool examination (11). Cunha et al. (12), who reported that a single oral dose of 60 mg/kg praziquantel cured only 29% of patients when cure was evaluated by rectal biopsy (13), showed that a new therapeutic schedule of 60 mg/kg per day for three consecutive days produced a cure rate of 91% evaluated over a six-month period (13).

In the light of conflicting published data on therapeutic evaluation, the present study was undertaken with two main aims. The first was to evaluate the clinical treatment of S. mansoni by oxamniquine and praziquantel, comparing these drugs with a placebo, in a prospective triple-masked and randomized clinical trial. The second aim was to compare the sensitivity of parasitological stool examinations by both qualitative and quantitative methods; the results obtained by quantitative stool examinations were also compared with those from quantitative oograms (rectal mucosa biopsy).

Methods

In total, 106 outpatients at the University Hospital, Universidade Federal de Minas Gerais (UFMG), Brazil, were selected for the trial on the basis of stool examinations that tested positive for S. mansoni. Children of pre-school age, aged patients, pregnant women, suckling infants, patients with acute or severe chronic concomitant diseases, patients with the hepatosplenic form of the disease and individuals whose behaviour (e.g. contact with natural waters suspected to contain cercariae) put them at risk for acquiring new infections, were excluded. In all, 101 (95.3%) of the selected patients had not taken any drugs for the treatment of S. mansoni infection, and five patients, previously treated more than five years ago, had had new contacts with natural waters after the first treatment.

The research was evaluated by the Ethical Committee for Human Research of the Santa Casa de Misericordia Hospital, Belo Horizonte, Brazil, which approved all the procedures of the present clinical trial. …

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