Efficacy and toxicity of praziquantel in helminth-infected barbel (Barbus barbus L.)

This study evaluated efficacy and toxicity of the pyrazinoisoquinoline anthelmintic praziquantel (PZQ) in barbel infected with metacercariae of Diplostomum spathaceum and adult Pomphorhynchus laevis, and assessed antioxidant biomarkers and the lipid peroxidation response in juvenile barbel post-treatment. The estimated 96-hr LC50 of PZQ was 28.6 mg/L. For evaluation of efficacy, barbel naturally infected with D. spathaceum were exposed to a 10 and 20 mg/L PZQ 4-day bath treatment. Both concentrations were 100% effective against D. spathaceum and significantly (p < .01) affected the activity of catalase, superoxide dismutase, glutathione reductase and glutathione-S-transferase as well as levels of reduced glutathione in liver and muscle. The efficacy of orally administered PZQ was assessed in adult barbel naturally infected with P. laevis. Fish were administered 10, 30 and 50 mg/kg of body weight and examined via gut dissection after 6 days. The 50 mg/kg dose significantly decreased the intensity of infection. Praziquantel is a feasible bath treatment for barbel infected with D. spathaceum and has potential for oral treatment of broodfish infected with P. laevis.

The effect of praziquantel applied per os on selected haematological and biochemical indices in common carp (Cyprinus carpio L.)

The aim of the study was to assess the effects of the anthelminthic, praziquantel, on the haematological and biochemical indices of the blood of common carp (Cyprinus carpio L.). Fish were divided into six groups: two groups received 30 mg kg(-1) body weight (bw) of praziquantel, and two groups were given 50 mg kg(-1) bw of praziquantel mixed into the heat-treated amyloid vehicle. Fish in the remaining two groups were given only the amyloid vehicle and were used as controls. Fish were examined either 24 or 96 h after administration. Praziquantel treatment was characterised by a significantly lower erythrocyte count, haemoglobin level, packed cell volume and total protein at both dose levels after 24 h compared with the controls, but these parameters were similar to the control values at 96 h. The activity of alanine aminotransferase (ALT) was significantly higher after 96 h in the treated groups, which could be attributed to slight hepatocyte damage caused by praziquantel. However, the differences between the treated and the control groups were not great, and we presumed that they were reversible.

A short review of some pharmacological, therapeutic and toxicological properties of praziquantel in man and animals

Praziquantel is the current drug of choice against many trematodes and cestodes in both man and animals. This article summarizes the main pharmacological, therapeutic and toxicological properties of the drug, especially that have been reported during the last 10 years. In most cases, the effectiveness and safety of the drug have been confirmed, although there are currently concerns about the resistance/decreased effectiveness of the drug to certain Schistosome isolates, and also about the mutagenicity of the drug.

Comparative study of the hepatotoxic, genotoxic and carcinogenic effects of praziquantel distocide & the natural myrrh extract Mirazid on adult male albino rats

Praziquantel (PZQ) is widely and effectively used in the control of bilharziasis which constitutes a major endemic health problem in Egypt. However, recent studies recommended that the drug must be re-evaluated because of its potential carcinogenicity and genotoxicity. Mirazid is a new natural anti-schistosomal drug formed of myrrh extract and considered to be a safe drug. This work was conducted to evaluate and compare hepatotoxic, genotoxic and carcinogenic effects of PZQ and Mirazid on adult male albino rats by assessment of serum levels of ALT, AST and bilirubin, histopathological study of the liver and cytogenetic study of bone marrow cells. 100 adult male albino rats were equally divided into 4 groups: (I): negative control, (II): control rats received distilled water, (III): received weekly single oral dose of PZQ (1500 mg/kg) for 6 weeks, (IV): received daily oral dose of Mirazid (500 mg/kg) for 6 weeks. At the end of the study 10 rats of each group were investigated by assessment of the levels of AST, ALT, & Bilirubin. After scarification, liver sections were examined by light microscopy. Another 10 rats of each group were submitted to cytogenetic examination. It was found that praziquantel induced a significant increase in the mean values of AST, ALT and bilirubin with areas of hyaline degeneration, fatty changes, dysplasia and necrosis in the liver sections. It also induced a significant increase in the incidence of chromosomal aberrations as polyploidy, fragment, deletion and ring chromosome as compared with control group. Mirazid induced a non significant increase in the mean values of AST, ALT and bilirubin, with a normal hepatic tissue, and a non significant increase in the incidence of chromosomal aberrations, as compared with the control group. On comparing both drugs, praziquantel induced a significant hepatotoxic, genotoxic and carcinogenic effects. It was concluded that, Praziquantel is considered to be a hepatotoxic, genotoxic and carcinogenic drug. On the other hand, Mirazid seemed to be a safe and promising antiparasitic drug, free from hepatotoxic, genotoxic and carcinogenic effects.

Investigation of induced biochemical and histopathological parameters of acetonitril extract of Jatropha carcus in albino rats

Toxicological and histopathological investigations were carried on the acetonitril extract from J. carcus in comparison to praziquantel, the known antischistosomal drug. On a constant weight dose bases (single dose of 50 mg/Kg body weight injected orally to albino rats), the acetonitril extract from J. carcus showed mild toxicological parameters (AST p < 0.001, ALT & creatinine, non-significant), biochemical parameters (total lipids, cholesterol, triglycerides, HDL, LDL, proteins, albumins globulins, ascorbic acid and bilirubin, non-significant) and histo-pathological profile (slight alterations in liver, kidney and spleen), in comparison to control. However, these side-effects were very little as compared to the severe side-effects caused by Praziquantel.

Albendazole, mebendazole and praziquantel. Review of non-clinical toxicity and pharmacokinetics

The pharmacokinetics and toxicity of albendazole, mebendazole and praziquantel are extensively reviewed, drawing on original published work and reviews in the open scientific literature and on assessments by international agencies and official regulatory bodies in Europe and the USA. Information about human and veterinary medical uses and adverse reactions is evaluated. The totality of the non-clinical information available about these long-established drugs may not comply with current official guidelines for new medicines but reasons are given why the "deficiencies" are only apparent and the data gaps can be replaced by other results, largely obtained from the target species and the many years of clinical experience of safe use of these drugs in humans and animals.

The toxicity of praziquantel against Mesocestoides vogae (syn. corti) tetrathyridia can be assessed using a novel in vitro system

We recently standardised Mesocestoides vogae (syn. corti) tetrathyridia cultures in the presence of sodium taurocholate. Parasite clustering and segmentation were observed as taurocholate-dependent effects in biphasic and monophasic media, respectively, and both were inhibited by a specific minimum inhibitory concentration (m.i.c.) of the cestocidal drugs albendazol and praziquantel. In the present study, we analysed the relationship between clustering inhibition and drug toxicity using praziquantel and a mouse experimental infection. In an "in vitro-in vivo" trial, a significant (ANOVA, P<0.05) reduction was observed in the infectivity of tetrathyridia previously cultured with praziquantel m.i.c. (0.06 micro g/ml) for 10 days. In an "in vivo-in vitro" trial, the clustering of tetrathyridia recovered from mice treated with praziquantel was found to be markedly reduced: 22%, compared with 83% cluster-containing wells of parasites from control mice. These results show that the outcome of infection and the suppression of taurocholate-induced clustering provide consistent indications of praziquantel toxicity against M. vogae, an observation confirmed by histological studies. The easily recorded clustering inhibition of M. vogae tetrathyridia in biphasic medium is a potentially useful system for the assessment of drug toxicity against cestode larvae.

Effect of bilirubin on toxicity induced by trifluoperazine, dibucaine and praziquantel to erythrocytes

Unconjugated bilirubin (UCB), like trifluoperazine (TFP), dibucaine (DBC) and praziquantel (PZQ), induces erythrocyte morphological changes, lysis and lipid exfoliation. In the present study we determined whether TFP, DBC and PZQ toxicity to erythrocytes was potentiated or reverted by UCB. Human erythrocytes were either treated or non-treated with 34.2 micromol/L UCB for 10 min prior to the incubation with toxic concentrations of TFP (0.12 mmol/L), DBC (1.5 mmol/L) or PZQ (3.0 mmol/L), for 1 h (37 degrees C). Studies of toxic effects included morphological analysis of erythrocytes, evaluation of hemoglobin release and loss of membrane lipids. Although UCB has an echinocytogenic effect, its co-incubation with TFP or PZQ did not alter the stomatocytogenic effect of the drug but enhanced DBC-induced stomatocytosis. Cell fusion was a common feature in experiments with DBC. Injurious effect of DBC to erythrocytes was potentiated by UCB as manifested by a marked increase in hemolysis (171%, p<0.05), and in elution of membrane cholesterol (73%, p<0.01) and phospholipids (123%, p<0.01). In opposite, toxic events produced by TFP and PZQ to erythrocytes were not aggravated by UCB. Interestingly, UCB prevented the loss of membrane cholesterol by PZQ (-36%, p<0.01), as well as that of phospholipids by TFP (-28%, p<0.05). These findings indicate that UCB potentiates DBC injury to erythrocytes, while protects membrane lipid elution by PZQ and TFP. Therefore, the relation of the benefits and risks of the administration of DBC to jaundiced patients should be carefully considered.

[The technology for manufacturing antiparasitic preparations. 9. The new preparation tizanox and an evaluation of its anti-Hymenolepis activity]

The paper describes a procedure for manufacturing the new anthelminthic Tizanox. It shows it necessary to administer a larger dose of the drug than that of azinox (praziquantel) to treat experimental hymenolepiasis. However, the lower toxicity of Tizanox enhances its chemotherapeutical index.

[The technology for manufacturing antiparasitic preparations. 6. The development of a technology for producing the anthelmintic Azinox (praziquantel) and the evaluation of its toxic and anthelmintic properties]

The paper outlines a procedure for manufacturing the anthelminthic Azinox (biltricide) using the new interfacial transfer catalyst benzyl-di-propyl (beta-hydroxyethyl)ammonium chloride. Azinox has been shown to be identical to biltricide (praziquantel) in its properties. Azinox tests on models of Opisthorchis felineus in golden hamsters and of Hymenolepis nana in albino outbred mice have indicated that the agent is not inferior to biltricide in its antitrematodal and anticestodal activities. Azinox displayed a high activity at the preimaginal stages of O. felineus and H. nana and at the larval stage of H.nana.

Experimental Schistosoma bovis infection in goats: pathological consequences of praziquantel treatment

Schistosoma bovis-infected goats were treated with praziquantel (60 mg/kg) and killed for examination 1, 7 or 28 days later. Infected non-treated goats and parasite-free, treated or non-treated goats were included for comparison. The gross pathological changes seen in the infected non-treated groups were mild to moderate. The liver appeared discoloured and moderately enlarged. The intestinal lesions were most prominent in the small intestines, which showed catarrhal inflammation with numerous tiny corpuscles beneath the luminal surface. The mesenteric lymph nodes were slightly to moderately enlarged. In contrast, on macroscopical examination, the infected treated groups invariably showed pronounced liver changes and marked enlargement of the lymph nodes, whereas the lesions in the intestines were comparatively slight. Histological lesions related to dead worms were seen in the livers of all treated animals. These lesions included pronounced inflammatory cellular infiltrates, thrombophlebitis, necrosis and periportal fibrosis, still severe 4 weeks after treatment. In the intestines, the deposition of new eggs with little cellular reaction had almost completely ceased 1 week after treatment. Four weeks after treatment, only a very few egg-associated lesions were noted in the intestines. The presence of severe lesions attributable to dead worms in the liver indicates the need for caution when treating animals with high worm loads or concomitant liver disease.

Effect of schistosomal infection and its treatment on some key enzymes of glucose metabolism in mice livers

Three antischistosomal drugs, praziquantel (CAS 55268-74-1, EMBAY 8440, Prz), oxamniquine (CAS 21738-42-1, Oxa) and oltipraz (CAS 64224-21-1, Olt) were examined for their ability to reverse the disturbances in carbohydrate metabolism induced by Schistosoma mansoni (S. mansoni) infection. The infected mice were screened every 2 weeks for 16 weeks for their body and liver weights in addition to assessment of the activities of liver pyruvate kinase (PK), phosphofructokinase (PFK) (glycolysis), citrate synthase (CS) (Krebs' cycle) glycogen phosphorylase (GP) (glycogenolysis), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) (hexose monophosphate shunt). Results of the study showed that infection with S. mansoni caused the following changes in mice livers: 1. significant increase in liver weights from the 6th week of infection, which coincided with schistosomal egg deposition, whereas body weights were reduced, 2. remarkable increase in the activities of PK and PFK from the 4th week of infection, 3. marked reduction in CS, GP, G6PDH and 6PGDH. These results lead to the conclusion that glycolysis is largely stimulated in the livers of infected mice on the expense of other metabolic pathways of glucose utilization. Administration of Prz to infected mice caused normalization of all measured enzyme activities almost from the 2nd week of infection, whereas liver and body weights were improved from the 10th week. Oxa was less effective in these regards while Olt was the least. These data support the selection of Prz as a drug of choice for S. mansoni infection.

Risk identification using structural concepts: the potential carcinogenicity of praziquantel

The potential of praziquantel (PZ) to induce cancers in rodents was evaluated using a structure-activity relational expert system (CASE/MULTICASE). The analyses indicated that based upon structural features PZ had the potential for being a "nongenotoxic" carcinogen. The potential risk to humans of nongenotoxic carcinogens is considered to be much less than that posed by "genotoxic" ones. Moreover, PZ has demonstrated therapeutic effectiveness against parasitic diseases that affect millions of individuals. Additionally, PZ was developed to replace antiparasitic agents which were genotoxic rodent carcinogens. Thus, on balance, the beneficial effects of PZ appear to outweigh its potential for causing harm to humans.

Lethal effect of oxamniquine and praziquantel on mice experimentally infected with Schistosoma mansoni

Lethality caused by administration of oxamniquine and praziquantel to mice infected with Schistosoma mansoni, and their respective controls (uninfected), has been studied. As the results indicate, the infected animals clearly showed higher mortality rates when praziquantel was used. Surprisingly, it may be noted that exactly the contrary occurs in relation to the use of oxamniquine, inasmuch as marked higher mortality rates were seen in the control animals (uninfected). These observations lead to the conclusion that further toxicological studies of antischistosomal drugs using. S. mansoni infected animals are needed.

The effect of praziquantel on the activities of some drug-metabolizing hepatic enzymes in rabbits

The effect of oral administration of praziquantel at different dose levels on the activities of metabolizing hepatic enzymes (aminopyrine N-demethylase, aniline 4-hydroxylase and UDP-glucuronyltransferase) was studied in healthy locally bred rabbits. The pathological changes resulting from drug's toxicity were assessed histologically, by measurement of total plasma protein concentration and of the activities of the plasma enzymes sorbitol dehydrogenase (SD), glutamate dehydrogenase (GD) and aspartate aminotransferase (AST). No significant changes were obtained after praziquantel administration at dose levels of 40 and 800 mg/kg body weight, whereas 1600 mg/kg and 2000 mg/kg of praziquantel resulted in a significant decrease in the activities of the three drug-metabolizing hepatic enzymes under investigation in the livers of treated rabbits. All rabbits which received praziquantel at the dose rate of 2000 mg/kg died 10-20 hours following praziquantel treatment.

Praziquantel (antischistosomal drug): is it clastogenic, co-clastogenic or anticlastogenic?

Schistosoma haematobium infection is the most common health problem in Egypt. It is strongly associated with the development of urinary bladder carcinoma. The actual cause for the development of cancer is still under investigations, it can be due to mechanical irritation from schistosomiasis ova, the infection itself or the drugs which are used to treat the patients. Praziquantel (PQ) is a commonly used drug to treat schistosomiasis patients. In mice, an in vivo cytogenetic study showed that PQ is not clastogenic in mice. The frequency of micronuclei in all the study groups were insignificantly different from the control group (p > 0.05). However, it enhanced the clastogenicity of benzene at a very high dose. Results from combined exposure with benzene and PQ showed a significant PQ dose-dependent increase in micronucleus frequency (p < 0.05). A metabolite study revealed that PQ enhanced the metabolism of benzene to form muconaldehyde which may be responsible for the enhancement effect. In schistosomiasis patients, two cytogenetic studies were carried out before and after treatment with PQ. In one of these studies, peripheral blood lymphocytes were examined from schistosomiasis patients to detect chromosomal aberrations (CAs) and micronuclei (MN) before and after treatment with PQ. There was no significant increase in CAs in patients compared with the controls (p > 0.05). The frequency of MN was significantly higher in the infected persons (0.59 +/- 0.44) than the control individuals (0.23 +/- 0.23) (p < 0.05). After treatment, there was no significant change in both parameters. The other study was conducted to determine whether infection with this parasite resulted in an increase of chromosomal breakage, micronuclei, in exfoliated urothelial cells. Micronucleus frequencies were significantly higher in the infected group (mean frequency, 0.84 +/- 0.69%) than among controls (mean frequency, 0.12 +/- 0.21%, p < 0.001). Micronucleus frequencies were higher in infected individuals who smoked compared with those who were non-smokers, although this effect was not significant (p > 0.05). The mean micronucleus frequencies were reduced significantly in the group of patients who were followed up (before treatment, 0.80 +/- 0.70%, after treatment, 0.19 +/- 0.23%, p < 0.001), thus supporting a direct involvement of the infection in increased chromosomal breakage in the urothelium and provide proof of the role of PQ in decreasing the risk of cancer development. At this stage, we still need to study the cytogenetic effect of human exposure to environmental agents such as pesticides, smoking, etc., together with treatment with PQ.

Evaluation of the carcinogenic and genotoxic potential of praziquantel in the Syrian hamster embryo cell transformation assay

Praziquantel, a drug used for the treatment of neurocysticercosis, was tested for its ability to induce morphological transformation of Syrian hamster embryo fibroblasts. Results indicate that praziquantel transforms these cells without affecting their viability. Further experiments were carried out to investigate its possible mechanism of action in the same cell system. Micronucleus formation was observed in cultures treated with concentrations which induced morphological transformation, about 40% of these micronuclei were positive to a kinetochore antibody. No induction of DNA repair synthesis was observed even at cytotoxic concentrations. These results suggest that praziquantel has an aneugenic effect which could be responsible for its ability to transform morphologically these cells. Risk-benefit analysis should be carried out whenever this drug is utilized.

Mutation at the HPRT locus in patients with neurocysticercosis treated with praziquantel

Praziquantel (PZQ) is the drug of choice in the treatment of neurocysticercosis (NC), a parasitic disease caused by Taenia solium larvae. Variant frequencies at the hprt locus were analyzed in a group of NC patients before and after treatment with PZQ as well as in two control groups: healthy donors and non-parasitic neurological patients. Data show that PZQ does not induce hprt mutations, but that cysticerci by themselves or together with palliative treatment administered to NC patients could induce mutations in some patients.

Levo-praziquantel versus praziquantel in experimental and clinical treatment of schistosomiasis japonica

Levo-praziquantel is the left isomer of racemic praziquantel. Animal experiments showed that it is an active component of schistosomicidal activity, while dextro-praziquantel is almost ineffective. Clinical trials in three endemic areas of Schistosomiasis japonica indicated that the therapeutic efficacy of levo-praziquantel is superior to racemic praziquantel. Pharmacokinetic and pharmacodynamic activities of the stereoselectivity of praziquantel isomers (enantiomers) are discussed.

An experimental study on the effect of praziquantel and oltipraz on some lysosomal enzymes

The in-vivo effect of the schistosomicidal drugs praziquantel and oltipraz on the activities of the liver lysosomal enzymes in Schistosoma mansoni-infected and non-infected mice was studied. The effect of S. mansoni infection and the administration of the schistosomicidal drugs on the activities of beta-glucuronidase, acid ribonuclease and alpha-naphthyl acetate esterases may be considered as indices for carcinogenicity. Drugs were given orally in subcurative doses, either in a single dose of 400 mg kg-1 for praziquantel or in five daily doses of 50 mg kg-1 oltipraz. The increase in enzymatic activities in infected animals was attributed to deranged metabolic function as a result of liver cell injury. Treatment of uninfected animals with either praziquantel or oltipraz significantly increased the activities of the three lysosomal enzymes. Praziquantel possesses reversible and less toxic effects on the liver than oltipraz. The role of these antischistosomal drugs cannot be ignored as a possible aetiological factor implicated in the process of carcinogenesis associated with schistosomiasis infection through modulation of the operating potential of the enzymes concerned with detoxification, protein and fat metabolism.

[The search for new antiparasitic agents. 11. The acute toxicity and anticestodal activity of the new anthelmintic Tizanox compared with Azinox]

A synthesis is described and the results of toxicological trial of the potential anthelmintic agent G-1587 are presented. The agent is 2-(cyclohexylcarbonyl)-1,2,3,6,7,11b-hexahydro-2H-[1, 2,5] thiadiazino [3,2-a] isoquinoline-4,4-dioxide. The agent was shown to have a low toxicity, the maximal sublethal dose for mice being 4.0 g/kg when given per os.

Repeated exposure to Opisthorchis viverrini and treatment with the antihelminthic Praziquantel lacks carcinogenic potential

The effects of repeated Praziquantel administration, subsequent to infection and reinfection with Opisthorchis viverrini (OV), on lesion development in the Syrian hamster liver were investigated. Five applications of the antihelminthic drug were made (300 mg/kg body wt, i.g.), each time approximately 5 weeks after dosing with 60-80 OV metacercariae at weeks 0, 8, 16, 24 and 32. The animals were then maintained until week 40 when they were killed; histopathological investigation revealed no significant development of either hepatocellular of cholangiocellular preneoplastic/neoplastic lesions. The results indicate that repeated exposure to Praziquantel at levels sufficient for successful removal of parasite infestation does not itself carry carcinogenic risk.

[The structure and anthelmintic action of tricyclic analogs of praziquantel and 4-acylpiperazinones-2]

The toxicity and anthelminthic activity of the earlier synthetized tricyclic analogues of praziquantel and 4-acylpiperazinones-2 have been studied. Tricyclic compounds have shown the acute toxicity similar to that of praziquantel and neurotoxic effect typical of praziquantel. 4-acylpiperazinones-2 toxicity correlated with their anthelminthic effect. The determination of anthelminthic activity of the above compounds in opisthorchiasis and hymenolepiasis has shown that they are less effective than praziquantel or have no anthelminthic activity. A biological activity-structure relationship has been traced in the compounds under study.

Effect of praziquantel versus hycanthone on deoxyribonucleic acid content of hepatocytes in murine schistosomiasis mansoni

Cytophotometric measurement of the effect of praziquantel (500 mg/kg for 2 days) versus hycanthone (60 mg/kg for 3 days) on hepatocyte nuclear deoxyribonucleic acid (DNA) content was evaluated in Schistosoma mansoni infected mice. Drugs were given 8 weeks post-infection and repeated weekly for 4 weeks. DNA values of infected untreated control and infected drug treated groups were related to the median and upper diploid DNA values of normal control. Schistosoma mansoni infection per se did not change the hepatocyte DNA content, yet aneuploidy was 16.7%. Praziquantel did not result in significant change of DNA content or ploidy, while hycanthone resulted in marked significant increase of DNA content (328.9%) and aneuploidy (100%), compared to infected untreated control. Histopathological examination revealed hyperchromatic nuclei with mitosis in the hepatocytes of hycanthone treated mice, but not in praziquantel treated animals. These DNA changes were found to correlate with the reported safety of praziquantel and the carcinogenicity of hycanthone.

Praziquantel did not exhibit hepatotoxicity in a study with isolated hepatocytes

The effect of praziquantel in different concentrations on isolated rat hepatocytes as a cellular target was studied to detect any possible toxicity. Leakage of cytosolic enzymes, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase (LDH) was monitored after one hour of incubation of all the cells with the drug. Levels of reduced glutathione (GSH) and cytochrome P450 were also assayed. The drug, in concentrations of 5, 25, 50 and 100 micrograms/ml, had no effect on any of these parameters. In contrast, the hepatotoxic compound trichloroethylene showed dose-dependent toxicity, as measured by trypan blue (TB) exclusion, LDH leakage, and reduction in GSH content in the present cellular model. These results suggest that praziquantel is a relatively safe drug with respect to liver function.

A study of the ultrastructure of the intestines of mice experimentally infected with S. mansoni and treated with praziquantel

The present experimental work studied the ultrastructural changes occurring in the intestines of mice infected with S. mansoni and treated with praziquantel. Mild degenerative changes of the intestinal cells together with degranulation of the APUD cells were observed. The enterochromaffin cells in the intestines secrete serotonin which is a vaso constrictor and a strong stimulator of the smooth muscles. A possible explanation of the side effects of praziquantel is thus offered.

Enhancement of benzene clastogenicity by praziquantel in mice

Praziquantel (PQ) is a commonly used drug to treat patients with schistosomiasis. Previous studies using cells in vitro have shown that PQ can enhance the mutagenic activities of known mutagens. We have conducted a cytogenetic - urine metabolite study to determine the in vivo clastogenic and co-clastogenic potential of PQ with a ubiquitous environmental contaminant, benzene (BZ). 16 groups of adult male ICR mice (5 animals per group) were used. They were negative control, solvent controls (cremophore E1 3%, olive oil and combined), positive control (BZ 440 mg/kg b.w.) and 11 exposed groups. To test for clastogenicity of PQ, mice were treated orally with 100, 400, 800 and 1200 mg/kg b.w. PQ and sacrificed 30 h later for determination of micronuclei (MN) frequency in bone-marrow polychromatic erythrocytes (PCE). None of these PQ does induced an increase of MN frequency. On the other hand, BZ induced, as expected, a high frequency of MN (46.4 +/- 6.34/1000 PCE). The enhancement effect of PQ was tested in 7 groups of mice using 3 different protocols. Mice were treated with 440 mg/kg b.w. BZ and 1 h later with 0, 100, 200, 400, 800 and 1200 mg/kg b.w. PZ. In another group, 800 mg/kg PQ was administered at 3 h after BZ exposure. In the last group, PQ (800 mg/kg) was administered at 1 h prior to BZ exposure. Results from the first combined exposure group showed a significant PQ dose-dependent increase in the frequency of MN in PCE (p less than 0.05). The increase with the two high doses of praziquantel is significantly higher (p less than 0.05) than the MN frequencies in the benzene control and the expected value based on the additive effects of the two agents. Studies with other combined treatment groups showed that the induction of MN was highest when PQ was administered at 1 h before BZ exposure. Moreover, the presence of BZ metabolites (muconic acid, phenol, catechol and hydroquinone) in urine was studied in 6 of the combined treatment groups. This metabolite study revealed that PQ enhanced the metabolism of BZ towards the pathway to form muconaldehyde which is converted to muconic acid in urine. In conclusion, our study showed that PQ is not a clastogen but can enhance the clastogenic activity of BZ in vivo by shifting the metabolic pathways of BZ towards formation of muconaldehyde which may be responsible for the enhancement effect.

Levamisole restored the compromised state of immunity after specific chemotherapy in experimental schistosomiasis mansoni

Mice infected for 45 days with 120 Schistosoma mansoni cercariae and treated with levamisole (25 mg/kg subcutaneously) have more efficient acquired immunity when challenged with 240 Schistosoma mansoni cercariae the same day of treatment (97.7% # 87.7% in infected challenged controls). In praziquantel-treated mice (500 mg/kg for 2 days orally), the reduction in the percent resistance (45.5%) was accompanied by a significant diminution in the size of granuloma, delayed foot pad swelling and granuloma proportionate T-helper cells number. Levamisole when given two weeks post praziquantel treatment and with the challenge infection increased the percent resistance to 79.2%. The increase in percent resistance recorded in mice receiving both praziquantel and levamisole was accompanied by restoration of granuloma size, delayed foot pad swelling and granuloma proportionate T-helper cells number to infected challenged untreated control values. Results reveal-beside efficacy of levamisole as immunoregulant in schistosome immunity--a possible role for the granuloma as a T-cell mediated response in maintenance of immunity.

Results of toxicological studies on praziquantel

Praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7, 11b-hexahydro-4H-pyrazino[2,1-a]isoquinolin-4-one, EMBAY 8440, Biltricide) is an anthelminthic drug with activity against all species of schistosomes pathogenic to man and a wide range of cestodes, including the cysticerci of Taenia solium in human tissues and organs, also the CNS. Praziquantel does not reveal any undesired pharmacodynamic effects. After oral administration praziquantel is quantitatively and rapidly absorbed, metabolized and excreted as a variety of metabolites predominantly via the kidneys. The acute toxicity in rats, mice, rabbits and dogs is very low. Rats tolerated by oral administration doses of up to 1000 mg/kg repeated daily for four weeks, and dogs up to 180 mg/kg for 13 weeks without any organ damage. Praziquantel did not disturb reproduction in rats (up to F2-generation), nor did it reveal teratogenic effects in mice, rats and rabbits. In extensive mutagenicity trials performed by different laboratories worldwide, in a variety of test systems, no induction of point mutations, gene conversion, DNA-repair, sister chromatid exchanges (SCEs), or X-linked recessive lethals was detected. Besides, Salmonella tests with urines of praziquantel treated mice, rats, healthy and Schistosoma-infected persons gave no indication of a mutagenic effect. In different in vivo mammalian assays praziquantel not mutagenic either. Low toxicity of praziquantel was not mutagenic either. Low toxicity of praziquantel was demonstrated also in the combined chronic toxicity and carcinogenicity tests which were performed in rats and Syrian hamsters. In none of these species praziquantel exerted a carcinogenic action, and both doses were tolerated.

Effects of praziquantel, a new antischistosomal drug, on the mutation and transformation of mammalian cells

Praziquantel (PQ), a tetrahydroquinoline derivative, is a new and clinically effective antischistosomal drug, which has been shown to lack or to possess very weak mutagenic activity. However, in bacteria, this compound can act as a weak comutagen that increases the mutagenicity of several chemical mutagens and carcinogens. We have found that PQ can act as a very weak comutagen in animal cells. At 10 to 50 micrograms/ml, PQ increased the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine and 2-methoxy-6-chloro-9-[3-(2-chloroethyl)amino-propylamino]acridine dihydrochloride about 2-fold in Chinese hamster V-79 cells. In C3H/10T 1/2 mouse embryo cells, PQ exhibited only negligible comutagenic activity. PQ did not oncogenically transform C3H/10T 1/2 cells but had a pronounced effect on 3-methylcholanthrene-induced transformation of these cells. When PQ was coadministered with or added after 3-methylcholanthrene treatment, the number of type III foci produced was about 5-fold lower than in cultures treated with 3-methylcholanthrene alone. Therefore, PQ can inhibit type III focus formation in C3H/10T 1/2 cells.

A chronic study of praziquantel in Syrian golden hamsters and Sprague-Dawley rats

Groups of Syrian golden hamsters and Sprague-Dawley rats received 100 mg or 250 mg praziquantel/kg body weight, intragastrically by oral gavage once weekly for 80 weeks and 104 weeks, respectively. In both hamsters and rats the observed differences in tumour incidence, latency and multiplicity revealed no positive dose response effect. Tumours observed corresponded in their origin and morphology to those which develop spontaneously in these species. Haematological and clinico-chemical values were normal. Whereas the average survival time was slightly shortened in rats, female hamsters showed reduced weight gains in the high dose level groups, although water intake and food consumption were increased.

Toxicological profile of praziquantel, a new drug against cestode and schistosome infections, as compared to some other schistosomicides

2-Cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a] isoquinolin-4-one (praziquantel, EMBAY 8440, Biltricide), a new anthelminthic drug with activity against all species of schistosomes pathogenic to man, and against a wide range of cestodes, did not reveal any undesired pharmacodynamic effects. After oral administration praziquantel is quantitatively and rapidly absorbed, metabolized and excreted as a variety of metabolites predominantly via the kidneys by all species tested, including man. Its acute toxicity tested in rats, mice, rabbits and dogs is very low as compared with other schistosomicidal drugs. After repeated oral administration rats tolerated daily doses of up to 1000 mg/kg for four weeks, and dogs up to 180 mg/kg for thirteen weeks without any organ damage. In contrast to some other schistosomicidal drugs praziquantel did not disturb the whole reproductive process (up to F2-generation) in rats, nor did it reveal teratogenic effects in mice, rats and rabbits. In extensive mutagenicity trials performed in different European laboratories in a variety of test systems no induction of point mutations, nor of gene conversion, nor of DNA-repair, nor of sister chromatid exchanges (SCEs), nor of X-linked recessive lethals was detected. Besides, Salmonella tests with urines of praziquantel-treated mice, rats, healthy and Schistosoma-infected persons gave no indication of a mutagenic effect. In different in vivo mammalian assays praziquantel was not mutagenic either. In contrast to these findings other schistosomicidal drugs demonstrated mutagenic potential, in bacterial tests at least. According to the results available so far from carcinogenicity studies with oral doses of 100 and 250 mg praziquantel/kg, given once weekly to Syrian hamsters for 80 weeks and to rats for 104 weeks, there is no hint of a carcinogenic potential of praziquantel in small rodents, while hycanthone had cancerogenic effects in mice and niridazole was carcinogenic in mice, rats and Syrian hamsters.