Dose-confirmation studies of the cestocidal activity of pyrantel pamoate paste in horses

Dose confirmation studies of the cestocidal activity of pyrantel pamoate paste were conducted at two sites in North America during 2001. Horses with naturally-acquired cestode infections were identified by detection of typical Anoplocephala spp. eggs in feces collected between 7 and 92 days prior to treatment. Twenty and 22 horses were enrolled at Site 1 (Urbana, IL) and Site 2 (Knoxville, TN), respectively. Candidate horses were acclimated to study conditions for 14 days, ranked by length of interval since coprologic confirmation, and allocated randomly to one of two treatment groups: (T1) pyrantel pamoate paste 13.2mg pyrantel base per kilogram body weight administered orally, and (T2) untreated controls. Individual doses of pyrantel pamoate paste were prepared on the basis of contemporaneous body weights and administered to Group T1 horses on Day 0. Trained personnel monitored the animals at regular intervals after treatment to detect potential adverse reactions. Horses were euthanatized and necropsied 10-12 days after treatment. The contents of the large and small intestines were collected, and the walls of each organ were rinsed with water and inspected. Attached cestodes were recovered and preserved in 10% formalin. The intestinal contents and rinsed ingesta were washed over a #10-mesh (2mm aperture) sieve and tapeworms were extracted and preserved. Recovered cestodes were counted and examined at 1-4x magnification for identification to genus and species. At Site 1, specimens of Anoplocephala perfoliata were recovered from seven of 10 control horses, and from one of 10 horses treated with pyrantel pamoate. Mean cestode numbers were 4.52 in the control group and 0.07 for treated horses. At Site 2, cestodes were found in 10 of 11 controls (mean 26.2) and in five of 11 horses (mean 1.2) treated with pyrantel pamoate. In both studies, Group T1 means were significantly lower than the control group (P<0.005). The calculated efficacies were 98.4 and 95.5% at Sites 1 and 2, respectively. In two dose-confirmation studies, a single, oral treatment of pyrantel pamoate paste (19.13% w/w pyrantel base) at 13.2mg/kg was >or=95.5% effective against A. perfoliata in naturally-infected horses.

Clinical field efficacy and safety of pyrantel pamoate paste (19.13% w/w pyrantel base) against Anoplocephala spp. in naturally infected horses

Clinical field trials were conducted at five geographical locations in the USA (Oklahoma, Wisconsin, Tennessee, Virginia and Idaho) to evaluate the efficacy and safety of pyrantel pamoate paste (19.13%, w/w, pyrantel base) administered at the recommended dosage of 13.2 mg pyrantel base/kg (6.0 mg pyrantel base/lb) body weight (b.w.) against tapeworm infections of Anoplocephala spp. in naturally infected horses. Horses at each study site were allocated by restricted randomization based on the cestode status (positive or negative) of pre-treatment fecal egg counts to complete sets of four animals each or incomplete sets of fewer than four animals. Within sets comprising of two to four horses, one animal was randomly allocated to receive placebo vehicle paste and the remaining horse(s) received pyrantel pamoate paste administered orally at a minimum dosage of 13.2 mg pyrantel base/kg b.w. on Test Day (TD) 0. Single animal sets received pyrantel pamoate paste. Fecal samples of horses were collected and examined for equine tapeworm (Anoplocephala spp.) eggs a minimum of four times (once or thrice between TD -28 and -14, twice between TD -14 and -7, and once on TD 0) prior to treatment on TD 0. Fecal samples of horses that were positive for cestode infection pre-treatment were examined for cestode eggs on TD 7, 8, 9, 14, 15 and 16. Cestode-negative pre-treatment horses were not sampled again after treatment. A total of 241 horses (141 mares, 16 stallions and 84 geldings; 6 months-30 yrs of age; 173-646 kg; 13 recognized breeds and various crossbreds) were evaluated. The prevalence of Anoplocephala spp. determined by pre-treatment fecal examination ranged from 38.3% in Idaho to 68.1% in Tennessee with an overall prevalence of 52.3%. Ninety cestode-positive and 88 cestode-negative horses were treated with pyrantel pamoate paste, 36 cestode-positive and 27 cestode-negative horses were treated with placebo vehicle paste. Overall, 178 horses were treated with pyrantel pamoate paste, and 63 horses were treated with placebo paste. Of the 178 horses treated with pyrantel pamoate paste, no drug related, adverse clinical or neurological health events were observed. No doses of pyrantel pamoate paste were refused or lost during dosing. At each post-treatment time sampling interval, significantly fewer cestode eggs (P < 0.0115) were passed by cestode-positive horses treated with pyrantel pamoate paste compared to cestode-positive horses that received placebo paste. Efficacy of the pyrantel pamoate paste treatment ranged from 92 to 96% from TD 7 to TD 16 with an overall efficacy of 95%. The results of these trials demonstrated that pyrantel pamoate paste (19.13%, w/w, pyrantel base) administered orally at a dosage of 13.2 mg pyrantel base/kg b.w. is highly efficacious (95%) against Anoplocephala spp. and safe for use in horses with no adverse clinical or neurological health events observed under field use conditions.

A modified critical test and its use in two dose titration trials to assess efficacy of praziquantel for Anoplocephala perfoliata in equids

Aims of this study with 43 equids naturally infected with Anoplocephala perfoliata in two dose titration trials were to document (i) the usefulness of a critical test with a 48 h treatment to necropsy period, (ii) efficacy of an oral paste of 0.5-2.0 mg praziquantel/kg body weight, and (iii) when after treatment would fecal egg counts provide best estimates of the tapeworm's prevalence in a herd. All feces passed by an equid after treatment and collected in successive 12 h batches were examined for tapeworms. At necropsy, tapeworms were identified as attached to the mucosa or unattached. Tapeworms were examined with a stereoscope and identified as normal or abnormal. Fecal samples were taken for egg counts at treatment and at 6 h intervals thereafter. In 32 of 36 treated equids, efficacy was 100% and mean efficacies for 0.5, 1.0, 1.5 and 2.0 mg praziquantel/kg body weight were 85.5, 99.7, 100 and 100%, respectively. Two equids treated with 0.5 mg praziquantel/kg body weight had low efficacies (5.4 and 38.1%) and normal tapeworms were found attached in the ventral colon and in one equid also in the dorsal colon. In seven untreated equids, tapeworms were primarily in the cecum with 21.3% detached. "Major fragments" or worms without a scolex but otherwise nearly a complete worm were 20.5% of the number of intact worms; they were not included in the efficacy analysis but should be. If the two equids with low efficacy were eliminated and if the number of all tapeworms and major fragments are combined less than 0.5% were in feces within 12 h of treatment, about 20% were in the 12-24 h period, 42% in 24-36h, 24% in 36-48 h and 13.5% in the equids at necropsy. One horse passed all its tapeworms in 24 h. This 48 h test when compared with a 24 h one with no examination of feces was more efficient in use of trial animals and reduced underestimation and overestimation of efficacy. However, a protocol similar to the 48 h test but with a 24 or 36 h post-treatment period should be investigated. The mean egg count peaked 18-24 h after treatment and samples taken at that time would provide the best estimate of prevalence. The Cornell-Wisconsin centrifugal flotation technique had a specificity of 100% and at 18 and 24 h its sensitivity was 94%. A brief discussion on critical and controlled tests for assessing efficacy of an anthelmintic for A. perfoliata is presented.

Effect of isoflavone from Flemingia vestita (Fabaceae) on the Ca2+ homeostasis in Raillietina echinobothrida, the cestode of domestic fowl

The alcoholic crude root-peel extract of Flemingia vestita and its major isoflavone, genistein, have been shown to have a vermifugal/vermicidal effect by causing a flaccid paralysis accompanied by alterations in the structural architecture of the tegumental interface and metabolic activity in Raillietina echinobothrida, the cestode of domestic fowl. In the present study, the crude root-peel extract and pure genistein were tested in vitro with respect to Ca2+ homeostasis and the occurrence of some metal ions was detected in the parasite. Live cestodes were incubated in pre-defined concentrations of the crude root-peel extract, genistein and praziquantel (as reference drug), till the paralysis time with simultaneous maintenance of respective controls. In the parasite tissue, a significant amount of Ca2+ (approximately 400 microg/g dry tissue wt) was found to be present besides magnesium, iron, zinc, lead and chromium, whilst manganese, cadmium and nickel were below the level of detection. The Ca2+ concentration was decreased significantly by 39%-49%, in the parasite tissue exposed to the test materials in comparison to the respective controls. There was also an increase in Ca2+ efflux by 91%-160% into the culture medium under similar treatments. The changes in Ca2+ homeostasis may be related to the rapid muscular contraction and consequent paralysis in the parasite due to the anthelmintic stress caused by the phytochemicals of F. vestita.

Evaluation of the efficacy of emodepside+praziquantel topical solution against cestode (Dipylidium caninum, Taenia taeniaeformis, and Echinococcus multilocularis) infections in cats

Emodepside+praziquantel topical solution was developed to provide broad-spectrum anthelmintic activity against gastrointestinal parasites in cats. Eight controlled studies were conducted to evaluate the efficacy of a topical solution of emodepside (3 mg/kg) and praziquantel (12 mg/kg) (Profender, BayerAG, Leverkusen, Germany) against feline infections with three species of cestodes. Studies featured naturally acquired infections of Dipylidium caninum or Taenia taeniaeformis, or experimental infections with Echinococcus multilocularis that were placebo-controlled, randomized and blinded. Cats were euthanatized and necropsied between 2 and 11 days after treatment, depending on the target parasite. The efficacy of emodepside+praziquantel topical solution was 100% against D. caninum and T. taeniaeformis, and 98.5- 100% against E. multilocularis. No significant systemic or local adverse reactions to treatment were noted in cats that received the combination. Topical treatment of cats with emodepside+praziquantel topical solution was safe and highly effective against cestode infections.

Target animal safety and tolerance study of pyrantel pamoate paste (19.13% w/w pyrantel base) administered orally to horses

Pyrantel pamoate paste (19.13% w/w pyrantel base) for the treatment of tapeworm, Anoplocephala spp was evaluated for target animal safety and tolerance in horses treated orally at 0, 1, 3, 5, and 10 times the clinical dose of 13.2 mg pyrantel base/kg body weight administered daily for six consecutive days. Parameters evaluated included clinical signs, food and water consumption, body weights, physical examinations, clinical pathology (hematology, coagulation, serum chemistry, urinalyses, and fecal examinations), complete necropsy, organ weights, and histopathology. No adverse events or test article-related effects were observed in any treatment group during daily clinical observations of the test animals. Statistically significant changes (P < .05) lacked a dose- and/or time-dependent trend and were considered incidental. Administration of pyrantel pamoate paste did not produce any macroscopic or microscopic tissue effects in any dose group of either sex. The no-observed-effect-level (NOEL) for pyrantel pamoate paste, when administered orally to horses once daily for 6 consecutive days, was determined to be 132 mg/kg/day. Pyrantel pamoate paste (19.13% w/w pyrantel base) can be safely administered orally to horses at 13.2 mg of pyrantel base/kg for the treatment of Anoplocephala infestations.

Anthelmintic efficacy of Flemingia vestita (Fabaceae): alterations in glucose metabolism of the cestode, Raillietina echinobothrida

The root-tuber peel of Flemingia vestita and its active component, genistein, were tested in respect of glucose metabolism in the cestode, Raillietina echinobothrida. Live R. echinobothrida, collected from the intestine of freshly slaughtered domestic fowl, were incubated at 39+/-1 degrees C in defined concentrations of the root-peel crude extract (5 mg/ml), genistein (0.2 mg/ml) and praziquantel (1 microg/ml) in phosphate buffered saline with 1% of dimethyl sulphoxide with simultaneous maintenance of controls. In the treated worms, there was a significant decrease in the glycogen concentration accompanied with the decrease of glucose by 14-32%, whereas the malate concentration increased by 49-134% as compared to controls. Both in controls and treated parasites, however, the pyruvate content was not measurable. While alanine and lactate contents showed a decline by 7-25% in the parasites exposed to all test materials, the lactate efflux into the incubation medium showed 37-71% increase in treatments indicating an overall increase of lactate production in comparison to controls. The results showing a decline in the glycogen and glucose contents and a significant rise in the malate content and lactate efflux under treatment conditions suggest that the energy demand in the parasites possibly got enhanced under stress, though it did not influence a switch over towards aerobic degradation of glucose in the parasites.

Effects of phytochemicals of Flemingia vestita (Fabaceae) on glucose 6-phosphate dehydrogenase and enzymes of gluconeogenesis in a cestode (Raillietina echinobothrida)

The crude root-peel extract of Flemingia vestita, containing genistein as the major isoflavone, has a vermifugal/vermicidal effect. It acts by causing flaccid paralysis accompanied by alterations in the activities of several tegumental enzymes and other metabolic activities in the fowl tapeworm, Raillietina echinobothrida. To elucidate the mode of action of the putative phytochemicals on energy metabolism, crude root-peel extract, pure genistein and praziquantel were tested on glucose 6-phosphate dehydrogenase (G6PDH) and enzymes of gluconeogenesis--pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK) and fructose 1,6-bisphosphatase (FBPase)--in R. echinobothrida. The activities of G6PDH, PEPCK and FBPase were largely restricted to the cytosolic fraction, while PC was confined to the mitochondrial fraction. Following treatments, the G6PDH activity was decreased by 23-31%, whereas the activities of PC and PEPCK were increased by 32-44% and 44-49%, respectively. There was no significant effect by any of the treatments on FBPase activity. We hypothesize that the phytochemicals from F. vestita, genistein in particular, influence the key enzymes of these pathways, which is perhaps a function of high energy demand of the parasite under anthelmintic stress.

Integrated pharmacological assessment of flubendazole potential for use in sheep: disposition kinetics, liver metabolism and parasite diffusion ability1

Flubendazole (FLBZ) is a broad spectrum benzimidazole methylcarbamate anthelmintic widely used in poultry and swine. However, there is no information available on the pharmacological behaviour of FLBZ in ruminants. The work reported here was addressed to evaluate the potential of FLBZ for use in sheep. The integrated assessment included evaluation of FLBZ and metabolites plasma disposition kinetics, liver metabolism and ex vivo ability to diffuse into the cestode parasite Moniezia benedeni. In a cross-over kinetic study, six healthy Corriedale sheep were treated with FLBZ by intravenous (i.v.) (4% solution) and intraruminal (i.r.) (4% suspension) administrations at the same dosage (5 mg/kg) with a 21-day washout period between treatments. Blood samples were collected between 0 and 72 h post-treatments. Sheep liver microsomes were incubated with 40 microm FLBZ and specimens of the cestode parasite M. benedeni, collected from untreated animals, were incubated (5-120 min) with FLBZ and its reduced (R-FLBZ) metabolite (5 microm). Samples of plasma, microsomal incubations and parasite material were prepared and analyzed by high-performance liquid chromatography to measure FLBZ and its metabolites. FLBZ parent drug showed a fast disposition being detected in the bloodstream up to 36 h after its i.v. administration. Both R-FLBZ and hydrolyzed FLBZ (H-FLBZ) metabolites were recovered in plasma as early as 5 min after the i.v. treatment in sheep. The plasma AUC ratios for R-FLBZ and FLBZ (AUC(R-FLBZ)/AUC(FLBZ)) were 4.07 i.v. and 5.55 i.r., respectively. R-FLBZ achieved a significantly higher (P < 0.01) C(max) value (0.14 microg/mL at 17.3 h post-treatment) than that observed for the parent drug FLBZ (0.04 microg/mL at 14.4 h post-treatment). Low plasma concentrations of FLBZ parent drug were measured between 6 and 48 h, and only trace concentrations of H-FLBZ were detected during a short period of time after the i.r. treatment. Consistently, sheep liver microsomes metabolized FLBZ into its reduced metabolite at a rate of 9.46 +/- 2.72 nmol/mg/h. Both FLBZ and R-FLBZ demonstrated a similar ability to quickly diffuse through the tegument of the cestode parasite. The data on FLBZ pharmacological behaviour presented here contribute to evaluate its potential to be developed as an anthelmintic for broad spectrum parasite control in ruminants.

Anthelmintic efficacy of Flemingia vestita (Fabaceae): alteration in the activities of some glycolytic enzymes in the cestode, Raillietina echinobothrida

The crude root-peel extract of Flemingia vestita, genistein and praziquantel were tested against some selected glycolytic enzymes--hexokinase (HK), phosphofructokinase (PFK), phosphoenolpyruvate carboxykinase (PEPCK), pyruvate kinase (PK), lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and malic enzyme (ME)--of the fowl tape worm, Raillietina echinobothrida. Following exposure to the various treatments, the activities of HK, PFK, PEPCK and LDH increased by 33-39%, 41-125%, 44-49% and 55-67%, respectively, and that of PK decreased by 14-26% in the parasite at the time of paralysis. The MDH and ME activities of the tissue homogenate were also found to be higher by 22-43% and 28-59%, respectively, in the treatments. However, whereas the activity of both cytosolic and mitochondrial MDH increased by 33-58% and 43-73%, respectively, the cytosolic ME activity showed an increase of 33-39%, and there was no significant enhancement in the mitochondrial ME activity. Histochemically, the enhancement in the activities of HK, LDH and MDH was clearly discernible. The enhanced glycolytic activity seems to be a function of anthelmintic stress caused by the phytochemicals.

A modified critical test for the efficacy of pyrantel pamoate for Anoplocephala perfoliata in equids

Aims of this study with 13 equids naturally infected with Anoplocephala perfoliata were to document (i) a critical test with a period of 48 h from treatment to necropsy to assess the efficacy of an anthelmintic against the tapeworm, (ii) the efficacy of pyrantel pamoate oral paste at 13.2 mg pyrantel base/kg body weight, and (iii) the time after treatment when fecal egg counts would best estimate the tapeworm's prevalence in a herd. Feces passed in successive 12-h periods after treatment were examined for tapeworms. At necropsy, tapeworms in equids were identified as attached to the mucosa or unattached and, with a stereoscope, as normal or abnormal. At the time of treatment and at 6-h intervals thereafter, fecal samples were taken for egg counts. The efficacy of pyrantel pamoate was 96.6%; in 1 equid the efficacy was 75.3%, and in 8 it was 100%. "Major fragments" (worms without a scolex) accounted for 10% of the tapeworms recovered; they were not included in the efficacy analysis but should be. In 3 untreated equids necropsied, tapeworms were in the cecum, and 21.3% were detached. This protocol, when compared with a 24-h one without examination of feces, was more efficient in the treatment of trial animals and reduced underestimation and overestimation of an anthelmintic's efficacy. However, a protocol similar to this 48-h critical test but with a 24- or 36-h post-treatment period should be investigated. The mean egg count peaked 18 to 24 h after treatment and the samples taken at that time would provide the best estimate of prevelance of tapeworms in a herd. The Cornell-Wisconsin centrifugal flotation technique had a sensitivity and specificity of 100% at 18 h and 92% and 100%, respectively, at 24 h.

Anthelmintic efficacy of Flemingia vestita (Fabaceae): Effect of genistein on glycogen metabolism in the cestode, Raillietina echinobothrida

The edible root-tuber peel of Flemingia vestita and its major active component, genistein, have been earlier shown to have a vermifugal/vermicidal effect on cestodes in vitro by causing a flaccid paralysis and alterations in the tegumental architecture and activity of several enzymes associated with the tegumental interface of the parasite. Pursuing further investigation on the mode of action of this putative anthelmintic, the crude peel extract and pure genistein were further tested in respect of glycogen metabolism in the fowl tapeworm, Raillietina echinobothrida. On exposure to the plant root peel crude extract (5 mg/ml) and genistein (0.2 mg/ml), the glycogen concentration was found to decrease by 15-44%, accompanied by an increase of activity of the active form of glycogen phosphorylase (GPase a) by 29-39% and decrease of activity of the active form of glycogen synthase (GSase a) by 36-59% in treated parasites as compared to untreated controls, but without affecting the total activity (a+b) of both the enzymes. Praziquantel (1 microg/ml), the reference drug, also caused quantitative reduction in glycogen level and alterations in enzyme activities somewhat at par with the genistein treatment. These results suggest that this plant-derived component may influence the glycogen metabolism of the parasite by directing it towards utilization of glycogen.

A comparative study on the effect of praziquantel and triclabendazole on Vampirolepis nana in vitro

V. nana was frequently associated with Schistosoma mansoni and Fasciola spp. This study was conducted to investigate and compare the effects of praziquantel and triclabendazole on V. nana worms, after in vitro exposure to 1 and 2 microg/ml of each of praziquantel or triclabendazole. All the worms were put under observation for 30 minutes. The worm mortality rates were recorded and the topographic tegumental changes were studied by scanning electron microscopy. The results demonstrated that praziquantel showed comparatively superior effect on adult V. nana worms than triclabendazole. The latter still revealed an anthelmintic effect.

In vitro anthelmintic activity of root-tuber extract of Flemingia vestita, an indigenous plant in Shillong, India

The in vitro activity of root-tuber-peel extract of Flemingia vestita, an indigenous plant consumed by the natives in Northeast India, was tested against helminth parasites. Live parasites (nematode: Ascaris suum from pigs, A. lumbricoides from humans, Ascaridia galli and Heterakis gallinarum from domestic fowl; cestode: Raillietina echinobothrida from domestic fowl; trematode: Paramphistomum sp. from cattle) were collected in 0.9 % physiological buffered saline (PBS) and maintained at 37 +/- 1 degrees C. In vitro treatment of the parasites with the crude extract (50 mg/ml) in PBS revealed complete immobilization of the trematode and cestode in about 43 and 20 min, respectively. However, the cuticle-covered nematodes did not show any change in physical activity and remained viable even after a long period of exposure to the extract. Exposure of R. echinobothrida to genistein (0.5 mg/ml), an active principle isolated from the root-tuber peel, caused spontaneous loss of movement (paralysis) in 4.5 h, which was slower than the time required for praziquantel, the reference flukicide and cestodicide. The treated parasites showed structural alteration in their tegumental architecture. This study suggests the vermifugal activity of this plant extract against trematodes and cestodes.

Identification and partial characterization of the proteases from different developmental stages of Schistocephalus solidus (Cestoda: Pseudophyllidae)

The proteolytic activities of extracts prepared from procercoids and plerocercoids as well as adults of the pseudophyllidean cestode Schistocephalus solidus were examined using several proteins and synthetic peptides as substrates. Whole bodies of procercoids and the isolated syncytial tegument of plerocercoids and adults prepared by freeze-thaw were studied. Extracts of procercoids contained a chymotrypsin-like proteinase exhibiting a molecular weight of 23,500 determined by gel filtration chromatography. The proteinase showed collagenolytic activity and had a pH optimum at 8. Such a proteinase was absent in plerocercoids and adults. In these developmental stages leucine aminopeptidases were detected in the isolated syncytial tegument having molecular weights of 93,500 (plerocercoids) and 89,000 (adults), respectively. The aminopeptidases in both stages displayed optimal activity at pH 8.5. The chymotrypsin-like proteinase of the procercoid is possibly necessary for the penetration of the host's intestinal wall, whereas the aminopeptidases of the plerocercoid and the adult of S. solidus may aid in parasite nutrition by degrading oligopeptides at the tegumental surface.

[Evaluation of 4 vermifuges against Bothriocephalus acheilognathi in carp]

With the aim to evaluate the efficacy of four vermicides, praziquantel, mebendazole, nitroscanate and triclorfon in the control of Bothriocephalus acheilognathi in carps, one hundred and sixty, two year-old carps (Ctenopharyngodon idellus) with an average weight of 120 g and a mean parasitic burden of 115.5 parasites/fish were used. Five groups of 30 fish each were randomly formed. Each group was then subdivided in three groups, each of 10 individuals/pond. The three subgroups of group A received 30, 50 and 70 mg/Kg of praziquantel, respectively. Groups B and C received 2.2, 4.4, and 6.8 mg/Kg of mebendazole suspension and mebendazole solution respectively; groups D and E received 10, 30, 50 mg/Kg; and 2.0, 4.0, 6.0 mg/Kg of nitroscanate and trichlorfon respectively. Group F of 10 fish remained as non-treated control. Praziquantel showed 100% of efficacy for all doses, therefore it was excluded from the statistical analysis. The subgroups B, C, D and E compared with the non-treated control were statistically significant (P < 0.01); showing in all treatments an additive effect, the higher the dose the better efficacy, except trichlorfon which showed a different tendency, having no explanation on that matter.

The nervous systems of helminths as targets for drugs

Processes that critically differentiate parasitic helminths and their hosts are obvious candidates for chemotherapeutic intervention. The recognition that neurobiology distinguishes helminths from their vertebrate hosts is due in part to the fact that several efficacious anthelmintics, derived generally from empirical screening, have been found to act selectively on the neuromuscular system of these parasites. In addition, basic physiological and pharmacological research has revealed considerable differences in the ways in which helminths and their hosts transmit information in the nervous system and respond to it in innervated tissues. Unfortunately, most of these differences have yet to be exploited in chemotherapy. The topics for this review include an analysis of mechanistic aspects of the pharmacology of anthelmintics that act on neuromuscular systems and a consideration of the prospects for discovery of novel drugs that act on this system.

Cu-Zn-superoxide dismutase activity in Moniezia expansa: inhibition by pyrimidine derivatives

Copper-zinc, cyanide-sensitive superoxide dismutase (Cu-Zn-SOD) was detected in homogenates of Moniezia expansa. The enzyme was purified by a sequence of multiple differential centrifugations, ammonium sulphate precipitation, ion-exchange and G-75 Sephadex column chromatography. The final enzyme preparation had a specific activity of 623.00 +/- 9.97U per mg protein and, after isolation, a single-staining band on acrylamide-SDS gels was detected which coincided with enzyme activity. The inhibitory activities of several benzimidazoles and several novel pyrimidine derivatives were determined on purified extracts of the M. expansa Cu-Zn-SOD. The results indicated that the percentage inhibition of Cu-Zn-SOD by some pyrimidine derivatives (6-amino-1, 3-dimethyl-5-nitroso-uracil, 6-amino-5-methyl-5-nitroso-uracil and 5-amino-uracil) was markedly higher than inhibition with the benzimidazoles.

Epsiprantel, a new tapeworm remedy. Preliminary efficacy studies in dogs and cats

The anthelmintic potential of epsiprantel, 2-(cyclohexylcarbonyl)-4-oxo-1,2,3,4,6,7,8,12b-octahydropyrazin [2,1-a] [2]benzapine, was revealed using the tapeworms Dipylidium caninum and Taenia taeniaeformis in the cat, and Taenia pisiformis and T. hydatigena in the dog. Subsequent controlled tests in cats demonstrated oral efficacy of 100% against D. caninum with a single dose of 2.5 mg/kg. Although consistently 100% effective against T. taeniaeformis at 5 mg/kg, a single worm was found in one cat treated at 7.5 mg/kg. In experimental infections of Taenia pisiformis in dogs, 100% activity was achieved from a single oral dose of 1 mg/kg. No adverse reaction or drug-associated toxicity were observed at dose levels used.