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Clinical pharmacokinetics of anthelmintic drugs.

A rational strategy for chemotherapy demands that dosage schedules be based on an adequate knowledge of clinical and biochemical pharmacology. Many anthelmintic drugs (e.g. suramin, diethylcarbamazine, hycanthone) were introduced before modern techniques for drug evaluation (controlled clinical trials) and before the development of specific and sensitive analytical methods for the assay of drugs and metabolites in biological fluids. Thus, many of the regimens used today for the treatment of parasitic diseases are largely empirically derived. By means of specific analytical methodology (high performance liquid chromatography, gas chromatography and mass-spectrometry) introduced in the 1960s, it is now possible to measure drugs and their metabolites with specificity and sensitivity. Much of this review deals with compounds which are active against the major systemic helminths, i.e., filariae (diethylcarbamazine, ivermectin and suramin) and schistosomes (niridazole, metrifonate, oxamniquine and praziquantel), but recent advances in the treatment of hydatid disease involving the benzimidazole carbamates albendazole and mebendazole are also discussed. Among the imidazole derivatives, mebendazole, a broad-spectrum anthelmintic, is poorly absorbed from the gastrointestinal tract after a therapeutic dose, but that fraction which is absorbed and escapes hepatic first-pass extraction is pharmacologically active against systemic helminths. Albendazole is more completely absorbed, but is almost undetectable in plasma due to its rapid conversion to an active sulphoxide metabolite. This compound may well become the drug of choice for the chemotherapy of echinococcosis. Levamisole, the 1-isomer of tetramisole, is rapidly and completely absorbed, but has not been widely used in systemic helminthiases because of severe side effects associated with prolonged dosage. Diethylcarbamazine is microfilaricidal against Onchocerca volvulus, but its use has been associated with major adverse effects resulting from its action on the microfilariae. These effects are related to the concentration of the drug in the plasma which, in turn, is influenced by urinary pH. The elimination half-life of diethylcarbamazine is prolonged and renal clearance reduced in alkaline urine. Under these conditions the microfilaricidal effect is enhanced, but the adverse reactions to treatment are more severe. Suramin is the only available antifilarial agent with macrofilaricidal activity. It has a long elimination half-life (36 to 54 days), and is highly (99.7%) bound to plasma protein which limits its removal from the blood.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Anthelmintics. A comparative review of their clinical pharmacology.

Virtually all the important helminth infections in humans can be treated with one of 5 anthelmintics currently in use: albendazole, mebendazole, diethylcarbamazine, ivermectin and praziquantel. These drugs are vital not only for the treatment of individual infections, but also useful in controlling transmission of the more common infections. This article reviews briefly the pharmacology of these 5 drugs, and then discusses current issues in the use of anthelmintics in the treatment and/or control of soil-transmitted nematode infections, filariasis, onchocerciasis, schistosomiasis (and other trematode infections), neurocysticercosis and hydatidosis. Mebendazole and albendazole are most effective against intestinal nematodes, but are contraindicated during the first trimester of pregnancy. The efficacy of prolonged therapy with these 2 drugs for treatment of larval cestode infections has not yet been established. Diethylcarbamazine is widely used to treat and control lymphatic filariasis, but adverse effects related to death of microfilariae or damage to adult worms may be marked. While ivermectin has been used in the treatment of patients with onchocerciasis, it is also undergoing investigation against lymphatic filariae. Praziquantel, used to treat schistosome infections, is also effective in other trematode infections and adult cestode infections.

Anthelmintics↗

Prevalence and clinical implications of anthelmintic resistance in cyathostomes of horses.

OBJECTIVE: To determine the prevalence and clinical implications of anthelmintic resistance in cyathostomes of horses. DESIGN: Prospective study. ANIMALS: 80 horses on 10 farms in a 5-county region of northeast Georgia. PROCEDURE: On each farm, horses were stratified in descending order according to pretreatment fecal egg count (FEC), blocked into groups of 4, and then randomly assigned to 1 of 4 treatment groups: no treatment (controls), and treatment with pyrantel pamoate, fenbendazole, or ivermectin. Fecal samples were collected 24 hours prior to treatment and 2, 4, and 6 weeks after treatment for determination of FEC. Mean percentage of reduction in FEC was then calculated for each treatment group. For horses from each farm, the efficacy of each anthelmintic was categorized on the basis of mean percentage of reduction in FEC at 2 weeks after treatment (< 80% reduction = ineffective; 80 to 90% reduction = equivocal; and > 90% reduction = effective). RESULTS: Pyrantel pamoate was effective at reducing FEC in horses from 7 farms, ineffective in horses from 2 farms, and equivocal in horses from 1 farm. Fenbendazole was ineffective at reducing FEC in horses from 9 farms and equivocal in horses from 1 farm. Ivermectin was effective at reducing FEC in horses from all 10 farms. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cyathostome resistance to fenbendazole is highly prevalent, and resistance to pyrantel pamoate is high enough to warrant concern. Resistance to ivermectin was not detected. On the basis of these data, it appears that ivermectin continues to be fully effective in horses. However, too few farms were used in this study to determine the prevalence of cyathostome resistance to ivermectin. Therefore, the efficacy of ivermectin should continue to be monitored closely.

Animals↗

Effects of ionophore feeding and anthelmintic administration on age and weight at puberty in spring-born beef heifers.

Two hundred eighty-eight heifer calves in two 1-yr replications were used to test the hypothesis that ionophore (ION) feeding, anthelmintic (ANT) administration, or the combination (COMB) would cause heifers to express pubertal estrus at a younger age than control (CONT) heifers. Heifers were assigned randomly within three weight blocks in a randomized complete block design with a 2 x 2 factorial arrangement of treatments. A high-fiber diet was fed for 172 d during yr 1 (Y1) and 199 d during yr 2 (Y2). Monensin sodium (200mg.animal-1.d-1) was fed to ION and COMB treatments and ivermectin (200 micrograms/kg of BW) was given to ANT and COMB groups at weaning and 84 d later. Rate of gain was monitored every 21 d and diet intake was adjusted to obtain equal rates of gain across treatments. Fecal samples were collected from one-third of the heifers in each group and analyzed for internal parasite egg counts every 21 d. Serum progesterone samples taken twice weekly were used to estimate onset of puberty. There was no treatment x year interaction in any parameter measured and the data were pooled across both years. Total weight gain was similar (P > .10) for all treatments. Fecal egg output decreased (P < .01) after initial application of anthelmintic. The ANT, ION, and COMB heifers had greater (P < .05) gain:feed ratios than did CONT (.132, .142, and .148 vs .125 kg for ANT, ION, COMB, and CONT, respectively). Age and weight at puberty were different (P < .05) for ION (425 d, 351.8 kg), COMB (425 d, 349.5 kg), and ANT (424 d, 348.8 kg) compared with CONT (433 d, 362.5 kg). There was no difference (P > .10) in age and weight at puberty between COMB, ION, or ANT heifers. During Y1, but not Y2, there were a greater (P < .05) number of COMB, ION, and ANT heifers pubertal before the breeding season. Additionally, there was a tendency (P = .12) for higher first-service conception in the COMB, ION, and ANT heifers than in the CONT heifers. Final pregnancy rates among treatments were similar (P > .10).

Aging↗

Anthelmintic activity of albendazole against adult Metastrongylus apri in artificially infected swine.

Three groups of five pigs experimentally infected with lungworm larvae (Metastrongylus apri) were treated with albendazole at 5, 7.5 or 10 mg/kg body weight at 35 days postinfection. The albendazole was administered in the feed. Anthelmintic efficacy, as determined by comparison of postmortem lungworm counts for the treated animals and five infected, untreated controls, was 32.6% at 5 mg/kg, 44.3% at 7.5 mg/kg and 60.7% at 10 mg/kg. The 60.7% reduction in lungworms was statistically different at the 5% level of significance. In a second experiment, three groups of five pigs experimentally infected with lungworm larvae (Metastrongylus apri) were treated continuously for 5 days with albendazole in the feed at 10, 20 or 30 ppm, starting at 35 days postinfection. The anthelmintic efficacy, again determined by comparison of postmortem lungworm counts for the treated pigs and five infected, untreated controls, was 99.2% at 10 ppm, 99.9% at 20 ppm and 100% at 30 ppm. These mean reductions from the control values were significant (P greater than .01).

Albendazole↗

Anthelmintic efficacy of extracts of Spigelia anthelmia Linn on experimental Nippostrongylus braziliensis in rats.

Spigelia anthelmia Linn is used as a herb and is a common annual weed of cultivation in open re-growths, on unused land in towns as well as on road sides. The plant can grow to approximately 30 cm in height. The aim of this study was to screen extracts of Spigelia anthelmia for their anthelmintic activity against an experimental Nippostrongylus braziliensis infection in rats. Acute oral toxicity occurred at a dose of 1,140 mg/kg, while anthelmintic trials against Nippostrongylus braziliensis in rats using the aqueous fraction showed a progressive decrease in worm count with increasing dose (10, 13, 16, 20 and 25 mg per kg body weight) (p < 0.05). At 25 mg per kg body weight, the worm count was significantly lower than that at 10 mg per kg body weight (p < 0.05).

Animals↗

Albendazole, an effective single dose, broad spectrum anthelmintic drug.

Albendazole, a new anthelmintic drug was evaluated in Malaysia in 91 patients, with single or mixed infections of Ascaris, Trichuris, and hookworm. Albendazole was administered as a single dose of 400 mg, 600 mg, or 800 mg. The cure rate for Ascaris at all three doses was 100% at days 14 and 21 post-treatment; for hookworm it was 98.8%, 100% and 98%, respectively, at day 14 and 68.8%, 100% and 84%, respectively, at day 21; for Trichuris it was 31.2%, 57.1% and 42.3%, respectively, at day 14 and 27.3%, 60.9% and 48.0%, respectively, at day 21. The egg reduction rate at day 21 was 100% at all three doses for Ascaris, 94.5%, 100% and 96.1%, respectively, for hookworm; and 39.2%, 85.1% and 72.8%, respectively, for Trichuris. There were no side effects, and biochemical examination of blood and urine did not indicate any unfavourable changes. Based on this trial, the recommended dosage for Ascaris and hookworm is a 400 mg single dose, and for Trichuris is a 600 mg single dose. Albendazole appears to be more effective than other available anthelmintic drugs.

Adolescent↗

A novel series of milbemycin antibiotics from Streptomyces strain E225. I. Discovery, fermentation and anthelmintic activity.

A novel series of milbemycin antibiotics were produced by soil isolate, strain E225 which was shown to be a Streptomyces species. The antibiotics displayed anthelmintic activity against Trichostrongylus colubriformis in the gerbil. Two of the compounds, VM 44857 and VM 44866 were shown to be potent anthelmintics against mixed nematode infections in sheep.

Animals↗

A new anthelmintic cyclodepsipeptide, PF1022A.

The novel anthelmintic cyclodepsipeptide PF1022A was isolated from cultured mycelia of Mycelia Sterilia PF1022 (FERM BP-2671). It showed strong anthelmintic activities against Ascaridia galli in chickens. The structure of PF1022A was determined to be cyclo(D-lactyl-L-N-methylleucyl-D-3-phenyllactyl-L-N-meth ylleucyl-D-lactyl-L-N- methylleucyl-D-3-phenyllactyl-L-N-methylleucyl) by spectroscopic analyses and chemical studies.

Animals↗

Anthelmintic activity of dioxapyrrolomycin.

Dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 produced by UC 11065 were evaluated as anthelmintics. Assays used to examine these compounds included effects on the free-living nematode Caenorhabditis elegans, ability to clear target nematodes (Haemonchus contortus and Trichostrongylus colubriformis) from jirds, and clearance of Haemonchus contortus from lambs. A crude extract of UC 11065 containing dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 was active against C. elegans and against H. contortus in the jird. Purified and/or synthetic samples of dioxapyrrolomycin, pyrrolomycin C, pyrrolomycin D, and piericidin C2 were tested in the jird model; only dioxapyrrolomycin exhibited appreciable activity against H. contortus (greater than or equal to 90.9% clearance at 0.33 mg/jird), while none of the compounds showed appreciable activity against T. colubriformis. Dioxapyrrolomycin cleared 99.9% of H. contortus from lambs at 12.5 mg/kg. An in vitro migration study using susceptible and closantel-resistant H. contortus showed there is cross-resistance between dioxapyrrolomycin and closantel. Dioxapyrrolomycin appears to be a narrow-spectrum anthelmintic which works through a closantel-like mode-of-action.

Actinomycetales↗

Novel anthelmintic metabolites from an Aspergillus species; the aspergillimides.

Two members of a novel class of anthelmintics, the aspergillimides, have been isolated from the Aspergillus strain IMI 337664. This novel fungus also produced two known and one structurally novel paraherquamide. This paper describes the fermentation, isolation, structure elucidation and anthelmintic activity of aspergillimide (VM55598, 1), 16-keto aspergillimide (SB202327, 2), and the paraherquamides VM54159 (3), SB203105 (4) and SB200437 (5). The aspergillimides are equivalent to paraherquamides which have lost both the dioxygenated 7-membered ring and the phenyl ring to which this is fused; gaining in their place a C8-keto group. SB203105 is the first example of a 4-substituted paraherquamide.

Alkaloids↗

Anthelmintic activity of 13-alkoxy milbemycin derivatives.

A number of 13-alkoxy milbemycin derivatives were synthesized to evaluate their anthelmintic activity. We report the strategy for developing a potent anthelmintic product, 13-[4-(N-methanesulfonyl-N-methylamino)-phenylethyloxy]milbemycin. The details of the structure-activity relationships of those derivatives are also discussed.

Anthelmintics↗

Gastrointestinal helminths of free-ranging Florida panthers (Puma concolor coryi) and the efficacy of the current anthelmintic treatment protocol.

Thirty-five Florida panthers (Puma concolor coryi [Bangs, 1899]) collected from six counties in southern Florida between 1978 and 2003 were examined at necropsy for gastrointestinal helminths. The panthers were placed into two groups: 1) treated with anthelmintics (n = 17), and 2) untreated (n = 18). Nine species of helminths (one trematode, six nematodes, and two cestodes) were identified in the untreated panthers. The most prevalent helminths were Alaria marcianae (LaRue, 1917) (100%), Spirometra mansonoides (Mueller, 1935) (91%), and Ancylostoma pluridentatum (Alessandrini, 1905) (89%). Ancylostoma caninum (Ercolani, 1859) is reported from the Florida panther for the first time. The intensities of helminths with prevalences >10% did not differ between untreated panthers collected in 1978-1983 and 1996-2003. Treated panthers had helminth faunas similar to those of untreated panthers. The current anthelmintic treatment being used reduced the intensity of both A. marcianae and A. pluridentatum in panthers < or =6 mo posttreatment (PT); however, treated panthers between 6 and 9 mo PT, and >9 mo PT were similar to untreated panthers. Treatment was less effective on S. mansonoides and Taenia omissa Lühe, 1910. Treated panthers had slightly lower intensities of S. mansonoides at < or =6 mo PT; however, between 6 and 9 mo PT and >9 mo PT they had significantly higher intensities than untreated panthers. At all periods PT, the intensity of T. omissa for the treated panthers was similar to that of untreated panthers. We suggest that Mesocestoides sp. may not be present in the Florida panther population as reported earlier by Forrester et al. (1985), due to parasite misidentification by those authors.

Animals↗

Evaluation of efficacy of school-based anthelmintic treatments against anaemia in children in the United Republic of Tanzania.

OBJECTIVE: To determine the impact of deworming on anaemia as part of a large-scale school-based anthelmintic treatment programme in the Tanga Region of the United Republic of Tanzania. METHODS: Both the reduction in the prevalence of anaemia and the cost per case prevented were taken into consideration. Cross-sectional studies involved parasitological examination and anaemia evaluation before and at 10 months and 15 months after schoolchildren were dewormed. FINDINGS: Baseline studies indicated that the prevalence of anaemia (haemoglobin < 110 g/l) was high (54%) among schoolchildren, particularly those with high intensities of hookworm and schistosomiasis. Attributable fraction analysis suggested that hookworm and schistosomiasis were responsible for 6% and 15% of anaemia cases, respectively. Fifteen months after deworming with albendazole and praziquantel the prevalence of anaemia was reduced by a quarter and that of moderate-to-severe anaemia (haemoglobin <90 g/l) was reduced by nearly a half. The delivery of these anthelmintics through the school system was achieved at the relatively low cost of US$ 1 per treated child. The cost per anaemia case prevented by deworming schoolchildren was in the range US$ 6-8, depending on the haemoglobin threshold used. CONCLUSIONS: The results suggested that deworming programmes should be included in public health strategies for the control of anaemia in schoolchildren where there are high prevalences of hookworm and schistosomiasis.

Albendazole↗

Anthelmintics: a review.

Helminths infect 25% of the world's population. In the last 50 years specific, safe and effective anthelminitic drug therapy for various parasitic infestations have been developed. The population of the developing countries across the globe suffers not only as a direct result of these infections but due also to co-morbidity such as anemia, malnutrition and reduced immunity status. Earlier anthelmintic drugs suffered from serious drawbacks such as hepatotoxicity and required specific preparation of the patient before treatment such as 12-hour fasting and pre-post purging caused considerable inconvenience to the patient. However, successive discoveries were born out of rationale approach that contributed to the effective, more specific and more easily tolerated drugs i.e. benzimidazoles, piperazine derivatives, avermectins, pyrazinoquinoline, etc. The present approach is to identify the causative parasite on the basis of stool examination and as a result of this approach, different drugs are prescribed for different parasitic infections. Examples include thiabendazole for cutaneous larva migrans, mebendazole for ascariasis, trichiuriasis and hookworm, albendazole for inoperable cases of cystic hydatid disease, DEC for Toxocara induced visceral larva migrans and loiasis, ivermectin for onchocerciasis, praziquantel for schistosomiasis and niridazole for Dracunculus medinensis. The cure rates with these drugs is also high e.g. thiabendazole produces a cure-rate of 98% in cutaneous larva migrans while mebendazole gives cure rate of 76-95% in ascariasis, trichiuriasis and hookworm infestations. A cure rate of 96% is produced by praziquantel in schistosomiasis. Most of these drugs have broad-spectrum anthelmentic effect. The present review aims at evaluating the currently available anthelmintics with respect to their efficacy and adverse effects. Steps to prevent impending helminthic drug resistance are also discussed.

Anthelmintics↗

[Committee on anthelmintics. Residual group].

A number of the older and a few recent anthelmintics are enumerated or briefly discussed. Moreover some attention is paid to anthelmintics, used for nematodes and trematodes which have a limited effect on cestodes.

Animals↗

The resistance of a field strain of Haemonchus contortus to five benzimidazole anthelmintics in current use.

Using artificially infected sheep, the response of a laboratory strain of Haemonchus contortus, which had not been subjected to anthelmintics for three years, was compared with that exhibited by a parbendazole resistant field strain following treatment with each of seven anthelmintics, the laboratory strain proved fully susceptable to thiabendazole, parbendazole, cambendazole, mebendazole, fenbandazole, levamisole and haloxon, in contrast to the field strain which showed a moderate to marked resistance to all five benzimidazoles, but was fully susceptible to levamisole and haloxon.

Animals↗

Acute toxicity of paraherquamide and its potential as an anthelmintic.

Paraherquamide, an oxindole alkaloid metabolite of Penicillium paraherquei and P charlesii, is a new anthelmintic with potential broad-spectrum use. In initial trials, it had an excellent safety profile in cattle and sheep at doses efficacious against a dozen or more helminths, but recently it produced unexpected and severe toxicosis in dogs at doses far below those that were safe in the ruminants. To provide data on which to build rational safety tests in the future, we tested the acute toxicity of paraherquamide administered PO to male CD-1 mice and compared its profile with the most potent anthelmintic known, ivermectin. The estimated doses lethal to 50% of a group of mice were 14.9 and 29.5 mg/kg of body weight for paraherquamide and ivermectin, respectively. The no-effect doses were 5.6 and 18.0 mg/kg for paraherquamide and ivermectin, respectively. Signs of intoxication in paraherquamide-treated mice, if they developed, emanated within 30 minutes of administration, irrespective of dose, and consisted of either mild depression with complete recovery or a 5- to 10-minute period of breathing difficulty followed by respiratory failure and death by 1 hour after treatment. Gross necropsy findings in paraherquamide-treated mice that died in the high-dose group were normal. Ivermectin-related toxicity was slower and more predictable, taking place over a 3-day period, with dose-dependent signs of intoxication consisting of tremors, ataxia, recumbency, coma, and death. Necropsy of ivermectin-treated mice that died in the high-dose group revealed dehydration, a condition most likely resulting from the coma-induced state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗