unchanged drug is undetectable in plasma. most of it is oxidized into albendazole sulfoxide (also known as ricobendazole and albendazole oxide) in the liver by cytochrome p450 oxidases (cyps) and a flavin-containing monooxygenase (fmo), which was discovered later. in humans, the cytochrome p450 oxidases are thought to include cyp3a4 and cyp1a1, while those in the rats are thought to be cyp2c6 and cyp2a1. oxidation to albendazole sulfoxide by fmo produces r(+) enantiomers, while oxidation the cytochromes and by some enzymes in the gut epithelium produce s(-). different species produce the r(+) and s(-) enantiomers in different quantities; humans, dogs, and most other species produce the r(+) enantiomer more (with the human auc ratio being 80:20). compared to the s(-) enantiomer, the r(+) has greater pharmacological activity, lasts longer in the bloodstream, is found in higher concentrations in the infected host tissues, and is found in higher concentrations within the parasites themselves. some albendazole is also converted to hydroxyalbendazole, mainly by cyp2j2. for systemic parasites, albendazole acts as a prodrug, while albendazole sulfoxide reaches systemic circulation and acts as the real antihelminthic. albendazole sulfoxide is able to cross the blood–brain barrier and enter the cerebrospinal fluid at 43% of plasma concentrations; its ability to enter the central nervous system allows it to treat neurocysticercosis. albendazole sulfoxide is converted to the inactive albendazole sulfone by cytochrome p450 oxidases, thought to include cyp3a4 or cyp2c. other inactive metabolites include: 2-aminosulfone, ω-hydroxysulfone, and β-hydroxysulfone. the major final metabolites that are excreted by humans are: methyl carbamate, methyl carbamate, methyl carbamate, 5-(n-propylsulfonyl)-1h-benzimidazole-2-yl amine, and 5-(n-propysulfinyl)-1h-benzimidazole-2-yl amine. there are also some minor hydroxylated sulfated or glucuronidated derivatives. no unchanged albendazole is excreted, as it is metabolized too quickly. in humans, the metabolites are excreted mostly in bile, with only a small amount being excreted in urine (less than 1%) and feces. in ruminants, 60–70% of the metabolites are excreted in urine. like all benzimidazoles, albendazole has no residual effect, and thus protects poorly against reinfestations. history albendazole, patented in 1975, was invented by robert j. gyurik and vassilios j. theodorides and assigned to smithkline corporation. it was introduced in 1977 as an antihelminthic for sheep in australia, and was registered for human use in 1982. society and culture discarded bottles of albendazole distributed in africa brand names brand names include: albenza, alworm, andazol, eskazole, noworm, zentel, alben-g, abz, cidazole, wormnil etc. economics the pharmaceutical company amedra increased the price after purchasing the rights to the drug, instead of lowering it as generics are predicted to do, drawing criticism from patients' rights advocates. in 2013, glaxosmithkline donated 763 million albendazole tablets for the treatment and prevention of parasitic infections in developing countries, bringing the total to over 4 billion tablets donated since 1998. research albendazole and related compounds or metabolites like albendazole sulfone (alb-so2) exhibit antibacterial effects via an unknown, possibly ftsz-related, mechanism. it inhibits division of wolbachia and mycobacterium tuberculosis, turning them into a long "filament" shape as they grow and fail to divide. since brugia malayi relies on symbiotic wolbachia, this would mean that albendazole is targeting both the worm and its essential symbioant. veterinary use albendazole is mainly used in cattle and sheep, but has found some use in cats and dogs as well; it is also used in ratite birds for flagellate parasites and tapeworms. it is also used off-label to treat endoparasites in goats and pigs. albendazole use in animals cattle sheep others platyhelminthes (flatworms) trematodes dicrocoelium (liver flukes) d. dendriticum (lancet liver fluke) d. dendriticum fasciola (liver flukes) f. hepatica f. hepatica for f. hepatica and f. gigantica in people fascioloides (liver flukes) f. magna f. magna also for f. magna in south american camelids (ex. llama and alpaca) paragonimus (lung flukes) — — for p. kellicotti in cats and dogs platynosomum — — for platynosomum infections in cats opisthorchiidae — — for opisthorchiidae infections in cats cestodes (tapeworms) echinococcus – — for echinococcus cysts in horses and humans moniezia m. expansam. benedini m. expansa taenia t. saginata larvae — for t. saginata, t. solium, and t. crassiceps in humans and taenia infections in dogs thysanosoma — t. actinoides nematodes (roundworms) ancylostoma — – for ancylostoma infections in dogs, cats, and humans bunostomum b. phlebotomum – capillaria — — for causative agents of various forms of capillariasis in cats and dogs (including c. philippinensis, c. hepatica, c. aerophila, and c. plica) and intestinal capillariasis (c. philippinensis) in humans. chabertia — c. ovina cooperia c. oncophorac. punctata c. oncophora dictyocaulus (lungworm) d. viviparus d. filaria for d. amfieldi infections in horses filaroides (lungworm) — — for f. hirthi and f. osleri in dogs haemonchus h. contortus h. placei h. contortus marshallagia — m. marshalli metastrongylus — — for m. apri in swine nematodirus n. spathigern. helvetianus n. spathigern. filicollis parascaris — — for p. equorum in horses ostertagia o. ostertagi o. circumcincta for o. bifurcum in humans oesophagostomum o. radiatum o. columbianum strongyloides — — for s. stercoralis in dogs and humans strongylus — — for s. equinus in horses toxocara — — for t. canis infections in dogs and toxocariasis in humans (caused by t. canis and t. cati) trichostrongylus t. axeit. colubriformis t. axeit. colubriformis for any trichostrongylus infection in humans trichuris (whipworm) most species, but those usually found in cattle are:t. discolort. globulosa t. ovis most species, but those usually found in sheep are:t. discolort. globulosa t. ovis albendazole is also used for trichuris infections in humans (usually t. trichiura, causative agent of trichuriasis), dogs (usually t. vulpis and t. campanula), cats (usually t. serrata and t. campanula), pigs (usually t. suis), and other ruminants (same species as those found in cattle and sheep). other encephalitozoon — — for e. cuniculi infections (microsporidiosis) in humans and rabbits giardia g. lamblia (causative agent of giardiasis) — also treats giardiasis in humans, dogs, and small mammals leishmania — — treats leishmaniasis, caused by various species of leishmania, in dogs albendazole has been used as an antihelminthic and for control of flukes in a variety of animal species, including cattle, sheep, goats, swine, camels, dogs, cats, elephants, poultry, and others. side effects include anorexia in dogs and lethargy, depression, and anorexia in cats, with more than 10% of dogs and cats having anorexia. of dogs and cats, 1–10% experience elevated liver enzymes, nausea, vomiting, and diarrhea. less than 1% experience neutropenia or aplastic anemia, though these require a use of at least 5 days. while it is also associated with bone marrow suppression and toxicity in cats and dogs at high doses, albendazole has a higher margin of safety in other species. thus, it is usually only prescribed in cats and dogs when an infection is present that is resistant to the commonly prescribed metronidazole and fenbendazole. it is extensively used for ruminant livestock in latin america. it is marketed for this purpose by zoetis (formerly pfizer animal health) in numerous countries (including the united states and canada) as valbazen in oral suspension and paste formulations; by interchemie in the netherlands and elsewhere as albenol-100; by channelle animal health ltd. in the united kingdom as albex; and by ravensdown in new zealand (as albendazole). although most formulations are administered orally, ricomax (ricobendazole, or albendazole sulfoxide) is administered by subcutaneous injection. albendazole has greater bioavailability in ruminants: some albendazole sulfoxide, when released back into the rumen, is reduced to albendazole by the resident microbiota, with a preference of the (+) enantiomer being the substrate. cats and dogs, having no rumen reservoir, sometimes need higher or more frequent doses as compared to ruminants. in dogs, albendazole sulfoxide is detectable in the plasma for less than 12 hours, but in sheep and goats, it remains at measurable levels for around three days. meat the limitations in early pregnancy are due to a limited period during which teratogenic effects may occur. summarized research data relating to the durations of these preslaughter and early pregnancy periods when albendazole should not be administered are found in us fda nada 110-048 (cattle) and 140-934 (sheep). some data and inferences regarding goats are found in us fda supplemental nada 110-048 (approved january 24, 2008). maximum residue limits (mrls) for albendazole in food, adopted by the fao/who codex alimentarius in 1993, are 5000, 5000, 100, and 100 micrograms per kilogram of body weight (μg/kg) for kidney, liver, fat, and muscle, respectively, and 100 μg/l for milk. for analysis purposes, mrls of various nations may pertain to concentration of a marker substance which has been correlated with concentrations of the administered substance and its metabolized products. for example, in canada, the marker substance specified by health canada is albendazole-2-aminosulfone, for which the mrl in liver of cattle is 200 μg/kg. there is a 27-day cattle withdrawal time for meat.