ALBENDAZOLE
ALBENDAZOLE
Albendazole, methyl[5-(propylthio)-1H-benzimidazol-2-yl] carbamate, is widely used for treating
ruminant roundworms and flukes. The drug is available as an intraruminal bolus
for ruminants.
ACTIVITY Broad
spectrum against a variety of nematodes, cestodes & protozoa; labeled for
cattle & sheep (suspension only). Albendazole
is active against all important nematodes and their larvae, including
hypobiotic or inhibited forms. It is also effective against tapeworms and
adult fluke.
PHARMACOKINETICS
METABOLISM The drug is rapidly metabolized to the sulphone and sulphoxide which may
provide the liver fluke and tapeworm activity. In sheep, 51% of the dose is
excreted in the urine, mostly in the first 48 h. Very little albendazole
remains unmetabolized. Drug residues persist for many days; consequently, a
period of 10 days from dosing must elapse before sheep may be slaughtered (14
days for cattle) for meat, and cows producing milk for human consumption
should not be treated.
Pharmacokinetic data for albendazole
in cattle, dogs and cats was not located. The drug is thought better absorbed
orally than other benzimidazoles. Approximately 47% of an oral dose was
recovered (as metabolites) in the urine over a 9-day period.
After oral dosing in sheep, the
parent compound was either not detectable or only transiently detectable in
plasma due to a very rapid first-pass effect. The active metabolites,
albendazole sulphoxide and albendazole sulfone, reached peak plasma
concentrations 20 hours after dosing.
INDICATIONS Gastro-intestinal
roundworms, lungworms, tapeworms, and adult Fasciola in cattle, sheep;
Type II ostertagiosis; gastrointestinal roundworms and lungworms in goats and
deer. Albendazole is labeled for the following endoparasites of cattle (not
lactating): Ostertagia ostertagi, Haemonchus spp., Trichostrongylus spp.,
Nematodius spp., Cooperia spp., Bunostomum phlebotomum, Oesphagostomum
spp., Dictacaulus vivaparus (adult and 4th stage larva), Fasciola
hepatica (adults), and Moniezia spp.
In sheep, albendazole is approved
for treating the following endoparasites: Ostertagia circumcincta,
Marshallagia marshalli, Haemonchus contortus, Trichostrongylus spp.,
Nematodius spp., Cooperia spp., Oesphagostomum spp., Chibertia
ovina, Dictacaulus filaria, Fasciola hepatica, Fascioides
magna, Moniezia expansa, and Thysanosoma actinoides.
Albendazole is also used
(extra-label) in small mammals, goats and swine for endoparasite control.
In cats, albendazole has been used
to treat Paragonimus kellicotti infections. In dogs and cats,
albendazole has been used to treat capillariasis. In dogs, albendazole has been
used to treat Filaroides infections. It has been used for treating giardia
infections in small animals, but concerns about bone marrow toxicity have
diminished enthusiasm for the drug’s use.
CONTRA-INDICATIONS Concurrent administration of other ruminal
boluses, treatment of ewes at a dosage of 7.5 mg/kg during the mating period
and until 1 month after rams are removed. Contraindicated with hepatic failure,
pregnancy, lactating dairy cattle. Do not use in pigeons, doves or crias.
WARNINGS Care not to
exceed ‘fluke and worm dose’ in cows during first month of pregnancy; coughing
for some weeks after treatment in cattle suffering from severe lung damage at
time of treatment; operators should wear suitable protective clothing. The drug
is not approved for use in lactating dairy cattle. The manufacturer recommends
not administering to female cattle during the first 45 days of pregnancy or for
45 days after removal of bulls. In sheep, it should not be administered to ewes
during the first 30 days of pregnancy or for 30 days after removal of rams.
Pigeons and doves may be susceptible
to albendazole and fenbendazole toxicity (intestinal crypt epithelial necrosis
and bone marrow hypoplasia). Nine alpaca crias receiving albendazole at dosages
from 33 – 100 mg/kg/day once daily for 4 consecutive days developed neutropenia
and severe watery diarrhea. All required treatment and 7 of 9 animals treated
died or were euthanized secondary to sepsis or multiple organ failure (Gruntman
and Nolen-Walston 2006). In humans, caution is recommended for use in patients
with liver or hematologic diseases. Albendazole was implicated as being an
oncogen in 1984, but subsequent studies were unable to demonstrate any
oncogenic or carcinogenic activity of the drug.
TOXICITY
The
safety index has been reported to be 7.5-20 times the recommended dose. High
doses may be embryotoxic. May cause GI effects (including hepatic dysfunction)
& rarely blood dyscrasias (aplastic anemia).
ADVERSE EFFECTS
Albendazole is tolerated without
significant adverse effects when dosed in cattle or sheep at recommended
dosages. Dogs treated at 50 mg/kg twice daily may develop anorexia. Cats may
exhibit clinical signs of mild lethargy, depression, anorexia, and resistance
to receiving the medication when albendazole is used to treat Paragonimus.
Albendazole has been implicated in causing aplastic anemia in dogs, cats, and
humans.
REPRODUCTIVE/NURSING SAFETY
Albendazole has been associated with
teratogenic and embryotoxic effects in rats, rabbits and sheep when given early
in pregnancy. The manufacturer recommends not administering to female cattle
during the first 45 days of pregnancy or for 45 days after removal of bulls. In
sheep, it should not be administered to ewes during the first 30 days of
pregnancy or for 30 days after removal of rams. In humans, the FDA categorizes
this drug as category C for use during pregnancy (Animal
studies have shown an adverse effect on the fetus, but there are no adequate
studies in humans; or there are no animal reproduction studies and no adequate
studies in humans.)
Safety during nursing has not been
established.
OVERDOSAGE/TOXICITY
Doses of 300 mg/kg (30X recommended)
and 200 mg/kg (20X) have caused death in cattle and sheep, respectively. Doses
of 45 mg/kg (4.5X those recommended) did not cause any adverse effects in
cattle tested. Cats receiving 100 mg/kg/day for 14 – 21 days showed signs of
weight loss, neutropenia and mental dullness.
DRUG INTERACTIONS
The following drug interactions have
either been reported or are theoretical in humans or animals receiving
albendazole and may be of significance in veterinary patients:
CIMETIDINE: Increased albendazole
levels in bile and cystic fluid
DEXAMETHASONE: May increase
albendazole serum levels
PRAZIQUANTEL: May increase
albendazole serum levels
DOSAGE By mouth
CATTLE: roundworms and tapeworms,
7.5 mg/kg
Adult flukes, roundworms, and
tapeworms, 10 mg/kg
For susceptible parasites:
a) 10 mg/kg PO
b) 7.5 mg/kg PO; 15 mg/kg PO for
adult liver flukes
c) For adult liver flukes: 10 mg/kg
PO; best used in fall when the majority are adults (little or no efficacy
against immature forms). A second treatment in winter may be beneficial.
d) For gastrointestinal cestodes: 10
mg/kg PO
SHEEP: roundworms and tapeworms,
5 mg/kg
Adult flukes, roundworms, and
tapeworms, 7.5 mg/kg
GOATS, DEER: roundworms, 10 mg/kg
SHEEP & GOATS:
For
susceptible parasites:
a) 7.5 mg/kg PO (0.75 mL of the
suspension per 25 lb. body weight).
b) 7.5 mg/kg PO; 15 mg/kg PO for
adult liver flukes
c) For adult liver flukes in sheep:
7.6 mg/kg
d) For treatment of nematodes in
sheep: 3 mL of suspension per 100 lbs of body weight PO
HORSES: 5 mg/kg.
SWINE:
For
susceptible parasites:
a) 5 – 10 mg/kg PO
DOGS:
For
Filaroides hirthi infections:
a) 50 mg/kg q12h PO for 5 days;
repeat in 21 days. Clinical signs may suddenly worsen during therapy,
presumably due to a reaction to worm death.
b) 25 mg/kg PO q12h for 5 days; may
repeat in 2 weeks (also for Oslerus osleri) For Filaroides osleri (also
known as Oslerus osleri) infections:
a) 9.5 mg/kg for 55 days or 25 mg/kg
PO twice daily for 5 days. Repeat therapy in 2 weeks.
For
Capillaria plica:
a) 50 mg/kg q12h for 10 – 14 days.
May cause anorexia.
For
Paragonimus kellicotti:
a) 50 mg/kg PO per day for 21 days
b) 30 mg/kg once daily for 12 days
c) 25 mg/kg PO q12h for 14 days
For Giardia:
a) 25 mg/kg PO q12h for 4 doses
b) 25 mg/kg PO twice daily for 5
days
c) 25 mg/kg PO twice daily for 2 – 5
days
For
Leishmaniasis:
a) 10 mg/kg PO once daily for 30
days or 5 mg/kg PO q6h for 60 days
CATS:
For
Paragonimus kellicotti:
a) 50 mg/kg PO per day for 21 days
b) 25 mg/kg PO q12h for 10 – 21 days
c) 30 mg/kg once a day for 6 days
d) 25 mg/kg PO q12h for 14 days
For
Giardia:
a) 25 mg/kg PO twice daily for 5
days
b) 25 mg/kg PO q12h for 3 – 5 days;
may cause bone marrow suppression in dogs and cats.
For
treatment of liver flukes (Platynosum or Opisthorchiidae families):
a) 50 mg/kg PO once daily until ova
are gone
RABBITS/RODENTS/SMALL
MAMMALS:
a)
Rabbits:
For
Encephalitozoon phacoclastic uveitis: 30 mg/kg PO once daily for 30 days,
then 15 mg/kg PO once daily for 30 days
b)
Chinchillas: For Giardia:
50 – 100 mg/kg PO once a day for 3 days
BIRDS:
a)
Ratites: Using the suspension: 1 mL/22 kg of body weight twice daily for 3
days; repeat in 2 weeks. Has efficacy against flagellate parasites and
tapeworms.
Monitoring
Efficacy
Adverse effects if used
in non-approved species or at dosages higher than recommended
Consider monitoring
CBC’s and liver enzymes (q4 – 6 weeks) if treating long-term (>1 month)
Note. For therapeutic purposes
albendazole and albendazole oxide may be considered equivalent in effect.
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