Small Animal Clinical Pharmacology - CYF MEDICAL DISTRIBUTION

CHAPTER 10 ANTIPARASITIC DRUGS
Table 10.4 Extra-label uses of fenbendazole
Parasite
Aelurostrongylus abstrusus
Angiostrongylus vasorum
Crenosoma vulpis
Encephalitozoon cuniculi
Eucoleus (Capillaria) aerophila
Pearsonema (Capillaria)/plica
Filaroides hirthi/osleri
Giardia
Lagochilascaris major
Mesocestoides metacestodes
Ollulanus tricuspis
Paragonimus kellicotti
Schistosoma/Heterobilharzia
Fenbendazole
[5-(phenylthio)-1 H-benzimidazol-2-yl]carbamic acid
methyl ester.
Clinical applications
Fenbendazole was described by Hoechst in 1973 and
retains an important role in the chemotherapy of parasites
of dogs. Fenbendazole has a broad spectrum of
activity that includes prevention of transplacental transmission
of T. canis if administered at 25 mg/kg PO daily
from day 40 of pregnancy until 2 days post partum.
Other approved clinical applications are set out in Table
10.3. However, extra-label uses that have been described
are listed in Table 10.4.
Adverse effects
Rare cases of bone marrow hypoplasia and thromboischemic
pinnal necrosis have been reported.
Albendazole
Dose of fenbendazole
25–50 mg/kg PO q.12 h
14 days
50 mg/kg PO q.24 h 3 days
50 mg/kg PO q.24 h 3 weeks
50 mg/kg PO q.24 h
3–14 days
(20 mg/kg PO q.24 h
4 weeks – rabbit study)
25–50 mg/kg PO q.12 h
10–14 days
50 mg/kg PO q.24 h
10–21 days
50 mg/kg PO q.24 h or
25 mg/kg PO q.12 h
3–5 days
50 mg/kg PO q. 24 h, 3 days
50–100 mg/kg PO q.24 h
28 days
50 mg/kg PO q.24 h 3 days
25–50 mg/kg PO q.12 h
14 days
40–50 mg/kg PO q.24 h
10 days
[5-(propylthio)-1 H-benzimidazol-2-yl]carbamic acid
methyl ester.
Clinical applications
Albendazole was developed in 1973 by Smith Kline &
French and has had an important and continuing role
as an antiparasitic agent in ruminants and humans.
Despite the fact that it has never been approved for use
in dogs or cats, it has a number of applications for the
control of unusual parasites. Bioavailability of albendazole
is increased by concurrent fatty meals (2.6-fold),
administration of praziquantel (4.5-fold) or of dexamethasone
(twofold).
Albendazole has perhaps the broadest spectrum of
activity of the benzimidazoles, being active against a
variety of nematodes, trematodes, cestodes and protozoa
of companion animals.
Formulations and dose rates
Pearsonema (Capillaria ) plica
Filaroides hirthi/osleri
Trichinella spiralis
Paragonimus kellicotti
Giardia intestinalis
50 mg/kg PO q.12 h 10–14 days
25 mg/kg PO q.12 h 5 days
50 mg/kg PO q.12 h 7 days – tissue
stages
25 mg/kg PO q.12 h 14 days
25 mg/kg PO q.12 h 2–3 days (dog)
or 5 days (cat)
Adverse effects
Albendazole should be used cautiously as it is potentially
teratogenic and its use has uncommonly been
associated with bone marrow toxicosis in dogs.
Febantel
[[2-[(methoxyacetyl)amino]-4-(phenyl-thio) phenyl]
carbonimidoyl]biscarbamic acid dimethyl ester).
Formulations and dose rates
Febantel is available in combination with other anthelmintics to
provide a wider spectrum of activity. Dose rates and available
products are presented in Table 10.3. It should be noted that a dose
rate of 15 mg/kg is recommended in dogs and cats less than 6 months
of age, and 10 mg/kg for those older than 6 months.
Clinical applications
Febantel is a pro-benzimidazole, developed by Bayer in
1975. It is biotransformed in the liver to the anthelmintically
active metabolites fenbendazole and fenbendazole
sulfoxide (oxfendazole).
Adverse effects
While usually well tolerated, cats appear more likely
than dogs to manifest adverse signs after treatment,
most commonly vomiting and diarrhea.
NICOTINIC ANTHELMINTICS
The nicotinic anthelmintics include the tetrahydropyrimidines
(pyrantel and oxantel) and the imidazothiazole,
levamisole.
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