Small Animal Clinical Pharmacology - CYF MEDICAL DISTRIBUTION

SELECTIVE TOXICITY
Table 10.1 Antiparasitic drugs approved for use or reported as efficacious in dogs and cats
Species of approval
Active constituents
Endoparasiticidal drugs
Dog and cat
Dichlorophen 1,2,4 ; disophenol 1 ; epsiprantel 1,4 ; flubendazole 1 ; ivermectin 1,2,4 ; levamisole
hydrochloride 1,2 ; milbemycin oxime 1,2,3,4 ; moxidectin 1,3 ; niclosamide 1,2 ; oxibendazole 1 ;
piperazine (adipate, citrate, dihydrochloride, phosphate) 1,2,3,4 ; praziquantel 1,2,3,4 ; pyrantel
embonate# 1,2,3,4 , selamectin 1,3,4
Dog only Abamectin 1 ; diethylcarbamazine citrate 1 ; febantel 1,2,3,4 ; melarsomine dihydrochloride 1,4 ;
fenbendazole 1,2,3,4 ; mebendazole 1,2 ; nitroscanate 2,3 ; oxantel embonate# 1,2 ;
thiacetarsamide sodium 1
Cat only Emodepside 1,3
Approved only in other species
Albendazole (sheep, cattle) 1,2,3,4 ; oxfendazole (sheep, cattle) 1,2,3 ; triclabendazole (sheep,
cattle) 1,2,3
Ectoparasiticidal drugs
Dog and cat Bioallethrin (d-trans-allethrin) 2,4 ; carbaryl 1,2,4 ; citronella oil 1,4 ; cypermethrin 1,2 ; cythioate 1 ;
diazinon 1,2,4 ; diethyltoluamide 1 ; di-N-propyl isocinchomeronate 1,2,4 ; eucalyptus oil 1,4 ;
fenthion 1,2 ; fipronil 1,2,3,4 ; imidacloprid 1,2,3,4 ; d-limonene 4 ; lufenuron 1,2,3,4 ; malathion
(maldison) 1 ; melaleuca oil 1 ; metaflumizone 3 , S-methoprene 1,2,3,4 ; N-octyl bicycloheptene
dicarboximide 1,2,4 ; nitenpyram 1,2,3,4 ; permethrin* (cis : trans 25 : 75 or 40 : 60) 1,2,3,4 ;
phenothrin 4 ; piperonyl butoxide 1,2,4 ; propoxur 1,2,3 ; pyrethrins 1,2,4 ; pyriproxyfen 1,2,4 ;
rotenone 1,4 ; selamectin 1,3,4 , sulfur 1,4 ; temephos 1 ; tetramethrin 4
Dog only
Amitraz 1,2,3,4 ; bendiocarb 1 ; benzyl benzoate 4 ; chlorfenvinphos 1,2 ; chlorpyrifos 1,2,4 ; lambda
cyhalothrin 4 ; deltamethrin 2,3 ; dichlorvos 2,4 ; flumethrin 1,2 ; lindane (benzene hexachloride
or BHC) 2,4 , pyriprole 3
Approved for other indications or in other species Macrocyclic lactone injections and oral solutions: doramectin (sheep, cattle, pigs) 1,2,3,4 ,
ivermectin (sheep, cattle, pigs) 1,2,3,4 , moxidectin (sheep and cattle) 1,2,3,4
Antiprotozoal drugs
Dog and cat Clindamycin 1,2,3,4 ; metronidazole 1,2,3 (± spiramycin); sulfonamide-trimethoprim 1,2,3,4 ;
doxycycline 1,2,3,4
Dog only
Diminazene 2 ; febantel 1,2,3,4 ; fenbendazole 1,2,3,4 ; imidocarb dipropionate 2,4 ; isometamidium
chloride 2 ; trypan blue 2
Approved only in other species
Diclazuril (poultry, pigs, sheep) 1,2,3,4 ; ronidazole (pigeons) 1,2 ; toltrazuril (poultry) 1,2,3 ; ponazuril
(horses) 4 ; decoquinate (poultry, cattle) 2,4 ; nitazoxanide (horse) 4
1 Australia (APVMA 2006); 2 South Africa (IVS 2006); 3 UK (NOAH 2007); 4 USA (CVP 2007).
# Embonate is the British Approved Name (BAN) and International Non-proprietary Name (INN) and is synonymous with pamoate, the US
Approved Name (USAN).
* Concentrated permethrin products can be lethal to cats.
SELECTIVE TOXICITY
In an address to the International Congress of Medicine
in 1913 [Lancet, August 16, pp 445–451] Nobel Laureate
Paul Ehrlich described in detail for the first time the
special characteristics of selective antiparasitic chemotherapy.
He noted that ‘if we can succeed in discovering
among [the chemoreceptors of parasites] a grouping
which has no analogue in the organs of the body, then
we should have the possibility of constructing the ideal
remedy’. Amongst the examples described by Ehrlich,
trypan blue as a remedy for babesiosis and arsenic as
an antiparasitic treatment remain in use today. Trypan
blue exemplifies many of the characteristics of an ideal
remedy but arsenic has little selectivity for parasites over
hosts and the margin of safety is low.
Since Ehrlich’s time there has been a continuous
search for antiparasitic agents with high efficacy against
parasites and high safety for the host. In many (but not
all) parasitoses ideal remedies have been identified and
introduced. However, the longevity of ideal remedies is
eventually threatened by the emergence of resistance
and the need for discovery of new antiparasitic agents
with novel modes of action remains important. Use of
comparative genomic, proteomic and bio-informatic
tools is allowing significant progress to be made in the
discovery of new targets for parasite control. There are
a multitude of parasite physical and pharmacological
peculiarities that have been and can be exploited in the
development of selectively toxic drugs.
● The surface area-to-volume ratio of parasites is vastly
higher than that of the host.
● Ion channels that are either unique to parasites (e.g.
the GluCl is present in invertebrates but not vertebrates)
or have distinct structural, physiological and
pharmacological characteristics (e.g. nAChR, VGCC
of platyhelminths, voltage-gated sodium channels of
arthropods).
● Motoneurones of invertebrates are unmyelinated
(unlike those of vertebrates).
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