Small Animal Clinical Pharmacology - CYF MEDICAL DISTRIBUTION

EXTERNAL PARASITICIDES
an acute oral LD 50 in the dog of more than 10,000 mg/
kg. Efficacy and safety are improved if coadministered
with food and efficacy is further enhanced if the drug is
micronized.
Use in cats is not advised, with vomiting, inappetence
and posterior paresis being reported.
EXTERNAL PARASITICIDES
Perhaps because of the visibility of external parasites
and their effects (both psychological and physical) on
humans in close contact, external parasiticides are
among the most widely used and misused drugs in dogs
and cats. Without professional advice from veterinarians
concerning the most appropriate treatment and
control programs, continued failures of long-term management
can be expected. External parasiticides alone
can never be expected to completely control infection
as they must be combined with measures to ensure that
sources of reinfection are eliminated.
Typical claims are summarized in Table 10.5. It
should be emphasized that label directions take priority
and must be followed. In many countries (e.g. Australia
and the USA) most external parasiticides must be used
only as labeled; even veterinarians are not permitted by
law to deviate from labeled directions.
Contraindications and precautions
While warnings and precautions vary between countries
and labeled statements must be observed, typical considerations
that may apply are presented below.
● Concurrent treatments. Other insecticides and
acaricides that could interact should be used
carefully or avoided.
● Sick and convalescing animals. Use should be
avoided or particular care taken.
● Lactating animals. Use should be avoided or
particular care taken.
● Pregnant animals. Use should be avoided or
particular care taken.
● Young animals. Use of organophosphates in
animals less than 3–6 months is usually avoided.
● Paralysis tick. Where complete efficacy is necessary
(e.g. with Ixodes holocyclus control) parasiticide
treatment should be supplemented with thorough
daily searching of the coat.
● Human safety:
– Do not permit children access to pesticide
formulations.
– Keep away from food.
– Wash hands thoroughly with soap and water
after handling.
– Protective clothing may be necessary.
Formulations and dose rates
While some dosage forms for external parasite control
are available for oral administration or injection, most
are administered externally. Some of the features of
these formulations are described below.
Collars
A description of typically available collars is presented
in Table 10.5.
Table 10.5 Ectoparasiticide dosage forms
Dosage
form
Active constituent Use rate Species Indication and typical duration of action
Ticks 1 Ix. holocyclus Fleas Other
Collars
g/kg collar
FORM Amitraz 90 D 2 m 2 m
OP Chlorpyrifos 80/40 D/C 5/4 m 9/8 m
SP Deltamethrin 40 D 5–6 m 6 m Ph 5–6 m
OP Diazinon 150 D,C 5 m 9 m
SP
Flumethrin
22.5
D 5 m 6 w 5 m
[
CARB
+ propoxur
100
OP Naled 150/100 D/C 1 m 4 m
BOT
Pennyroyal oil +
40
D,C
10 w
[
BOT
eucalyptus oil
10
SP Permethrin 80 D,C 4 m 4 m
CARB Propoxur 100 D,C 5 m
IGR Pyriproxifen 5 C 13 m
IGR
Pyriproxifen
2.5
D,C 5 m 5 m
[
OP
+ diazinon
150
IGR S-methoprene 10/20 D/C 6 m
221