Small Animal Clinical Pharmacology - CYF MEDICAL DISTRIBUTION

CHAPTER 10 ANTIPARASITIC DRUGS
function of ubiquinone or coenzyme Q, blocking cellular
energy production.
Related to the mechanism of action is the likelihood
of hemolytic anemia in animals with glucose-6-
phosphate dehydrogenase deficiency. Primaquine can
cause marked hypotension if administered parenterally.
After oral treatment, primaquine is nearly completely
absorbed, with a large volume of distribution. There is
extensive hepatic metabolism and slow elimination.
The principal clinical application of primaquine phosphate
is in the treatment of infection with Babesia felis
at a dose regimen of 0.5 mg/kg PO on three occasions
at an interval of 3 d. Reductions in parasitemia are
dramatic and quick. Primaquine use in cats is frequently
associated with vomiting after oral administration
and mortality if doses exceed 1 mg/kg. In addition,
infections are not sterilized, which could lead
to recurrence.
Quinacrine hydrochloride
Quinacrine hydrochloride (mepacrine hydrochloride) is
a yellow dye with a bitter taste that is administered
orally for the treatment of Giardia infection and cutaneous
leishmaniasis. It is well absorbed and widely distributed,
with concentration in the liver and sustained
release for up to 2 months following a single dose. It
may cause skin and sclera to develop a yellowish tinge.
It is administered at 6.6 mg/kg PO q.12 h for 3–5 d. For
cutaneous leishmaniasis, quinacrine has been administered
by intralesional injection or infiltration of a 5%
solution three times at intervals of 3–5 d.
Trypan blue
3,3′-[(3,3′-dimethyl(1,1′-biphenyl)-4,4′-diyl)bis(azo)]
bis(5-amino-4-hydroxy-2,7-naphthalenedisulfonic acid)
tetrasodium salt.
Trypan blue is an antiprotozoal drug first used to
treat Babesia infection in 1909 and still commonly used
to treat Babesia canis. The complex chemical structure
has been progressively simplified, yielding such other
widely used drugs as imidocarb. Trypan blue is administered
IV at a rate of 10 mg/kg as a 1% solution.
Babesia are cleared from the blood within 24–48 h, corresponding
to noticeable signs of recovery in dogs with
uncomplicated cases. Trypan blue can cause blue discoloration
of mucous membranes and plasma following
administration and there is a potential for relapse of
babesiosis.
FURTHER READING
Books
Campbell WC, Rew RS (eds) 1986 Chemotherapy of parasitic diseases.
Plenum Press, New York
Greene CE 2006 Infectious diseases of the dog and cat, 3rd edn.
Saunders Elsevier, St Louis, MO
Hayes WJ, Laws ER (ed.) 1991 Handbook of pesticide toxicology.
Academic Press, San Diego, CA
Plumb DC 2005 Veterinary drug handbook, 5th edn. Blackwell
Publishing Professional, Ames, IA
Quinn PJ, Donnelly WJC, Carter ME et al 1997 Microbial and parasitic
diseases of the dog and cat. WB Saunders, London
Vercruysse J, Rew RS (eds) 2002 Macrocyclic lactones in antiparasitic
therapy. CABI Publishing, Wallingford, UK
Journals
In additional to the major veterinary clinical journals, the following
journals frequently contain reviews of parasiticide pharmacology.
Advances in Parasitology
Annual Reviews of Entomology
International Journal for Parasitology
Journal of Veterinary Pharmacology and Therapeutics
Medical and Veterinary Entomology
Parasitology Research
Trends in Parasitology
Veterinary Parasitology
Websites
Websites referred to in Chapters 1 and 3 contain information relevant
to antiparasitic drugs. Safety and toxicology summaries are available
for many antiparasitic drugs at: www.inchem.org/ (Chemical Safety
Information from Intergovernmental Organizations). Latest review of
agents used in the prevention and treatment of heartworm available
at the website of the American Heartworm Society: www.
heartwormsociety.org/heart.htm.
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