Small Animal Clinical Pharmacology - CYF MEDICAL DISTRIBUTION

ANTIPROTOZOAL DRUGS
Table 10.6 Clinical applications and dose rates of antiprotozoal drugs in dogs and cats (continued)
Benznidazole (classified as a 2-nitroimidazole)
Trypanosoma cruzi 5–7 mpk PO q.24 h 2 months
After oral administration to dogs, rapid and complete absorption has been observed with T max at 1–5 h. The drug is widely distributed,
concentrating 4–7-fold in a variety of tissues, including lung, kidney, liver and brain. Elimination half-life is 6–10 h. Reported to have fewer
side effects than nifurimox.
PENTAVALENT ANTIMONIALS
Available drugs are prepared by reacting gluconic acid (sodium stibogluconate) or meglumine (N-methyl-d-glucamine; meglumine
antimonate) with pentavalent antimony. The reaction mixture is allowed to age and a complex mixture of antimony-sugar polymeric
compounds is isolated. The dose rate of either compound is designed to deliver equal Sb v doses.
Meglumine antimonate
Leishmaniasis 50–75 mg/kg IM or SC q.12 h for 10 days. Best activity associated with combined use with allopurinol.
Sodium stibogluconate (antimony sodium gluconate)
Leishmaniasis 30–50 mg/kg q.24 h SC, IV 20–30 days
POLYENE ANTIFUNGAL
See Chapter 9, Systemic Antifungal Therapy
Amphotericin B
Leishmaniasis Dose rates are 1–2 times higher than those recommended for the treatment of systemic mycoses in dogs.
PURINE ANALOG
Allopurinol
Leishmaniasis 15 mg/kg q.12 h PO 3–6 months; 6–10 mg/kg q.8 h PO 3–24 months; maintenance treatment 20 mg/kg q.24 h, 1 week per
month.
THIAMINE INHIBITOR
Amprolium
Cystoisospora infections in dogs and cats 300–400 mg/kg PO q.24 h 5 days
TRIAZINES/BENZENE ACETONITRILES
Triazines interfere with normal apicomplexan parasite division, leading to the presence of multinucleate schizonts, within which large vacuoles
develop before they eventually degenerate. This class (originally developed as herbicides) may act on enzyme pathways (respiratory chain
and pyrimidine synthesis) within apicoplasts and mitochondria.
Toltrazuril
Cystoisospora 5–10 mg/kg PO (single dose)
Hepatozoon canis (and possibily Neospora caninum) 5–10 mg/kg PO q.24 h for 2–6 days
Toltrazuril is a broad-spectrum antiprotozoal drug widely used for coccidiosis control in poultry and pigs. The drug is slowly absorbed after
oral administration and has prolonged elimination with a half-life of several days. It has been observed that the outcome of treatment of
neosporosis is improved if T cell function is normal. Other members of the class include diclazuril and the active toltrazuril metabolite
ponazuril.
ANTIBACTERIAL DRUGS WITH ANTIPROTOZOAL ACTIVITY
The recent finding of a remnant chloroplast (the plastid or apicoplast) in most apicomplexan protozoa helps to explain the presence of many
(but not all) antibacterial prokaryotic drug targets in eucaryotic protozoa. Further details of pharmacology are presented in Chapter 8.
Aminoglycoside
Paromomycin
Cryptosporidiosis 125–165 mg/kg PO q.12 h 5 days
Absorption from gastrointestinal tract usually poor. However, acute renal failure has been described in cats. Used topically and parenterally in
humans to treat cutaneous and visceral leishmaniasis respectively.
Dihydrofolate reductase inhibitor (diamino pyrimidine)
Ormetoprim
Cystoisospora spp 66 mg/kg q.24 h 7–23 days
Combined with sulfadimethoxine in a ratio of 1 : 5 in tablets for dogs.
Pyrimethamine
Cats appear particularly sensitive to bone marrow suppression by pyrimethamine, and toxicity may be prevented or reduced by
administration of folic acid or yeast supplements.
Toxoplasma gondii Pyrimethamine 0.25–1 mg/kg PO q.24 h + trimethoprim/sulfonamide 15–30 mg/kg PO q.12 h 2–4 weeks
Hepatozoon americanum Pyrimethamine 0.25 mg/kg q.24 h + trimethoprim/sulfadiazine 15 mg/kg PO q.12 h + clindamycin 10 mg/kg PO q.8 h
14 days (relapses noted within 3–4 months) (+ decoquinate)
Neospora caninum Pyrimethamine 1 mg/kg PO q.24 h + trimethoprim/sulfadiazine 15–30 mg/kg PO q.12 h 2–4 weeks
Trimethoprim
Acanthamoeba, Pneumocystis, Cystoisospora, Neospora and Toxoplasma (CNS and enteric forms) 15–30 mg/kg PO q.12 h 10–30 days in
combination with a sulfonamide (usually sulfadiazine)
239