Page 7 - TBAS-may-2018

TBAS May 2018 .................... -7-
Cesol, and Droncit (Merck, 7714, 11th Ed .)
Praziquantel is rapidly absorbed after oral administration, reaching a peak
concentration in the blood plasma 1 to 3 hours later. It undergoes rapid metab-
olism in the liver so that it has a half life of only about 1-11/2 hrs. (Martindale,
p. 64). It is effective against cestodes, digeneans, and monogeneans, but not
against nematodes or protozoans.
Schmahl recommends 10 mg/liter for 3 hours at 20°C, 68°F, as a bath
against monogeneans since at this exposure no adult gyrodactylus remained on
the skin of the fish; juvenile worms however, were not affected until an exposure
time of 16 hours (Schmahl and Taraschewski , 1987). Dactylogyrus vastator did
not drop from the gills even when killed by Praziquantel whereas Dactylogyrus
extensus often dropped from the gills (Schmahl and Mehlhorn, 1985). At the
higher temperatures discus are often maintained at 30°C, 86°F, it would be
reasonable to expect this effect in about 11/2 hours.
Praziquantel causes vacuoles to open under the skin and crater like holes
to form in the skin surface of monogeneans, particularly in the area of the haptor,
the result is severe damage to the skin of the monogenean. At 50 ppm Prazi-
quantel, after one hour the test fish, sticklebacks, swam upside down, but they
recovered in freshwater (Schmahl and Taraschewski, 1987).

(F) Trichlorophon , C H Cl 0 P [Fig. 2]
4 8 3 4
This compound, O, O, -Dimethyl-2,2,2-trichloro-1-
hydroxyethylphosphonate, is a chlorinated organophos-
phate which exists as colorless, highly water soluble
crystals. The LD50 (LD50 = dosage lethal to 50% of
test animals) for rats is 630 mg/kg (Ullmann , Vol. 13 , p.
23 1). It is very toxic when inhaled, swallowed, or spilled
on the skin. It can be removed from the skin by washing
with soap and water. Animal tests for carcinogenicity
were negative (Martindale, p. 59).
It has been marketed as: Clout ,® Dipterex ,® Dylox,®
Life Bearer,® Masten ,® Metriphonate,® Neguvon,® and
Tugon. ® It is highly stressful to the fish, making them
turn dark, become skittish, and increase their respiration
rate.
Trichlorophon is an inhibitor of the enzyme acetylcho-
linesterase, this inhibition causes a continuous flow of
stimuli from the nerve cells to the terminal organs until
their complete exhaustion . Parasites are affected at
a lower dose than are vertebrates (Schmahl and

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