Panacur Article #2


By Dr. Dmitry B. Vassiliev D.V.M., PhD



Vassiliev, D.B. 2002. Panacur. Chameleons! Online E-Zine July 2002.

History of Panacur

Panacur is a manufacturer's name for a composition containing Fenbendazole as its active ingredient. Fenbendazole is also the active ingredient in other lesser known anti-parasitics such as Fencur. Fenbendazole is a synthetic chemical with a long history. The origin group that Fenbendazole belongs to was developed for treatment of parasitic diseases in cattle. The first member of this group was Tiabendazole and the second member was oxfendazole. Both drugs were highly toxic and had a narrower spectral of activity than the present day derivative Fenbendazole. In cattle, Fenbendazole has a broad spectrum of activity against most nematodes including lung nematodes, oxyurids, strongyloides and some flatworms (like moniezia). In cattle, Panacur works in almost all groups of parasites, excluding trematodes (flukes),. and has a very high margin of safety (up to 5000 times in cattle). Panacur is the most popular drug using Fenbendazole as it's active ingredient.
Panacur's Application in Reptiles

There are no drugs that have been made specifically for reptiles and we have to adapt medicines for use in chameleons and other reptiles. This is done empirically, and not under recommendation from the manufacturer. For example, 2.5% baytril is for use in small domestic animals such as dogs, cats, and chickens. Use of baytril in reptiles and other animals such as rodents and exotic birds is going beyond the manufacturers intention for the drug. The livestock anti-parasitic, Panacur, presents the reptile veterinarian with the same situation.

It has been the author's experience that reptiles may not enjoy the high safety rating that cattle do. A article written for the ARAV bulletin records my experience with an Azemiops feae (a rare viper from Vietnam and Burma) that died after receiving a dosage of Panacur around 10 times the recommended dosage. The snake showed moderate toxic changing in liver. The snake possibly died from photosensibilization (a rising in sensitivity to sunlight) that induced a changing in crypt of small gut. Specific testing for the drug's safety ratings in chameleons is ongoing.

In cattle this drug is effective against adult stages of parasites, migrating larvae, and eggs (ovocide activity). In reptiles, it works well only against adult stages of gastorintenstinal nematodes. See the accompanying article "The Worms Treated by Fenbendazole" for a description of these parasites. While Panacur is effective against lung nematodes in mammals, I have not observed effectiveness against lung nematodes in reptiles. Panacur is neither effective against worms outside the gastrointestinal tract nor inactive larvae in tissues.. This is actually an advantage as a drug which kills active and inactive larvae throughout the body may cause toxic shock to the animal due to large amount of dead material that the body must filter out at once. Toxic shock due to system overload from dead parasite bodies is common in drugs such as Droncit and Ivermectin. Panacur is the drug of choice for gravid females.
How Panacur Works

Panacur blocks metabolism of carbohydrates in nematodes. Essentially, the nematode can eat food, but cannot absorb the nutrients. Though it is eating, the worm starves to death. Panacur does not have the same effect on birds or mammals and as far as is known, does not block the metabolism of carbohydrates in chameleons.. This is the reason for the margin of safety.

The length of time that it takes for Panacur to start killing parasites depends on the location of the parasite. For oxyurids in the hind gut you can see effect of treatment within a day or two. For ascarids in stomach, though, the effect may never be seen as the bodies may be harmlessly digested. In a chameleon with a normal working gastrointestinal tract the drug may stay in it's system for five days.

No side effects are known within the safety dosage. An indirect effect may occur when there is a large number of parasites and the dead bodies cause the aforementioned toxic shock to the chameleon. Toxic shock may manifest itself as a lowering of activity and an appearance of depression. The flood of dead bodies can also limit the chameleon's peristaltic activity (the gut pushing food through) by the sheer bulk of the bodies of dead nematodes blocking the intestines.
How does a vet know to prescribe Panacur?

A veterinarian will prescribe Panacur after performing a fecal analysis and identifying eggs or adult males under a microscope. Adults may be seen more easily a few days after treatment as they weaken and are flushed out of the chameleon's system.

With any animal perform a fecal check seven days after the first dosage. If eggs and larvae are still seen then the dosage must be repeated. On the average, almost all reptiles need two dosage with the second dosage two weeks after the first. Different veterinary references contain different dosages. This is a result of each author's personal experiences. As touched on before, there is no real research in pharmacology of this drug in reptiles and veterinarians working with reptiles have had to experiment on their own. There is much room for work as each reptile may react differently and the dosage tested and proved effective for an iguana may be different than what is needed in a turtle. Although tests to determine the appropriateness of any drug is recommended, there is no known danger to the animal if Panacur is used in a "shot-gun" manner (medicine given to an animal with only a suspicion that parasites are present).

Formatting, compilation, and editing for this article provided by Bill Strand

Dr. Dmitry B. Vassiliev D.V.M., PhD


Dr. Dmitry B. Vassiliev D.V.M., PhD is the senior herpetologist at the Moscow Zoo in Russia. He is an ARAV member and has published many articles in Russian, Japanese, and German journals on topics such as captive breeding of elapid snakes, shiniasaurus, and a variety of pythons. In the last ten years he has worked in veterinarian support of reptiles particularily in the field of parasitology, comparative pathology, and surgery. His travels have led him from Irian Jaya to Mongolia to Europe.

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