Hungary's first
scientific site about Boa constrictors
Do not poison your snake!2015-03-11

In our latest article, we are describing the most common medicines, that could cause toxicosis in your snake and may even lead to death...

Only a few literatures describe toxicosis in snakes. However, as more and more pharmaceutical products are being used by reptiles owners deliberately (or carelessly) these days, toxic cases and accidents of captive reptiles have become more common.

Before we jump into the middle of major pharmaceutics, we must start by emphasizing that the majority of pharmaceutics used in reptile medicine are unregistred for reptiles! Instead, most of them are registred for farm animals (swine, cattle, ovine, etc) and small animals (dog, cats, etc.). The manufacturers do not suggest them to be used "off-label" in reptiles, nor do they take any reponsibility for possible side-effects in those "off-label" species. Does that mean we can not use them in reptiles at all? No, but a certain knowledge and experience is necessary to use them properly nonetheless.

Consequently, most pharmaceutics are used off-label in reptiles, based on experimental learning.

It must be noticed that pharmacology of different reptile species is just as diverse as is their morphology itself. One medicine may be efficient in one species, but it can also be toxic for another. Therefore, before using any medicine/anti-parasite treatment you should contact your vet for your own repiltes’ safety.

Generally, those medicines are recommended that had previously been used successfully in the same species. If there is no pharmacologycal information available with a certain species, extrapolation to a closely related species may be helpful.

Anti-Parasite products

This may be the most common and significant cause of toxicosis in captivity, as the majority of topical (external) products are available to everyone with no prescription needed. Snake mites are a frequent problem, snake keepers will certainly meet this phenomenon sooner or later, and if one chooses or applies a product improperly, his/her pet may suffer the consequences. Reptile keepers should also make sure their food source is reliable and it contains no chemicals for their snakes, as toxic agents may enter by preys, as well.

Piretrines and pirethroids (permethrin)

Piretrines are topical (external) anti-parasite pharmaceutics extracted from Chrysanthemums, pirethroids are their synthetic derivatives. Most of them can be used in mammals and birds safely, however they are very toxic even in low doses for most cold-blooded animals, including fishes and the majority of reptiles.

Acutally, there has been published several articles that described the toxic effects to reptiles of this pharmaceutical group. What’s more, these chemicals had also been used to kill invasive snake species in certain geographic regions, and they did it with great success. Therefore, it is a wonder why whould someone use permethrin sprayed directly on the snake’s skin as a first choice anti-mite treatment. Permethrin is highly toxic when inhaled as an aerosol, or sprayed within a closed enclosue and will lead to acute respiratory disease and central nervous system (CNS) failure. Pirethroids do not have an antidote, therefore symptomatic treatment is the only option, once the snake has been exposed. As there are several other groups of medicines available that are more reliable and have less side-effects, I do not recommend using pirethroids in reptiles.

Fipronil (Frontline, Effipro)

Fipronil agents like Frontline and Effipro are also used off-label, however when it comes to snake mites, they are very effective and reliable, safe products. It is important to know that fipronil agent is diluted in alcohol (isopropil alcohol), therefore they must be used only in open space with proper ventilation. Animals can be put back to their cages/enclosures only when the alcohol has already completely evaporated. One must not use them in closed spaces (f.i.: a closed cage) as evaporating alcohol will certainly cause CNS symptoms. Once alcohol has evaporated and the snake’s skin is dry, animals can return to their cages.

Ivermectin (Ivomec)

Ivermectin is an endectocid anti-parasite agent, which means they are against both external (mite, ticks, etc) and internal (nematodes, threadworms, larvas, etc.). This is a highly effective agent, their use require a great precaution, however.

For reptiles they are recommended to use parenteral (subcutaneous injection) mostly, effectiveness of external products are unreliable in general. Treatments must be repeated at least once, in 10-14 days. They are successully used in Boa constrictors and most other boid species, when it comes to getting rid of mites and/or nematodes. A relative sensitivity in Ball pythons (Python regius) has been reported. We are also aware a case in which a Reticulated python (Python reticulatus) preyed a rabbit that had previously been treated with ivermectin and that ultimately lead to death of the snake (fat tissue absorbs ivermectin and makes a residue for a long time after applying). Ivermectin products must not been used in chelonians and young animals where they penetrate through blood-brain barrier, nor in small animals, where dosage can not be made precise enough. When used improperly, lethargy, muscle weakness, and CNS symptoms may appear and death is to be expected. There is no specific antidote.



This antibiotic belongs to aminoglicozides, their nephrotoxicity (kidney) and ototoxicity (ear) is well-documented in mammals and may have similar side-effects in reptiles, as well. They can not be used in dehydrated specimens and a supportive fluid therapy is suggested even when applied in a well-hydrated specimen. Instead of gentamicin, amikacin (also an aminoglicozide) is a reasonable alternative that is less toxic and has broader spectrum against bacteria.

Enrofloxacin (Baytril)

This is probably the most commonly used antibiotic agent these days. It is safe and has a broad spectrum against bacteria. Injections must be given intra muscular, as it may cause skin necrosis when applied subcutaneous. Larger amounts should also be devided and given into different sites. When applying a longer cure, injection sites should also be changed each time (must not be given into the same site over and over again). They should not be used in young specimens, because it may cause cartilage demage in those.

Metronidazol (Klion)

This is a well-estabished antibiotic agent against anaerob bacteria (, which require no oxigen in order to reproduce). When overdosed, prominent neurological symptoms will appear.

Vitamin overdose

In snakes, vitamin overdose is always an iatrogenic (caused by a vet or the owner) harm. Fat soluble vitamins (D,E,K,A) are relatively easy to overdose, especially A- and D-. Overdosing vitamin A may cause skin disorders, shedding problems, optical disorders, blindness and even death. Over supplementation of vitamin D can cause abnormal ossification, calcification in abnormal sites, muscular weakness. Fresh preys are the best way to ensure your snakes will get everything they need, but not more than needed.

As a matter of course, this article does not cover the entirety of possible toxications in reptiles, nor supposed to encourage reptiles enthusiasts to do veterinary interventions in their homes by themselfes. My intent was rather to draw reptile keepers’ attention to be careful before using one medicine or another.

I must also emphasize when one has no experience with a certain pharmeceutic, we strongly suggest to contact a reptile specialist vet beforehand.

Dr. Botond Ádám

Send email:
on the site:

CB 2016 Tumbes longtail boas

(Boa c. longicauda)details..