Brand: LIBERTY 50
Company: STAR HORSE
CHEMICAL CLASS of the active ingredient(s):
PARASITES CONTROLLED* (spectrum of activity)
- Ticks including Brown dog tick (Rhipicephalus sanguineus), American dog tick (Dermacentor variabilis) & deer ticks (Ixodes scapularis)
- Chewing lice (Trichodectes canis)
* Can be slightly different in some countries: read the product label!
- For Small Dogs 33 lbs or Less: Apply 1.35 cc of LIBERTY® 50 Plus IGR Spot-On for Dogs (1 tube) to the skin of the dog’s back between the shoulder blades.
- FOR LARGE DOGS 33-66 LBS: Apply 1.35 cc of LIBERTY® 50 Plus IGR Spot-On for Dogs to the skin of the dog’s back between the shoulder blades and 1.35 cc to the skin directly in front of the base of the dog’s tail.
- FOR XL DOGS OVER 66 LBS: Apply 2.70 cc of LIBERTY® 50 Plus IGR Spot-On for Dogs to the skin of the dog’s back between the shoulder blades and 2.70 cc to the skin directly in front of the base of the dog’s tail.
- LD50 (acute oral) in rats: Permethrin 400 mg/kg (in oil vehicle) to 1350-4000 mg/kg (in aqueous vehicle, depending on the study); Pyriproxyfen >5000 mg/kg.
- LD50 (acute dermal) in rats: Permethrin 4000 mg/kg; Pyriproxyfen >2000 mg/kg.
Suspected poisoning? Read the article on permethrin safety in this site. Pyriproxyfen is an insect development inhibitor virtually non-toxic to dogs, cats, humans and other mammals.
WARNING !!!: Never use on cats pipettes approved only for dogs. Permethrin is toxic to cats! Never use on small dogs pipettes approved for large dogs. Learn more about spot-ons and their safety.
You may be interested in the following articles in this site dealing with the general safety of veterinary products:
- Safety for humans
- Safety for domestic animals
- Safety for the environment
- Hazard classifications of pesticides
Risk of resistance? YES:
- fleas, mainly the cat flea, Ctenocephalides felis
- brown dog ticks, Rhipicephalus sanguineus
Resistance to pyrethroids (including permethrin) is common in fleas and mosquitoes worldwide, and in brown dog ticks (Rhipicephalus sanguineus) in some countries (e.g. the USA, Panama, Brazil. Möxico and Spain). Mosquito resistance is mostly due to large scale spraying of pyrethroids for vector control or pest control in agriculture.
Resistance of brown dog ticks (Rhipicephalus sanguineus) to permethrin and other pyrethroids is not uncommon in many countries, including the USA. Since pyriproxyfen has no effect on brown dog ticks, protection against these parasites may be lower than expected.
Alternatives to prevent resistance through product rotation:
- Amitraz (T*): toxic to cats!
- Carbamates (F+T*), e.g. carbaryl, propoxur
- Indoxacarb (F*)
- Insect Development Inhibitors (F*), e.g. lufenuron
- Isoxazolines (F+T*), e.g. afoxolaner, fluralaner, sarolaner
- Macrocyclic lactones (F*), e.g. selamectin
- Organophosphates (F+T*), e.g. chlorpyrifos, coumaphos, diazinon, fenthionn, etc.
- Phenylpyrazoles (F+T*), e.g. fipronil, pyriprole
- Spinosyns (F*), e.g. spinetoram, spinosad
*F = effective against fleas; T = effective against ticks.
These alternative products may not be available in all countries, or may not be available as spot-ons.
Resistance of fleas, mosquitoes, brown dog ticks to carbamates and organophosphates is not uncommon in several countries, including the USA.
Are the active ingredients of this product ORIGINAL* or GENERICS**?
- Permethrin: GENERIC (introduced in the 1970s)
- Pyriproxyfen: GENERIC (introduced in the 1980s)
*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.
COUNTRIES where this product is marketed (maybe under another TM): USA
GENERIC BRANDS available? YES. This product contains generic permethrin and pyriproxyfen.
Click here to learn more about GENERIC vs. ORIGINAL drugs.
Permethrin is a veteran broad-spectrum insecticide and acaricide pyrethroid introduced in the 1970s (by several companies). It is massively used in pets and livestock, as well as in agriculture and hygiene (public and domestic). There are thousand of antiparasitic brands with permethrin worldwide. It is effective against fleas, ticks (e.g. Dermacentor spp, Ixodes spp, Rhipicephalus sanguineus, Amblyomma americanum, Amblyomma maculatum), lice, and mosquitoes However, resistance of some of these parasites to permethrin and other pyrethroids is not uncommon, in the USA and elsewhere. This means that protection against some of these parasites may be lower or shorter than expected, particularly against mosquitoes, because the dinotefuran in the formulation does not contribute to their control.
Pyriproxyfen (Nylar) is a veteran insect development inhibitor introduced in the 1980s (by SUMITOMO) scarcely used in pets and not at all in livestock. It is also used moderately in agriculture and for vector control. In this product it stops development of flea eggs and larvae. It has no protective effect whatsoever against fleas, ticks or mosquitoes. The logic of combining it with permethrin is to ensure that if a few fleas survive the killing effect of permethrin (what usually happens) development of their offspring is inhibited, because the eggs of the surviving fleas will not develop further.
This combination of two active ingredients of different chemical classes makes also sense regarding resistance prevention, because it means attacking fleas through two different mechanisms of action, which is vastly assumed to help preventing or at least delaying resistance development.
- Most topical products kill or sterilize the parasites before they bite and suck blood on the pet, whereas systemic products kill or sterilize the parasites only after their blood meal.
- Topical products cannot be vomited.
- Spot-ons and collars are very convenient to administer.
- There is a larger choice of topical products.
But topical products have also some disadvantages:
- Topical products contaminate the pet's hair coat and it is advisable for children and also adults to avoid contact with the pet for several days after treatment.
- Topical products may not control parasites in some parts of the pet's body (e.g. the ears, below the tail, between the legs, etc.), whereas systemic products reach the blood-sucking parasites through the blood wherever they are.
- Efficacy of topical products may be reduced or shortened through exposure to dirt, sun, shampooing, washing, rain, baths, etc., whereas efficacy of systemic products is independent from these factors.
This product is one of many examples of a questionable practice regarding the use of pyrethroids at very high concentrations in pets, mainly in dogs. Photostable pyrethroids (including permethrin, cypermethrin, deltamethrin, cyphenothrin, phenothrin, etc.) can have a dose-dependent irritant effect on mammals. Most of them are toxic to cats at the therapeutic dose used on dogs. Pyrethroid-related irritation is a well-known problem in livestock. Ready-to-use pour-ons are frequently used on cattle, comparable to ready-to-use spot-ons por dogs, but usually at a concentration of 1%-5% active ingredient and at a much lower dose of 1-5 mg/kg. Even at this dose some cattle show signs of irritation, particularly dairy cows and calves. In this particular dog spot-on permethrin is delivered at a concentration of 50.0%, which results in a dose rate of up to >500 mg/kg for a small dog dog, about 100 times more than on cattle. It is not surprising that not all dogs tolerate such a dose, particularly small breeds, puppies and weaker animals (sick, stressed, old).
A comparable situation occurs with amitraz for dogs (and cats, to which amitraz is also toxic). There are no amitraz ready-to-use pour-ons for cattle, because cattle just don't tolerate it at high concentrations. Instead there are topical amitraz sprays or dips that are applied to cattle at concentrations of ~0.025% (250 ppm = mg/L), which results in a dose of 3-5 mg/kg body weight. Even at this dose cattle may not tolerate amitraz and show undesirable side-effects (sedation, depression, etc). Spot-ons for dogs may contain up to 10% amitraz and can result in doses of up to 45 mg/kg body weight! Chihuahuas and puppies are particularly at risk of amitraz side effects.
It is also not surprising that such products erroneously administered to cats can be deadly.
In fact, serious problems with adverse reactions after use of certain spot-ons have been reported in the USA, especially on cats and small dogs. According to a report by the EPA from 2010, most problems occurred with spot-ons containing permethrin, phenothrin, cyphenothrin (all are synthetic pyrethroids) and amitraz, not approved for use on cats but erroneously used on them. There have been also numerous overdosing cases of small dogs, apparently because some users buy large vials for large dogs but use them several times in smaller dogs to save money. It seems also that small dogs are more sensitive than large ones and don't support the treatment as well as large ones. It also seems that some insufficiently investigated inert ingredients (e.g. solvents) in the formulations are not as harmless as they were supposed to be.
Deeper information on the misuse of synthetic pyrethroids in dogs and pets can be found in: Anadón et al. 2009. Use and abuse of pyrethrins and synthetic pyrethroids in veterinary medicine. The Veterinary Journal, 182, 7-20.
My personal opinion is that the fierce competition for market share in this largest and most profitable veterinary market has pushed some companies to take too many risks in order to launch products that are "different" to those of their competitors. In fact it has become very difficult to be "new" or really "superior" in a market driven mainly by generic active ingredients during the last decade. Once one company has taken the risk, others will follow and launch their "me-too" brand, to be sure they don't miss an opportunity.
For an overview and a list of the most popular pet antiparasitics for flea, tick, lice and/or mite control click here.
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