Veterinary parasiticides - what do they contain?
There are dozens of brands of veterinary parasiticides on the UK market for treating external parasite (ectoparasite) infestations in cats and dogs. They contain one or more active ingredients out of a range of over 20 different active ingredients. Making sense of the huge range of products is easier if you think about them in terms of the active ingredient.
Type of ingredient in veterinary parasiticides
Ectoparasiticide products usually contain an insecticide (also known as an adulticide) to kill fleas. Some insecticide ingredients also have an acaricide (tick-killing) effect. Some insecticides also have a flea larvicide effect. A few insecticide/acaricide ingredients also have a tick-repellent effect.
Different formulations
Ectoparasiticide products are available in a variety of formulations: collar, injection, powder, shampoo, spot-on, spray, tablet. Some have only an immediate effect, others have a prolonged effect (lasting one month or longer). Some products work by remaining on the skin of the pet and coming into direct contact with parasites; others must be absorbed into the body and work when the parasites take a blood meal from the pet.
Active ingredients in topical-acting products (that remain on the skin)
Insecticide only
dinotefuran - prescription-only spot-ons
imidacloprid (also larvicidal) - prescription and non-prescription spot-ons and collars
indoxacarb (also larvicidal) - prescription and non-prescription spot-ons
pyrethrins - non-prescription shampoos and sprays
Insecticide and acaricide
dimpylate - non-prescription collars
fipronil - prescription and non-prescription spot-ons
Insecticide, acaricide and tick repellent
deltamethrin - non-prescription collars
flumethrin - prescription and non-prescription collars
permethrin - non-prescription collars and shampoos, prescription-only spot-ons (spot-ons containing permethrin must never be used on cats).
Insect growth regulators
Some insecticide products also contain an insect growth regulator. This disrupts the flea life cycle by preventing female insects from laying viable eggs and/or preventing larvae from developing into adults.
(S)-methoprene - prescription and non-prescription spot-ons
pyriproxyfen - prescription and non-prescription spot-ons
Ingredients in systemic-acting products (absorbed into the bloodstream)
Insecticide only
nitenpyram - non-prescription tablets
spinosad - prescription-only tablets
selamectin - prescription-only spot-ons
Insecticide and acaricide
afoxolaner - prescription-only tablets
esafoxolaner - prescription-only spot-on
fluralaner - prescription-only spot-on, tablets, injection
lotilaner - prescription-only tablets
sarolaner -prescription-only spot-ons, tablets
tigolaner - prescription-only spot-on
Insect growth regulator
lufenuron - non-prescription suspension, tablet, prescription-only injection
Drug classes
You’ve probably heard of neonics. This is short for neonicotinoid, the name of a chemical class of parasiticide/pesticide substances. You will see below that a few of the ingredients we’ve talked about are in the neonic class. The others are representives of a variety of other different classes of chemical. It is important to be aware that all of the insecticide and acaricide ingredients work in the same way, irrespective of chemical class. They interact with the nerve cell receptors of parasites; this disrupts central nervous system activity in the parasite leading to death.
Bispyrazole - tigolaner
Chloronicotinyl (a.k.a. neonicotinoid, ‘neonic’) - dinotefuran, imidacloprid, nitenpyram
Isoxazoline - afoxolaner, esafoxolaner, fluralaner, lotilaner, sarolaner
Oxadiazine - indoxacarb
Phenylpyrazole - fipronil
Pyrethroid - deltamethrin, flumethrin, permethrin
Spinosyn - spinosad
Prescription or non-prescription?
A veterinary product is classed as prescription-only (POM-V) if:
it is intended for administration following a diagnosis or clinical assessment by a vet;
special precautions are needed in order to avoid any risk to the animal, a person administering the product or the environment;
use of the product might impede or interfere with subsequent diagnosis or treatment;
it contains a new active ingredient (i.e. one that has not been included in any veterinary medicine for at least 5 years.
Prescription-only products cannot be advertised to pet owners. After a product has been on the market for at least 5 years, a company can apply to the regulator for it to be reclassified for supply without a prescription. In response to requests for reclassification, the regulator makes a judgement about the suitability (on the grounds of safety) for supply without a prescription, either with professional supervision (NFA-VPS) or for general (unsupervised) sale (AVM-GSL). It is also possible for a product to be reclassified in the opposite direction if safety concerns emerge.
Apart from products that must be prescription-only, the supply category may be a commercial decision. Some active ingredients are included in products in prescription and non-prescription products.
Not all products are licensed for treating all types of ectoparasite infestation – check the product information.
Want to know more about parasiticides?
Veterinary Prescriber is an independent learning and information resource for veterinary professionals, on all aspects of veterinary medicines. The companion-animal parasiticides market is particularly complex because of the huge choice of products, which continues to evolve, It is an area in which there is intense promotion by the pharmaceutical industry and there is growing evidence of the potential for parasiticides to cause environmental harm. This means it is crucial that the products are used judiciously. Our reviews and Parasiticide Guide are unparalleled in helping make sense of the complex area of companion animal parasiticides and ensuring that veterinary professionals have access to unbiased information.