Merial Frontline Plus for Dogs Review

Merial Frontline Plus for Dogs Review

Manufacturer’s dog supplement description: “Stop a flea infestation with the mighty killing force of Frontline Plus. It doesn’t just kill adult fleas and ticks but also slays the next generation of flea eggs and larvae. Plus, it works non-stop for 30 days on dogs and cats. Save now on the #1 choice of vets for their pets1 and yours.”

[tabs][tab title =”Overview”]Frontline Plus, manufactured by Merial, is an Australian product designed to be active against flea infestation in dogs (by both Ctenocephalides canis and Ctencephalides felis types of fleas), and to control brown dog ticks (Rhipicephalus sanguineus), paralysis ticks (Ixodes holocyclus) and biting lice (Trichodectes canis) in dogs and puppies.[/tab] [tab title =”How It Works”]The product contains fipronil, which is a parasiticide that is effective on all stages of a flea’s life cycle. It also contains methoprene which prevents ticks from completing their life cycle.[/tab] [tab title=”Uses”]All the studies done on fipronil and methoprene separately, and on Frontline itself show that the product is extremely effective, when used correctly, at treating and preventing the re-infestation of pet animals with fleas and ticks.[/tab] [tab title =”Side Effects”]Very occasionally, eating the product (e.g. licking it off another treated pet) will make animals salivate a lot. Animals may also occasionally have a skin reaction to Frontline, but this generally stops if the product is washed off the skin with soap and water.

Incredibly rarely (a study showed 15 reports over a 7 year period) there may be some kind of neurological issues associated with treating with fipronil, though these numbers are so small as to possibly be coincidental.[/tab] [tab title =”Dosage”]According to the manufacturer, treating every 4 weeks will keep fleas under control, but the product needs to be applied every 2 weeks to prevent tick bites. Merial states that Frontline Plus will kill fleas in all stages of their life cycle.

Frontline is applied to the skin in an area where the animal can’t lick it off (e.g. between the shoulder blades). It comes in a disposable pipette, and to treat the animal the top is snapped off the pipette, and the contents squeezed onto the skin.[/tab][/tabs]

Merial Frontline Plus for Dogs

Merial Frontline Plus for Dogs ReviewNaturVet Digestive Enzymes that includes probiotics and prebiotics (explained below) is a concentrated enzyme blend for dogs derived from vegetable sources and not from animal sources. It contains a source of live/viable naturally occurring in nature microorganisms recommended to help support a healthy digestive tract of pets. Alpha Amylase will technically hydrolyze starch, Protease will hydrolyze proteins, Cellulase will break down cellulose, Lipase can hydrolyze triglycerides, and probiotics enhance normal digestion.

Frontline Plus is a topical parasiticide that contains Fipronil at a concentration of 100g/L and S-Methoprene at 90 g/L, (as per manufacturer). The product has ovicidal activity (kills eggs), larvicidal activity (kills larvae and pupae) and prevents re-infestation of the dog with adult fleas.

Frontline Plus is applied at the base of the neck, and it diffuses to local epidermis and sebaceous glands. The product that is stored in the sebaceous glands can then act as a reservoir [1].

Effectiveness as a parasiticide

Under laboratory conditions, Frontline Plus was 100% effective against C. Felis and R. Sanguineus in a study of 4o dogs. Treated pets became clear of fleas (that had been introduced as part of the test) within 18 hours, and clear of introduced ticks within 48 hours [2].

Similar results were observed under non-laboratory conditions for clearing of ticks, with dogs naturally infested with R. Sanguineus treated with Frontline. The clearance rate of both immature ticks and adults was found to be very significantly increased against an untreated control group, with 96% of ticks killed off 48 hours after first administration, and persistence of efficacy for up to four weeks [3].

Side effects of Merial Frontline Plus

An extremely tiny minority of people appear to have had problems with Frontline in their dogs. Some side effects are discussed in the pack inserts with instructions on how to avoid them (e.g. allowing a dog to lick the application site before the product has had time to be completely absorbed can lead to hypersalivation due to the effect of the active ingredients on ion channels in the salivary glands).

Other potential problems such as lethargy and joint problems appear to be so infrequent as to be not statistically significant, and may easily be coincidental. Toxicity testings have shown that Frontline Plus is very safe to use on dogs, and no side effects were shown even after large doses were administered to the skin and overdosed orally.

A few dogs may have a skin reaction to Frontline Plus; this is likely to be a response to the inactive carrier. If necessary, the product can be washed off within 48 hours of application using a simple dish soap.

A review of Adverse Drug Events for Frontline Plus in Australia between 1996 and 2003 showed 57 reports of a skin reaction in response to dosing, 15 reports of neurological issues and 5 gastrointestinal problems. The authors of the report note that in some cases the neurological or GI issues occurred as secondary to the skin reaction, and hypothesise that self-trauma to a painful area of skin induces greater systemic uptake of the Frontline Plus active compounds.

Difference between Frontline Plus and Frontline Combo

Frontline Plus is sold via vets, retailers and pharmacies in Australia. It is also sold internationally online, often despite the fact that a similar product is available that is in closer compliance with national labeling standards. In the UK, Frontline Plus is sold as Frontline Combo.

The concentration of Fipronil and Methoprene are exactly the same in Frontline Combo as in Frontline Plus, but the labeling is different (active ingredient concentrations are given in mg/ml rather than g/L, and absolute amounts are given in the UK data sheet). There are no other substantial differences of consumables themselves.

Life cycle of parasites

Fleas. Dog fleas have a 4-stage life cycle: egg, larva, pupa and adult. In ideal for the parasite conditions, the eggs fall off the host and hatch 2-5 days after being produced. The larva feed on organic matter for 8-15 days and then pupate. The pupae can remain in their cocoons for up to 12 months before maturing into adults, mating and producing eggs.

Ticks. Unlike fleas, which spend their entire life cycle on and around the same host, ticks generally pass through three different host genera. They also have four life cycle stages, and can take up to three years to pass from egg to adult, with the majority dying before adulthood due to lack of a host to feed off.

Analysis of Frontline Plus ingredients


Fipronil is a broad spectrum insecticide that works by inhibiting the action of chloride channels in nervous cell membranes, causing paralysis and death of the adult parasite. Fipronil prevents inhibitory nerve impulses from passing to the muscle and hence prevents the muscle from relaxing.


S-Methoprene is a pesticide that acts by mimicking the action of insect juvenile growth hormone. This process disrupts the normal development cycle from immature phase to mature phase. It is not toxic to the pupal or adult stages of the life cycle, but is effective against the larval stage. Larvae treated with Methoprene will pupate, but the pupae will not hatch into adults, preventing reproduction.



  1. Cochet P1, Birckel P, Bromet-Petit M, Bromet N, Weil A. Skin distribution of fipronil by microautoradiography following topical administration to the beagle dog. Eur J Drug Metab Pharmacokinet. 1997 Jul-Sep;22(3):211-6. [link]
  2. Cruthers L1, Slone RL, Guerrero AJ, Robertson-Plouch C. Evaluation of the speed of kill of fleas and ticks with Frontline Top Spot in dogs. Vet Ther. 2001 Spring;2(2):170-4. [link]
  3. Brianti E1, Pennisi MG, Brucato G, Risitano AL, Gaglio G, Lombardo G, Malara D, Fogliazza A, Giannetto S. Efficacy of the fipronil 10%+(S)-methoprene 9% combination against Rhipicephalus sanguineus in naturally infested dogs: speed of kill, persistent efficacy on immature and adult stages and effect of water. Vet Parasitol. 2010 May 28;170(1-2):96-103. doi: 10.1016/j.vetpar.2010.01.033

Disclaimer: The purported effects of the supplements or ingredients discussed in this article may, or may not, have been subject to rigorous scientific investigation.  This article is an introductory document which is not intended to be a scientific review either endorsing or refuting the claimed effects of the supplements or ingredients. The information is NOT to be used for diagnosis or treatment of your pet. You should always consult your own veterinarian for specific advice concerning the treatment of your pet. The supplement has not been tested or tried by the author of this content.

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