There are three different sorts of heartworm pills available. Daily tablets are most suitable for larger breeds of dogs. Monthly ivermectin based tablets or chewables are the most widely used heartworm preventative medicine. Growing in popularity are the newer monthly Milbemycin oxime based tablets or chewables.

The monthly preventatives are available for dogs and cats of all sizes. Always ensure you have a product specified for your pet's species and weight range to ensure you keep your pets safe.

There are still daily heartworm pills available.  Diethylcarbamazine or DEC has been sold under the names Filaribits, Nemacide and Dimmitrol.  It is an effective way of destroying heartworm larvae so preventing the disease in dogs.

However, missing even a day of these pet meds puts your dog at risk of catching heartworm.  This medication would be extremely dangerous if inadvertantly given to an animal already suffering from the disease.  Add to those two problems, the hassle factor of giving a daily heartworm pill and you can see why many pet owners have stopped using these in favour of more convenient monthly meds, even though this is the cheapest form of dog heartworm control.

The most widely form of dog and cat heartworm prevention are montly heartworm pills.  There are two widely used active ingredients on which all the monthly heartworm pills are based. Either Ivermectin of Milbemyclin oxine will be the active ingredient found in branded or generic heartworm medicines.

Both are great at destroying larval heartworms with such efficiency that either sort of heartworm pill will ensure your dog doesn't get the disease. Ivermectin works a little slower than Milbemclin oxine making it a suitable drug in the treatment of heartworm positive dogs. It is also a little more forgiving if you mistime a treatment as it is able to destroy heartworms which have been in the system of an animal for longer than the 30 days when treatment is due.

Heartgard Plus and Iverhart Plus add Pyrantel Pamoate to the Ivermectin to provide control for intestinal worms, hookworm and roundworm along with heartworms. While Tri-Heart Plus and Iverhart Mac also contain Praziquantel to add tapeworms to the list of controlled parasites.

Milbemclin oxine is favoured by owners of breeds (notably Collies and Old English Sheepdogs) which have a genetic mutation making them more susceptible to reactions to the alternative. This is a faster acting killer of larval worms and must never be given to a dog unless sure that it does not already have the disease.

Milbemclin is a better choice of heartworm pill if you want to combine an intestinal dewormer without further chemicals being included in your pet meds. It effectlvely controls hookworm, roundworm and whipworm as well as the heartworms.

Interceptor is the leading Milbemclin oxine heartworm pill offering complete parasitic worm control in your pet. By adding Lufenuron (which stops fleas laying viable eggs) Sentinel provide and monthly heartworm pill tackling intestinal worms and controlling fleas too.

Most commonly found in dogs, heartworm is also a serious threat to feline health.  It is thought that cat heartworm is a growing problem both in terms of cases and locality.   There are equivalent products available to prevent cats contracting the disease too.

Again the leading brand is Heartgard for cats which uses Ivermectin as its active ingredient, reliably destroying all heartworm larvae if given every 30 days.

The alternative is Interceptor which uses Milbemclin oxine to prevent heartworm, hookworm and roundworm in cats.

At present there are fewer branded or generic products available to prevent heartworm in cats but the two above have exceptional safety records and are widely stocked.

Whichever brand you chose, make sure to visit your vet prior to starting any heartworm prevention course.  All animals should be checked over to ensure they are not already carrying the parasite first.

Dogs and cats should always have seperate medicines specifically sold for use on their own species.  Ensure you choose the correct dosage depending on the weight of your pet too.