Using a preventive heartworm medicine is the only way to ensure your dog does not contract the life-threatening heartworm disease. But, how to choose which oral heartworm meds are best for you and your pet.

Most widely used are monthly oral heartworm pills as these are much more reliable and easier to administer than the old fashioned daily tablets. Although there are several brands to choose from all are based on one of two active ingredients. In allheartworm pills either 'Ivermectin' or 'Milbemyclin Oxine' will be used as the active ingredient. Both these ingredients are able to kill any larval worms which have infested your pet's bloodstream during the previous month. They also both discourage reproduction in adult worms.

The ingredients, however are not identical. Ivermectin kills larvae relatively slowly so the host animal should be able to absorb the dead parasites with ease, even if in large volume. Milbemyclin oxine however kills much more rapidly. If this product were given to an animal already positive for heartworm disease, the large volume of dead worms would be too much for the animal to deal with and some form of shock reaction would be very likely.

Ivermectin is much more effective at killing older larvae and adult heartworms than milbemyclin oxine. So, if a treatment is missed the ivermectin based products are likely to still have a significant impact destroying most worms in the animal's system. This ability can not be relied on andheartworm pills should be given every 30 days as stated on the pack. But, if a treatment has been mistimed, ivermectin is the product most likely to be successful.

Because Ivermectin is so good at destroying adult worms and discouraging female reproduction it is the most widely used active ingredient used in the treatment of animals already infected withheartworm disease. Used in larger dosages by vets to treat cases in infected dogs, means this ingredient is the one coming under closest scrutiny on a day to day basis. Any problems with the drug would be recognised by animal health-care professionals rapidly.

So, why use the alternative Milbemyclin oxine based products, you may ask. Well, the main reason is fear. Because some breeds (notably collies) have a common genetic mutation which meansIvermectin is toxic too them. However, though that sounds alarming, the dosages in preventative heartworm pills is so tiny that even these breeds will receive no ill effect from the product. A reaction to Ivermectin is only seen in those breeds when given the larger doses required to treat the disease once established. However, understandably many owners of the sensitive breeds choose aMibemyclin based product to ease their minds.

Also, Milbemyclin is able to destroy other parasites so a heartworm medicine containing it provides control for hookworms and roundworms too. Although Ivermectin is a strong insecticide the quantities contained in preventative heartworm pills are so low that it cannot destroy other intestinal worms without the addition of more active ingredients Pyrantel Pamoate and Praziquantel.

Another plus point for the Milbemyclin based products is that with an addition of Lufenuron they can also offer flea control too.

Although the heartworm medicines market is dominated by large brands, there are a few generic products available too. These offer exactly the same volume of active ingredients but usually in less exciting packaging and for a significantly reduced price. There is no reason not to buy generic petmeds as they come under the same rules and restrictions as the branded ones so you still get a safe and effective heartworm pill for your pet.

The key points when choosing oral heartworm meds are firstly that your vet must check your pet for signs of the disease prior to commencing preventative measures. Secondly, all heartworm pills must be given at the correct time interval and during the whole of the mosquito season. Thirdly always ensure your pet meds are produced for your size and species of animal. Altering doses to suit different types of animal is extremely dangerous and should be left to the professionals.