Most dogs carry parasites at some point in their lives; often, their immune system keeps the parasite population low. By contrast, older dogs may or may not be harboring worms; your veterinarian will conduct a fecal or blood test to determine if they are present. While most anti-parasitic medications are safe, you should seek guidance from your veterinarian before administering them to your dog -- even with over-the-counter products.
Matching the Medicine to the Worm
Although many deworming medications are effective for treating more than one type of parasite, none is effective against all. This reinforces the need to work with your veterinarian, who can carry out tests to determine the type of parasites present, and prescribe an appropriate medication. Do let the fact that a medication is available over-the-counter create a sense of false-security. Anti-parasitic medications are poisonous; ideally, they kill the worm, while the dog remains healthy. To ensure they work correctly and do not harm your pet, follow the dosage guidelines to the letter.
Your pet can contract tapeworms by ingesting fleas or wild animals, such as mice or rabbits. Most over-the-counter worming products are not effective on tapeworms; so as with all other types of parasites, consult your veterinarian to ensure the best treatment for your pet. The most common medications used to treat tapeworms include ivermectin, pyrantel pamoate, epsiprantel and praziquantel -- all of which require a prescription. However, fenbendazole is effective for some types of tapeworms, and is available over-the-counter.
Ascarids are some of the most common parasites that infect dogs. A 1996 study that sampled dogs from all over the United States found that 30 percent harbored ascarid infestations. Part of the phylum Nematoda, the family Ascarididae contains members such as Toxocara canis and Toxascaris leonina that generally infect dogs. The family also contains the parasite Baylisascaris procyonis, which normally infects raccoons but sometimes plagues dogs as well. Currently, the Companion Animal Parasite Council (CAPC) lists fenbendazole, milbemycin oxime, moxidectin and pyrantel pamoate as approved for treating Toxocara canis and Toxascaris leonina. Additionally, these medications are effective, but not approved, for treating Baylisascaris worms. CAPC states that febantel can also be administered in conjunction with pyrantel and praziquantel for Baylisascaris worms. Your veterinarian may also prescribe the combination of pyrantel and ivermectin to eradicate Toxocara or Toxoascaris worms.
Heart Worm Medication
CAPC recommends controlling heartworms by administering a broad-spectrum medication on a year-round basis. Ivermectin is a common component of many heartworm medications, though others feature milbemycin oxime or pyrantel pamoate. All heartworm medications require a prescription, so you will need to see your veterinarian. However, some dogs become too weak or stressed by heartworms to adequately combat the medication, and become seriously ill.