When to Start Giving Puppies Heartworm Medication

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If your puppy vomits or has diarrhea immediately after taking the heartworm prevention medication or on the same day that the medication was administered, contact your veterinarian. The veterinarian can determine if your dog is allergic to the medication or if an alternative medication is necessary. If you ever see worms in your dog’s stools or if your dog vomits worms, take your dog to the veterinarian immediately. Never forget to give your dog heartworm prevention medication when the weather is warm enough for mosquitoes. A mild, persistent cough accompanied by lack of appetite, weight loss and fatigue are signs of heartworm. Always have a persistent cough or any other signs of heartworm evaluated by a veterinarian.


Take your dog to the vet every year for a heartworm check. Annual veterinary exams and heartworm check-ups keep your dog healthy and prolong her life. Keep track of your dog’s heartworm prevention medication schedule on a calendar. Some medications come with reminder stickers for your calendar. Mix the heartworm prevention medication with canned dog food if your dog dislikes the taste of the medication. Wrap the medication in a ball of canned food and offer it to your dog as a treat. Keep newborn puppies indoors in areas where mosquitoes are a nuisance. Begin heartworm prevention medication as soon as the veterinarian allows it.

A little girl and her puppy

Heartworm prevention medication protects dogs from a life-threatening parasite. Mosquitoes carry heartworm and when a mosquito bites an infected dog, it ingests microfilariae (microscopic forms of the heartworm), which develop into heartworm larvae within 10 to 17 days. When the mosquito bites another dog, the heartworm larvae enter the dog's skin, develop into immature worms and then enter the dog's bloodstream. Heartworm prevention medication is available for every stage of a dog's life. Puppies as young as 6 weeks can begin heartworm prevention medication. This guide will help you select a heartworm prevention medication for your puppy.


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Step 1

Research heartworm medications. Find out what types of medication are available and which ones are considered most effective. Heartworm medications prevent heartworms and interrupt heartworm development before the parasites become adults and enter the lungs. Some heartworm medications also protect your dog from other parasites such as hookworms and roundworms. You can find information on heartworms and preventative medications online (see Resources).


Step 2

Take your puppy to the veterinarian for a heartworm test. Heartworms can be fatal if left untreated. Early detection gives your dog a strong chance for a complete recovery. The veterinarian will perform a blood test to determine if your puppy has heartworms. Sometimes a chest x-ray and echocardiography are also performed if the blood test is negative but heartworms are still suspected. If heartworms are present, the dog will receive an arsenic compound drug therapy to kill the heartworms. The drug therapy depends upon the severity of the heartworms and whether the heartworms are male or female. If your puppy is healthy, he can begin a heartworm prevention medication.


Step 3

Request a recommendation for a heartworm prevention medication from the veterinarian. Inquire about the effectiveness of popular heartworm protection medications. Ask the veterinarian why he prefers one medication over other types. Your veterinarian will recommend a heartworm prevention medication that meets the specific needs of your puppy.


Step 4

Consider how your puppy will receive the medication. Some heartworm prevention medications come in the form of a chewable meat-flavored treat. Other types include pills and topical medication. Most dogs are receptive to the chewable medication over other types.

Step 5

Find out how often to administer the medication. Most heartworm prevention medications are administered once a month during heartworm season. Heartworm season occurs during warm weather months, which can be year-round in some areas or only six months in climates that have snow during the winter. However, some states with cold climates have high incidents of heartworm and veterinarians recommend year-round heartworm prevention medication. Dogs that come in constant contact with other dogs in apartment and kennel settings are also required to have year-round heartworm protection.


Step 6

Compare prices and availability of heartworm prevention medications. Some medications may be harder to find at your local veterinarian's office. You can purchase many medications online with a veterinarian's prescription. Online pet pharmacies Pet Care RX often offer discount prices on a variety of heartworm protection medications (see Resources).

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.