Will Heart Guard & Advantage Meds Make a Dog Sick?

Introduction

Heartguard, Heartguard Plus and Advantage for dogs control heartworm disease. In addition, Advantage Multi for dogs also protects against and treats fleas, hookworm and whipworm. These medicines---as with all medications---do have side effects and have the potential to make your dog sick.

Before starting either medication, your veterinarian will make sure your dog does not already have a heartworm infection. According to the product information available at both companies' websites, neither medication treats active heartworm infections (a separate medicine is needed), and clinical trials have shown that dogs with existing heartworm could have a reaction to the treatment, including diarrhea (this may be a result of the dying worms rather than an active ingredient in the medicine itself).

Advantage product information specifically warns you should not give either medication to breeding, pregnant or lactating dogs, puppies under seven weeks old and puppies or dogs weighing less than 3 pounds. Heartguard's manufacturer, Merial, states that the product has been safety tested for puppies over six weeks.

Side Effects

Merial, the manufacturer of Heartguard, states that some dogs might experience "Depression/lethargy, vomiting, anorexia, diarrhea, mydriasis [pupil dilation], ataxia [lack of coordination of muscle movements], staggering, convulsions and hypersalivation [excess salivation]. Vomiting and diarrhea are not unusual, with one out of 100 dogs experiencing these side effects. Advantage's manufacturer, Bayer, reports the following side effects in Advantage's product information sheet: Over 10 percent of dogs in clinical trials itched and scratched, 1.5 percent of dogs lost their appetite and 1.5 percent of dogs became lethargic. One laboratory dog became weak, depressed and unsteady a week after having Advantage applied. Other laboratory dogs, states Bayer, had "diarrhea, bloody stools, vomiting, anorexia, lethargy,coughing, ocular [eye] discharge and nasal discharge."

Many dogs take these products without experiencing side effects. Some of the side effects can be serious--speak to your veterinarian about the risks of heartworm in your area and make an informed decision about whether these medicines are right for your dog.

Warning for Collie Owners

Merial states that Collies and related dog breeds are more sensitive to the ingredients in Heartguard at high levels. Overdoses of this drug can lead to numerous problems in these breeds, including depression, coma and death. The product information sheet for Advantage contains a strong warning for Collie owners: in a clinical trial of five Ivermectin-Sensitive Collies (Ivermectin is the active ingredient in Advantage) who were given just 40 percent of the dose, four of the collies experienced side effects so severe that they had to be euthanized.

References

• Heartguard--Protection to Live
• Heartguard Product Information
• Bayer Product Info Site: Advantage for Dogs