I too agree with Hound Dog Mom BUT there is an alternative to giving the full dose — you can have a compounding pharmacy make a product specific to your pups weight. Dr. Becker mentions it in an article she wrote a year or so ago
“•Providing your dog is healthy with good kidney and liver function, go with a chemical preventive at the lowest effective dosage (compounded if necessary for dogs that weigh at the low end of dosing instructions), at six (not four) week intervals, for the minimum time necessary during mosquito season.” http://healthypets.mercola.com/sites/healthypets/archive/2010/08/03/why-havent-pet-owners-been-told-these-facts-about-heartworm.aspx
I also agree to only use heartworm meds as fleas are not, in most cases, life threatening and can be treated naturally as HDM mentioned. I also agree with giving every 6 weeks instead of 4 weeks. Additionally, look into the herb called milk thistle. Milk thistle helps the liver process toxins more efficiently. If you decide to give milk thistle, the product needs to be standardized to at least 70% silymarin (the “active ingredient”).
