Feasability of weight based dosage for Frontline

Question
As a healthcare professional working in an Emergency Department I can attest to the common practice of calculating medications on the basis of the patient's weight.For example Heparin infusins are given on a weight based formula, as well as OTC medications such as Tylenol and Motrin. Aside from the concern of compound decay once the Frontline container is opended, can anyone give me a solid argument against using this method to calculate the dosage for my dog? For example, my dog is 13 lbs, the application is for dogs up to 22lbs contained in 0.67 ml.
This calculates to .395 ml for my dog per application, which would render a significant savings and, it seems to me, still give the appropriate dose. It also seems to me that if the unused portion is kept in a capped syringe with all of the air expelled, the likelihood
that the compound will degrade over a month's time is minimal. Your opinion please.


Answer
We dose all medications in veterinary medicine by weight much more so than human medications....we never have a standard pill for a dog as the tylenol and motrin are labeled for either a child or an adult regardless if the adult weighs 100 pounds or 300 pounds.  As far as the Frontline, there are four different sizes for dogs based on weight categories--this is a pesticide and not a medication so it is not exactly the same as saying the dose is X amount of MG per pound.  Frontline does not get absorbed in the blood stream--just in the sebaceous glands.  I can not comment on altering doses based on your calculations.  You certainly can try it, but the product will not be guaranteed when not used according to label instructions.  If you are concerned about saving money, then you should purchase the Frontline Spray.