One of the biggest problems in the veterinary field is owner compliance with our instructions. I believe that for the most part it's simply misunderstanding or common forgetfulness rather than any malicious will on the part of the pet owner. Unfortunately the consequences of such inactions can affect the pet.
There are good reasons why we prescribe medications at a certain regimen and duration. People may not truly understand, but there is a plan to saying that a medicine has to be given twice daily, three times daily, or whatever. By not following these recommendations the treatment may not work effectively and the problem may not be resolved.
Some medicines simply don't last long in the body and are quickly metabolized. In the case of eye medications the tears and blinking can wash away drops more quickly than when they are applied to the skin. Even within a category such as oral antibiotics some will stay in the blood stream longer than others. Personally I always try to prescribe medications that have to be given as infrequently as possible, realizing that the more times daily a drug has to be given the more likely it will be that a client forgets a dose.
Another factor related to antibiotics is that a certainly level must be maintained in the blood for a certain period of time in order to properly kill the bacteria. The organisms aren't destroyed with a single dose or two. I certainly wish that was the case! When doses are skipped there is a period of time where bacteria can reproduce and grow again in number. The bacteria that survive this kind of intermittent dosing are also more likely to develop resistance to antibiotics, making further treatment more difficult.
My most recent poll shows that the majority of people forget medications at least sometimes. I am at fault for this myself, having forgotten my own medications or to give it to my children, so I certainly can't cast the first stone. But I know the real reasons why I need to follow doctors' orders, and I get mad at myself when I don't do so.
Remember that we don't necessarily like making pet owners have to give numerous medications throughout the day. But we as doctors are limited by the realities of the biomechanics of drugs and the body's physiology. When we say that something needs to be done twice daily for two weeks, that's because it needs to be done that way. Stopping too early or failing to give it at the right intervals can result in a prolonged illness or a lack of resolution.
It's so frustrating as a doctor to try to send home an antibiotic with a client and have them say "Oh, I still have some left from the last time. I'll just give that for a few days." Why did you not finish it the first time? I wasn't giving you those instructions just because I like to hear myself talk.
To clients: Please follow the directions from your doctor. Don't decide to stop or alter dosages without consulting with them. There are legitimate reasons why we gave those instructions that have nothing to do with money.
To vets (soon-to-be or otherwise): Communicate clearly to clients, passing on why the treatment needs to be done a certain way and what can happen if those instructions are not followed.