Why/how do meds work?

Actually, it doesn't matter which route - it's all a little fuzzy for me...

This is well beyond the ability for us to explain on this forum. Some medications are chemical copies of our bodies own substances. Adrenergic meds for example. Some meds block receptor sites, open or close electrolyte channels, or even inhibit the action of cell organelles. Inhibiting ribosome subunits for example.

In addition, some meds are inactive until they are transformed into their active metabolites within our body. Your question is very broad. Do you have specific examples?

The drug doesn't "know" where to go at all- it gets distributed throughout the body tissue roughly equally (varies due to molecular weight, halflife, metabolites, affinities, etc).

For a specific example, take metoprolol: It is a beta-1 selective beta blocker.

It binds to and competitively agonizes beta-1 adrenergic receptors located on cellular membranes.

Beta-1 receptors are found in sufficient quantities in certain tissues-- predominantly the heart.

If, purely hypothetically, beta-1 receptors were found in significant quantities only in your great toe, it would bind there just as surely.

Does this make sense?

Not all drugs affect receptors, but they are all get distributed throughout the entire body. This is one of the many problems with medical therapy and why we deal with side effects, which often are the result of a drug exerting it's effects on something aside from the target area.

this may take a year or two, just to barely cover the subject superficially. any way, at the cellular level, a drug or drugs must contend with many things such as interacting with a specific receptor(s), ion channels, cell membrane, etc. some drugs are specifically designed to prevent a pathway from occurring, e.g. protease inhibitors which inhibits the enzyme which cleaves proteins into functional units thusly preventing the creation of a virus, etc. an excellent primer to answer your question of "actually seeing" what is happenning with drugs in the human body is a biochemistry book, just familiarize or get a gist of some major pathways, e.g. HMG-CoA and how statins work in that pathway, i.e. disrupts the production of cholesterol, etc. fun stuff, really.

Thanks everyone for your help. Sorry to have such difficulty verbalizing my question.

And you are right, I know that pharmacology, patho & phys are huge bodies of knowledge that I dont expect anyone to cover here.

I think I am missing something in the bigger picture of the pathways and will take your advice dirtysleepynurse and choose a drug and follow it that way. I understand the way drugs enter cells etc.

To take an earlier example of an infected great toe, lets say we hang an abx. How does the drug "know" that the big toe is the infected place?

The drug does not "know" an infection exists. Antibiotics work on the principle of selective toxicity. For example, macrolide antibiotics such as Zithromax bind to the 50s subunit of bacterial ribosomes. Eukaryotic cells have ribosomes, but no 50s subunits.

Zithromax does not know an infection exists, the antibiotic simply binds to the 50s subunit. If there are no 50S subunits, then the antibiotic does not do much of anything aside from any other interactions or side effects may occur.

You seem to be stuck on this "knowing" concept. Perhaps a simple analogy will help. Humans and Xylon aliens are at war. Being the blood thirsty and generally destructive creatures we are, humans study the xylons. Apparently, humans are made of cell B and xylons are made of cell A. Humans develop a ray that only kills cell A's. Cool, war over, the ray does not know or care if it kills humans or xylons; however, it only kills the xylon's A cells. Therefore, humans are left unscathed. Same concept.

As stated other medications will only bind to a specific receptor site or work on a specific process. The drug does not know anything, it simply attaches or acts upon whatever receptor or process it was designed to act on. (Obviously, I am talking about active drug metabolites if that is the case.)

GilaRN than you for your explanation. I am getting there. I appreciate your taking time to explain.

I'm embarrased to say that I am a last semester BSN student and wonder how will I ever know all of this???

It took me years to understand the things I need to understand to do my job. There are still many things I do not understand and so I'm learning every day. You will never know it all, but you will know enough to care for your patients.