Medicines and Drugs – Do Doctors and Scientists Know What They’re Talking About?!

I think an accurate description would be, “doctors and scientists mostly understand one or few aspects of how the active compound of a drug could/should work for a particular biological pathway that has been attributed to causing or contributing to a particular condition.”

If you look at the prescribing information (also called a package insert or PI) of many drugs, it will often say that how the drug actually works is unknown – “the mode of therapeutic action {for a drug} in {a condition} is not known” – I think you would be shocked at how prevalent this statement is for all the drugs available on market today.

We don’t know all of the pathways that the drug may be acting on, and we can’t even begin to uncover all of the compensatory or countering pathways that will be activated as a result of this drug being introduced into our bodies (or at least, that’s why we have “post-marketing surveillance and post-marketing studies”) once the drug is released into the general public and gets into thousands and thousands of patients.

One example is a class of novel anti-cancer biological drugs that target the angiogenesis (blood vessel creating) pathways of cancer cells. Oncologists were excited by the prospect that now we have “targeted” therapies and can now go after specific pathways that cancer cells appear to have hijacked or show dominance in the body, and our desire is that, by going after cancer-specific pathways, we can then design treatments or find drugs that specifically affect cancer cell pathways but not “normal” cell pathways.

Another hope for the advent of these targeted therapies is the better side effect profile as opposed to the traditional chemotherapies that kill all cells that have fast replication (cancer cells, hair cells, stomach lining cells), giving rise to a very difficult-to-tolerate side effect for the patient receiving treatment. It turned out that these targeted therapies, while appearing to have more favorable side effect profiles compared to traditional chemotherapy, have other side effects that scientists did not anticipate or see until late in clinical trials, including cardiovascular side effects that were potentially fatal.

This is one “common” illustration of how what we see in the laboratories and even in preclinical studies and in vivo animal models are not completely predictive of what we will see once the drug goes into the human body.

Another illustration of how scientists “make do” with the little that they can feasibly understand during the timeline of drug development is how the “side effect” of some drugs have become the de facto “Indication” approved for treating another condition for which the drug was originally not studied to treat. Viagra (sildenafil) is one such serendipitous blockbuster drug. The compound was originally studied for treating hypertension, and scientists saw quite a rousing side effect (pun intended) and realized that the side effect of the drug may very well be the key use of the drug.
[link to the quora question]
[link to my original answer]

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