I am a med student, and as far as I see from our pharmacology lectures, pharmacologists work almost completely experimental. Quite typically they take a substance (e.g., from nature), they add, change or remove some chemical groups, and then they test it (either with high throughput screening or on animals), for example to see whether the new drug is active or not. To me, this sounds a bit indirect.

Ideally, we should know exactly what we are targeting, and then custom-make a new drug. For example, if we know which receptor (the 'lock') we wish to activate or inhibit, why do pharmacologists not simply design a fitting key (a plug to block, or a substrate-resembling activator) to the specific lock?

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    $\begingroup$ I edited the question in the hopes to improve clarity. Feel free to roll back. $\endgroup$
    – AliceD
    Apr 15, 2015 at 11:06
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    $\begingroup$ You can be pretty sure that this would be done if it would be that easy. This kind of design is done using computers, but real life looks very often different. So you are stuck to test a lot of substances. $\endgroup$
    – Chris
    Apr 15, 2015 at 12:01
  • $\begingroup$ Thank you. What you mean by 'real life looks very often different' is chemical synthesis techniques being shortfall compared to the complex design in computers, so the problem here is chemistry is not enough to do such things, am I right? $\endgroup$
    – user13196
    Apr 15, 2015 at 13:49
  • $\begingroup$ Sometimes during drug discovery, you'll just array hundreds of wells of cell culture, hit it with similar compounds featuring slight modifications, and see which compound(s) produced the greatest effect. $\endgroup$
    – CKM
    Apr 15, 2015 at 14:25
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    $\begingroup$ Even if we could design the perfect compound (key) to fit the target (key), you're ignoring all of the other things that have to go right for a drug to work: it has to get to the target; it has to survive the body trying to get rid of it; it has to not harm the patient in some other way; amongst other things. $\endgroup$
    – jerepierre
    Apr 15, 2015 at 15:22

1 Answer 1


The First thing is that that you can't study any process until it happens. So even if you know the structure of receptor molecule, you can't always be sure that it is completely safe.

It does seem a bit random in beginning but this is how it works. You can't just derive a medicine or drug and send it for mass production. You never know what are the side effects of the drug. For this reason, the drugs are tested on other animals (usually rats because they are quite in number, having short lifespan and not many oppose experiments on rats ethically.)

If the side effects are severe, then the drug is banned from mass production. But if such drug is produced,more harm will be done than good. Also you can't give it to humans first. If all tests are successful, then only the drug is tested on humans.

So Screening and Testing are indirect but essential steps for studying the effects of it.

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    $\begingroup$ 'it does seem a bit random'. Random was the word I was looking for drug discovery process. It's like shooting around with an automatic weapon and checking if enemy is dead or not. It seems that's because of the complexity of system. $\endgroup$
    – user13196
    Apr 15, 2015 at 17:48

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