Resistant as in not effective anymore?
If this is the above question, antibiotics is one of the famous
groups.
Bugs need to be killed in the body with a complete course of
antibiotics, and that is why you often hear your doc advising you
to finish your course of medication, and don't stop just because
you feel better...
If you stop halfway, the bugs that are half-dead will become
resistant towards the medication (like what they say, what won't
kill you makes you stronger) and in future, when you succumb to the
similar illness, the same antibiotics will never be able to help in
curing your problems...
Some other medications when taken excessively at one time will
cause the receptors (to which it binds) in the body to become less
sensitive (numb) towards it, and a higher dose will often be needed
to see the desired effect.
Hence when giving such medications, you often need to split the
doses out... Give it for a few weeks, and then stop for a few weeks
to allow the receptors to get used to the condition so that it does
not develop resistance... With this method, the medication used can
be very effective for a longer period of time.
For pharmacology receptor actions, I can't really help you there...
