There's a medical term for when one's muscles go weak and soft temporarily so, such as in reaction to a medication. I believe that it's not 'atrophyism' as, to me, that implies wastage and long-term loss of muscle strength. I'm writing something and the proper term would help describe the condition.....
Thanks in advance to Sqad or anyone else who would know the term.....
I bow to the learned Sqad over this, but I just wonder from the OP's first sentence if rhabdomyolosis might fit the bill. Its bandied about a great deal nowadays in the context of statin side-effects so would indeed be a "reaction to a medication".
I think a little more information would help here.