EMG and biopsy

How long after an EMG can one have a muscle biopsy done on that muscle.  And can any medications affect the results of an EMG or biopsy.  I am currently on Soma Cmpd 350 mg 3x, Flexeril 10 mg 3x, Baclofen 20 mg 4x, Valium 5mg 2x, Amitriptyline 25 mg 1x.  And still with no relief.

[Dr Sharma]

Hi there. I can understand your plight well.  You are right, certain medications particularly muscle relaxants and antichlinergics, interfere with the results of EMG like baclofen and flexeril or cyclobenzaprine that you are taking. It would be prudent to apprise your neurologist of all the medications you are on, so that the EMG results are appreciated in that light. Muscle biopsy can be taken up after an EMG. Consult your neurologist for his preferences and expertise. Take care.

[momofsixkids]

Thank you for your quick response to my question.  What would these drugs do to interfere with the outcome?