Do you mean Clenbuterol?
This is a Beta-2 agonist, and will act on the heart, causing increased HR, changes in the EKG[QRS interval shortening in the lab on tested mice] tremor[shaking], nervousness, and an increase in cardiac arrhythmias in someone who has an underlying heart condition. If your friend wishes to take "Clen", then I would advise them to see their doc first, since they have something going on which caused the PE, and should be evaluated.
This is the best advise I can give.
Hope I helped.