Complex sentence: Pethidinic acid (meperidinic acid, pethidine intermediate C) is a 4-phenylpiperidine derivative that is both a metabolite of and a precursor to pethidine (meperidine) scheduled by UN Single Convention on Narcotic Drugs.
Split into simpler sentences: Pethidinic acid (meperidinic acid, pethidine intermediate C) is a 4-phenylpiperidine derivative that is both a metabolite of and a precursor to pethidine (meperidine). It is scheduled by UN Single Convention on Narcotic Drugs.