1909
Meperidine - associated central nervous system ( CNS ) excitatory toxicities are believed to be caused by accumulation of the active metabolite normeperidine .
 accumulation of the active metabolite normeperidine, Meperidine; central nervous system ( CNS ) excitatory toxicities, Meperidine
Please list all entity pairs containing a certain relationship in the given options.Output format is "word1, word2; word3, word4". 
Option: adverse effect 
Text: {0} 
Answer:
 accumulation of the active metabolite normeperidine, Meperidine; central nervous system ( CNS ) excitatory toxicities, Meperidine