In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: However , of the medications surveyed , only the fenfluramines had a significant preferential association with PPH as compared with SPH ( adjusted odds ratio for use > 6 months , 7 . 5 ; 95 % confidence interval , 1 . 7 to 32 . 4 ) .
### Output Text:
However , of the medications surveyed , only the <span class="chemical">fenfluramines</span> had a significant preferential association with PPH as compared with SPH ( adjusted odds ratio for use > 6 months , 7 . 5 ; 95 % confidence interval , 1 . 7 to 32 . 4 ) . 