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: In a risk analysis of neuropsychiatric side effects in Germany , it is estimated that one of 8 , 000 mefloquine users suffers from such reactions .
### Output Text:
In a risk analysis of neuropsychiatric side effects in Germany , it is estimated that one of 8 , 000 <span class="chemical">mefloquine</span> users suffers from such reactions . 