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: The incidence calculation revealed that one of 215 therapeutic users had reactions , compared with one of 13 , 000 in the prophylaxis group , making the risk of neuropsychiatric reactions after mefloquine treatment 60 times higher than after prophylaxis .
### Output Text:
The incidence calculation revealed that one of 215 therapeutic users had reactions , compared with one of 13 , 000 in the prophylaxis group , making the risk of neuropsychiatric reactions after <span class="chemical">mefloquine</span> treatment 60 times higher than after prophylaxis . 