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: Compared with placebo subjects , alprazolam patients developed more adverse reactions ( 21 % v . 0 % ) of depression , enuresis , disinhibition and aggression ; and more side - effects , particularly sedation , irritability , impaired memory , weight loss and ataxia .
### Output Text:
Compared with placebo subjects , <span class="chemical">alprazolam</span> patients developed more adverse reactions ( 21 % v . 0 % ) of depression , enuresis , disinhibition and aggression ; and more side - effects , particularly sedation , irritability , impaired memory , weight loss and ataxia . 