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 effect of haloperidol in cocaine and amphetamine intoxication .
### Output Text:
The effect of <span class="chemical">haloperidol</span> in <span class="chemical">cocaine</span> and <span class="chemical">amphetamine</span> intoxication . 