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: Clinical safety of lidocaine in patients with cocaine - associated myocardial infarction .
### Output Text:
Clinical safety of <span class="chemical">lidocaine</span> in patients with <span class="chemical">cocaine</span> - associated myocardial infarction . 