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: After intravenous administration of labetalol , metoprolol and midazolam the patient ' s condition improved , and 15 min later he woke up .
### Output Text:
After intravenous administration of <span class="chemical">labetalol</span> , <span class="chemical">metoprolol</span> and <span class="chemical">midazolam</span> the patient ' s condition improved , and 15 min later he woke up . 