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: This is a case report of euphoria and choreoathetoid movements both transiently induced by rapid adjustment to the selective mu - opioid receptor agonist methadone in an inpatient previously abusing heroine and cocaine .
### Output Text:
This is a case report of euphoria and choreoathetoid movements both transiently induced by rapid adjustment to the selective mu - opioid receptor agonist <span class="chemical">methadone</span> in an inpatient previously abusing <span class="chemical">heroine</span> and <span class="chemical">cocaine</span> . 