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: MATERIALS AND METHODS : Carbetocin was given as an intramuscular injection immediately after the birth of the infant in 45 healthy women with normal singleton pregnancies who delivered vaginally at term .
### Output Text:
MATERIALS AND METHODS : <span class="chemical">Carbetocin</span> was given as an intramuscular injection immediately after the birth of the infant in 45 healthy women with normal singleton pregnancies who delivered vaginally at term . 