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: Corticosteroids ( dexamethasone and methylprednisolone ) , benzodiazepines ( midazolam ) and general anaesthesia have been the specific agents mentioned most frequently in the literature as being associated with the development of hiccups .
### Output Text:
Corticosteroids ( <span class="chemical">dexamethasone</span> and <span class="chemical">methylprednisolone</span> ) , <span class="chemical">benzodiazepines</span> ( <span class="chemical">midazolam</span> ) and general anaesthesia have been the specific agents mentioned most frequently in the literature as being associated with the development of hiccups . 