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: Administration of 50 mg / kg PDTC ( low - dose ) did not exert major effects on the development of a status epilepticus or the mortality rate .
### Output Text:
Administration of 50 mg / kg <span class="chemical">PDTC</span> ( low - dose ) did not exert major effects on the development of a status epilepticus or the mortality rate . 