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: Although conventional neuroleptics are more frequently associated with NMS , atypical antipsychotic drugs like ziprasidone may also be a cause .
### Output Text:
Although conventional neuroleptics are more frequently associated with NMS , atypical antipsychotic drugs like <span class="chemical">ziprasidone</span> may also be a cause . 