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: Azelastine , a novel antiallergic medication , was compared with chlorpheniramine maleate and placebo for efficacy and safety in the treatment of spring allergic rhinitis in a multicenter , double - blind , multiple - dose , parallel - groups study .
### Output Text:
<span class="chemical">Azelastine</span> , a novel antiallergic medication , was compared with <span class="chemical">chlorpheniramine maleate</span> and placebo for efficacy and safety in the treatment of spring allergic rhinitis in a multicenter , double - blind , multiple - dose , parallel - groups study . 