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: In contrast , in the nitrendipine - treated group albuminuria increased from 12 . 8 + / - 2 progressively to 163 + / - 55 compared with 19 . 2 + / - 9 mg / 24 hr in the hypertensive controls .
### Output Text:
In contrast , in the <span class="chemical">nitrendipine</span> - treated group albuminuria increased from 12 . 8 + / - 2 progressively to 163 + / - 55 compared with 19 . 2 + / - 9 mg / 24 hr in the hypertensive controls . 