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 the non - pretreatment group , mean arterial pressure ( MAP ) decreased from 107 . 4 + / - 8 . 4 mmHg to 86 . 7 + / - 11 . 4 mmHg ( P less than 0 . 01 ) two minutes after cimetidine .
### Output Text:
In the non - pretreatment group , mean arterial pressure ( MAP ) decreased from 107 . 4 + / - 8 . 4 mmHg to 86 . 7 + / - 11 . 4 mmHg ( P less than 0 . 01 ) two minutes after <span class="chemical">cimetidine</span> . 