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: Animals ( n = 42 ) were treated intraperitoneally with one of the following six regimens : 1 ) L - MED ( the inactive L - isomer of medetomidine ) , 30 micrograms / kg ; 2 ) D - MED , 10 micrograms / kg ; 3 ) D - MED , 30 micrograms / kg ; 4 ) D - MED [ 30 micrograms / kg ] and the central - acting alpha - 2 antagonist , idazoxan [ 10 mg / kg ] ; 5 ) D - MED [ 30 micrograms / kg ] and the peripheral - acting alpha - 2 antagonist DG - 5128 [ 10 mg / kg ] , or ; 6 ) saline .
### Output Text:
Animals ( n = 42 ) were treated intraperitoneally with one of the following six regimens : 1 ) L - MED ( the inactive L - isomer of <span class="chemical">medetomidine</span> ) , 30 micrograms / kg ; 2 ) <span class="chemical">D - MED</span> , 10 micrograms / kg ; 3 ) <span class="chemical">D - MED</span> , 30 micrograms / kg ; 4 ) <span class="chemical">D - MED</span> [ 30 micrograms / kg ] and the central - acting alpha - 2 antagonist , <span class="chemical">idazoxan</span> [ 10 mg / kg ] ; 5 ) <span class="chemical">D - MED</span> [ 30 micrograms / kg ] and the peripheral - acting alpha - 2 antagonist <span class="chemical">DG - 5128</span> [ 10 mg / kg ] , or ; 6 ) saline . 