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: Increased plasma malondialdehyde was also recorded in two other groups of animals subjected to the same experimental model , one receiving 20 mg / kg b . w . of the cyclooxygenase inhibitor acetylsalicylate intravenously immediately before ischemia , the other receiving 650 micrograms / kg b . w . of the hypotensive drug nitroprusside at a flow rate of 103 microliters / min intravenously during ischemia , although in this latter group malondialdehyde was significantly higher .
### Output Text:
Increased plasma <span class="chemical">malondialdehyde</span> was also recorded in two other groups of animals subjected to the same experimental model , one receiving 20 mg / kg b . w . of the cyclooxygenase inhibitor <span class="chemical">acetylsalicylate</span> intravenously immediately before ischemia , the other receiving 650 micrograms / kg b . w . of the hypotensive drug <span class="chemical">nitroprusside</span> at a flow rate of 103 microliters / min intravenously during ischemia , although in this latter group <span class="chemical">malondialdehyde</span> was significantly higher . 