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: After MTX administration a significant increase ( p = 0 . 0228 ) in the plasma creatinine concentration and a significant ( p = 0 . 0001 ) decrease in creatinine clearance was noted compared to controls .
### Output Text:
After <span class="chemical">MTX</span> administration a significant increase ( p = 0 . 0228 ) in the plasma <span class="chemical">creatinine</span> concentration and a significant ( p = 0 . 0001 ) decrease in <span class="chemical">creatinine</span> clearance was noted compared to controls . 