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: Two well - documented cases of bilateral retinal artery and choriocapillaris occlusions with blindness following head and neck soft - tissue injection with methylprednisolone acetate in combination with lidocaine , epinephrine , or penicillin are reported .
### Output Text:
Two well - documented cases of bilateral retinal artery and choriocapillaris occlusions with blindness following head and neck soft - tissue injection with <span class="chemical">methylprednisolone acetate</span> in combination with <span class="chemical">lidocaine</span> , <span class="chemical">epinephrine</span> , or <span class="chemical">penicillin</span> are reported . 