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: Induction of the ventricular tachyarrhythmia was prevented by oral d , l - sotalol in 35 ( 43 % ) patients ; the ventricular tachyarrhythmia remained inducible in 40 ( 49 % ) patients ; and two ( 2 . 5 % ) patients did not tolerate even 40 mg of d , l - sotalol once daily .
### Output Text:
Induction of the ventricular tachyarrhythmia was prevented by oral <span class="chemical">d , l - sotalol</span> in 35 ( 43 % ) patients ; the ventricular tachyarrhythmia remained inducible in 40 ( 49 % ) patients ; and two ( 2 . 5 % ) patients did not tolerate even 40 mg of <span class="chemical">d , l - sotalol</span> once daily . 