Answer
Dextrorphan, which also has antitussive action, is the main metabolite of dextromethorphan in Covonia Original Bronchial Balsam Syrup.
Sources for this answer
- Covonia Original Bronchial Balsam SyrupThornton & Ross Ltd · emc · SmPC §5.2 Pharmacokinetic properties · Version 8Document updated
Sources checked