Answer
Do not combine it with codeine or another cough suppressant without medical advice, as suppressing the cough may interfere with clearing phlegm.
Sources for this answer
- Benylin Herbal Chesty Coughs Sugar Free Syrup — Current selected SmPCemc · Summary of Product Characteristics
General medicine information. Follow the instructions for your own medicine and speak to a pharmacist or clinician about your individual circumstances.