Answer
Yes. A metabolite can interfere with some colour-based urinary 5-HIAA and VMA tests, so tell the laboratory about recent use.
Sources for this answer
- Boots Mucus Cough Relief 100mg/5ml Oral Solution — Current selected SmPCemc · Summary of Product Characteristics
- Benylin Children's Chesty Coughs — 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.