For your 9-year-old son, the dosing of Grilinctus DX syrup, which contains Chlorpheniramine Maleate 2 mg and Dextromethorphan 10 mg, should be carefully followed according to pediatric guidelines and the instructions provided by your healthcare provider or the medication leaflet.

Typically, for children aged 6 to 12 years, the usual dose is around 5 ml of the syrup taken 3 times a day. However, this can vary based on the child's weight, severity of symptoms, and specific medical advice.

Important points to consider:

• Always use the measuring device provided with the syrup to ensure accurate dosing.
• Do not exceed the recommended dose or frequency.
• Avoid giving this medication to children under 6 years without medical advice.
• If your child has any other medical conditions or is taking other medications, consult your pediatrician before use.
• If symptoms persist for more than a few days or worsen, seek medical attention.

If you have any doubts or concerns, it is best to consult your child's pediatrician to get personalized advice and ensure safe use of this medication.