Norco is generally used for short-term treatment. It should not be used for persistent coughs from smoking or long-term breathing problems (e.g., asthma, emphysema), or for coughs with a lot of mucus or fluids (productive coughs), unless directed by your doctor.
Opioid cough suppressants should not be used in children younger than 18 years. Children are at higher risk for serious (even fatal) side effects, especially breathing problems. Talk with the doctor about the risks and benefits of this medication.