what cough medicine can be taken with rynatan

My 31 month old son is taking 2.5 ML of rynatan every twelve hours for a cold - runny nose and eyes. He started on it yesterday morning - Feb. 3rd. Since then he has also developed a cough and coughs so much he gags. Can I give him a triacting cough and sore throat medicine containing acetaminophen 160 mg, dextromethorphan 7.5 mg and pseudoephedrine 15 mg??

Thank you - Peggy Adams