Recommended review on the subject matter: Strategies to improve adherence in children - Gardiner P, Dvorkin L. Promoting medication adherence in children.
Am Fam Physician. 2006 Sep 1;74(5):793-8. PMID: 16970023.
As a clinician, you must interrogate the legal tutor that he effectivly gives the medication to his child. If you have any doubt, thant you must hospitalize the patient and you very by your eyes the syrup intake. In an another hand, if the medication is strictly observef, than the health's child will positively evoluate.