Drowsiness, sedation, nervousness, dizziness, dry mouth, nose or throat, indigestion (nausea, vomiting), attention and coordination disorders, hallucinations (especially in children), headaches, insomnia, excitation, tremors, tachycardia, palpitations, arrhythmias, difficulty urinating, and allergies (redness of the skin, sometimes accompanied by difficulty breathing, swelling of the face or throat).