Common Nausea, Palpitations, Drowsiness, Dizziness, Dryness in mouth, Fainting, Fatigue, Headache, Hydrodipsomania (periodic episodes of uncontrollable thirst), Loss of appetite, Sleepiness.

Expert advice for Tussmark Syrup

Do not drive or operate machinery as levocloperastine may cause dizziness. 
Do not consume alcohol as it may worsen the side effects.
Do not consume this drug if you are allergic to levocloperastine or any of its ingredients. 
Do not consume this drug if you have excessive discharge of mucus, severe liver impairment.
Patients with hypertension, cardiovascular disease, uncontrolled diabetes mellitus, hyperthyroidism, seizures should not consume this drug
Tell your doctor if you are pregnant, planning to become pregnant or are breastfeeding.