This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Pharmacology
Mechanism of action of anti-tussives in cough syrup is:- 
Select and explain. 
A. Raise threshold of cough centre, B. Inhibition of breathing centre, C. Inhibition of respiratory centre, D. Increase tussal impulses
A: Raise threshold of cough centre
Answer: A: Raise threshold of cough centre 
Explanation: Anti-tussives These drugs suppress cough, either by o Acting directly in the CNS to raise the threshold of cough centres or o By inhibiting tussal (cough) impulses in the respiratory tract. o Or Both. These drugs should be used only for dry (non productive) cough. Anti-tussives include o Codeine o Pholcodeine o Noscapine o Dextromethorphan.