<prompt> Mechanism of action of anti-tussives in cough syrup is:-Raise threshold of cough centreInhibition of breathing centreInhibition of respiratory centreIncrease tussal impulses  <response>: 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. 