Mechanism of action of anti-tussives in cough syrup is:-

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.