Chloramphenicol inhibits bacterial protein synthesis by binding to 50s subunit of the bacterial ribosome, thus preventing peptide bond formation by peptidyl transferase. It has both bacteriostatic and bactericidal action against H. influenzae, N. meningitidis and S. pneumoniae. Lidocaine is an amide type local anaesth. It stabilises the neuronal membrane and inhibits Na ion movements, which are necessary for conduction of impulses. In the heart, lidocaine reduces depolarisation of the ventricles during diastole and automaticity in the His-Purkinje system. Duration of action potential and effective refractory period are also reduced.