1. Myelinated fibres are blocked more easily than unmyelinated fibres. Activated pain fibres fire rapidly; thus, pain sensations appear to be selectively blocked by local anaesthetics.

2. a. These drugs can be used in the heart as group 1 antiarrhythmic drugs.

2.b Most local anaesthetics also have weak blocking effects on the skeletal muscles but this hasn’t been found to have any use clinical application.

2.c The mood elevation that is caused by cocaine reflects action on dopamine and amine-mediated synaptic transmission in the CNS rather than local anaesthetic effect on the membranes.

3. The type of procedure required, the type of tissue they can be used on and the duration of the effect required.
4. CO2 acts a buffer and this then potentiates the effects of the local anesthetic.
5. Benzocaine, cocaine and oxybupirocaine.