Local anaesthetics
• stop action potentials by blocking sodium channels
• are weak bases which get into cells in the unionised form, become ionised and bind to the channels in the open or inactivated state.
• show use dependence - rate of onset and depth of block are dependent on action potential frequency
• block pain fibres before motor fibres
• are mainly used for analgesia - particularly in ruminants
• block most excitable tissues if you give too much
commonly used drugs
lignocaine

Local anaesthetics

anaesthesia = no feeling
local anaesthesia (= local analgesia) = blockade of transmission in peripheral nerves or spinal cord, usually to try to stop pain signals. (Since most nerves are mixed, motor as well as sensory fibres are nearly always blocked.) The term “local analgesia” is better since pain, but not all feeling, is blocked.
regional anaesthesia / analgesia = block of a major nerve supplying an area of the body using a local anaesthetic drug.
spinal anaesthesia / analgesia = blockade of sensation from large areas of the body by putting a local anaesthetic around the spinal cord.
general anaesthesia = a combination of unconsciousness, analgesia and muscle relaxation produced by a completely different set of drugs (more later)
Some local anaesthetics are used as anti-arrhythmics or anti-convulsants (see cardiovascular notes).

Chemistry
Mechanism of action
Pharmacokinetics
Use dependence
Differential block
Toxicity
Use
Drugs
Politics