1. Awatif B. Al-Backer

2. Definition  They are drugs used to abolish pain sensation in certaion area of the body.  They depress the afferent nerve impulses which travel to the CNS.  They cause reversible block of nerve conduction when applied locally to the nerve tissue in appropriate concentration.

3. Awatif B. Al-Backer Mechanism of action of L.A 1.(-) the generation & propagation of the nerve impulses at its site of action on the cell membrane. 2.(-) Na+/ k+ ATPase, so no Na+ influx & no K+ outflux membrane stabilization. 3. the activity of Na+ / Ca+ exchange causing membrane stabilization. 4. the threshold of excitability or block the conduction of nerve impulses.

4. Awatif B. Al-Backer Method for administration of L.A 1.Surface anesthesia. 2.Infiltration anesthesia. 3.Nerve block anesthesia. 4.Spinal anesthesia.

5. Awatif B. Al-Backer 1. Surface Anesthesia: By direct application of the drug to the surface. E.g. eye, skin, cornea. 2. Infiltration Anesthesia: The local anesthetic is injectected S.C in order to paralyze nerve ending at the site of operation.

6. Awatif B. Al-Backer 3. Nerve Block Anesthesia: The local anesthetic is injectected in the ………. Of the major nerve trunks like trachea plexus (neck) e.x. lidocaine, procaine 4. Spinal Anesthesia: The local anesthetic is injectected in the subarachnoid space so that it reaches the roots of the spinal nerves between lumber e.x. procaine

7. Awatif B. Al-Backer Identification & Evaluation of L.A 1.Corneal method. 2.Intradermal wheel method. 3.Nerve block ( frog plexus method).

8. Awatif B. Al-Backer Corneal method (Surface) Principle: The L.A. is applied & the change in the response of the animal to the painful stimulus is recorded. Animal: Rabbit Painful stimulus: is induced by a fine cotton applicators applied on the cornea. Anesthetic used: Lidocaine 1 % Response: blinking of the eye. N.B. The response is compared Before and after application of lidocaine

9. Awatif B. Al-Backer Intradermal wheel method Animal: Guinea pig Painful stimulus: Pin prick Anesthetic used: Lidocaine 0.2 % Response: shrinkage of the skin (L.A. will prevent feeling of pain during the prick)

10. Awatif B. Al-Backer Nerve Block Method (frog plexus method) Animal: Frog Painful stimulus: dil. Hcl Anesthetic used: Procaine Response: Withdrawal of the leg

11. Awatif B. Al-Backer