Awatif B. Al-Backer

Awatif B. Al-Backer

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.

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.

Awatif B. Al-Backer

Method for administration of L.A

1. Surface anesthesia.

2. Infiltration anesthesia.

3. Nerve block anesthesia.

4. Spinal anesthesia.

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.

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

Awatif B. Al-Backer

Identification & Evaluation of L.A

1. Corneal method.

2. Intradermal wheel method.

3. Nerve block ( frog plexus method).

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

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)

Awatif B. Al-Backer

Nerve Block Method(frog plexus method)

Animal: FrogPainful stimulus: dil. Hcl Anesthetic used: ProcaineResponse: Withdrawal of the leg

Awatif B. Al-Backer