د. نور الهدى.pptx1234567890poiuytrewsdfghjk

pharma

1. Local anesthetics

2. DEFINITION Drugs which produce a REVERSIBLE loss of sensation i n a localized part of the body….. Interfering with nerve conduction w ithout loss of consciousness . when applied directly onto nerve tissues or mucous membranes ..

3. Mechanism of action Blocking of Na –channels which are responsible for depolarization . S o :: No depolarization No action potential R ising threshold of action potential S lowing impulse conduction Progressively increasing conc. of a LA applied to a nerve fiber produce blockade of more & more Na+ channels .

4. Properties Desirable in a Local Anesthetic Non-irritating Do not cause permanent damage to nerve structure Systemic toxicity should be low Effective : Injected or Applied locally Onset of action as short as possible

5. CLASSIFICATION ACCORDING TO CHEMISTRY ☆ ESTERS ☆ AMIDES ◇ Cocaine ◇ Lignocaine/ Lidocaine ◇ Procaine ◇ Bupivacaine ◇ Tetracaine ◇ Mepivacain ◇ Benzocaine ◇ Prilocaine ◇ Ropivacaine

6. CLASSIFICATION ACCORDING TO CLINCIAL USES ☆ SURFACE ANESTHESIA ☆ INFILTRATION ANESTHESIA / FIELD BLOCK ANESTHESIA ♧ Tetracaine ♧ Lignocaine ♧ Lignocaine ♧ Procaine ♧ Cocaine ♧ Bupivacaine ♧ Benzocaine

7. ☆ NERVE BLOCK ANESTHESIA ☆ SPINAL ANESTHESIA ◇ Tetracaine ◇ Tetracaine ◇ Lignocaine ◇ Lignocaine ◇ Bupivacaine ◇ Bupivacaine ◇ Procaine

8. ☆ EPIDURAL ANESTHESIA Lignocaine Bupivacaine ☆ ANESTHETIC USED IN OPHTHALMOLOGY Proparacaine

9. ORDER OF BLOCKADE AUTONOMIC PAIN TEMPERATURE TOUCH MOTOR

10. Cocaine Medical use limited to surface or topical anesthesia Avoid epinephrine because cocaine already has vasoconstrictor properties. (EXCEPTION!!!) A toxic action on heart may induce rapid and lethal cardiac failure. A marked pyrexia is associated with cocaine overdose

11. SELECTIVE PHARMACOLOGICAL Benzocaine Available for relief of pain and irritation for surface anesthesia (topical) only ... ointments, sprays, etc. Used to produce anesthesia of mucous membranes

12. LIDOCAINE (Xylocaine) Most widely used LA Effective by all routes. Faster onset, more intense, longer lasting than procaine. Good alternative for those allergic to ester type More potent than procaine but about equal toxicity More sedative than others

13. Bupivacaine (Marcaine) No topical effectiveness Slower onset and one of the longer duration agents Unique property of sensory and motor dissociation can provide sensory analgesia with minimal motor block has been popular drug for analgesia during labor More cardiotoxic than other LA

14. Clinical aspects Applications of local anesthesia: nerve block : injected locally to produce (e.g., dental and other minor surgical procedures) . topical application : to skin for analgesia (e.g., benzocaine) or mucous membranes (for diagnostic procedures) .

15. spinal anesthesia : injection into CSF to produce anesthesia for major surgery (e.g., abdomen) or childbirth . local injection : at end of surgery to produce long-lasting post-surgical analgesia (reduces need for narcotics)

16. i.v. Infusion : for control of cardiac arrhythmias (e.g., lidocaine for ventricular arrhythmias)

17. Notes L.A are not effective in case of abscess because inflammation lead to acidosis that prevent ionization of the cationic amine group so prevent binding to receptor. To prolong the duration of action of L.A vasoconstrictor agents are added like adrenaline. To terminate the action of NA α- blockers are used as phentolamine.

18. To avoid systemic side effects of NA in patients with CVS diseases , another vasoconstrictor agent is used. In case of impaired liver function , large repeated doses of amide compounds may predispose to toxicity . Lignocain is one of antiarrhythmic drugs ( class1b)

19. Adverse effects of L.A I n case of systemic absorption: CNS: parasthesia, visual disturbances, convulsions. CVS: hypotension , brady cardia. Respiratory: hyperventilation, alkalosis and resp. failure.