Mellss pharm cns amide local anaesthatic
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Transcript of Mellss pharm cns amide local anaesthatic
Amide Local
Anaesthatic
Nur Amalina bt. Aminuddin Baki60
Introduction • Amide link: covalent chemical bond
Amide Local Anaesthetics
Longer acting • Bupivacaine • Ropivacaine • Etidocaine • Dibucaine
Intermediate acting • Lignocaine • Mepivacaine• Prilocaine
Bupivacaine
Ropivacaine • Intermediate onset• Compared to bupivacaine – Less potent– less cardiotoxic– Similar action duration– More motor sparing
• For infiltration, epidural and regional anaesthesia • Continuous epidural use for post-operative and
labour pain relief
Etidocaine• Fast onset, analgesia 2-3 times longer• For infiltration and nerve block anaesthesia• Peridural analgesia ( more motor blockade and
abdominal muscle relaxation)• Limited use in vaginal delivery ( block expulsion)• X spinal anaesthesia – May produce convulsion
• Similar cardiotoxic with bupivacaine
Dibucaine / Cinchocaine • Very potent, longest acting, slow onset, rarely
used • For surface anaesthesia in anal canal and
rectum and spinal anaesthesia of long duration
• More toxic than bupivacaine• Pseudocholinesterase inhibitor
Intermediate Acting
Lignocaine / Lidocaine / Xylocaine
• Most widely used ,multipurpose, fast, • Max. effect : 2-5 minutes, lasts for 30-45 min• Useful for all types of blocks• Available as: 4% topical solution, 2% jelly, 5% ointment,
1%, 2% injection ,5% spinal anaesthesia and 10% spray• Formulation with epinephrine:– Delay absorption ,prolong action,reduce toxicity
• Intratechal/ epidural of lidocaine with opioid analgesic (SYNERGISTIC)
• Cause – (low) drowsiness– (increased) dizziness, paraesthesia, euphoria – (high)confusion, vertigo, tinnitus, nausea
• Precipitate seizure, respiratory depression, coma– Treatment: Diazepam/ Thiopental
• Other uses: – IV : ventricular arrythmia during MI
• Propanolol impair clearance, increasing toxicity
Mepivacaine • Compared to lidocaine :– More rapid onset – Longer action – Not effective as topical
• Similar toxicity to lidocaine
Prilocaine • Intermediate onset and duration• Poor VSD • Cause CNS toxicity – Restricted to dental procedure (infiltration, nerve
block )• Used in eutectic mixture• Similar lidocaine toxicity except:– Orthotoluidine cause neonatal methaemoglobinaemia– IV methyl blue
Eutectic Mixture• Lignocaine + Prilocaine• Preparation for anaesthesia of intacted skin• Low melting point of mixture penetrate
intact skin• Dermal anaesthesia during venesection, skin
graft, IV cannulation • Apply an hour before procedure
Conclusion Ester• Poor penetrability • Short duration • Hydrolysed by plasma and
liver esterases• Hypersensitivity common
Amide • Good penetrability• Longer duration • Degraded by hepatic
microsome• Rare hypersensitivity
Referance • HL Sharma and KK Sharma, Principles of
Pharmacology,2nd edition, 2012.• Padmaja Udaykumar, Textbook of Medical
Pharmacology, 2nd edition, 2010.