Ropivacaine is homologous to Bupivacaine . If local anaesthetics are administered into the vein or artery it results to very high systemic levels possibly causing CNS and CV toxicity due to rapid penetration into these regions. Both bupivacaine and ropivacaine are amide linked esters. They are extensively bound in the plasma. Amides extensively bind to the alpha-1 acid glycoprotein (AAG) with ~94% ropivacaine bound to it; it has a higher affinity even though albumin binds to greater amount due to its relative abundance in the human plasma. AAG concentration increases after operative surgery. Ropivacaine is metabolised by the cytochrome P450 isoenzymes CYP1A2 and CYP3A4 to four metabolites, 3-OH-2’6’-pipecoloxylidide, 4-OH-ropivacaine, 3-OH-ropivacaine, and N-dealkylated PPX. Reduced protein binding means that there is higher fraction of the unbound drug circulating in the plasma. Furthermore, amides are hepatically metabolised by amidases. Amidase metabolism is much slower than plasma hydrolysis in which ester linked local anaesthetics undergo. This means that amides are prone to accumulation when administered by continuous infusion. Drug accumulation is also influenced by reduced hepatic perfusion and hepatic dysfunction. It has been reported that high concentrations of unbound bupivacaine are linked with higher rates of early symptoms of CNS toxicity.
Various paediatric studies have been carried out to assess the efficacy and effectiveness of ropivacaine as the choice of local anaesthesia in children. Bosenberg et al evaluated the PK and efficacy of ropivacaine for continuous epidural infusion in neonates and infants under the age of one. The results showed that there were higher concentrations of unbound ropivacaine in neonates compared with infants, but were below the threshold concentration for CNS toxicity. Researchers suggest the need to be cautious with the use of ropivacaine infusions in neonates rather than excluding the option of use. Previous studies have not addressed clinical factors associated with variability in pharmacokinetics of ropivacaine. The aim of this study was to evaluate the PK according to inter patient variability and from this evaluate the appropriateness of recommended dosage regimens in place for neonates, infants and children. Effects of high unbound plasma concentrations of anaesthetics have been linked to systemic toxicity. The present study examines the factors affecting PK and analyse differences in PK of the drug in the different age groups. This information will help to establish effective and safe dose recommendations and provide essential information needed for a thorough PK evaluation of ropivacaine and its active metabolite PPX in the entire paediatric population. The study investigates the use of post operative infusion of anaesthesia in neonates, infants and children.
‘Bupivacaine leading to ropivacaine analysis ’