Plasma protein binding of bupivacaine and its interaction with other drugs in man

A hybrid nanoparticle-protein hydrogel system for prolonged local anesthesia

Local anesthetics are effective in relieving pain, but their duration of action is short. Therefore, the development of injectable sustained release systems to prolong the effect of local anesthetics has been of interest. In such systems delivering conventional local anesthetics, it has been challenging to achieve long durations of effect, particularly without incurring tissue toxicity. To overcome these challenges, we created a platform comprising a protein hydrogel incorporating hydrophobic local anesthetic (bupivacaine) nanoparticles. The nanoparticles were prepared by anti-solvent precipitation stabilized with bovine serum albumin (BSA), followed by crosslinking with glutaraldehyde (GA). The resulting BSA hydrogels prolonged release of bupivacaine in vitro. When bupivacaine nanoparticles within crosslinked BSA were injected at the sciatic nerve in rats, a duration of nerve block of 39.9 h was obtained, compared to 5.5 h for the commercial bupivacaine liposome suspension EXPAREL®. Tissue reaction was benign. We further demonstrated that this system could control the release of the amphiphilic drug diphenhydramine and the hydrophobic paclitaxel.

Population pharmacokinetic and safety analysis of ropivacaine used for erector spinae plane blocks

INTRODUCTION

Erector spinae plane blocks have become popular for thoracic surgery. Despite a theoretically favorable safety profile, intercostal spread occurs and systemic toxicity is possible. Pharmacokinetic data are needed to guide safe dosing.

METHODS

Fifteen patients undergoing thoracic surgery received continuous erector spinae plane blocks with ropivacaine 150 mg followed by subsequent boluses of 40 mg every 6 hours and infusion of 2 mg/hour. Arterial blood samples were obtained over 12 hours and analyzed using non-linear mixed effects modeling, which allowed for conducting simulations of clinically relevant dosing scenarios. The primary outcome was the Cmax of ropivacaine in erector spinae plane blocks.

RESULTS

The mean age was 66 years, mean weight was 77.5 kg, and mean ideal body weight was 60 kg. The mean Cmax was 2.5 ±1.1 mg/L, which occurred at a median time of 10 (7-47) min after initial injection. Five patients developed potentially toxic ropivacaine levels but did not experience neurological symptoms. Another patient reported transient neurological toxicity symptoms. Our data suggested that using a maximum ropivacaine dose of 2.5 mg/kg based on ideal body weight would have prevented all toxicity events. Simulation predicted that reducing the initial dose to 75 mg with the same subsequent intermittent bolus dosing would decrease the risk of toxic levels to <1%.

CONCLUSION

Local anesthetic systemic toxicity can occur with erector spinae plane blocks and administration of large, fixed doses of ropivacaine should be avoided, especially in patients with low ideal body weights. Weight-based ropivacaine dosing could reduce toxicity risk.

TRIAL REGISTRATION NUMBER

NCT04807504; clinicaltrials.gov.

[Acute toxicity of local anesthetics as a function of the patient's condition]

A patient's condition may alter the pharmacokinetic and pharmacodynamic characteristics of local anaesthetics and so increase the risk of toxicity. In the elderly patient, the elimination half-life is increased for both lidocaine and bupivacaine; the risk of overdose is therefore increased when the local anaesthetic agent is given in repeated doses and as a continuous infusion. Cardiotoxicity due to bupivacaine seems to be worsened by pregnancy. In the foetus and newborn, local anaesthetic toxicity gives the same clinical picture as in the adult and is increased in the presence of acidosis and anoxia. Bupivacaine depressive effects are increased by tachycardias, intraventricular blocks and all the conditions which are known to depolarize the cardiac cell membrane (e.g. hyperkaliemia, acidosis, severe hypoxia, myocardial ischaemia). Drug interactions may also potentiate the toxicity of lidocaine and bupivacaine, such as calcium blockers and diazepam. The effects of other conditions (cirrhosis, renal failure, epilepsy) and other drug interactions, specially those modifying free fraction and elimination of local anaesthetics, are also discussed.

Evidence for a specific receptor site for lidocaine, quinidine, and bupivacaine associated with cardiac sodium channels in guinea pig ventricular myocardium

According to the modulated receptor hypothesis, sodium channels have a specific receptor site for local anesthetic and antiarrhythmic drugs. Thus, in the presence of a high concentration of two drugs, competitive displacement of one drug by another may occur. Furthermore, if a drug that has relatively rapid post-stimulation recovery kinetics (e.g., lidocaine) displaces another drug with relatively slow recovery kinetics (i.e., quinidine or bupivacaine), then a net reduction in sodium channel blockade is expected at certain stimulation rates. We tested this prediction, using the maximum upstroke velocity of the ventricular action potential as an indicator of drug-free sodium channels. A single sucrose gap technique was used to stimulate guinea pig papillary muscles, and to control membrane voltage at all times except during the action potential upstroke. Drug-induced inhibition of maximum upstroke velocity increased as the stimulation rate was increased, and was significant (P less than 0.05) at stimulation rates between 2.5 and 4 Hz in the presence of 43 microM lidocaine (n = 5), and between 0.15 and 4 Hz in the presence of 3.5 microM bupivacaine (n = 4). The addition of 43 microM lidocaine to a perfusate containing 3.5 microM bupivacaine resulted in a net increase in maximum upstroke velocity that was significant at rates between 1 and 3.3 Hz, with a maximum increase of 25 +/- 6% at 1.6 Hz. In contrast, addition of 43 microM lidocaine to a perfusate containing 15 microM quinidine did not result in a significant change in maximum upstroke velocity at driving rates between 0.05 and 3.3 Hz (P greater than 0.2; n = 4). However, evidence for displacement of quinidine by lidocaine could be demonstrated by measuring post-stimulation recovery after a conditioning train of 19 10-msec pulses applied at 28 Hz. With this stimulation protocol, 41 +/- 4% of maximum upstroke velocity recovered slowly from block with a time constant of 3.7 +/- 1.2 seconds at - 100 mV in the presence of 15 microM quinidine (n = 5). In the presence of a mixture of 43 microM lidocaine and 15 microM quinidine, this slow component was significantly reduced to 16 +/- 7% (n = 5; P less than 0.01), while 71 +/- 13% of maximum upstroke velocity recovered with a time constant of 115 +/- 21 msec, typical of lidocaine-blocked channels. A two-drug version of the modulated receptor theory was formulated. The effects of drug mixtures could be accounted for by this model.(ABSTRACT TRUNCATED AT 400 WORDS)

Intravenous regional analgesia using bupivacaine. A double blind comparison with lignocaine

A double-blind comparison of bupivacaine and lignocaine for intravenous regional analgesia (Bier's block) was carried out in seventy-two patients presenting for upper limb surgery. Thirty-eight patients received lignocaine and thirty-four received bupivacaine. Onset of analgesia and recovery times were similar for the two drugs. The degree of both analgesia and muscle relaxation was significantly better in the bupivacaine group. Adverse effects were seen only in patients who had received lignocaine and these were unrelated to the tourniquet time.