Clinical effects and maternal and fetal plasma concentrations of 0.5% epidural levobupivacaine versus bupivacaine for cesarean delivery

The Options for Neuraxial Drug Administration

Neuraxial drug administration, i.e., the injection of drugs into the epidural or intrathecal space to produce anesthesia or analgesia, is a technique developed more than 120 years ago. Today, it still is widely used in daily practice in anesthesiology and in acute and chronic pain therapy. A multitude of different drugs have been introduced for neuraxial injection, only a part of which have obtained official approval for that indication. A broad understanding of the pharmacology of those agents is essential to the clinician to utilize them in a safe and efficient manner. In the present narrative review, we summarize current knowledge on neuraxial anatomy relevant to clinical practice, including pediatric anatomy. Then, we delineate the general pharmacology of neuraxial drug administration, with particular attention to specific aspects of epidural and intrathecal pharmacokinetics and pharmacodynamics. Furthermore, we describe the most common clinical indications for neuraxial drug administration, including the perioperative setting, obstetrics, and chronic pain. Then, we discuss possible neurotoxic effects of neuraxial drugs, and moreover, we detail the specific properties of the most commonly used neuraxial drugs that are relevant to clinicians who employ epidural or intrathecal drug administration, in order to ensure adequate treatment and patient safety in these techniques. Finally, we give a brief overview on new developments in neuraxial drug therapy.

Comparison Between the Effects of Bupivacaine and Levobupivacaine for Spinal Anesthesia on QT Dispersion

BACKGROUND

Bupivacaine and Levobupivacaine are frequently used local anesthetic drugs in spinal anesthesia practice. Both agents have arrhythmic effects on the heart. However, there is no clear information about which agent is more arrhythmogenic.

OBJECTIVE

The aim of this article is to investigate the effects of bupivacaine and its S (-)-enantiomer, levobupivacaine, on cardiac arrhythmias in patients.

METHODS

The study included 40 patients scheduled for inguinal hernia surgery. Patients were randomly divided into the following two groups using a sealed envelope method: Group I, the bupivacaine group (n = 20); and Group II, the levobupivacaine group (n = 20). The QT values were taken preoperatively and during the 10th of the spinal block, the 10th of the surgical incision, and the 10th postoperative minute. Additionally, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), oxygen saturation (SO₂), and heart rate (HR) values, in addition to motor block (Bromage scale) levels and durations, were recorded for each patient.

RESULTS

HR values measured at 10 min after spinal block were significantly higher than the baseline values in the levobupivacaine group (p < 0.05). The corrected QT interval (QTc) values increased significantly at 10 minutes after spinal block and at 10 min postoperatively in the bupivacaine group (p < 0.05). QTd and QTcd measurements were taken at the 10th minute of spinal anesthesia, the 10th minute of the incision, and the 10th minute postoperatively. When compared to the levobupivacaine group, a statistically significant increase was found in the bupivacaine group (p < 0.05).

CONCLUSION

Levobupivacaine allows greater hemodynamic stability, while bupivacaine affects QTc and QTd measurement times more. As such, we believe that levobupivacaine may be a better alternative to bupivacaine during clinical practice, particularly in patients with cardiac problems.

Levobupivacaine versus Racemic Bupivacaine in Spinal Anaesthesia for Urological Surgery

Racemic bupivacaine is the most common local anaesthetic used intrathecally. This prospective, randomized, double-blind study compared the clinical efficacy and motor block of 0.5% levobupivacaine with 0.5% racemic bupivacaine in spinal anaesthesia for urological surgery. The surgery required an upper level of sensory block of at least the tenth thoracic dermatome. Fifty patients were recruited (levobupivacaine group n=24; bupivacaine group n=26). Spinal anaesthesia was achieved with 2.6 ml of study solution injected in the subarachnoid space at the lumbar 3/4 interspace. One patient from the levobupivacaine group was excluded due to technical failure. There were no significant differences between the two groups in the quality of sensory and motor block or in haemodynamic change. Anaesthesia was adequate and patient satisfaction good in all cases.

We conclude that 0.5% levobupivacaine can be used as an alternative to 0.5% racemic bupivacaine in spinal anaesthesia for surgery when a sensory block to at least T10 is required.

Lopinavir/ritonavir treatment increases the placental transfer of bupivacaine enantiomers in human immunodeficiency virus-infected pregnant women

AIMS

The present study evaluated the placental transfer and amniotic fluid distribution of bupivacaine enantiomers in health pregnant women and in human immunodeficiency virus (HIV)-infected pregnant women receiving epidural anaesthesia for caesarean section.

METHODS

Twelve HIV-infected pregnant women (HIV group) were treated long-term (at least 8 weeks) with lopinavir/ritonavir (400/100 mg twice daily), and 12 healthy pregnant women (Control group) who submitted to epidural anaesthesia with racemic bupivacaine (75 mg) during caesarean section were investigated. At delivery, samples of maternal and fetal blood and amniotic fluid were collected (10-20 min after drug administration).

RESULTS

The placental transfer ratio of bupivacaine enantiomers was significantly higher among the pregnant women from the HIV group when compared with those from the Control group (Mann-Whitney test, P ≤ 0.05). Placental transfer ratios (median and 25th - 75th percentiles) for (+)-(R)-bupivacaine were 0.58 (0.38-0.82) in the HIV group vs. 0.25 (0.18-0.33) in the Control group, and for (-)-(S)-bupivacaine, they were 0.54 (0.34-0.69) in the HIV group vs. 0.25 (0.19-0.29) in the Control group. The transplacental distribution of bupivacaine was stereoselective only in the HIV group. The umbilical artery/umbilical vein ratio and amniotic fluid/maternal vein ratio were low and nonstereoselective, and no statistically significant differences were observed between the groups.

CONCLUSIONS

This study supports that the placental transfer of both bupivacaine enantiomers was 100% higher in HIV-pregnant women treated with lopinavir/ritonavir when compared with that in healthy pregnant women receiving epidural anaesthesia for caesarean section.

Inflammation and Epidural-Related Maternal Fever: Proposed Mechanisms

Intrapartum fever is associated with excessive maternal interventions as well as higher neonatal morbidity. Epidural-related maternal fever (ERMF) contributes to the development of intrapartum fever. The mechanism(s) for ERMF has remained elusive. Here, we consider how inflammatory mechanisms may be modulated by local anesthetic agents and their relevance to ERMF. We also critically reappraise the clinical data with regard to emerging concepts that explain how anesthetic drug-induced metabolic dysfunction, with or without activation of the inflammasome, might trigger the release of nonpathogenic, inflammatory molecules (danger-associated molecular patterns) likely to underlie ERMF.

Evaluation of levobupivacaine passage to breast milk following epidural anesthesia for cesarean delivery

BACKGROUND

Following maternal administration, local anesthetics pass into breast milk. In the present study, we aimed to compare the passage of levobupivacaine and bupivacaine into breast milk following epidural anesthesia for cesarean delivery.

METHODS

A total of 20 women undergoing elective cesarean delivery under epidural anesthesia were randomized to receive either 0.5% levobupivacaine or 0.5% racemic bupivacaine via an epidural catheter. Immediately before and 30min, 1h, 2h, 6h, 12h and 24h after administration of epidural local anesthetic, maternal blood and breast milk samples were taken simultaneously. Drug concentrations in plasma and milk were determined via high-performance liquid chromatography. The infant's drug exposure was determined by calculating milk/plasma ratios of levobupivacaine and bupivacaine.

RESULTS

Both levobupivacaine and bupivacaine were detected in breast milk 30min after epidural administration. Concentrations of both agents showed constant and similar decreases in milk and plasma and were nearly undetectable at 24h. The milk/plasma ratios were 0.34±0.13 for levobupivacaine and 0.37±0.14 for bupivacaine.

CONCLUSIONS

Both levobupivacaine and bupivacaine pass into breast milk following epidural administration. The concentration of both drugs was approximately three times lower in breast milk than in maternal plasma.

Adding sufentanil to levobupivacaine or ropivacaine intrathecal anaesthesia affects the minimum local anaesthetic dose required

BACKGROUND

We carried out this prospective, randomized, double-blind study in order to evaluate whether the intrathecal addition of sufentanil 3.3 mcg affects both the minimum local anaesthetic dose (MLAD) of spinal levobupivacaine and ropivacaine for a caesarean section and enhances the spinal block characteristics.

METHODS

One hundred and eighty women were randomly allocated into four groups: levobupivacaine (Group L), levobupivacaine plus sufentanil (Group L+S), ropivacaine (Group R) and ropivacaine plus sufentanil (Group R+S). Each received 3 ml of the study solution intrathecally as part of a combined spinal/epidural technique. The initial dose was 12 mg for Groups L and L+S, and 15 mg for Groups R and R+S. The test solution was required to achieve a visual analogue pain score (VAPS) of 30 mm or less to be considered effective at skin incision, uterine incision, birth, peritoneal closure and at the conclusion of surgery. Effective or ineffective responses determined a 0.5 mg decrease or increase of the same drug, respectively, for the next patient in the same group, using an up-down sequential allocation.

RESULTS

Using the Dixon and Massey formula, the MLAD was 10.65 mg [confidence interval (CI) 95%: 10.14-11.56] in Group L, 4.73 mg (CI 95%: 4.39-5.07) in Group L+S, 14.12 mg (CI 95%: 13.50-14.60) in Group R and 6.44 mg (CI 95%: 5.86-7.02) in Group R+S.

CONCLUSIONS

The addition of sufentanil reduced the MLAD of both the local anaesthetics. It did not affect their potency ratio significantly and resulted in enhanced spinal anaesthesia.

A comparison of the inhibitory effects of bupivacaine and levobupivacaine on isolated human pregnant myometrium contractility

BACKGROUND

Epidural analgesia with levobupivacaine and bupivacaine is a common and effective method of labor pain relief. However, its use is associated with an increased instrumental delivery rate. One of the mechanisms postulated to account for this unwanted effect is the direct effect of local anesthetics on myometrial contractility. We determined the effects of bupivacaine and levobupivacaine on the amplitude and frequency of contractions of human term myometrium.

METHODS

Uterine specimens were obtained from nonlaboring parturients scheduled for elective lower-segment cesarean delivery at term. Longitudinal muscle strips were prepared and mounted vertically in tissue chambers, and changes in the amplitude (peak force) and the frequency of contractions were recorded. Spontaneous contractions commenced after a period of application of 1 g (9.81 mN) of tension to the myometrial strips. No uterotonic drugs were used. The muscle strips were then exposed to cumulative concentrations of bupivacaine and levobupivacaine and dose-response curves were generated.

RESULTS

Both bupivacaine and levobupivacaine decreased the amplitude of contractions in human myometrium in a concentration-dependent manner, reaching significance at 1x10(-4) M for both bupivacaine and levobupivacaine compared with the internal control amplitude. With both drugs, the decrease in amplitude was accompanied by an increase in the frequency of contractions reaching significance at 3x10(-5) M for both bupivacaine and levobupivacaine compared with the internal control frequency.

CONCLUSIONS

The concentrations required for the effects on amplitude are much higher (33 fold) than the clinically relevant plasma concentrations of these drugs after epidural administration, and are unlikely to be significant in the setting of low-dose epidural analgesia in labor.

Epidural lidocaine-bicarbonate-adrenaline vs levobupivacaine for emergency Caesarean section: a randomised controlled trial

Epidural mixtures containing lidocaine with or without additives are commonly used to convert epidural analgesia in labour to anaesthesia for emergency Caesarean section, but direct comparisons with alternative, single agents in this situation are few. In a prospective double-blinded trial, we compared a freshly prepared lidocaine-bicarbonate-adrenaline mixture (final concentrations 1.8%, 0.76% and 1:200,000, respectively) with our standard agent, levobupivacaine 0.5%, for extending epidural blockade for emergency Caesarean section. Using a sequential analysis technique, with data analysed in blocks of 40, women receiving epidural analgesia in labour who required top-up for Caesarean section were randomly assigned to receive 20 ml of epidural solution over 3 min. The first analysis (n = 40) indicated that the study should be stopped, as significant differences were found in our primary outcome data. Median (IQR [range]) times to reach a block to touch to T5 and cold to T4 were, respectively, 7 (6-9 [5-17]) min and 7 (5-8 [4-17]) min for lidocaine-bicarbonate-adrenaline, and 14 (10 -17 [9-31]) min and 11 (9-14 [6-30]) min for levobupivacaine (p = 0.00004 and 0.001, respectively). Pre- and intra-operative supplementation/pain, maternal side-effects and neonatal outcomes (excluding five women who underwent instrumental delivery) were similar between the groups. Intra-operative maternal sedation (scored by the mother on a 10-point scale) was greater with lidocaine-bicarbonate-adrenaline (4.5 (3-8 [1-9])) than with levobupivacaine (3 (1-4 [1-7])), but not significantly so (p = 0.07). We conclude that epidural lidocaine-bicarbonate-adrenaline halves the onset time when extending epidural analgesia for Caesarean section although there is a possibility of increased maternal sedation.

Anaesthesia for caesarean section

Although anaesthesia for Caesarean section is predominantly performed using regional techniques of anaesthesia, general anaesthesia will remain essential for subgroups of obstetric patients, especially those who are at high risk of complications. In the present review, recent reports that addressed issues regarding general and regional anaesthesia in Caesarean section will be discussed.

[Levobupivacaine for parturients undergoing elective caesarean delivery. A dose-finding investigation]

BACKGROUND

The optimum intrathecal dose of hyperbaric levobupivacaine for spinal anaesthesia during elective caesarean section has not yet been investigated.

METHODS

A total of 30 parturients undergoing elective caesarean section were included in this prospective, randomised, double-blind study. Parturients received either 7.5, 10 or 12.5 mg hyperbaric 0.5% levobupivacaine intrathecally. Analgesic, sensory and motor block characteristics as well as maternal and fetal levobupivacaine plasma concentrations were determined.

RESULTS

Of the parturients receiving 7.5 mg levobupivacaine 40% required supplementary intravenous opioid analgesics intraoperatively and none achieved complete motor block. Compared to 7.5 mg levobupivacaine, 10 and 12.5 mg significantly prolonged duration of effective analgesia postoperatively (median: 45 vs. 81 and 96 min, respectively). Both maternal and fetal levobupivacaine plasma concentrations were low, with dose-dependent, statistically significant differences in maternal plasma concentrations.

CONCLUSIONS

Levobupivacaine 7.5 mg did not provide satisfactory intraoperative analgesia in all parturients. There were no statistically significant differences between 10 and 12.5 mg levobupivacaine with respect to analgesic, sensory and motor block characteristics. Therefore, based on these data, 10 mg levobupivacaine is recommended for parturients undergoing elective caesarean section with spinal anaesthesia.

Incisional and epidural analgesia after caesarean delivery: a prospective, placebo-controlled, randomised clinical study

BACKGROUND

This study evaluated efficacy, safety and patient satisfaction with incisional analgesia with a subfascial catheter compared to epidural analgesia for pain relief following caesarean section.

METHODS

Forty patients were randomised after elective caesarean section to receive either intermittent 10-mL boluses of 0.125% levobupivacaine into the epidural space and physiologic saline into the surgical wound or intermittent 10-mL boluses of 0.25% levobupivacaine into the wound and epidural saline with a repeated 10-dose regimen. Analgesic efficacy was evaluated by numerical pain scores (0-10, 0=no pain, 10=worst pain) and based on the consumption of supplemental opioid. Side effects, patient satisfaction and plasma concentrations of levobupivacaine were recorded.

RESULTS

In the epidural group average pain scores were lower (1.8 vs. 3, P=0.006) and the consumption of local anaesthetic (29 mL vs. 38 mL, P=0.01) was smaller during the first four postoperative hours, after which both groups had pain scores of 3 or less at rest. All parturients were able to walk after the 24-h study period. The total consumption of rescue opioid oxycodone (32 vs. 37 mg, P=0.6) during the whole 72-h study period was low in both study groups. Side effects were mild and rare. Satisfaction scores were equally high in the two groups. Peak plasma concentrations of levobupivacaine were below the toxic range.

CONCLUSION

Incisional local analgesia via a subfascial catheter provided satisfactory pain relief with patient satisfaction comparable to that seen with epidural analgesia. This technique may be a good alternative to the more invasive epidural technique following caesarean section as a component of multimodal pain management.

Anesthetic efficacy of bupivacaine solutions in inferior alveolar nerve block

The purpose of this study was to compare the anesthetic efficacy of 2 bupivacaine solutions. Twenty-two volunteers randomly received in a crossover, double-blinded manner 2 inferior alveolar nerve blocks with 1.8 mL of racemic bupivacaine and a mixture of 75% levobupivacaine and 25% dextrobupivacaine, both 0.5% and with 1 : 200,000 epinephrine. Before and after the injection, the first mandibular premolar was evaluated every 2 minutes until no response to the maximal output (80 reading) of the pulp tester and then again every 20 minutes. Data were analyzed using the Wilcoxon paired test and the paired t test. No differences were found between the solutions for onset and duration of pulpal anesthesia and duration of soft tissue anesthesia (P > .05). It was concluded that the solutions have similar anesthetic efficacy.

Levobupivacaine and fentanyl for spinal anaesthesia: a randomized trial

BACKGROUND AND OBJECTIVE

Levobupivacaine 0.5% and racemic bupivacaine 0.5% are equally effective in spinal anaesthesia. Fentanyl has been used as an adjunct to racemic bupivacaine in spinal anaesthesia. At the time this study was designed, there was no published study on the intrathecal use of 0.5% levobupivacaine with fentanyl.

METHODS

This prospective, randomized, double-blind study compared the clinical efficacy, motor block and haemodynamic effects of using 2.6 mL of 0.5% levobupivacaine alone (25 patients) and 2.3 mL of 0.5% levobupivacaine with fentanyl 15 microg in 0.3 mL (25 patients) for spinal anaesthesia in urological surgery. The study solution was injected into the subarachnoid space at the L3-L4 interspace.

RESULTS

There were no significant differences between the two groups in the haemodynamic changes, and quality of sensory and motor block. Anaesthesia was adequate and patient satisfaction was good in all cases. Side-effects were minor and infrequent with both regimes.

CONCLUSIONS

We conclude that 2.3 mL of 0.5% levobupivacaine with fentanyl 15 microg is as effective as 2.6 mL of 0.5% levobupivacaine alone in spinal anaesthesia for urological surgery. Further studies may be directed to find the optimal combination of levobupivacaine and opioid with maximal haemodynamic stability and least motor block.

Minimum local anaesthetic dose (MLAD) of intrathecal levobupivacaine and ropivacaine for Caesarean section*

We determined the minimum local anaesthetic dose (MLAD) of spinal levobupivacaine and ropivacaine for Caesarean section. Ninety women were randomly allocated to two groups and received 3 ml of study solution by a combined spinal/epidural technique. The initial dose was 12 mg for levobupivacaine and 17 mg for ropivacaine groups. To be considered effective, a test solution had to achieve a visual analogue pain score (VAPS) of 30 mm or less at skin incision, uterine incision, birth, peritoneal closure, and at the end of surgery. Effective or ineffective responses determined, respectively, a 0.3 mg decrease or increase of the same drug for the next patient in the same group, using up-down sequential allocation. The MLAD of levobupivacaine was 10.58 mg (CI 95%: 10.08-11.09) and the MLAD of ropivacaine 14.22 mg (CI 95%: 13.67-14.77), using the Dixon and Massey formula. The potency ratio between spinal levobupivacaine and spinal ropivacaine was 1.34.

A double-blind comparison of 0.5% bupivacaine with 1:200,000 epinephrine and 0.5% levobupivacaine with 1:200,000 epinephrine for the inferior alveolar nerve block

This double-blind cross-over study compared the anesthetic success and onset and duration of lip and pulpal anesthesia of 0.5% bupivacaine and levobupivacaine solutions, both with 1:200,000 epinephrine, when administered for inferior alveolar nerve anesthesia. Thirty healthy volunteers were randomly anesthetized using one of the solutions. The inferior canine, second premolar, and molar were tested with electric stimulation. The pulpal anesthetic success rates for bupivacaine and levobupivacaine were 80% and 76.66%, respectively, for molars, 76.66% (both solutions) for premolars, and 70% (both solutions) for canines. At least 250 minutes of pulpal anesthesia was achieved. There were no significant differences between the solutions considering the measured parameters (P > .05). Because of the similar anesthetic behavior of the 2 solutions in this study and the low toxicity related in the literature for levobupivacaine, there is justification for replacing bupivacaine with levobupivacaine for inferior alveolar nerve local anesthesia.

[Levobupivacaine for regional anesthesia. A systematic review]

Levobupivacaine [S(-)bupivacaine], the levorotatory S-enantiomer of racemic bupivacaine, is commercially available in the U.S. and in most European countries. We performed a systematic review (MEDLINE database) and identified 88 articles on the clinical application of levobupivacaine in more than 3,000 patients. The use of levobupivacaine is described for epidural, caudal, and spinal anesthesia, for peripheral nerve blocks, for ophthalmic and dental anesthesia, for different pediatric indications and for intravenous regional anesthesia. In these regional techniques, levobupivacaine was used for all common indications in a wide range of clinical settings. Epidural levobupivacaine was combined with fentanyl, morphine, sufentanil, epinephrine, and clonidine, spinal levobupivacaine was combined with sufentanil, fentanyl, and epinephrine. In most studies, levobupivacaine was compared to bupivacaine and/or ropivacaine.

Pharmacokinetics of 0.5% levobupivacaine following ilioinguinal-iliohypogastric nerve blockade in children

BACKGROUND

Bupivacaine (2 mg kg(-1)) has been recommended for blockade of the ilioinguinal and iliohypogastric nerves in paediatric patients undergoing inguinal surgery. We determined the plasma concentrations of levobupivacaine following ilioinguinal-iliohypogastric block.

METHODS

Twenty children scheduled for elective surgery for inguinal surgery received 2 mg kg(-1) of 0.5% levobupivacaine. Surgical anaesthesia was maintained with mask inhalation of oxygen, nitrous oxide and sevoflurane. Venous blood samples were drawn at regular intervals up to 2 h and plasma was separated. Total venous plasma concentrations were determined by gas chromatography. Bupivacaine concentrations from a study with a similar protocol were used as historical controls for comparison.

RESULTS

The groups were similar with respect to age, weight and dosage of local anaesthetic. The initial distribution half-time (Talpha), the peak plasma concentration (Cmax) achieved, the time to the peak plasma concentration were similar (Tmax), and the mean areas under the concentration time curve (AUC) were similar between the two local anaesthetics.

CONCLUSIONS

Levobupivacaine and bupivacaine are equally absorbed to similar maximum concentrations.

Extending low-dose epidural analgesia for emergency Caesarean section using ropivacaine 0.75%

We compared ropivacaine 0.75% and bupivacaine 0.5% for extending low-dose epidural analgesia for emergency Caesarean section, using a prospective double-blind randomised controlled trial design. The trial was halted after 45 patients were studied (23 ropivacaine; 22 bupivacaine) because bupivacaine was replaced by levobupivacaine in our unit. Time to reach T4 for loss of cold sensation was similar in both groups, although analgesic supplementation was required less often in the ropivacaine group than in the bupivacaine group (2/23 vs. 9/21; p = 0.01).

Stereoselectivity in the placental transfer and kinetic disposition of racemic bupivacaine administered to parturients with or without a vasoconstrictor

The aim of the present study was to investigate the stereoselectivity in the kinetic disposition and the transplacental distribution of bupivacaine in term parturients during labor. Maternal age ranged from 18-37 years and fetal gestational age from 37.6-41.5 weeks. Healthy parturients (n = 23) received epidural 0.5% racemic bupivacaine alone (group A) or combined with epinephrine (group B). Maternal venous blood was sampled at regular intervals until 8 h after drug administration and umbilical venous blood was obtained at delivery. Bupivacaine enantiomers were determined in plasma samples by HPLC using a Chiralcel(R) OD-R column and a UV detector. One- or two-compartment models were fitted to data and differences between the (+)-(R) and (-)-(S) enantiomers were compared with the paired Wilcoxon test (P< 0.05). The influence of epinephrine was evaluated using the unpaired Mann-Whitney test (P< 0.05). The disposition of bupivacaine in maternal plasma was stereoselective, with higher V(d/f) (140.60 vs. 132.81 L for group A and 197.86 vs. 169.46 L for group B) and C(l/f) (29.00 vs. 25.43 L/h for group A and 33.15 vs. 26.39 L/h for group B) and lower t(1/2)beta (3.24 vs. 3.30 h for group A and 4.36 vs. 4.45 h for group B) being observed for (+)-(R)-bupivacaine. The combined administration of epinephrine resulted in higher V(d/f) (197.86 vs. 140.60 L for (+)-(R) and 169.46 vs. 132.81 L for (-)-(S)) and t(1/2)beta values (4.36 vs. 3.24 h for (+)-(R) and 4.45 vs. 3.30 h for (-)-(S)). The transplacental distribution of bupivacaine was stereoselective only when bupivacaine was administered without epinephrine (group B), with a higher cord blood/maternal blood ratio being observed for (-)-(S)-bupivacaine (0.40 vs. 0.35). Chirality 16:65-71, 2004.

The central nervous system and cardiovascular effects of levobupivacaine and ropivacaine in healthy volunteers

We compared the central nervous system (CNS) and cardiovascular effects of levobupivacaine and ropivacaine when given IV to healthy male volunteers (n = 14) in a double-blinded, randomized, crossover trial. Subjects received levobupivacaine 0.5% or ropivacaine 0.5% after a test infusion with lidocaine to become familiar with the early signs of CNS effects (e.g., tinnitus, circumoral paresthesia, hypesthesia). The development of CNS symptoms was assessed at 1-min intervals and study drug administration was terminated when the first CNS symptoms were recognized. Thereafter, symptoms were recorded at 1-min intervals until symptom resolution. Hemodynamic variables were assessed by transthoracic electrical bioimpedance. Continuous 12-lead electrocardiogram monitoring was also performed. There was no significant difference between levobupivacaine and ropivacaine for: the mean time to the first onset of CNS symptoms (P = 0.870), mean total volume of study drug administered at the onset of the first CNS symptom (P = 0.595), stroke index (P = 0.678), cardiac index (P = 0.488), acceleration index (P = 0.697), PR interval (P = 0.213), QRS duration (P = 0.637), QT interval (P = 0.724), QTc interval (P = 0.737), and heart rate (P = 0.267). Overall, fewer CNS symptoms were reported for levobupivacaine than ropivacaine (218 versus 277). This study found that levobupivacaine and ropivacaine produce similar CNS and cardiovascular effects when infused IV at equal concentrations, milligram doses, and infusion rates.

IMPLICATIONS

This study compared directly, for the first time, the toxicity of levobupivacaine and ropivacaine in healthy volunteers. Levobupivacaine and ropivacaine produced similar central nervous system and cardiovascular effects when infused IV at equal concentrations, milligram doses, and infusion rates.

New local anesthetics. Are they worth the cost?

Epidural analgesia that uses dilute concentrations of bupivacaine with fentanyl or sufentanil provides excellent analgesia, good sensory-motor discrimination, and minimal toxicity and is inexpensive. The new local anesthetic agents, ropivacaine and levobupivacaine, offer potential improvements in the risk of toxicity when administered in large doses but probably no important clinical difference when used in dilute concentrations for labor analgesia. After accounting for the potency difference, ropivacaine offers little or no motor-sparing advantage over bupivacaine. Currently, epidural anesthesia with concentrated bupivacaine is rarely used for cesarean section, so there is little indication for the newer anesthetic agents in this setting either. The authors believe that large difference in cost cannot be justified on the basis of currently available data.

The effects of analgesia in the vulnerable infant during the perinatal period

Although our knowledge of pain and its management in the perinatal period has increased, little is known about the first hours and days of life when major physiologic transition events occur. Prematurity and critical illnesses further complicate analgesic use during this time. Increased morbidity and mortality have been shown in infants receiving placebo infusions after surgery compared with infants with analgesia, highlighting the negative consequences of pain in infants. Opioids can help promote hemodynamic stability, promote respirator synchrony, and decrease the incidence of grade III & IV intraventricular hemorrhage in ventilated preterm neonates. Long-term follow-up studies suggest improved behavioral and cognitive outcomes in children given morphine infusions during NICU confinement. The necessity of fetal analgesia is dictated by the ability of the fetus to feel pain and by the adverse effects of noxious stimuli on future sensory development. Effects of drugs given to the pregnant woman on the (preterm) newborn might be influenced by decreased or absent transplacental transport, compression of the umbilical cord during delivery, or diminished blood flow in the placenta in pre-eclamptic women, resulting in higher serum concentrations. Pharmacokinetics and drug metabolism change in the last trimester, and pain sensitivity may be altered after 32 weeks of gestation. Consequently, dose and dose interval may vary considerably between neonates and within an individual during the first days of life. This subpopulation is not homogenous, and drug doses in a term neonate with a postnatal age of 2 weeks may be quite different from those at birth and are certainly different from those in a premature neonate. Size must be disentangled from age-related factors when examining developmental pharmacokinetic parameters. There are no longitudinal studies published investigating the pharmacokinetic properties of any analgesic more than once per infant. Polymorphisms of the genes encoding for the enzymes involved in the metabolism of analgesics or in genes involved in receptor expression may contribute to the large interindividual pharmacokinetic parameter variability. Polymorphism of the human mu opioid receptor has not yet satisfactorily explained pharmacodynamic variability.

Levobupivacaine versus racemic bupivacaine for spinal anesthesia

Levobupivacaine is the pure S(-)-enantiomer of racemic bupivacaine but is less toxic to the heart and central nervous system. Although it has recently been introduced for routine obstetric and nonobstetric epidural anesthesia, comparative clinical studies on its intrathecal administration are not available. We therefore performed this prospective randomized double-blinded study to evaluate the anesthetic potencies and hemodynamics of intrathecal levobupivacaine compared with racemic bupivacaine. Eighty patients undergoing elective hip replacement received either 3.5 mL levobupivacaine 0.5% isobaric or 3.5 mL bupivacaine 0.5% isobaric. Sensory blockade was verified with the pinprick test; motor blockade was documented by using a modified Bromage score. Hemodynamic variables (e.g., blood pressure, heart rate, pulse oximetry) were also recorded. Intergroup differences between levobupivacaine and bupivacaine were insignificant both with regard to the onset time and the duration of sensory and motor blockade (11 +/- 6 versus 13 +/- 8 min; 10 +/- 7 versus 9 +/- 7 min; 228 +/- 77 versus 237 +/- 88 min; 280 +/- 84 versus 284 +/- 80 min). Both groups showed slight reductions in heart rate and mean arterial pressure, but there was no intergroup difference in hemodynamics. We conclude that intrathecal levobupivacaine is equal in efficacy to, but less toxic than, racemic bupivacaine.

IMPLICATIONS

Levobupivacaine, the pure S(-)-enantiomer of racemic bupivacaine is an equally effective local anesthetic for spinal anesthesia compared with racemic bupivacaine.

A comparison of epidural levobupivacaine 0.5% with or without epinephrine for lumbar spine surgery

Levobupivacaine, the S(-) isomer of bupivacaine, is less cardiotoxic than racemic bupivacaine. In this prospective, randomized, double-blinded study of epidural anesthesia, we compared the onset, extent, and duration of sensory and motor blockade produced by plain 0.5% levobupivacaine (15 mL, 75 mg) with that of 0.5% levobupivacaine with the addition of 1:400,000 or 1:200,000 epinephrine in 117 patients undergoing elective spine surgery. The time to onset of adequate sensory block (T10 dermatome) was similar in all groups (12.4 +/- 6.6 min for plain levobupivacaine, 13.9 +/- 7.9 min for levobupivacaine with 1:400,000 epinephrine, and 12.7 +/- 4.9 min for levobupivacaine with 1:200,000 epinephrine), with an average peak block height of T5. Time to complete regression of sensory blockade was also similar between groups (357 +/- 119 min for plain levobupivacaine, 378 +/- 98 min for levobupivacaine with 1:400,000 epinephrine, and 348 +/- 80 min for levobupivacaine with 1:200,000 epinephrine). Peak serum levobupivacaine levels were reduced in each of the epinephrine-containing groups. We conclude that 0.5% levobupivacaine with or without 1:200,000 or 1:400,000 epinephrine produced effective epidural anesthesia in patients having lumbar spine surgery. Epinephrine 1:400,000 is as effective as 1:200,000 in reducing the resultant serum levobupivacaine levels after epidural anesthesia.

Levobupivacaine

Regional anaesthesia has seen the development of a new local anaesthetic: levobupivacaine. This review aims to outline the rationale underlying the development of levobupivacaine and to consider its place in modern regional anaesthesia.

Tolerability of large-dose intravenous levobupivacaine in sheep

In preclinical pharmacological studies of levobupivacaine (S-bupivacaine), we determined its tolerability, cardiovascular actions, and pharmacokinetics, and we estimated its margin of safety compared with bupivacaine in conscious sheep. Levobupivacaine HCl. H(2)O was infused IV for 3 min into 10 previously instrumented ewes (approximately 50 kg). On subsequent days, the doses were increased by 50 mg from 200 or 250 mg until fatality occurred. All doses produced convulsions, QRS widening, and cardiac arrhythmias. With incremental doses, 4 of 4 animals survived 200 mg, 7 of 10 survived 250 mg, 3 of 7 survived 300 mg, but 0 of 3 survived 350 mg. Death resulted from sudden onset ventricular fibrillation (n = 3, within 2-3 min), electromechanical dissociation-pump failure (n = 5, within 4-5 min), or ventricular tachycardia-induced cardiac insufficiency (n = 2, >10 min). The estimated fatal dose (mean +/- SD) was 277 +/- 51 mg for levobupivacaine (compared with 156 +/- 31 mg found previously for bupivacaine). Pharmacokinetic analysis indicated initial and total distribution volumes = 4.5 (+/-1.6) and 97 (+/-22) L, total clearance = 1.7 (+/-0.4) L/min, and slow half life = 70 (+/-29) min; these values did not differ from those found previously with smaller doses. Heart and brain tissue levobupivacaine concentrations were approximately 3 times those in arterial blood. The doses of levobupivacaine survived were larger than found previously for bupivacaine, indicating its greater margin of safety.

IMPLICATIONS

Levobupivacaine produced fatal cardiac toxicity at doses significantly greater than those found in previous studies with bupivacaine. As the two drugs have similar potency for producing clinical nerve blocks, the data imply that levobupivacaine should provide a safer alternative to bupivacaine in practice.

Levobupivacaine: a review of its pharmacology and use as a local anaesthetic

Based on findings that the cardiotoxicity infrequently observed with racemic bupivacaine shows enantioselectivity, i.e. it is more pronounced with the R(+)-enantiomer, the S(-)-enantiomer (levobupivacaine) has been developed for clinical use as a long acting local anaesthetic. The majority of in vitro, in vivo and human pharmacodynamic studies of nerve block indicate that levobupivacaine has similar potency to bupivacaine. However, levobupivacaine had a lower risk of cardiovascular and CNS toxicity than bupivacaine in animal studies. In human volunteers, levobupivacaine had less of a negative inotropic effect and, at intravenous doses >75 mg, produced less prolongation of the QTc interval than bupivacaine. Fewer changes indicative of CNS depression on EEG were evident with levobupivacaine. Levobupivacaine is long acting with a dose-dependent duration of anaesthesia. The onset of action is < or = 15 minutes with various anaesthetic techniques. In studies of surgical anaesthesia in adults, levobupivacaine provided sensory block for up to 9 hours after epidural administration of < or = 202.5 mg, 6.5 hours after intrathecal 15 mg, and 17 hours after brachial plexus block with 2 mg/kg. Randomised, double-blind clinical studies established that the anaesthetic and/or analgesic effects of levobupivacaine were largely similar to those of bupivacaine at the same dose. Sensory block tended to be longer with levobupivacaine than bupivacaine, amounting to a difference of 23 to 45 minutes with epidural administration and approximately 2 hours with peripheral nerve block. With epidural administration, levobupivacaine produced less prolonged motor block than sensory block. This differential was not seen with peripheral nerve block. Conditions satisfactory for surgery and good pain management were achieved by use of local infiltration or peribulbar administration of levobupivacaine. Levobupivacaine was generally as effective as bupivacaine for pain management during labour, and was effective for the management of postoperative pain, especially when combined with clonidine, morphine or fentanyl. The tolerability profiles of levobupivacaine and bupivacaine were very similar in clinical trials. No clinically significant ECG abnormalities or serious CNS events occurred with the doses used. The most common adverse event associated with levobupivacaine treatment was hypotension (31%).

CONCLUSIONS

Levobupivacaine is a long acting local anaesthetic with a clinical profile closely resembling that of bupivacaine. However, current preclinical safety and toxicity data show an advantage for levobupivacaine over bupivacaine. Clinical data comparing levobupivacaine with ropivacaine are needed before the role of the drug can be fully established. Excluding pharmacoeconomic considerations, levobupivacaine is an appropriate choice for use in place of bupivacaine.

Levobupivacaine

Each month, subscribers to The Formulary® Monograph Service receive five to six researched monographs on drugs that are newly released or are in late Phase III trials. The monographs are targeted to your Pharmacy and Therapeutics Committee. Subscribers also receive monthly one-page summary monographs on the agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation (DUE) is also provided each month. The monographs are published in printed Form and on diskettes that allow customization. Subscribers to the The Formulary Monograph Service also receive access to a pharmacy bulletin board called The Formulary InFormation Exchange (The F.I.X). All topics pertinent to clinical pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The November 1999 Formulary monographs are on rapacuronium, rabeprazole, zaleplon, alosetron, and ganirelix acetate. The DUE is on zaleplon.