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PubMed1990

[Axillary blockade of the brachial plexus using 60 ml prilocaine 0.5% vs. 40 ml prilocaine 1%. A clinical study of 144 patients carried out by the determination of the prilocaine concentration in the central venous blood and by the measurement of the subfascial pressure in the plexus following the injection].

We estimated in this study the efficacy of axillary plexus blockade with 60 ml prilocaine 0.5% (300 mg). Following electrostimulation of the median, radial or ulnar nerve (depending on the area of the hand to be operated on), we injected prilocaine in two groups of patients (large volume group, 60 ml prilocaine 0.5% in 20 s; n = 114 patients; normal volume group, 40 ml prilocaine 1% in 20 s; n = 30 patients). Anesthesia of the median and ulnar nerves was virtually complete in all patients, but anesthesia of the radial and musculocutaneous nerves was complete in only 67% (radial) and 75% (musculocutaneous) in the group with normal injection volume. The injection of a larger volume but a lower concentration of prilocaine (300 mg) achieved better anesthesia of the radial (81%) and musculocutaneous (92%) nerves by 30-60 min after the injection. This difference was significant (p less than 0.05). The measurement of higher subfascial pressure in the axillary plexus following the larger volume of 60 ml than after 40 ml could explain the improved efficacy in overcoming anatomical hindrances in the plexus space. Estimation of the prilocaine concentration in the central venous blood 120 min after injection did not reveal different plasma concentrations in the two groups. The plasma concentrations were far below toxic levels. Only the time of plasma peak was earlier in the group with the larger volume, which was attributed to the larger area of diffusion of the vascular system in the plexus space.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1999

Toxic methaemoglobin concentrations in premature infants after application of a prilocaine-containing cream and peridural prilocaine.

UNLABELLED: We report on a retrospective analysis of eight episodes of toxic methaemoglobinaemia in seven premature infants after the combined exposure to prilocaine by EMLA cream (12.5 mg prilocaine) and caudal anaesthesia (5.4-6.7 mg/kg prilocaine). The causative relationship between prilocaine and the infants' deterioration came to our attention through an anonymous voluntary incident-reporting system. The highest methaemoglobin concentration found was 30.6% (5.5 h after anaesthesia). All infants were symptomatic (mottled skin, paleness, cyanosis, poor peripheral perfusion) and two were exposed to unnecessary diagnostic and therapeutic procedures for unspecified deterioration in their conditions. Pharmacokinetic evaluation indicated a single compartment first-order elimination with a methaemoglobin half-life of 8 h. Normal levels (<1%) were reached 36 h after exposure to prilocaine. CONCLUSION: Whereas local skin application of prilocaine to premature babies is safe, peridural administration is not because premature infants are more sensitive to methaemoglobin inducing agents and tolerate methaemoglobinaemia less well.

Anesthesia, Caudal↗

PubMed1994

Simultaneous determination of lidocaine, prilocaine and the prilocaine metabolite o-toluidine in plasma by high-performance liquid chromatography.

An HPLC assay is described for the measurement of prilocaine and lidocaine (components of the local anesthetic cream EMLA) as well as the prilocaine metabolite, o-toluidine, in plasma. The method uses UV detection, is simple, sensitive and most important, only a single 200-microliters plasma sample is needed for simultaneous analysis of prilocaine, lidocaine and o-toluidine with a detection limit of 4 ng/ml. The plasma, together with the internal standard (bupivacaine) is extracted with diethyl ether under alkaline conditions, followed by the extraction of the analytes from the organic phase into dilute sulphuric acid. An aliquot of the acid extract is injected onto the HPLC system and the effluent is monitored by a UV detector.

Animals↗

PubMed2003

Effects of the prilocaine and of the association of prilocaine with different vasoconstrictors on the isolated hearts of rats.

This study aimed to observe the effects of prilocaine chloridate (P) and the associations of P with felypressin (P+F), and epinephrine (P+E) on the heart rate and force of contraction on the isolated hearts of rats. The hearts were perfused according to Langendorff's method. The experiments were performed with the following substances: prilocaine (P), felypressin (F), and epinephrine (E). P was used in doses of 1.25, 2.5, and 5.0 mg. The same doses of F and P (1.0, 1.5 and 3.0 microg) were used in association with the P, respectively. Right after the application of the three doses of P, a reduction in the force of contraction was observed, with higher intensity at a higher dose, which led to cardiac arrest. A similar result was obtained with the administration of the three associations of P+F. Also the application of the three associations P+E resulted in a reduction of the force of contraction, that was, however, less intense with the associations of 1.25 mg P + 1.0 microg E and 2.5 mg P+1.5 microg E, as compared to the same doses of P alone and P+F. The two higher doses of P and P+F on the heart rate elicited a significant reduction in relation to the control, but with the associations of P+E no alterations were observed, with any one of the doses used. The results obtained in the present study suggest that an association of P and E must be used in local anesthesia, since epinephrine may well protect the heart from the depressive effects of the anesthetic salts.

Animals↗

PubMed1991

[Fetal methemoglobinemia caused by prilocaine--is use of prilocaine for pudendal block still justified?].

17 women received 2 x 10 ml prilocaine 1% as a pudendal block sub partu. At delivery, the foetomaternal distribution ratio of the local anaesthetic was evaluated and the development of Met-Hb-concentration in the neonate was measured up to six hours post partum. The Met-Hb-concentration in the neonate was relatively low with a maximum of 1.8% after two hours, followed by a steady decline. A probable explanation for the Met-Hb-concentration could be the unexpected low foetomaternal ratio of distribution (0.5) and the increased renal elimination of the amide-type local anaesthetic in the neonate, respectively. According to these results, no contraindication for prilocaine in pudendal block is indicated.

Administration, Intravaginal↗

PubMed1987

Plasma concentrations of prilocaine and lidocaine and methaemoglobin formation in infants after epicutaneous application of a 5% lidocaine-prilocaine (EMLA).

The aim of the study was to measure the plasma levels of lidocaine and prilocaine after dermal application of EMLA in infants and to evaluate whether this procedure increases the levels of methaemoglobin (Met-Hb). Two groups of infants, 3-6 (n = 12) and 6-12 months (n = 10) of age, were studied. In total, 2 ml of EMLA was applied to 4 x 4 cm of skin surface for 4 h and blood samples for detection of Met-Hb and plasma levels of local anaesthetics were taken at 0, 2, 4 and 8 h after the application. After removal of the cream the infants were operated mainly for minor procedures under general anaesthesia. The plasma concentrations of lidocaine and prilocaine were in all cases below toxic levels and there were only minor increases in Met-Hb in a few infants. In conclusion, EMLA can be used safely in infants above 3 months of age provided that the recommendations with regard to dose, application area and time are followed. The use of EMLA in smaller infants and in children taking other Met-Hb-inducing drugs needs further evaluation.

Administration, Topical↗

PubMed1999

Pharmacokinetics of prilocaine after intravenous administration in volunteers: enantioselectivity.

BACKGROUND: Prilocaine exists in two stereoisomeric configurations, the enantiomers S(+)- and R(-)-prilocaine. The drug is clinically used as the racemate. This study examined the pharmacokinetics of the enantiomers after intravenous administration of the racemate. METHODS: Ten healthy male volunteers received 200 mg racemic prilocaine as a 10-min intravenous infusion. Blood samples were collected for 8 h after the start of the infusion. Plasma concentrations were measured by stereoselective high-performance liquid chromatography (HPLC). Unbound fractions of the enantiomers in blank blood samples, spiked with racemic prilocaine, were determined using equilibrium dialysis. RESULTS: The unbound fraction of R(-)-prilocaine (mean +/- SD, 70%+/-8%) was smaller (P < 0.05) than that of S(+)-prilocaine (73%+/-5%). The total plasma clearance of R(-)-prilocaine (2.57+/-0.46 l/min) was larger (P < 0.0001) than that of S(+)-prilocaine (1.91+/-0.30 l/min). The steady-state volume of distribution of R(-)-prilocaine (279+/-94 l) did not differ from that of S(+)-prilocaine (291+/-93 l). The terminal half-life of R(-)-prilocaine (87+/-27 min) was shorter (P < 0.05) than that of S(+)-prilocaine (124+/-64 min), as was the mean residence time of R(-)-prilocaine (108+/-30 min) compared with S(+)-prilocaine (155+/-59 min; P < 0.005). CONCLUSIONS: The pharmacokinetics of prilocaine are enantioselective. The difference in clearance is most likely a result of a difference in intrinsic metabolic clearance. The difference in the pharmacokinetics of the enantiomers of prilocaine does not seem to be clinically relevant.

Adult↗

PubMed2004

Liposomal prilocaine: preparation, characterization, and in vivo evaluation.

PURPOSE: This study reports the development and in vivo evaluation of a liposomal system for the local anesthetic, prilocaine. METHODS: Liposomal prilocaine was prepared with egg phosphatidylcholine, cholesterol and a-tocopherol (4:3:0.07 molar ratio). The size of the liposomes was measured by laser light scattering and the effect of prilocaine on membrane fluidity made use of electron spin resonance (ESR). The anesthetic effect of liposomal prilocaine was compared to that of plain prilocaine solution (with or without vasoconstrictor) in a rat infraorbital nerve blockade model. RESULTS: Laser light-scattering analysis showed one major vesicle population of liposomes with ca 400 nm (100%), without size changes after prilocaine incorporation. The ESR results showed a decrease in the orientation of the phospholipid molecules into the liposomes (ca 11%) in the presence of prilocaine, which characterized the prilocaine-liposome interaction. A prolongation of anesthetic effect was produced by liposomal prilocaine in comparison to plain prilocaine (without vasoconstrictor, p<0.001). However, no statistical differences were found after comparison between liposomal prilocaine and vasoconstrictor-containing prilocaine. CONCLUSIONS: We suggest that the encapsulation of prilocaine in liposomes facilitates the controlled release of prilocaine (increasing the time of duration of the sensory nervous blockade) and constitutes a good choice to replace vasoconstrictor-containing local anesthetic formulations.

Anesthetics, Local↗

PubMed1997

Efficacy and safety of lidocaine-prilocaine cream for pain during circumcision.

BACKGROUND: Neonatal circumcision is a painful surgical procedure often performed without analgesia. We assessed the efficacy and safety of 5 percent lidocaine-prilocaine cream (Emla) in neonates undergoing circumcision. METHODS: We carried out a double-blind, randomized, controlled trial in 68 full-term male neonates: 38 were assigned to receive lidocaine-prilocaine cream, and 30 to receive placebo. One gram of lidocaine-prilocaine or placebo cream was applied to the penis under an occlusive dressing for 60 to 80 minutes before circumcision. Behavioral (facial activity and time spent crying) and physiologic (heart rate and blood pressure) responses were recorded during the procedure. Blood samples were obtained at various times after drug application for measurements of methemoglobin and plasma lidocaine, prilocaine, and o-toluidine (a metabolite of prilocaine). RESULTS: A total of 68 and 59 neonates were included in the safety and efficacy analyses, respectively. Demographic characteristics such as gestational age and birth weight did not differ between the lidocaine-prilocaine and placebo groups. During circumcision, the neonates in the lidocaine-prilocaine group had less facial activity (P= 0.01), spent less time crying (P<0.001), and had smaller increases in heart rate (P=0.007) than the neonates in the placebo group. Facial-activity scores were 12 to 49 percent lower during various steps of the procedure in the lidocaine-prilocaine group. As compared with neonates in the placebo group, infants in the lidocaine-prilocaine group cried less than half as much and had heart-rate increases of 10 beats per minute less. Blood methemoglobin concentrations (expressed as a percentage of the hemoglobin concentration) were similar (1.3 percent) in both groups. Lidocaine and prilocaine were detected in plasma in 23 (61 percent) and 21 (55 percent) of the infants treated with lidocaine-prilocaine cream, respectively. CONCLUSIONS: Lidocaine-prilocaine cream is efficacious and safe for the prevention of pain from circumcision in neonates.

Anesthesia, Local↗

PubMed1999

Prilocaine induces apoptosis in osteoblastic cells.

PURPOSE: To determine whether prilocaine, a local anesthetic, induces apoptosis in osteoblastic cells. METHODS: After reaching subconfluence, human osteoblastic Saos-2 and MG63 cells and mouse osteoblastic MC3T3-E1 cells were exposed for 48 hr to varying concentrations of prilocaine up to 10 mM and the cytotoxicity of the cells was analyzed by phase-contrast microscopy and WST-1 assay. Saos-2 cells treated for 48 hr with 5 mM prilocaine were stained with Hoechst 33342 and nuclear fragmentation was examined under a fluorescence microscope. DNA was extracted from the cells treated with 5 mM prilocaine and DNA ladder formation (a hallmark of apoptosis) was analyzed by agarose gel electrophoresis. RESULT: Prilocaine induced cell death in Saos-2 cells in a dose- and time-dependent manner up to the concentration of 10 mM. Marked nuclear condensation and fragmentation of chromatin were observed in the prilocaine-treated cells. DNA ladder formation also was induced by prilocaine treatment. Prilocaine-induced DNA ladder formation was dose-dependent with maximal effect at a concentration of 5 mM and was time-dependent from 12 to 48 hr. DNA ladder formation was also induced by prilocaine treatment in human osteoblastic MG63 cells and mouse osteoblastic MC3T3-E1 cells. Cycloheximide prevented prilocaine-induced apoptosis in Saos-2 cells in a dose-dependent fashion up to 20 microM as determined by WST-1 assay and DNA ladder formation in agarose gel electrophoresis. CONCLUSION: Osteoblastic cells treated with prilocaine exhibit both morphological and biochemical features indicative of apoptosis. The apoptotic mechanisms involve transcriptional regulation of specific proteins or protein synthesis.

Anesthetics, Local↗

PubMed1996

Effects of prilocaine local anaesthetic solutions on pulpal blood flow in maxillary canines.

The effects of prilocaine local anaesthetic solutions on pulpal blood flow (PBF) in maxillary canines were investigated in nine adult subjects. Buccal infiltration of 2 ml of the following solutions were carried out: 3% prilocaine; 3% prilocaine with 0.03 IU/ml felypressin; and 3% prilocaine with 1:100,000 adrenaline. Blood flow in the anaesthetized tooth was monitored by a laser Doppler flowmeter and data stored in a computer. An electric pulp tester was used to assess pulpal anaesthesia. The duration of anaesthesia was recorded. After administration of plain prilocaine, PBF changed little throughout the experiment in all nine subjects. When prilocaine with felypressin was injected. PBF fluctuated greatly, but there was no sustained increase or decrease. In comparison, prilocaine with adrenaline caused a significant decline in PBF in every subject (p < 0.05), but then gradually started to return to the pre-injection level: there was no such change in PBF of the contralateral tooth. Injection of 3% plain prilocaine achieved a short duration of pulpal anaesthesia (median 7 min) in only three subjects. When prilocaine with felypressin was injected, eight out of nine subjects experienced pulpal anaesthesia (median duration 10.5 min). Injection of prilocaine with adrenaline caused pulpal anaesthesia in six of nine subjects (median duration 10.5 min). The use of vasoconstrictors with prilocaine anaesthetics had less pronounced effects on blood flow and shorter periods of anaesthesia than those reported previously for lignocaine with adrenaline.

Adult↗

PubMed1988

[Clinical effectiveness and systemic toxicity of various mixtures of prilocaine and bupivacaine in axillary plexus block].

The presently existing local anesthetics (LA) do not guarantee a rapid onset and simultaneously a long duration of action. The combination of a medium-long acting LA with bupivacaine, a long-acting LA with slow onset, could be means to achieve these aims. Prilocaine was chosen as the medium-long acting LA because it has the lowest toxicity of this group and for pharmacological reasons. METHODS. In a prospective, controlled double-blind study 100 patients scheduled for axillary block for elective surgical procedures of the hand or wrist were randomly assigned to five groups. Twenty patients in each group received either 40 ml prilocaine 1.5%; 40 ml bupivacaine 0.375%; 20 ml prilocaine 1% + 20 ml bupivacaine 0.5%; 20 ml prilocaine 2% + 20 ml bupivacaine 0.5%; or 20 ml prilocaine 2% + 20 ml bupivacaine 0.375%. The LA mixtures were freshly mixed 15 min prior to the axillary block. The blocks were performed using an immobile, short-beveled needle by anesthesiologists who were familiar with this technique. Analgesia was classified using the pin-prick method with 0 = no analgesia, 1 = analgesia, 2 = anesthesia. Motor blockade was classified with 0 = no motor block, 1 = paresis, 2 = paralysis. The following nerves were analyzed: ulnar, radial, median, musculocutaneous, and medial antebrachial. In 6 patients of each group plasma levels of the LA were measured by gas chromatography and methemoglobinemia was determined. Statistical analysis of the data was performed using the Student t-test and chi-square test on a level of significance of P less than 0.05. Results. All surgical procedures could be performed as planned in regional anesthesia. Twenty minutes after injection of the LA only 15% of the blocks were sufficient in the bupivacaine group, while in the other four groups 40%-50% of the blocks were complete (P less than 0.05). The degree of analgesia was deeper in the groups with 2% prilocaine and prilocaine alone than in the group with 1% prilocaine. Forty minutes after injection there were no significant differences between the groups. Motor blockade after 20 min was significantly lower in the bupivacaine group than in the prilocaine group (P less than 0.05). After 4 h all three prilocaine-bupivacaine mixtures showed a significantly more pronounced analgesia of the median nerve than the prilocaine group (P less than 0.02-0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1999

Relative efficacy of amethocaine gel and lidocaine-prilocaine cream for Port-a-Cath puncture in children.

BACKGROUND: Lidocaine-prilocaine cream (EMLA) is currently standard therapy to alleviate procedural pain in children. One of the disadvantages of lidocaine-prilocaine is the need to wait for 60 minutes for adequate skin anesthesia. Amethocaine gel (Ametop) is a new topical anesthetic that requires a shorter application time for skin anesthesia. OBJECTIVES: To compare the relative efficacy and safety of amethocaine gel and lidocaine-prilocaine cream in children with cancer undergoing Port-a-Cath puncture and to determine which patient factors influence judgments about pain. METHODS: Randomized, blinded, crossover study. Each child received either 1 g of amethocaine gel for 30 minutes, preceded by a placebo gel for 30 minutes, or 1 g of lidocaine-prilocaine cream for 60 minutes. Children rated the pain using the faces scale, for which scores ranged from 0 to 5. Parents and attending nurse operators rated pain on a 10-cm visual analog scale. RESULTS: Thirty-nine children participated. The mean age was 10.2 years (range: 5-16 years), and 69% were male. There were no differences in mean pain assessments between amethocaine and lidocaine-prilocaine as rated by the children (2.0 vs 0.5), parents (2.6 vs 6.4), or nurse operators (2.0 vs 0.9). No serious adverse effects were detected with either preparation. Pain scores assigned by parents and children were not influenced by age, gender, duration of diagnosis, or anesthetic regimen (amethocaine versus lidocaine-prilocaine) in the child. Nurses, however, rated pain higher for younger children, and in males during pretreatment with lidocaine-prilocaine. CONCLUSION: Amethocaine achieves similar anesthesia to lidocaine-prilocaine during Port-a-Cath administration in children, with an application time that is half of lidocaine-prilocaine. Pain assessments were not influenced by age, gender, or duration of diagnosis of the child. Nurses may perceive that pain is greater for younger children and in males. lidocaine-prilocaine, amethocaine, pain, children, Port-a-Cath puncture.

Adolescent↗

PubMed2004

Prilocaine plasma levels and methemoglobinemia in patients undergoing tumescent liposuction involving less than 2,000 ml.

BACKGROUND: As a reaction to reported adverse outcomes after lidocaine infiltration in tumescent liposuction, prilocaine has gained increasing popularity. Previous studies investigating large-volume liposuction procedures found maximum prilocaine levels and methemoglobinemia up to 12 h postoperatively, suggesting that liposuction should be performed as a hospital procedure only. The aim of this study was to determine prilocaine plasma levels and methemoglobinemia in patients after low- to average-volume liposuction for the purpose of defining the required postoperative surveillance period. METHODS: In 25 patients undergoing liposuction involving less than 2,000 ml prilocaine levels and methemoglobinemia were measured over 4 h postoperatively. Liposuction was conducted after the tumescent technique using a 0.05% hypotonic prilocaine solution with epinephrine. RESULTS: The average prilocaine dose was 6.8 + 0.8 mg/kg, with a maximum dose of 15 mg/kg. The peak prilocaine plasma level of 0.34 mug/ml occurred 3 h after the infiltration. The mean methemoglobinemia at this time point was 0.65%. Only one patient demonstrated a slightly elevated methemoglobin level of 1.4%, but lacked any clinical signs of methemoglobinemia. The prilocaine recovery in the aspirate averaged 36 +/- 4%, indicating that a large amount is removed by suctioning. CONCLUSIONS: The patients did not experience high plasma levels of prilocaine or methemoglobinemia undergoing liposuction involving less than 2,000 ml using a 0.05% hypotonic prilocaine solution. The authors therefore conclude that this procedure can be performed safely with a monitoring period of 12 h.

Adult↗

PubMed1991

The addition of sodium bicarbonate to prilocaine solution during i.v. regional anesthesia.

A comparison of plain prilocaine and bicarbonated prilocaine in intravenous regional anesthesia was studied in 30 patients undergoing upper extremity surgery. The patients were divided into two groups: one group was given anesthesia in the form of 1% prilocaine and the other group was given 1% prilocaine plus sodium bicarbonate. The onset of analgesia and anesthesia and recovery from analgesia and anesthesia were investigated in both groups. Bicarbonated prilocaine produced faster onset of analgesia when compared with plain prilocaine (P less than 0.01). The onset of anesthesia and recovery from analgesia and anesthesia were not statistically different between the two groups. Clinically, the intensity of anesthesia was better when bicarbonated prilocaine solution was used instead of plain prilocaine. We conclude that bicarbonated prilocaine is better than plain prilocaine during IVRA.

Adult↗

PubMed1999

Topical lidocaine-prilocaine versus lidocaine for neonatal circumcision: a randomized controlled trial.

OBJECTIVE: To evaluate epicutaneous application of 5% lidocaine-prilocaine and 30% lidocaine cream anesthetics for neonatal circumcision. METHODS: The efficacy of 5% lidocaine-prilocaine and 30% lidocaine creams was compared in a randomized, double-blind, placebo-controlled trial. Sixty-one neonates were randomly assigned to one of three groups: 5% prilocaine-lidocaine (n = 20), 30% lidocaine (n = 20), and a control group that received an acid-mantle cream (n = 21). Heart rate, oxygen saturation, and crying time were monitored before, during, and after circumcision. Blood pressure was measured before and after circumcision. RESULTS: Mean peak heart rates for the 5% lidocaine-prilocaine, 30% lidocaine, and control groups (+/- standard deviation) were 146 +/- 16, 157 +/- 10, and 164 +/- 16 beats per minute, respectively. During four of six active phases of circumcision, the 5% lidocaine-prilocaine group suppressed significant increases in heart rate better than 30% lidocaine, which was more effective than control (dorsal clamp, P < .001; bell clamp on, P = .001; tightening, P = .001; bell clamp off, P < .001). During tightening of the bell clamp, significantly less crying was seen in the 5% lidocaine-prilocaine group (13 +/- 12 seconds) compared with 30% lidocaine (24 +/- 14 seconds) and controls (38 +/- 27 seconds) (P < .001). The group that received 5% lidocaine-prilocaine also had no significant increase in systolic (t = 1.6, P = .12) or diastolic (t = 1.9, P = .067, respectively) blood pressure, unlike the group receiving 30% lidocaine (t = 4.8, P = .001 and t = 2.9, P = .009, respectively) and the placebo group (t = 2.5, P = .023 and t = 2.3, P = .032). There were no significant differences in oxygen saturation (alpha = .05, power 0.79). CONCLUSION: Epicutaneous 5% lidocaine-prilocaine was more effective than 30% lidocaine for neonatal circumcision, better reducing neonatal stress indicators. Lidocaine-prilocaine significantly shortened crying time during one of the most painful phases of circumcision. Both topical anesthetics were more effective than placebo in attenuating the behavioral and physiologic indicators of neonatal pain.

Anesthesia, Local↗

PubMed1995

Prilocaine elimination by isolated perfused rat lung and liver.

Prilocaine is assumed to undergo significant elimination by extrahepatic organs and to differ in this respect from other commonly used local anaesthetics. In order to clarify whether the lung may play an important role as a site of elimination of prilocaine, the kinetic parameters were studied in isolated perfused rat lungs and were compared to those of isolated livers. Furthermore, the structurally related compounds bupivacaine and mepivacaine were also investigated in this system. Prilocaine was dispersed into a relatively large apparent distribution volume in perfused rat lung (139 ml versus 97 ml in controls). In single-pass perfused lungs the observed maximum of concentration was decreased by about 60% compared to controls. The mean residence time was prolonged by about 40%. These observations suggest that prilocaine is substantially retained by rat lung and that this effect occurs particularly during first-pass. However, the ability of rat lung to degrade prilocaine was relatively low. The clearance values were about 0.3 ml/min equal to about 20% of the hepatic capacity calculated per g of tissue. Thus it must be assumed that prilocaine is only transiently retained by the lung and will gain systemic availability later on. In rat lungs the kinetics of prilocaine elimination were not substantially different from those of bupivacaine and mepivacaine (16 and 12%). These observations do not support the assumption that especially prilocaine undergoes extrahepatic elimination.

Animals↗

PubMed1996

[Combined "3-in-1"/sciatic nerve block. Block effectiveness, serum level and side effects using 700 mg mepivacaine 1% without and with adrenaline and prilocaine 1%].

UNLABELLED: A high dose of local anaesthetic is necessary for the combined "3-in-1"/sciatic nerve block. Prilocaine is recommended for its low toxicity. However, in some patients prilocaine results in pronounced methaemoglobin formation due to toludine. Little has been known hitherto about the use of high-dose mepivacaine for the combined 3-1/sciatic nerve block. This study was undertaken to compare the use of 700 mg mepivacaine 1% and of 700 mg prilocaine 1%. METHODS: The study was approved by the ethics committee of our hospital. Once their informed consent had been obtained in writing 3 x 20 patients (ASA 1-2) undergoing planned surgery on the foot or ankle joint were enrolled in the study. The patients were randomized to the following three groups on a double-blind basis: group 1,700 mg mepivacaine without epinephrine; group 2,700 mg mepivacaine with 0.2 mg epinephrine (1:350,000); group 3,700 mg prilocaine 1%. Arterial blood samples for determination of local anaesthetic serum levels were collected over a 120-min period. We determined methaemoglobin and oxygen saturation before and 120 min after the blockade and continued these measurements for 6 h in group 3. At 15-min intervals, all patients were questioned about early signs of toxicity. The perioperative monitoring including blood pressure, ECG and pulse oximetry. Data were analysed using ANOVA and Student's t-test, P < 0.05 considered statistically significant. RESULTS: The blocking efficacy did not differ among the groups (groups 1, 2, 3:90%, 95%, 90%). The maximum mepivacaine serum level in group 1 was 3.91 micrograms/ml +/- 0.95 and 2.94 micrograms/ml +/- 0.58 in group 2 (Fig. 2). Over the entire observation period the addition of epinephrine resulted in a significant reduction of the serum level (between 60.3% at t = 15 min and 19.7% at t = 120 min). In the prilocaine group the maximum serum level was 2.07 micrograms/ml +/- 0.56, significantly less than in either mepivacaine group. No patient showed signs or symptoms of local anaesthetic toxicity. In the prilocaine group there was wide variation in methaemoglobin formation among the patient, with a median of 10.1% (Fig. 3, Table 3). Three patients showed a maximum methaemoglobinemia between 16% and 17%. Five patients were still cyanotic after 6 h when they were transferred to the ward. The fractional SaO2 values amounted to 88% (median) with a minimum of 80.3%. CONCLUSION: Both mepivacaine 1% and prilocaine 1% are appropriate local anaesthetics for the combined 3-in-1/sciatic nerve block at a dose of 700 mg. There was no difference in the blocking efficacy. No patient showed clinical signs or symptoms of a local anaesthetic toxicity. Following prilocaine we are sometimes faced with high methaemoglobinemia, which may necessitate prolonged monitoring.

Adult↗