Atracurium, one of the newly developed nondepolarizing muscle relaxants, is remarkable due to the intermediate duration of action from the other previously known nondepolarizing agents and the broad safety margin in patients with renal or liver disease. There have been many reports suggesting that the pharmacologic effects of the nondepolarizing muscle relaxants are influenced by dosage. In this study, we attempted to identify the specific mechanism of muscle relaxation of atracurium. Particular attention was paid to the actually delivered atracurium dose and to the degree of muscle relaxation in rabbits. The results were as follows; 1) In the atracurium 0.4 mg/kg group, the onset of action was shortened and in the atracurium 0.6 mg/kg group, it was shortened more significantly. 2) The duration of action was increased with the increase of dose: the mean duration was 895 seconds in the atracurium 0.1 mg/kg group, 1,113.7 seconds in the 0.2 mg/kg group, and 1,199.3 second is in the 0.4 mg/kg group. It was prolonged to 1,730 seconds in the atracurium 0.6mg/kg group. 3) The spontaneous recovery index showed no differences in the atracurium 0.1 mg/kg group, 0.2 mg/kg group and 0.4 mg/kg group (196.7 sec., 195.0 sec, 202.7 sec. each). But in the atracurium 0.6 mg/ kg group, it was markedly prolonged to 334 seconds. In conclusion, atracurium, like other nondepolarizing agents, produces a dose related duration of action in muscle relaxation.
Atracurium* ; Humans ; Liver Diseases ; Muscle Relaxation* ; Rabbits*

The interaction between succinylcholine(SCC) and non-depolarizer; atracurium or vecuronium, was investigated in 36 cats of either sex using the sciatic nerve-anterior tibialis muscle preparation. And also, its relation to the pseudocholinesterase activity was examined. The duration of action of vecuronium(6.5+/-1.3 to 7.3+/-2.2 minutes) in cats pretreated with SCC was greater than those(2.0+/-0.6 minutes) in non-pretreated cats. However, SCC had no influence on the duration of atracurium. The serum pseudocholinesterase activity was decreased after the injection of atracurium or neostigmine in contrast to vecuronium. The authors conclude that the prior administration of SCC prolongs the duration of vecuronium but not that of atracurium, and pseudocholinesterase activity is not related to the prolonging effect of SCC.
Animals ; Atracurium* ; Cats* ; Neostigmine ; Pseudocholinesterase ; Succinylcholine* ; Vecuronium Bromide*

The neuromuscular blocking effsct of mivscurium 0.15mg/kg and atracurium 0.5mg/kg were compared in 17 adult patients (ASA class I and II) during N2O propofol-fentanyl anesthesia. Neuromuscular transmission was monitored by recording the compound electromyogram of the hypothenar muscles resulting from supramaximal train of four stimulation applied to the ulnar nerve. Neuromuscular block was recovered spontaneously in all cases. Onset time of over 95% block was not different significantly between mivacurium and atraeurium (201+/-37.6vs 176.6+/-28.5sec, p>0.05, mean SD). Duration from injection of mivacurium to 25% recovery of control twitch height was significantly shorter than that of atracurium (13.0+/-2.2vs 38.8+/-4.9min, p<0.05). The recovery index was also significantly shorter for mivacurium than for atracurium (6.9+/-1.1vs 14.5+/-53.0min, p<0.05). In conclusion, we have confirmed that duration and recovery of action of mivacurium were shorter than those of atracurium, but onset times of both agents were not different.
Adult* ; Anesthesia* ; Atracurium* ; Humans ; Muscles ; Neuromuscular Blockade* ; Ulnar Nerve

BACKGROUND: The train-of-four(TOF) fade known as expression of prejuntional receptor binding was useful for evaluating the residual neuromuscular blockade(NMB). The present study was undertaken to investigate the effect of the neostigmine(Neo) on TOF ratio during the recovery from vecuronium(V) or atracurium(A) induced NMB under the general anesthesia. METHODS: Forty healthy adult patients were randomly divided into 4 groups as follows; spontaneous recovery from V-induced NMB(V-C group) or A-induced NMB(A-C group), reversed recovery with Neo at 20% recovery of control first twitch height(T) from V-induced NMB(V-R group) or A-induced NMB(A-R group). TOF ratio at 25 and 75% recovery of T and recovery index(RI) defined as time from 25 to 75% recovery of T were measured. RESULTS: TOF ratios at 25 and 75% recovery of T were 3.7 & 35.8%(V-C group), 8.4 & 46.9%(A-C group), 3.7 & 48.7%(V-R group) and 15.2 & 55.6%(A-R group) respectively(P>0.05). RI were 19.2 min(V-C group), 19.5 min(A-C group), 3.5 min(V-R group), and 5.6 min(A-R group) respectively (P<0.05). CONCLUSIONS: RI were significantly shortened in reversed recovery groups with Neo than spontaneous recovery groups (P<0.05). However TOF ratio at 75% recovery of T1 were not significantly different between spontaneous recovery and reversed recovery groups.
Adult ; Anesthesia, General ; Atracurium ; Humans ; Neostigmine* ; Neuromuscular Blockade* ; Vecuronium Bromide

The purpose of this study is to investigate the effects of doxapram on the rates of spontaneous and neostigmine-induced recovery from neuromuscular block with vecuronium and atracurium. Following intravenous injection of either vecuronium (40 patients) or atracurium (40 patients), recovery index (RI) was measured without administering either doxapram or neostigmine (Group 1), or after administration of a combination of neostigmine 40 ug/kg and doxapram 1 mg/kg (Group 2), neostigmine 40 ug/kg (Group 3) or doxapram 1 mg/kg (Group 4) when twitch tension returned to 25% block of train of four response, each of the four group had 10 patients. The results were such that RI was significantly prolonged after vecuronium in the presence of doxapram compared with Group 1 (13.5 min vs 8.2 min). There was no significant difference in the RI after atracurium in the presence of doxapram compared with Group 1 (7.0 min vs 7.1 min). There was rapid recovery which was significant when neostigmine was administered with or without doxapram (2.4 min vs 2.3 min respectively after vecuronium; 2.3 min vs 2.4 min respectively after atracurium). The authors conclude that administration of doxapram in situation where neuromuscular block with vecuronium is not adequately antagonized does not contribute to rapid recovery from neuromuscular block.
Atracurium* ; Doxapram* ; Humans ; Injections, Intravenous ; Neostigmine ; Neuromuscular Blockade ; Vecuronium Bromide*

A major goal in pharmacokinetic-pharmacodynamic (PK/PD) modeling of neuromuscular blockade (NMB) is to quantitatively estimate the dose-response relationship.Our PK/PD model consists of three submodels:PK, link kinetics, and PD.A virtual effect compartment in which the drug concentration is in equilibrium with the observed concentration is used to extract the kinetic component (keo) from the pharmacodynamic data alone.Parameters of this model are keo, Ce(50), and gamma.The underlying structural pharmacokinetics and pharmacodynamics for NMB have been well understood, and new novel PK/PD models have been substituted for the gold standard PK/PD model for NMB.The purpose of this review was to describe progress in the field of PK/PD modeling of NMB from the first model, a simultaneous PK/PD model developed by Sheiner et al in the 1970s, to some of the more complicated models.Specific PK/PD models, which accurately described the behaviors of rocuronium, mivacurium, atracurium, and cisatracurium, include the recirculatory model, the peripheral link model, the peripheral elimination model, and a nonparametric model for link kinetics.
Aluminum Hydroxide ; Androstanols ; Atracurium ; Carbonates ; Isoquinolines ; Kinetics ; Neuromuscular Blockade

BACKGROUND: Atracurium, a nondepolarizing muscle relaxant, is eliminated by Hofmann elimination and not affected by pseudocholinesterase(pChe). Many reports show fall in pChe activity during pregnancy and our measurement failed to prove it. However, the authors found previously the infusion rate of mivacurium, which is metabolized by pChe, to achieve surgical relaxation is decreased. So, we compared the difference in the infusion rate of atracurium between full-term pregnant and nonpregnant women. METHODS: Muscle relaxation of full-term pregnant women(C group, n=10) and nonpregnant women (Non-C group, n=10) was maintained by continuous infusion of atracurium to keep 1st response of TOF at 5 1%. After discontinuance of infusion, recovery index was measured without reversals using the accelerograph. RESULTS: There was no significant difference in infusion rate of atracurium to maintain 1st twitch response of TOF at 5 1% and recovery index between two groups. There was little correlation between the total infusion time and infusion rate, or between the total infusion time and recovery index. CONCLUSION: The atracurium infusion rate in parturients to maintain muscle relaxation was not different from that in non-parturients. For Cesarean section, the usual infusion rate of atracurium is recommended to achieve the adequate surgical relaxation.
Atracurium* ; Cesarean Section* ; Female ; Humans ; Muscle Relaxation ; Obstetrics ; Pregnancy ; Relaxation

BACKGROUND: Succinylcholine is metabolized by plasma cholinesterase (PChE). When it was pretreated by small doses of nondepolarizing muscle relaxants in order to minimize the side effects, there are evidences to be associated with alteration in the duration of action. This study is investigated whether the responses would be related to the enzymatic activities. METHODS: In 21 adult patients, ASA class I or II, PChE levels were measured by the modified Garry method after induction of anesthesia (control value) and at 3, 10, 20 and 30 min following administration of pancuronium 0.1 mg/kg, vecuronium 0.1 mg/kg and atracurium 0.5 mg/kg. Data were expressed as mean (SEM). RESULTS: The levels of PChE were significantly lower (p<0.05) than the control values at 3, 10, 20 and 30 min after given pancuronium as 4764 (270), 4777 (261), 4796 (306) and 4740 (332) IU/L respectively and after given vecuronium as 5004 (341), 5051 (329), 4969 (340) and 4960 (340) IU/L respectively whereas enzyme levels after given atracurium were not significant differences to compare the control values as 5153 (336), 5136 (320) 5124 (312) and 5151 (275) respectively. CONCLUSIONS: The results of present study show that both pancuronium and vecuronium may possibly inhibit PChE activity but this was not affected by atracurium.
Adult ; Anesthesia ; Atracurium* ; Cholinesterases* ; Humans ; Pancuronium* ; Plasma* ; Succinylcholine ; Vecuronium Bromide*

The usefulness of nondepolarizing muscle relaxants for intubation is limited by a relatively slow onset of neuromuscular block compared to that achived with succinylcholine. But, authors have reported that larger doses of nondepolarizing muscle relaxants produce a more rapid onset of maximal neuromuscular block and conditions conductive to endotracheal intubation and recent reports support the use of the "priming principle in the clinical practice of anesthesiology. This phenomenon may apply to all nondepolarizing relaxants: it is reported to facilitated neuromuscular blockade and tracheal intubation when used with atracurium, vecurouium, alcuronium or pancuronium. In this study, administering a small subclinical dose of atracurium (75ug/kg) Smin. prior to the remainder of an intubating doae of atracurium (250ug/kg) had no different on grade of block for intubation compared to single IV bolus of atracurium (500ug/kg).
Alcuronium ; Anesthesiology ; Atracurium* ; Intubation ; Intubation, Intratracheal* ; Neuromuscular Blockade ; Pancuronium ; Succinylcholine

The usefulness of nondepolarizing muscle relaxants for intubation is limited by a relatively slow onset of neuromuscular block compared to that achived with succinylcholine. But, authors have reported that larger doses of nondepolarizing muscle relaxants produce a more rapid onset of maximal neuromuscular block and conditions conductive to endotracheal intubation and recent reports support the use of the "priming principle in the clinical practice of anesthesiology. This phenomenon may apply to all nondepolarizing relaxants: it is reported to facilitated neuromuscular blockade and tracheal intubation when used with atracurium, vecurouium, alcuronium or pancuronium. In this study, administering a small subclinical dose of atracurium (75ug/kg) Smin. prior to the remainder of an intubating doae of atracurium (250ug/kg) had no different on grade of block for intubation compared to single IV bolus of atracurium (500ug/kg).
Alcuronium ; Anesthesiology ; Atracurium* ; Intubation ; Intubation, Intratracheal* ; Neuromuscular Blockade ; Pancuronium ; Succinylcholine