Influence of 19-nortestosterone and androgens on progesterone biosynthetic enzymes in early human placental explants

We recently showed that the production of progesterone (P4) in human placental explant culture from early gestation is enhanced by treatment with 19-nortestosterone (19-NT) or with certain androgens, namely androstenedione (A-dione), 5 alpha-androstane-3 alpha,17 beta diol (3 alpha-diol) and 5 alpha-androstane-3 beta,17 beta diol (3 beta-diol). This stimulation of P4 was explored further in this study. There was little metabolism of radioactive P4 when incubated for 24 h in the presence or absence of these steroids. The role of different steroids in the regulation of P450 cholesterol side-chain cleavage enzyme (P450scc) and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) was evaluated by measuring the conversion of P4 derived from unlabelled 25-hydroxycholesterol and from labelled pregnenolone, respectively. The results showed that 19-NT, A-dione and 3 alpha-diol stimulated P450scc activity; however, 3 beta-diol was ineffective. While 19-NT and 3 beta-diol enhanced the bioconversion of pregnenolone to P4, A-dione and 3 alpha-diol were without effect. The initial rapid stimulation of P4 by 19-NT within 2 h of incubation was not blocked by concurrent treatment with cycloheximide (CH). However, after incubation for 24 h, 70% of the 19-NT-stimulated P4 was abolished by CH. During the same incubation period, P4 stimulation by A-dione, 3 alpha- and 3 beta-diol were completely blocked by treatment with CH. Thus our observations suggest that 19-NT-stimulated P4 accumulation is due to the combined effects on P450scc and 3 beta-HSD enzyme activities. A-dione and 3 alpha-diol increase biosynthesis of P4 by acting selectively on P450scc enzyme. However, the stimulatory action of 3 beta-diol on P4 is only at the level of 3 beta-HSD. Since CH blocks the stimulatory actions, the mechanism(s) by which androgens (A-dione, 3 alpha-diol and 3 beta-diol) and norandrogen (19-NT) augment the biosynthetic enzyme activities appears to be mediated by a process inhibited by CH. Since CH interference was absent during the initial rapid P4-stimulation by 19-NT, there may be a direct action of this steroid at the cellular level which is not dependent on new protein synthesis.

Newer neuromuscular blocking drugs. An overview of their clinical pharmacology and therapeutic use

Four new nondepolarising muscle relaxants, pipecuronium bromide, doxacurium chloride, mivacurium chloride and Org 9426 (rocuronium) offer alternatives to the established agents atracurium besilate and vecuronium bromide. Pipecuronium and Org 9426 are steroidal compounds, the latter being a monoquaternary agent, whereas doxacurium and mivacurium are bisquaternary benzylisoquinolinium compounds. Pipecuronium and doxacurium have a relatively slow onset and a long duration of action. Pipecuronium produces maximum block in 3 to 6 min when given in a dose of 45 to 80 micrograms/kg, and a duration of clinical relaxation of between 40 and 110 min. Doxacurium is more potent, but is the least rapid and the longest acting relaxant currently available. When administered in doses of 37 to 80 micrograms/kg, it produces maximum block within 3.5 to 10 min, with a duration of clinical relaxation of 77 to 164 min. The advantage of both pipecuronium and doxacurium is their cardiovascular stability. Both agents are primarily eliminated via the kidneys and both have now been licensed for use in the US. Mivacurium is a muscle relaxant with a short duration of action. When administered in doses of 0.1 to 0.25 mg/kg it produces maximum block in 2 to 4 min, but the duration of clinical relaxation is less than 20 min. Higher doses which could induce a faster neuromuscular block are unfortunately associated with some histamine liberation. The drug is metabolised by plasma cholinesterase. Mivacurium has also been licensed for use in the US. Org 9426 is an agent with a rapid onset but an intermediate duration of action. A dose of 0.5 to 0.6 mg/kg induces maximum block in about 1.5 min and has a duration of clinical relaxation of about 30 min. The rapid onset of effect could be useful for early intubation as an alternative to suxamethonium chloride. However, much more clinical experience is needed with this agent, particularly with regard to duration of action of larger doses and occurrence of side effects. The drug is mainly eliminated via the liver.

Pipecuronium-induced neuromuscular blockade during nitrous oxide-fentanyl, enflurane, isoflurane, and halothane anesthesia in surgical patients

This study was designed to determine the capacity of several anesthetics to augment pipecuronium neuromuscular blockade. The potency of pipecuronium was determined with single-bolus administration of 20-50 micrograms/kg in 160 patients. Patients were anesthetized with N2O/O2 (60:40) supplemented with fentanyl (4-5 micrograms/kg), halothane (0.8%), isoflurane (1.2%), or enflurane (1.7%). Neuromuscular blockade was measured by an acceleration-responsive transducer (the Accelograph, Biometer International, Odense, Denmark). Responses were defined in terms of percent depression in first-twitch height and train-of-four response, and the dose-response curves were constructed after probit transformation of the responses. The dose-response curves were found to be parallel for both first twitch height and train-of-four responses. The dose-response lines for the enflurane and isoflurane groups were displaced significantly (P less than 0.01) to the left of the line for the fentanyl-N2O group. The calculated doses producing 50% depression of first twitch height were 21.9, 21.2, 18.9, and 17.8 micrograms/kg for the N2O-fentanyl, halothane, isoflurane, and enflurane groups, respectively. Corresponding calculated doses for 50% depression of train-of-four response were significantly smaller (15.5, 14.4, 13.7, 11.9 micrograms/kg, respectively). The enhancing effects of the volatile anesthetics were reflected by significant prolongation of the clinical duration of neuromuscular blockade by pipecuronium. It is concluded that the potency of pipecuronium is enhanced more by enflurane and isoflurane than halothane or fentanyl-N2O anesthesia.

Effect of intravenous hypnotics on the actions of pipecuronium

Seventy-five ASA Grades I-III patients (18-85 years, 45-90 kg) were randomized into five groups. All patients received N2O/O2 (2/1) and alfentanil: loading dose (LD) 0.015 mg kg-1 and maintenance dose (MD) 0.045 mg kg-1 h-1 (groups 1-4). Group 1 received propofol (LD 2 mg kg-1 and MD 6 mg kg-1 h-1); Group 2 etomidate (LD 0.3 mg kg-1 and MD 0.6 mg kg-1 h-1); Group 3 midazolam (LD 0.2 mg kg-1 and MD 0.120 mg kg-1 h-1); Group 4 methohexitone (LD 1.5 mg kg-1 and MD 4 mg kg-1 h-1); Group 5 dehydrobenzperidol 0.05-0.23 mg kg-1 and alfentanil (LD 0.100 mg kg-1 and MD 0.060 mg kg-1 h-1). The neuromuscular block induced by pipecuronium (50 micrograms kg-1) was evaluated. No statistically significant differences were found between the five groups as concerned degree of block (expressed as % twitch amplitude in response to the first of the TOF stimuli (Ta1) at intubation, T1 minimum and recovery to Ta1 = 20%, 25% and 75%. Slightly faster intubation was possible when midazolam was used in comparison with propofol, methohexitone or NLA and when etomidate was used in comparison with propofol. A wide range of individual values of maximal neuromuscular blocking activity was found.

Pharmacokinetics and pharmacodynamics of pipecuronium bromide (Arduan) in elderly surgical patients

The neuromuscular response to pipecuronium bromide (Arduan), 70 micrograms/kg, was studied in 20 elderly (greater than 70 yr) and 10 younger patients (less than 60 yr) during nitrous oxide, fentanyl, and droperidol anesthesia. The adductor pollicis response to single 0.2-ms supramaximal pulses was recorded. Although all younger patients were completely paralyzed, 2 of 20 elderly patients did not attain 90% paralysis. Onset time in the elderly was prolonged (6.9 +/- 2.6 vs 4.3 +/- 1.5 min, P less than 0.02). Spontaneous recovery was similar in both groups, with 75% recovery occurring at 133 +/- 52 min in the elderly and 146 +/- 46 min in the younger patients. The pharmacokinetic variables were similar for the two groups, and pharmacodynamic analysis revealed a similar sensitivity at the neuromuscular junction. The pharmacologic actions of pipecuronium in otherwise healthy patients do not differ between young and elderly adults.

[Pharmacologic effects of pipecuronium bromide (Arduan)]

The experimental results in animals suggest that pipecuronium bromide offers the possibility of a neuromuscular blocking agent without side effects for surgical procedures of long duration. Its mechanism of action is twofold: 1. antagonism of acetylcholine effect at neuromuscular junction (postsynaptic nicotine receptors), 2. inhibition of acetylcholine release (presynaptic nicotine receptors). Its neuromuscular blocking potency is somewhat greater (2.0-3.0) than that of pancuronium in all species studied, and the duration of action is twice of that. It has no remarkable cumulative effect. Neostigmine rapidly and completely antagonises the neuromuscular blockade caused by pipecuronium. Certain structural properties (e.g. pipecuronium has no acetylcholine-like fragments in contrast with pancuronium and the interonium distance is also considerably larger than in pancuronium) may predict advantages. This has been proved by low vagal blocking--and ganglion--blocking potencies. On the basis of these a wide margin of safety can be expected in humans as well in preventing cardiovascular side effects. Pipecuronium is also characterized by interactions--only slight interactions--with other drugs used mainly in perioperative period.

[Synthesis of a new neuromuscular blocking agent, pipecuronium bromide (Arduan)]

A series of bisquaternary ammonio steroids having androstane skeleton have been prepared some of which possessed high neuromuscular blocking activity. One of the series 3 alpha, 17 beta-diacetoxy-2 beta, 16 beta-bis (4,4-dimethyl-1-piperazinyl)-5 alpha-androstane dibromide (19, pipecuronium bromide, ARDUAN) has proved to be a clinically useful agent of long duration of action without side effects. The preparation of pipecuronium bromide and its metabolites and the impurities are also described. The structure of 19 and related compounds was elucidated by spectrometric methods IR, NMR and MS.

[Clinicopharmacology of Arduan]

The paper presents clinicopharmacological investigations of Arduan carried out in Hungary and in other countries. The aim of the research work is to find an ideal muscle relaxant without side-effects, which are mainly cardiovascular. Pipecuronium bromide (Arduan) is a compound with steroid structure; it has a long duration of action and, most importantly, it does not affect circulation. The properties of pipecuronium bromide will be discussed and compared to those of pancuronium and vecuronium bromide.

[Myorelaxants and intracranial pressure (ICP) in neurosurgery. Preliminary clinical results of pipecurium bromide (Arduan) on ICP and on cerebral perfusion pressure (CPP)]

Pipecurium bromide, a new non-depolarizing myorelaxant, was administered intravenously, at a dose of 0.06 mg/kg, to 10 patients suffering from expansive endocranial lesions, who had been anesthetised to undergo neurosurgery. The following parameters were recorded simultaneously, before and after drug administration: intracranial pressure, mean arterial blood pressure, central venous pressure, heart rate and end tidal CO2. No statistically significant changes in the above parameters were observed following the administration of the myorelaxant; these observations, which were considered together with the long duration of action, confirm that pipecurium bromide is a valuable tool in anesthesia for neurosurgery.

Pipecuronium versus high dose vecuronium

The onset time and tendency to cumulation of pipecuronium and high-dose vecuronium were compared during nitrous oxide anaesthesia supplemented with a propofol infusion. Pipecuronium 0.06 mg.kg-1 had a similar duration of action to vecuronium 0.2 mg.kg-1 (49 vs 43). Patients who received vecuronium had a shorter onset time of neuromuscular blockade (p less than 0.01). Neither pipecuronium nor vecuronium showed marked cumulation.

5-alpha androstane diol stimulates the pituitary growth hormone responsiveness to growth hormone releasing hormone more effectively than testosterone or dihydrotestosterone in rats

The effect of different androgens and estradiol on pituitary responsiveness to growth hormone releasing hormone was studied in intact and orchidectomized adult male Wistar rats, by injecting subcutaneously immediately after orchidectomy for two weeks with testosterone, dihydrotestosterone, 5-alpha androstane, 3-alpha,17 beta-diol or estradiol dissolved in olive oil (in doses of 0.2 or 2.0 mg.kg-1.day-1) or vehicle. Pituitary responsiveness was tested in pentobarbital anaesthetized rats by measuring growth hormone plasma levels at different times after administration of growth hormone releasing hormone (1-29) NH2. We found that: (a) High doses of testosterone, dihydrotestosterone and 5-alpha androstane, 3-alpha,17 beta-diol restored gonadotropin plasma concentrations and organ weights altered by orchidectomy; (b) both pituitary growth hormone content and concentration remained unaffected after orchidectomy or androgen replacement and decreased significantly after estradiol injection; (c) orchidectomy significantly reduced growth hormone-stimulated growth hormone releasing hormone secretion; (d) treatment with 5-alpha androstane,3-alpha,17 beta-diol increased more than testosterone or dihydrotestosterone both the peak concentration and the mean growth hormone secretion after growth hormone releasing hormone stimulation; (e) no differences were observed in the treatment with testosterone or dihydrotestosterone; (f) estradiol given at a dose of 0.2 mg.kg-1.day-1 increased pituitary responsiveness to growth hormone releasing hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Pipecuronium versus high dose vecuronium

The onset time and tendency to cumulation of pipecuronium and high-dose vecuronium were studied during nitrous oxide anaesthesia supplemented with isoflurane. Pipecuronium 0.06 mg.kg-1 had a similar duration of action to vecuronium 0.015 mg.kg-1 (42 vs 49 min). Patients who received vecuronium had a shorter onset time of neuromuscular blockade (p less than 0.01). The use of pipecuronium was associated with marked cumulation.

Clinical evaluation of different doses of pipecuronium bromide during nitrous-oxide-fentanyl anaesthesia in adult surgical patients

The neuromuscular and cardiovascular effects of three different doses of pipecuronium were studied in 60 adult patients. Neuromuscular blockade was measured using electromyographic activity of the adductor pollicis muscle after supramaximal stimulation of the ulnar nerve at 0.1 Hz and 2 Hz. Three subgroups (A, B, C) of 20 patients received pipecuronium doses of 60, 80 and 100 micrograms kg-1, respectively, as an intubating dose and, when necessary, maintenance doses were administered at 25% single twitch recovery in a dose of one-quarter of the initial one. The onset time was 5.4 +/- 2.0 min for 60 micrograms kg-1 and similar for 80 and 100 micrograms kg-1 (3.9 +/- 1.1 and 3.6 +/- 1.1 min). The duration of action was 45 +/- 10 min for 60 micrograms kg-1, 74 +/- 25 and 94 +/- 21 for 80 and 100 micrograms kg-1, respectively. The recovery indices were measured in all patients after neostigmine administration (Groups B and C) and after neostigmine and edrophonium (Subgroup A, 10 patients each). TOF ratio was significant only 2 min after edrophonium administration in Group A patients. Variations of heart rate and blood pressure were not significant.

Comparative evaluation of the neuromuscular and cardiovascular effects of pipecuronium, pancuronium, atracurium, and vecuronium under isoflurane anesthesia

The neuromuscular and cardiovascular effects of intubating doses of pipecuronium 80 micrograms/kg, pancuronium 100 micrograms/kg, atracurium 500 micrograms/kg, and vecuronium 100 micrograms/kg were compared in 62 patients under isoflurane (end-tidal concentration = 0.5-1%) anesthesia. Pipecuronium, pancuronium, and vecuronium had no significant effect on systolic or diastolic blood pressure. In one patient the administration of atracurium resulted in significant hypotension. Heart rate was significantly increased only after the administration of pancuronium. The neuromuscular-blocking effect of pipecuronium and pancuronium appears to be twice as long as that of vecuronium and atracurium. Administration of neostigmine resulted in significantly faster recovery of muscle function in patients receiving vecuronium or atracurium. Although pipecuronium's neuromuscular-blocking effect is similar to that of pancuronium, its lack of cardiovascular effects more closely resembles that of vecuronium.

The pharmacokinetics, urinary and biliary excretion of pipecuronium bromide

The pharmacodynamics and -kinetics of pipecuronium were studied in 12 patients, six of whom received 100 micrograms kg-1 for laryngectomy (Group L), and six who underwent choledochotomy after insertion of the T-drain and were given 50 micrograms kg-1 (Group C). Onset time and clinical duration were 2.3 and 109 min and 2.8 and 39 min in Groups L and C, respectively. All patients could be sufficiently reversed with neostigmine. Terminal half-lives were 101.5 min (Group L) and 179 min (Group C) in a three-exponent decay; the distribution volumes at steady state 0.339 l kg-1 (Group L) and 0.506 l kg-1 (Group C); the plasma clearance 3.4 ml kg-1 min-1 (Group L) and 2.5 ml kg-1 min-1 (Group C). Within 24 h, 38.6% and 37% were excreted unchanged in the urine and 4.4% and 1% as 3-desacetyl pipecuronium in Groups L and C, respectively. Within 24 h only 2% was excreted into the bile in Group C. Distribution volume and terminal half-life in Group C were positively correlated with pre-operative serum aminotransferase levels (P less than 0.005).

Characteristics of the biphasic action of androgens and of the potent antiproliferative effects of the new pure antiestrogen EM-139 on cell cycle kinetic parameters in LNCaP human prostatic cancer cells

The most potent steroid in human prostatic carcinoma LNCaP cells, i.e., dihydrotestosterone (DHT), has a biphasic stimulatory effect on cell proliferation. At the maximal stimulatory concentration of 0.1 nM DHT, analysis of cell kinetic parameters shows a decrease of the G0-G1 fraction with a corresponding increase of the S and G2 + M fractions. In contrast, concentrations of 1 nM DHT or higher induce a return of cell proliferation to control levels, reflected by an increase in the G0-G1 fraction at the expense of the S and especially the G2 + M fractions. Continuous labeling for 144 h with the nucleotide analogue 5'-bromodeoxyuridine shows that the percentage of cycling LNCaP cells rises more than 90% after treatment with stimulatory concentrations of DHT, whereas in control cells as well as in cells treated with high concentrations of the androgen, this value remains below 50%. Although LNCaP cells do not contain detectable estrogen receptors, the new pure steroidal antiestrogen EM-139 not only reversed the stimulation of cell proliferation and cell kinetics induced by stimulatory doses of DHT but also inhibited basal cell proliferation.

Comparative effects of pipecuronium and tubocurarine on plasma concentrations of histamine in humans

We have examined the effects of a rapid bolus dose of pipecuronium 0.1 mg kg-1 or tubocurarine 0.5 mg kg-1 on plasma histamine concentration, heart rate and arterial pressure in 20 patients (n = 10 in each group). Anaesthesia was induced with thiopentone 6 mg kg-1 i.v. and maintained with 70% nitrous oxide and halothane in oxygen. Neuromuscular blocking drugs were administered 4 min after administration of thiopentone. Venous blood samples were obtained before induction, 1 min after thiopentone and 1, 3 and 5 min after the administration of the neuromuscular blocking drugs. Tubocurarine caused 240% and 210% increases in plasma concentration of histamine at 1 and 3 min, respectively. These changes were significant (P less than 0.05) at 1 min and associated with a decrease in mean arterial pressure and an increase in heart rate. None of the 10 patients receiving pipecuronium had a significant change in plasma concentration of histamine or in haemodynamic variables.

Edrophonium priming alters the course of neuromuscular recovery from a pipecuronium neuromuscular blockade

This study was designed to investigate the effect of divided administration of edrophonium on the course of neuromuscular recovery from a pipecuronium neuromuscular blockade. During thiopentone-nitrous oxide-halothane anaesthesia 48 patients were given pipecuronium 70 micrograms.kg-1. Patients were randomly assigned to one of four groups (n = 12 in each) to receive either edrophonium 1 mg.kg-1 (Groups I and II) or edrophonium 0.75 mg.kg-1 (Groups III and IV). In Groups I and III (single-dose groups), edrophonium was administered as a single bolus dose. In Groups II and IV (divided-dose groups) edrophonium was administered as an initial dose of 0.25 mg.kg-1 followed three minutes later by either 0.75 or 0.50 mg.kg-1 respectively. Reversal was attempted at 20% spontaneous recovery of twitch height. Administration of edrophonium in divided doses (Groups II and IV) accelerated the reversal of the pipecuronium neuromuscular blockade. At ten minutes post-reversal, train-of-four (TOF) ratio recovery reached 0.75 or more in 12 (100%) and in ten (83%) patients in Groups II and IV respectively. Similarly, times to attain a TOF of 0.75 (SEM) were shorter in the divided-dose groups than in the single-dose groups (P less than 0.05), being 354.5 (38.7) and 398.3 (49.1) sec in Groups II and IV vs 705.4 (66.6) and 651.2 (54.3) sec in Groups I and III respectively. Time was counted from the first administration of edrophonium. It is concluded that administration of edrophonium in divided doses produced a faster reversal of residual pipecuronium-induced neuromuscular blockade than single bolus administration. Also, administration in divided doses reduced the requirements of edrophonium needed for reversal of pipecuronium neuromuscular blockade.

Comparison of the haemodynamic effects of pipecuronium and pancuronium during fentanyl anaesthesia

Haemodynamic variables were measured following administration of pipecuronium 70 micrograms.kg-1 and pancuronium 90 micrograms.kg-1 (approximately equivalent to 1.5 x ED95) in patients anaesthetised with fentanyl 50 micrograms.kg-1 and scheduled to undergo coronary artery bypass grafting. There were significant increases in heart rate (22%), mean arterial pressure (10%), cardiac index (16%), and the rate pressure product (35%) following administration of pancuronium. The absolute values of these parameters were, however, within acceptable clinical limits. Administration of pipecuronium produced minimal and insignificant changes in these parameters. Other measured or derived indices showed only small changes with both agents and these were generally insignificant. There were no incidences of significant bradycardia following pipecuronium administration. The results from the present study suggest that pipecuronium would have advantages for use in patients with significant cardiovascular disease.

Comparison of cardiovascular effects of pipecuronium versus vecuronium in patients receiving sufentanil anesthesia for myocardial revascularization

This study was designed to compare the cardiovascular effects of pipecuronium bromide (PIP) to vecuronium (V) when combined with sufentanil (SF) in patients undergoing coronary artery bypass surgery. Eighty-two patients were studied; 40 were normotensive and 42 had hypertension currently controlled by pharmacological therapy. All patients were randomly assigned to receive either intravenous V, 0.12 mg/kg, or PIP, 0.10 mg/kg. Anesthesia was induced with SF, 6 micrograms/kg, while breathing 100% oxygen. Hemodynamic data including heart rate, mean arterial pressure, pulmonary capillary wedge pressure, central venous pressure, cardiac index, systemic vascular resistance, pulmonary vascular resistance, and left ventricular stroke work index were collected at five points: prior to induction, 3 and 6 minutes after the complete administration of PIP or V, and 3 and 6 minutes after intubation. There were no statistical differences in hemodynamic changes associated with either PIP or V. In addition, there were no statistical differences in the hemodynamic parameters measured at the five time points between the normotensive and hypertensive patient groups. This study demonstrates that there are no significant hemodynamic changes between SF/PIP and SF/V when used during coronary artery surgery. Due to its associated stable hemodynamics, as well as its long duration of action, PIP could become a commonly used muscle relaxant for anesthesia for cardiac surgery.

Neuromuscular effects of pipecuronium bromide

The neuromuscular effects of pipecuronium bromide have been evaluated in 90 adult patients anaesthetized with thiopentone, nitrous oxide in oxygen and intravenous fentanyl with or without halothane. Eighty patients received pipecuronium 45 micrograms kg-1 and the remaining ten 70 micrograms kg-1. A separate group of 10 patients received pancuronium in a dose of 60 micrograms kg-1 (equipotent to pipecuronium 45 micrograms kg-1). Neuromuscular block was measured using a single-twitch or train-of-four mode of stimulation. The time to onset of maximum block with pipecuronium 45 micrograms kg-1 varied between 3.5 and 5.7 min depending on the mode of stimulation and the anaesthetic technique used. The time to 25% recovery of this dose varied between 41 and 54 min. The recovery index (time from 25 to 75% recovery) averaged 29 min. These values were generally similar in the group receiving pancuronium 60 micrograms kg-1. The time to onset of complete block with 70 micrograms kg-1 of pipecuronium averaged 2.5 min and the duration to 25% recovery 95 min. There were no significant changes in heart rate and arterial pressure with the use of pipecuronium. The results show pipecuronium to be a drug resembling pancuronium in its neuromuscular effects when used in equipotent doses.

Effects of succinylcholine on the pharmacodynamics of pipecuronium and pancuronium

To study the effects of succinylcholine on subsequent pharmacodynamics of nondepolarizing muscle relaxants, a comparative pharmacodynamic study was carried out in patients having balanced anesthesia (thiopental, fentanyl, nitrous oxide/oxygen) in whom equipotent doses of pipecuronium (80 micrograms/kg) and pancuronium (100 micrograms/kg) were given with or without prior administration of succinylcholine (1 mg/kg). Fifty-two patients were randomly assigned to one of the following four groups: 1, pancuronium (100 micrograms/kg); 2, pipecuronium (80 micrograms/kg); 3, succinylcholine (1 mg/kg) plus pancuronium (100 micrograms/kg); and 4, succinylcholine (1 mg/kg) plus pipecuronium (80 micrograms/kg). In groups 3 and 4, the nondepolarizing relaxant was given after succinylcholine when the twitch height recovered to 75% of its control value. For maintenance of neuromuscular blockade, additional increments of pancuronium (20 micrograms/kg) or pipecuronium (15 micrograms/kg) were given. Neuromuscular function was monitored throughout induction, maintenance, spontaneous recovery, and pharmacologic reversal of the neuromuscular block. Mean onset times for pancuronium (group 1) and pipecuronium (group 2) given without succinylcholine were (mean +/- SEM) 2.5 +/- 0.3 and 2.8 +/- 0.2 min, respectively. Mean onset times (times to maximum twitch depression) of the two drugs given after succinylcholine (groups 3 and 4) were significantly shorter (1.4 +/- 0.4 and 1.6 +/- 0.1 min, respectively). Clinical durations (i.e., until 25% twitch recovery of pancuronium and pipecuronium) were not significantly different among the four groups, varying from 81.1 +/- 5.4 (group 4) to 107.0 +/- 17.0 (group 2) min.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical pharmacology of pipecuronium in infants and children during halothane anesthesia

We determined the cumulative dose-response relations of pipecuronium in infants and children during nitrous oxidehalothane anesthesia. Neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle resulting from supramaximal stimulation of the ulnar nerve at 2 Hz for 2 s at 10-s intervals. Patients were stratified into four groups according to age: 3 mo or older but not yet 6 mo (n = 10), 6 mo or older but not yet 12 mo (n = 10), 1 yr or older but not yet 3 yr (n = 10), and 3 yr or older but not yet 6 yr (n = 9). The mean ED50 of pipecuronium in these age groups was 18, 20, 21, and 24 micrograms/kg, respectively; the mean ED95 was 33, 38, 47, and 49 micrograms/kg, respectively. The ED95 of pipecuronium was statistically significantly less for the 3-6-mo-old patients than for children between 1 and 6 yr of age. Similarly, pipecuronium dosage requirements calculated on the basis of body surface area were significantly less in infants 3-12 mo of age than in children 1-6 yr of age. Thus, compared with children, infants appear to be more sensitive to the neuromuscular blocking effects of pipecuronium. Duration (T25) of action after cumulative dosing with pipecuronium was approximately 20 min in infants and 30 min in children. Spontaneous recovery indices were not prolonged in the younger patients. The average T25-75 recovery index was 27.1 +/- 9.6 min. There were no changes in cardiac rhythm, heart rate, or blood pressure attributable to pipecuronium during this study.

Neuromuscular and cardiovascular effects of pipecuronium

Pipecuronium bromide (Arduan) is a bisquaternary, steroid-type neuromuscular blocking agent in clinical use in Eastern Europe. Before its introduction into clinical practice in the USA, in the first phase of this study the neuromuscular potency of pipecuronium was determined under "balanced" and enflurance anaesthesia by the cumulative log dose-response method in 30 patients each. In the second phase the intubation and onset times, clinical duration of the first and repeated doses, spontaneous recovery index, reversibility of its residual neuromuscular effect by an anticholinesterase and its effect on heart rate and blood pressure was compared with the same variables observed in patients, anaesthetized with identical techniques but who had received vecuronium or pancuronium. The neuromuscular potency of pipecuronium was greater under enflurane (ED95 = 23.6 +/- 1.1 micrograms.kg-1 (mean +/- SEM)] than under balanced (ED95 = 35.1 +/- 17 micrograms.kg-1) anaesthesia. Pipecuronium was more potent than vecuronium under both balanced (ED95 = 45.8 micrograms.kg-1) and enflurane anaesthesia (ED95 = 27.4 micrograms.kg-1). Following the administration of 2 x ED95 doses there were no clinically significant differences in the intubation or onset times of pipecuronium, vecuronium and pancuronium. Under balanced anaesthesia the clinical duration of 2 x ED95 dose of pipecuronium (110.5 +/- 0.3 min) or pancuronium (115.8 +/- 8.1 min) were similar and about three times longer than that of vecuronium (36.3 +/- 2.1 min). The recovery indices of pipecuronium (44.5 +/- 8.2 min) and pancuronium (41.3 +/- 4.2 min) were also similar and about three times longer than that of vecuronium (14.3 +/- 1.4 min).(ABSTRACT TRUNCATED AT 250 WORDS)