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PubMedDate not supplied

[Effect of carboxyperitoneum on duration of the action of some non-depolarizing muscle relaxants].

Changing pharmacokinetics of muscle relaxants with the organ-dependent metabolism (pipecuronium), which is related with the effect exerted by carboxyperitoneum on the patient-body temperature hemostasis and on the renal function are under discussion in the paper. It was demonstrated that carboxyperitoneum affects independently the decreasing body temperature and prolonged effect duration of pipecuronium. The conclusion is that the use of muscle relaxants with the prevailing organ-dependent elimination (atracurium and cysatracurium) is more preferable versus pipecuronium in laparoscopic surgery.

Adult↗
PubMed2001

Choice of the muscle relaxant for rapid-sequence induction.

Muscle relaxants are given as part of a rapid-sequence induction to facilitate tracheal intubation. Among all the muscle relaxants available, succinylcholine is the only one with a fast (approximately equal to 1 min) onset and a fast recovery. Therefore it is still the most frequently used muscle relaxant for rapid-sequence induction despite its well-known side-effects. The short duration of action of succinylcholine is, however, no substitute for aggressive airway management in the case of an unexpectedly difficult intubation in order to prevent life-threatening hypoxia. A preoperative assessment of the airway is mandatory in any patient and may indicate the need for using intubation techniques without a muscle relaxant. Rocuronium in large doses (i.e. > or = 1 mg kg-1) is an alternative to succinylcholine in a classical rapid-sequence setting under relatively light anaesthesia. With respect to rapid tracheal intubation, the timing and priming principles offer little advantage over the use of rocuronium in doses of 0.6 mg kg-1 in combination with an appropriate induction technique (i.e. including an opioid) or over the use of larger doses of rocuronium (> or = 1.0 mg kg-1) under relatively light anaesthesia, and may even be potentially harmful. In contrast to rocuronium, the use of rapacuronium in a rapid-sequence setting has been associated with dose-dependent respiratory side-effects that limit its usefulness in doses higher than 1.5 mg kg-1 for this indication.

Androstanols↗
PubMedDate not supplied

Prolonged myasthenic syndrome after one week of muscle relaxants.

A child developed severe, generalized muscle weakness which persisted for 6 weeks, after receiving muscle relaxants for 1 week while requiring ventilator support. Electrodiagnostic studies indicated a presynaptic disorder of the neuromuscular junction which improved with high-frequency stimulation, similar to findings in Lambert-Eaton syndrome. Muscle specimens exhibited neurogenic targetoid fiber atrophy. Ultrastructure of the neuromuscular junction indicated terminal axon degeneration and atrophy with depletion of the secretory vesicles. Most reported patients with post-ventilator paresis have received steroids and muscle relaxants; muscle weakness commonly has been brief and attributed to steroids. We believe that this reversible myasthenic syndrome probably represents neurotoxicity due to high doses of steroidal nondepolarizing blocking agents; however, available data are insufficient to resolve this controversy.

Atrophy↗
PubMed1999

Investigation of fading responses induced by non-depolarising muscle relaxants in the evoked EMG of the gastrocnemius muscle of the cat.

BACKGROUND: During partial neuromuscular blockade indirect repetitive nerve stimulation causes fade in the response of the muscle. We studied the intensity of the fade induced by intravenous administration of three steroidal muscle relaxants, and investigated the mechanism of fade by comparing with results obtained during partial blockade with animal toxins and vesamicol. METHODS: In 60 cats, we measured the fade in the compound action potentials of the gastrocnemius muscle evoked by repetitive sciatic nerve stimulation at 100 Hz during partial neuromuscular blockade with rocuronium, vecuronium, pancuronium, alpha-bungarotoxin, mu-conotoxin and vesamicol, respectively. RESULTS: Profound fade was induced by all three non-depolarising muscle relaxants (rocuronium=vecuronium<pancuronium) and by vesamicol, in contrast to alpha-bungarotoxin and mu-conotoxin which induced no fading. CONCLUSION: Our results suggest that non-depolarising muscle relaxant-induced fade is caused by an inhibitory effect on acetylcholine release. Pancuronium seems to have a higher potency of presynaptic inhibition of acetylcholine release than both rocuronium and vecuronium.

Acetylcholine↗
PubMed1981

Cyclobenzaprine: a possible mechanism of action for its muscle relaxant effect.

Intravenously administered cyclobenzaprine (CBZ) (Flexeril), a clinically used, centrally acting muscle relaxant, abolished muscle rigidity in the intercollicular decerebrate rat. In animals in which the locus coeruleus was lesioned bilaterally previously, CBZ failed to attenuate the electromyogram. In the ventral horn of the cord, which receives a dense noradrenergic innervation from the locus coeruleus, CBZ caused an increase in the metabolism of noradrenaline. In the zona intermedia of the thoracic cord, which is not innervated by the locus coeruleus, CBZ caused only minimal effects on noradrenaline metabolism. Cells in the locus coeruleus were activated by CBZ. The results indicate that in the intercollicular decerebrate rat, an intact, coerulospinal, noradrenergic projection is essential for the muscle relaxant effect of CBZ. Muscle relaxation apparently results from an activation of locus coeruleus neurones, leading to an increased release of noradrenaline in the ventral horn of the cord and the subsequent inhibitory action of noradrenaline on alpha motoneurones.

Amitriptyline↗
PubMed1987

[Enhancement of the muscle relaxant action of baclofen by glucocorticoids].

Effects of pretreatment with hydrocortisone or prednisolone on the pharmacological effects of baclofen, particularly on the muscle relaxant action, were studied in young adult rats. Muscle relaxation was determined using an inclined board (50 degrees). A single injection of hydrocortisone (10 mg/kg, s.c.) 15 min prior to the administration of baclofen (5 mg/kg, i.p.) increased significantly the muscle relaxant time by baclofen. Prednisolone pretreatment (2 mg/kg, s.c.) also prolonged baclofen-induced muscle relaxation. Muscle relaxation due to tolperisone (50 mg/kg, i.p.) and mephenesin (80 mg/kg, i.p.) administration was enhanced by the pretreatment of hydrocortisone. Hydrocortisone pretreatment enhanced the muscle relaxant time of diazepam (2 mg/kg, i.p.) but at a lesser extent and only in males. No synergistic effect of hydrocortisone on the muscle relaxation time by suxamethonium (0.01 mg/kg, i.p.) was observed. Seven daily injections of 2 mg/kg hydrocortisone as well as of 0.4 mg/kg prednisolone did not enhance the muscle relaxation by baclofen when tested 24 hr after the last injection of the two steroids. Fifteen min priming with hydrocortisone had no effect on the antinociceptive and hypothermic effects of baclofen. 3H-Baclofen was injected i.v. as a tracer of 1 mg/kg unlabeled baclofen. In hydrocortisone-treated rats, the uptake of 3H-baclofen into the hippocampus, medulla oblongata and cerebellum was significantly higher than that in the vehicle-treated rats, whereas the radioactivity in the cervical, thoracic and lumbar spinal cord tended to decrease. The results indicate that acute priming with hydrocortisone enhances rather selectively the muscle relaxant action of the centrally acting muscle relaxant drugs. It is suggested that the primary site of the synergistic action of hydrocortisone to baclofen could be at the supraspinal level of the CNS.

Animals↗
PubMed1999

In vivo human brachial artery elastic mechanics: effects of smooth muscle relaxation.

BACKGROUND: The effects of smooth muscle relaxation on arterial wall mechanics are controversial. We used a new, in vivo, noninvasive technique to measure brachial artery wall mechanics under baseline conditions and following smooth muscle relaxation with nitroglycerin (NTG). METHODS AND RESULTS: Eight healthy, normal subjects (6 male, 2 female; age 30+/-3.1 years) participated in the study. The nondominant brachial artery was imaged through a water-filled blood pressure cuff using an external ultrasound wall-tracking system at baseline and following 0.4 mg sublingual NTG. Simultaneous radial artery pressure waveforms were recorded by tonometry. Transmural pressure (TP) was reduced by increasing water pressure in the cuff. Brachial artery area, unstressed area, compliance, stress, strain, incremental elastic modulus (Einc), and pulse wave velocity (PWV) were measured over a TP range from 0 to 100 mm Hg. Baseline area versus TP curves generated 30 minutes apart were not significantly different. NTG significantly shifted area versus TP (P<0.0001) and compliance versus TP (P<0.001) curves upward, whereas the Einc versus TP (P<0.05) and PWV versus TP (P<0. 01) curves were shifted downward. NTG also significantly shifted stress versus strain (P<0.01) and Einc versus strain (P<0.01) curves to the right. CONCLUSIONS: We conclude that brachial artery elastic mechanics can be reproducibly measured over a wide range of TP and smooth muscle tone using a new noninvasive ultrasound technique. Smooth muscle relaxation with NTG increases isobaric compliance and decreases isobaric Einc and PWV in the human brachial artery.

Adult↗
PubMed1990

Substantia nigra: a site of action of muscle relaxant drugs.

Sites of action of centrally active muscle relaxant drugs are not well defined. Clinical experience with such drugs suggests that the spinal cord may be one of the important regions from which pathologically increased muscle tone may be relieved. Supraspinal centers that may also be involved in the expression of muscle relaxant action have not yet been defined. We report here that microinjections of therapeutically relevant muscle relaxants into the midbrain tegmentum of genetically spastic rats decrease muscle tone. The substantia nigra is the region from which midazolam, baclofen, and tizanidine (drugs used clinically in the treatment of spasticity), or gamma-vinyl-GABA, (-)-2-amino-7-phosphonoheptanoate, and [D-pro2-D-phe7-D-trp9]-substance P (experimental drugs active in animal models of spasticity), reduce muscle tone in genetically spastic rats and Hoffmann reflexes in normal rats. The effects of muscle relaxant drugs are topographically restricted to the substantia nigra pars reticulata and are receptor specific. These observations disclose a previously unknown function of the substantia nigra in mediating muscle relaxation.

Animals↗
PubMed1997

The possible role of hydrogen sulfide as an endogenous smooth muscle relaxant in synergy with nitric oxide.

Hydrogen sulfide (H2S), which is well known as a toxic gas, is produced endogenously in mammalian tissues from L-cysteine mainly by two pyridoxal-5'-phosphate-dependent enzymes, cystathionine beta-synthetase and cystathionine gamma-lyase. Recently, we showed that cystathionine beta-synthetase in the brain produces H2S, and that H2S facilitates the induction of hippocampal long-term potentiation by enhancing NMDA receptor activity. Here we show that mRNA for another H2S producing enzyme, cystathionine gamma-lyase, is expressed in the ileum, portal vein, and thoracic aorta. The ileum also expresses cystathionine beta-synthetase mRNA. These tissues produce H2S, and this production is blocked by cystathionine beta-synthetase and cystathionine gamma-lyase specific inhibitors. Although exogenously applied H2S alone relaxed these smooth muscles, much lower concentrations of H2S greatly enhanced the smooth muscle relaxation induced by NO in the thoracic aorta. These observations suggest that the endogenous H2S may regulate smooth muscle tone in synergy with NO.

Animals↗
PubMed2006

Muscle relaxants and antispasticity agents.

Muscle relaxants make up a heterogeneous group of agents and can have a clinically significant role in the treatment of chronic muscle pain. These medications are not without possible serious side effects; hence, care should be taken in deciding on their appropriateness and ongoing monitoring performed, if prescribed.

Adult↗
PubMed1993

A pharmacological evaluation of the pull-up test for muscle relaxation in rats.

The pull-up test for muscle relaxation is described and validated. At testing, rats were evaluated for their ability to recover ('pull-up') from a fully inverted head-down position. Control animals rapidly regained position (median: 1 s). Known muscle relaxants increased latency to pull-up compared to controls. The test proved sensitive to the effects of barbiturates and benzodiazepines which produced graded dose-response functions. In general, results in the pull-up test corresponded with known potencies, with weaker muscle relaxants such as clobazam and oxazepam being less active. The test was relatively insensitive to non-benzodiazepine compounds (e.g., haloperidol, etomidate, morphine, fentanyl and risperidone) producing cataleptic, catatonic, neuroleptic, analgesic, sedative or hypnotic effects. In terms of ED50 values for barbiturates and benzodiazepines, the pull-up test correlated significantly with ED50s from the rotarod test, the antipentylenetetrazol test, ataxia in rats and muscle relaxation in cats. It was concluded that the pull-up test was relatively specific for muscle relaxation and provided a simple alternative to more time-consuming or equipment-intensive tests.

Animals↗
PubMed2003

Muscle relaxants for non-specific low back pain.

BACKGROUND: The use of muscle relaxants in the management of non-specific low back pain is controversial. It is not clear if they are effective, and concerns have been raised about the potential adverse effects involved. OBJECTIVES: The aim of this review was to determine if muscle relaxants are effective in the treatment of non-specific low back pain. SEARCH STRATEGY: A computer-assisted search of the Cochrane Library (Issue 2, 2002), MEDLINE (1966 up to October 2001) and EMBASE (1988 up to October 2001) was carried out. These databases were searched using the algorithm recommended by the Cochrane Back Review Group. References cited in the identified articles and other relevant literature were screened. SELECTION CRITERIA: Randomised and/or double-blinded controlled trials, involving patients diagnosed with non-specific low back pain, treated with muscle relaxants as monotherapy or in combination with other therapeutic modalities, were included for review. DATA COLLECTION AND ANALYSIS: Two reviewers independently carried out the methodological quality assessment and data extraction of the trials. The analysis comprised not only a quantitative analysis (statistical pooling) but also a qualitative analysis ("best evidence synthesis"). This involved the appraisal of the strength of evidence for various conclusions using a rating system based on the quality and outcomes of the studies included. Evidence was classified as "strong", "moderate", "limited", "conflicting" or "no" evidence. MAIN RESULTS: Thirty trials met the inclusion criteria. Twenty-three trials (77%) were of high quality, 24 trials (80%) were on acute low back pain. Four trials studied benzodiazepines, 11 non-benzodiazepines and two antispasticity muscle relaxants in comparison with placebo. Results showed that there is strong evidence that any of these muscle relaxants are more effective than placebo for patients with acute LBP on short-term pain relief. The pooled RR for non-benzodiazepines versus placebo after two to four days was 0.80 [95% CI; 0.71 to 0.89] for pain relief and 0.49 [95% CI; 0.25 to 0.95] for global efficacy. Adverse events, however, with a relative risk of 1.50 [95% CI; 1.14 to 1.98] were significantly more prevalent in patients receiving muscle relaxants and especially the central nervous system adverse effects (RR 2.04; 95% CI; 1.23 to 3.37). The various muscle relaxants were found to be similar in performance. REVIEWER'S CONCLUSIONS: Muscle relaxants are effective in the management of non-specific low back pain, but the adverse effects require that they be used with caution. Trials are needed that evaluate if muscle relaxants are more effective than analgesics or non-steroidal anti-inflammatory drugs.

Acute Disease↗
PubMed2004

Muscle weakness after muscle relaxants: an audit of clinical practice.

Residual muscle weakness after general anaesthesia, assessed using handgrip strength, was audited in a teaching hospital. The relationships between residual weakness, the use of muscle relaxants and patient characteristics were examined. Handgrip strength was measured preoperatively, one hour postoperatively and one day postoperatively using a hand dynamometer in 151 patients having general anaesthesia. Forty-nine patients received no muscle relaxant, 34 patients received vecuronium and 68 received rocuronium. Patients were managed by their anaesthetist according to that anaesthetist's clinical choice. All patients who received muscle relaxants received neostigmine. One hour postoperatively, there was a decline in handgrip strength of 16% for the no relaxant group, 24% for vecuronium and 29% for rocuronium. The degree of weakness for the relaxant groups was unrelated to age (P=0.89) but was strongly influenced by the patient's sex. Almost all of the increased weakness with relaxants was found in the female patients. The mean decline in handgrip strength in the male patients who received either vecuronium or rocuronium was similar to that seen when relaxants had not been used (P=0.40). One hour postoperatively, female patients showed a marked decrease in handgrip strength after both vecuronium and rocuronium (32% and 34% respectively, combined P=0.01). These results suggest that in usual clinical practice at our institution, female patients are more likely to have residual weakness after muscle relaxants.

Age Factors↗
PubMed1992

Iontophoretic study of speed of action of various muscle relaxants.

The speed of action of nondepolarizing muscle relaxants is inversely related to potency. The hypothesis that this effect occurs at the end plate was tested in a frog (Rana pipiens) cutaneous pectoris muscle preparation. Brief acetylcholine pulses (10-100 ms) were applied iontophoretically from a central barrel of a triple-barrelled microelectrode located near an end plate. Long pulses (10-200 s) of muscle relaxant (gallamine, rocuronium, d-tubocurarine, atracurium, vecuronium, pancuronium, and doxacurium) were applied from one of two other barrels. The responses were a voltage change at the end plate, measured with an intracellular electrode. To evaluate potency, intracellular voltage changes following iontophoretic acetylcholine pulses were measured after application of various concentrations of muscle relaxants. The following were the equilibrium dissociation constants, which represent concentration of relaxant for 50% inhibition of response (mean plus or minus standard deviation): gallamine, 4.56 +/- 0.44 microM (n = 5); rocuronium, 0.71 +/- 0.09 microM (n = 6); d-tubocurarine, 0.59 +/- 0.07 microM (n = 4); atracurium, 0.31 +/- 0.03 microM (n = 4); vecuronium, 0.23 +/- 0.02 microM (n = 5); pancuronium, 0.18 +/- 0.03 microM (n = 3); doxacurium, 0.11 +/- 0.03 microM (n = 5). Both onset and offset of effect of muscle relaxant proceeded with an exponential time course.(ABSTRACT TRUNCATED AT 250 WORDS)

Androstanols↗
PubMed2004

The use of muscle relaxant medications in acute low back pain.

STUDY DESIGN: Prospective cohort study. OBJECTIVES: To determine the characteristics of patients who take muscle relaxants for back pain after seeking care and to determine the relationship of muscle relaxant use with recovery from the episode of low back pain. SUMMARY OF BACKGROUND DATA: Low back pain is a common condition with a generally favorable short-term prognosis. Physicians in the acute setting commonly prescribe muscle relaxants. The indications for use and outcomes are not clear. METHODS: We performed a secondary data analysis of a cohort of 1633 patients who sought care from a variety of practitioners (primary care, physician of chiropractic, orthopedic surgeon, Health Maintenance Organization) for low back pain. Patients were enrolled in the physician's office and interviewed at baseline, 2, 4, 8, 12, and 24 weeks. Pain, functional status, medication use, health care utilization, and satisfaction with care were assessed. RESULTS: Muscle relaxants were used by 49% of patients; among those who sought care from doctors, 64% used muscle relaxants. Muscle relaxant users were more impaired at baseline. Over time, among patients with greater functional status impairment (Roland disability score > 12) at baseline, muscle relaxant users had somewhat slower recovery from the episode of back pain. This finding persisted after controlling for baseline functional status, age, worker's compensation status, and use of nonsteroidal inflammatory agents. CONCLUSIONS: Use of muscle relaxants was very common among patients with acute low back pain. Muscle relaxant use was not associated with more rapid functional recovery.

Acute Disease↗
PubMed1984

Effect of prior administration of suxamethonium on non-depolarising muscle relaxants in the dog.

The depolarising muscle relaxant suxamethonium (0.3 mg kg-1) was administered to six dogs. At 50 per cent return of the neuromuscular activity, as measured by the train-of-four technique, a non-depolarising muscle relaxant was administered. Three drugs, alcuronium (0.1 mg kg-1), gallamine (1.0 mg kg-1) and pancuronium (0.06 mg kg-1) were injected intravenously. At the 50 per cent return of neuromuscular activity, atropine and neostigmine were administered to reverse the neuromuscular block. The duration of action of the three non-depolarising relaxants was reduced by the prior administration of suxamethonium.

Alcuronium↗
PubMedDate not supplied

Comparative study in mice of tetrazepam and other centrally active skeletal muscle relaxants.

Tetrazepam is a 1,4 benzodiazepine (BZD) clinically used in France and Germany as a muscle relaxant. The activity of tetrazepam was compared to that of diazepam, baclofen, mephenesin and chlormezanone in mice, in pharmacological models which are predictive of muscle relaxant and sedative properties. Tetrazepam was active in all the 6 tests of muscle relaxation (traction, chimney, inclined screen, grip force, horizontal grid and morphine-induced Straub tail). The overall muscle relaxant potency of tetrazepam was inferior to that of diazepam, but was clearly superior to that of chlormezanone and mephenesin. Baclofen was less active than tetrazepam in 3 tests (traction, horizontal grid, and grip strength), but more active in the other 3 tests. The administration of the benzodiazepine receptor antagonist Ro 15-1788 blocked the effects of tetrazepam and diazepam in 2 representative tests, morphine-induced Straub tail and the rotarod test, but did not modify the activities of the other centrally acting muscle relaxants in these same models. The selectivity ratio (ED50 rotarod or ED50 locomotor activity/ED50 in each muscle relaxant test) for tetrazepam was superior to that of diazepam and all the other muscle relaxant drugs examined. It is concluded that tetrazepam exerts its muscle relaxant activity by stimulating central BZD receptors, and presents the advantage of a wide dissociation between muscle relaxant and sedative potencies.

Animals↗
PubMed1998

Effect of muscle relaxation splint therapy on the electromyographic activities of masseter and anterior temporalis muscles.

The purpose of this study was to compare the effectiveness of splint therapy on the electromyographic activity of masticatory muscles (anterior temporalis and masseter) before and after the application of a muscle relaxation splint. Electromyography recordings from the masseter and anterior temporalis muscles were analyzed quantitatively during maximal biting in the intercuspal position both before and after treatment without a splint. Fourteen patients whose chief complaint was masticatory muscle pain were selected for the study. After the initial evaluations muscle relaxation splints were applied, and the patients were instructed to use the splints for 6 weeks. Surface electromyographic recordings were taken from each patient before the beginning of clinical therapy and after 6 weeks of wearing the splints. The data obtained were analyzed through paired sample t tests and Wilcoxon's signed rank tests. The results of the study were as follows: (1) the electromyographic activity of the two muscles during maximal biting was not markedly changed after the muscle relaxation splint was used; and (2) the changes observed in electromyographic activity of the involved and noninvolved sides were insignificant as well.

Adult↗