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PubMed1980

Centrally acting oral skeletal muscle relaxants.

A critical examination of the literature on centrally acting, orally administered skeletal muscle relaxants (SMRs) is presented. The available comparative clinical studies are reviewed, and the pharmacology, metabolism and adverse effects of the oral SMRs are discussed briefly. The drugs covered are carisoprodol, chlorphenesin carbamate, chlorzoxazone, cyclobenzaprine hydrochloride, diazepam, metaxalone, methocarbamol, and orphenadrine citrate. The mechanism of action of these agents is not well defined, and their effects are measured mainly by subjective responses. Thus, acceptable evidence of efficacy is difficult to obtain, especially if clinical studies continue to be designed inadequately. There are inadequate data to support the superiority of any one drug. Further, unique clinical efficacy of any oral SMR in comparison to nonspecific sedation has not been established. Based on subjective responses, all agents, except diazepam, have been shown to be superior to placebo in acute disorders; cyclobenzaprine has not been evaluated in acute conditions. SMRs are less effective in chronic disorders. Combination muscle relaxant-analgesic products appear to be superior to their individual components, but the relative efficacy of these combination products in comparison to combined use of individual sedative and analgesic agents is unknown.

Analgesics↗
PubMed1992

Acute myopathy during treatment of status asthmaticus with corticosteroids and steroidal muscle relaxants.

Acute myopathy in patients being treated for severe asthma has been recognized with increasing frequency since first being described in 1977. We report three patients treated for status asthmaticus who developed severe generalized weakness. Electrophysiologic studies and muscle biopsy revealed evidence of muscle destruction. Each of these patients was treated with high-dose corticosteroids and underwent prolonged neuromuscular blockade with a steroidal muscle relaxant. A review of the literature revealed 15 similar cases. We postulate that the combined effects of corticosteroids and muscle relaxants on the muscle cell may be responsible for this myopathy. Patients treated with corticosteroids and NMBs should be carefully monitored for the development of myopathy.

Acute Disease↗
PubMed1999

Effects of muscle relaxants on EEG, ABR and EMG in rabbits.

The effects of baclofen and pancuronium bromide on evoked electromyogram (EMG), cortical electroencephalogram (EEG) and auditory brainstem responses (ABR) were studied in pentobarbital anesthetized normal rabbits. Evoked EMG was measured in the gastrocnemius muscle by electrical stimulation of the sciatic nerve. Intravenous injection of baclofen decreased EEG and arterial blood pressure and light reflex, however, it had no significant influence on EMG or ABR at doses of 10 and 20 mg/kg/h. Pancuronium bromide immediately inhibited respiration, decreased EEG and EMG, however, it had no significant influence on arterial blood pressure, ABR, or light reflex, at doses of 0.4 and 1.0 mg/kg/h in anesthetized rabbits. ABR waves were observed until just before cardiac arrest with both of the muscle relaxants. It is suggested that ABR are not influenced by central or peripheral muscle relaxants, or by pentobarbital.

Acoustic Stimulation↗
PubMed1997

Nitric oxide-induced ciliary muscle relaxation during contraction with endothelin-1 is mediated through elevation of cyclic GMP.

PURPOSE: Nitric oxide (NO) relaxes ciliary smooth muscle, and endothelin-1 (ET-1) is reported to regulate ciliary muscle tone. Despite the physiological significance of nitric oxide and ET-1, very few studies have attempted to characterize the mutual modes of action of these mediators in this tissue. Thus, the present experiments were designed to investigate a possible relaxation mechanism of nitric oxide in bovine ciliary muscle that has been contracted by ET-1. METHODS: The effects of sodium nitroprusside (SNP), as a nitric oxide donor, methylene blue, as an inhibitor of guanylate cyclase, and 8-bromo-cyclic GMP on the bovine ciliary muscle contracted with ET-1 were examined. The changes in cyclic GMP level and relaxation, in response to SNP alone or in combination with 3-isobutyl-1-methylxanthine (IBMX) as a nonselective inhibitor of phosphodiesterases, were also determined. RESULTS: Sodium nitroprusside (SNP) produced a concentration-dependent relaxation, which was significantly (p < 0.005) augmented by 10(-5) M 3-isobutyl-1-methylxanthine (IBMX) and significantly (p < 0.005) attenuated by 3 x 10(-5) M methylene blue as an inhibitor of guanylate cyclase. The relaxation in response to SNP was accompanied by an increase in the cyclic 3':5' guanosine monophosphate (cyclic GMP) level, which was again significantly (p < 0.05) augmented by 10(-5) M IBMX and significantly (p < 0.005) attenuated by 3 x 10(-5) M methylene blue. The exogenously applied 8-bromo-cyclic GMP relaxed the ciliary muscle strips during the contraction caused by ET-1. CONCLUSIONS: These results lead us to assume that NO generated from SNP is closely related to cyclic GMP production via the activation of guanylate cyclase and, in turn, causes a relaxation response in the bovine ciliary muscle contracted with ET-1.

1-Methyl-3-isobutylxanthine↗
PubMedDate not supplied

[The calcium pump in the sarcolemma controls smooth muscle relaxation].

In order to identify the functional role of the sarcolemma calcium pump in the control over smooth muscle relaxation there was studied the effect of temperature on relaxation kinetics of myometrium carbachol contracture, actomyosin superprecipitation isolated from this object and Mg2+, ATP-dependent transport of Ca2+ in the fraction of uterus sarcolemma vesicles. The activation energies of the processes under study were determined in comparison. It was concluded from the evidence obtained that relaxation of the smooth muscle contracture is controlled by the stimulated temperature increase and by Na(+)-independent trans-sarcolemma release of Ca2+ from the myocytes sensitive to La3+ effect. The release is provided by the calcium pump of the plasmic membrane.

Adenosine Triphosphate↗
PubMed2002

Role of catalase in the smooth muscle relaxant actions of sodium azide and cyanamide.

The aim of this study was to determine the role of catalase in the smooth muscle relaxant actions of sodium azide and cyanamide. The effects of 3-amino-1,2,4-triazole suggested a role for this enzyme in the relaxant actions of sodium azide on rat aorta and bovine retractor penis muscle and cyanamide on rat aorta. Moreover, results obtained using a difference spectrophotometric assay based upon the oxidation of haemoglobin were consistent with the catalase-dependent oxidation of sodium azide to nitric oxide (NO) and of cyanamide to nitroxyl anion. Surprisingly, however, no free nitric oxide or nitroxyl was detected in solution using a sensitive electrode. This anomaly might be explained if the stable complexes of catalase with nitric oxide or nitroxyl do not release their respective ligand except to sites of high affinity, such as the haemoglobin employed in the difference spectrophotometric assay, or indeed, the soluble guanylate cyclase within the smooth muscle.

Amitrole↗
PubMed1999

Myopathy following mechanical ventilation for acute severe asthma: the role of muscle relaxants and corticosteroids.

BACKGROUND: Acute myopathy following mechanical ventilation for near-fatal asthma (NFA) has been described recently, and some researchers have suggested that this complication is related to the use of neuromuscular blocking agents (NMBAs) and corticosteroids (CSs). OBJECTIVES: To determine the incidence of acute myopathy in a group of patients and to examine the most important predictors of its development. DESIGN AND METHODS: A retrospective cohort study over a 10-year period (1985 to 1995) of all asthma patients who received mechanical ventilation at two centers in Vancouver (designated center 1 and center 2). RESULTS: In center 1, there were 58 patients who had 64 episodes of NFA, and in center 2, there were 28 patients who had 30 episodes. NMBAs were used in 30 of 86 admissions for acute severe asthma (35%). The mean (+/- SD) duration of muscle paralysis was 3.1+/-2.3 days. A total of 9 patients (10.4%) developed significant myopathy. The incidence of myopathy was 9 of 30 (30%) among patients who received NMBAs. In a multiple logistic regression model, the development of myopathy was only significantly associated with the duration of muscle relaxation. The odds ratio for the development of myopathy increased by 2.1 (95% confidence interval, 1.4 to 3.2) with each additional day of muscle relaxation. The dose and the type of the CS were not significantly associated with the myopathy in the multiple logistic regression analysis. CONCLUSION: Our study showed that there is a high incidence of acute myopathy when NMBAs are used for NFA. The incidence of myopathy increases with each additional day of muscle relaxation.

APACHE↗
PubMed2004

Long-lasting smooth-muscle relaxation by a novel PACAP analogue in human bronchi.

We compared the relaxant effect of original pituitary adenylate cyclase-activating peptide (PACAP)1-27 with that of a newly developed, synthetic PACAP1-27 analogue, [Arg15,20,21 Leu17]-PACAP-Gly-Lys-Arg-NH2, in human bronchi in vitro (n=4-5 in each group). Using precontraction by carbachol (0.1 microM), cumulative administration of PACAP1-27 and salbutamol caused concentration-dependent smooth muscle relaxation with similar potencies and maximum relaxant effects. Non-cumulative administration of the PACAP1-27 analogue and the original PACAP1-27 caused concentration-dependent relaxation with a similar maximum relaxant effect and potency as well. However, the onset and offset of action was markedly slower for the PACAP1-27 analogue than for the original PACAP1-27 (>90% versus <10% of peak relaxation remaining 5 h after administration). Peptidase inhibition by captopril (10 microM) and phosphoramidon (1 microM) significantly increased the maximum relaxant effect and duration of action of PACAP1-27 but not of the PACAP1-27 analogue, during the 3 h of observation in the human bronchi. We conclude that [Arg15,20,21 Leu17]-PACAP-Gly-Lys-Arg-NH2 produces significant concentration-dependent and sustained bronchial smooth muscle relaxation in vitro. The sustained relaxant effect is due, at least in part, to the synthetic PACAP1-27 analogue being less susceptible to cleavage by peptidases than the original peptide PACAP1-27.

Amino Acid Sequence↗
PubMed1980

Anaphylaxis to muscle relaxants: cross sensitivity between relaxants.

Two patients are described who had clinical anaphylaxis due to muscle relaxants. One patient had systemic hypersensitivity and positive intradermal tests to d-tubocurarine and alcuronium. The second had systemic hypersensitivity to d-tubocurarine and positive intradermal tests to d-tubocurarine, alcuronium, and pancuronium. It is suggested that positive intradermal tests to more than one relaxant may mean allergy to more than one relaxant rather than false positive test. Cross sensitivity between alcuronium and d-tubocurarine occurs and a similar situation may exist for suxamethonium and gallamine. When intradermal testing is carried out after anaesthetic reactions all relaxants should be tested.

Adult↗
PubMed2005

Synthesis and bladder smooth muscle relaxing properties of substituted 3-amino-4-aryl-(and aralkyl-)cyclobut-3-ene-1,2-diones.

We have reported on the design, synthesis, and biological characterization of (R)-4-[3,4-dioxo-2-(1,2,2-trimethyl-propylamino)-cyclobut-1-enylamino]-3-ethyl-benzonitrile (1), a novel, potent, and selective adenosine 5'-triphosphate-sensitive potassium (K(ATP)) channel opener with potential utility for the treatment of urge urinary incontinence (UUI). Excising the aniline-derived nitrogen atom of 1 or replacing it with an aralkyl group, led to bladder smooth muscle relaxant chemotypes 3 and 4, respectively. Prototype compounds in these series were found to produce significant increases in an iberiotoxin (IbTx)-sensitive hyperpolarizing current, thus suggesting that these relatively modest structural modifications resulted in a switch in the mechanism of action of these smooth muscle relaxants from K(ATP) channel openers to activators of the large-conductance Ca2+-activated potassium channel (BK(Ca)). We report herein the syntheses and biological evaluation of a series of substituted 3-amino-4-aryl-(and aralkyl-)cyclobut-3-ene-1,2-diones.

Cyclobutanes↗
PubMed2003

Efficacy of IV Buscopan as a muscle relaxant in CT colonography.

The aim of this study was to examine the efficacy of IV Buscopan as a muscle relaxant in CT colonography in terms of colonic distension and polyp detection, and to determine its particular efficacy in patients with diverticular disease. Seventy-three consecutive patients were randomised to receive IV Buscopan or no muscle relaxant prior to CT colonography. CT colonography was performed using a Siemens Somatom 4-detector multislice CT scanner. The following parameters were recorded: degree of colonic distension using a 4-point scale; diagnostic adequacy of colonic distension; presence or absence of diverticular disease; and presence of colonic polyps. Accuracy of polyp detection was assessed using subsequent conventional colonoscopy as a gold standard. There was no significant difference between the two groups in the number of segments that were deemed to be optimally or adequately distended (p=0.37). Although IV Buscopan did improve distension of certain segments, this effect was not sufficient to improve the number of diagnostically adequate studies in the Buscopan group (p=0.14). In patients with diverticular disease, IV Buscopan did not have any significant effect on segments affected by diverticulosis but was associated with an improvement in distension of more proximal segments. There was no significant difference between the two groups in terms of polyp detection (p=0.34). The addition of prone scanning to supine scanning was found to be the most useful technique for maximising colonic distension. Intravenous Buscopan at CT colonography does not improve the overall adequacy of colonic distension nor the accuracy of polyp detection. In patients with sigmoid diverticular disease IV Buscopan improves distension of more proximal colonic segments and may be useful in selected cases, but our results do not support its routine use for CT colonography.

Adult↗
PubMed1976

Sterculia bulk-forming agent with smooth-muscle relaxant versus bran in diverticular disease.

Sterculia with and without a smooth-muscle relaxant (alverine citrate) had similar beneficial effects on constipation and reduced the transit times in diverticular disease. Intracolonic pressure, however, varied with the preparation used. Though both preparations relieved the symptoms of diverticular disease, the one containing alverine citrate was more effective. Part of the mode of action of bran may be to relax the smooth muscle of the gut, since its actions were more comparable to those of sterculia plus alverine citrate than to those of sterculia alone.

Clinical Trials as Topic↗
PubMed2002

[Mydeton: a centrally acting muscle relaxant drug from Gedeon Richter LTD].

Since its introduction in 1959 tolperisone hydrochloride (Mydeton) is still one of the leading products of Gedeon Richter Ltd. It has been successfully applied for treating different painful muscle spasms. The compound is successfully marketed also by several foreign, mostly Japanese, pharmaceutical companies, as a central muscle relaxant agent. The present summary overviews the pharmacology of tolperisone, with special emphasize on its still partly understood way of action. Data from the scientific literature as well as our own experimental results strongly support the hypothesis that inhibition of voltage gated sodium channels is a major component of the mechanism of action of tolperisone. The paper also summarizes the clinical results with tolperisone and the perspectives of the therapeutic use of centrally acting muscle relaxants.

Animals↗
PubMed1980

Effects of nonspecific smooth muscle relaxants on tissue concentrations of high energy phosphates and mechanical activity of normal polarized and depolarized intestinal smooth muscles from guinea pig.

Effects of nonspecific smooth muscle relaxants, an uncoupler and removal of Ca ions from physiological solution on the tissue concentrations of high energy phosphates, such as ATP and creatine phosphate (CP) and tension of the normal polarized and KCl-depolarized intestinal smooth muscles of guinea pig were studied. Decrease of CP-concentration induced by dinitrophenol (DNP; 10(-4) M) was accompanied by relaxation of the normal polarized and KCl-depolarized smooth muscles. DNP slightly (but significantly) decreased ATP-concentration in the normal polarized and KCl-depolarized smooth muscles. Application of papaverine ( 3 x 10(-5) M) relaxed the normal polarized taenia immediately but increased CP-concentration at 5 and 10 min and decreased the concentration at 20 min. When the depolarized smooth muscle was considerably relaxed by papaverine (3 x 10(10-5) M), there was little influence on the CP-concentration. After relaxation of the depolarized taenia as induced by papaverine had reached a maximal amplitude, CP-concentration decreased significantly. ATP-concentration was little influenced by papaverine in the normal polarized and KCl-depolarized muscles. Although the treatments with a synthetic antispasmodic drug, Aspaminol (3 x 10(-4) M), which was found to inhibit Ca-uptake by the intestinal smooth muscles, a Ca-blocker, D-600 (10(-6) M) and removal of Ca ions from physiological solution relaxed the polarized and depolarized smooth muscles, the tissue concentrations of CP and ATP increased. These phenomena are considered to be due to decrease of the intracellular Ca-concentration.

Adenosine Triphosphate↗
PubMed1988

The influence of respiratory-induced acid-base changes on the action of non-depolarizing muscle relaxants in rats.

The influence of respiratory-induced acid-base changes on the action of non-depolarizing muscle relaxants was investigated using the rat phrenic nerve-hemidiaphragm preparation. Changes in pH were induced by changes in the CO2 concentration aerating Krebs' solution. In the absence of muscle relaxants, an increase in CO2 from 5% to 7.5% decreased (P less than 0.01) indirectly elicited twitch tension by 5.4 +/- 0.7% (mean +/- SEM), while a decrease in CO2 from 5% to 2.5% increased (P less than 0.01) twitch tension by 2.3 +/- 0.7%. With a change in CO2 from 2.5% to 7.5%, partial neuromuscular blockade produced by d-Tc or vecuronium was augmented (P less than 0.01), while that produced by metocurine, pancuronium, or alcuronium was reduced (P less than 0.01). With the change in CO2 from 7.5% to 2.5%, the neuromuscular blockade produced by d-Tc or vecuronium was reduced (P less than 0.01), while that produced by metocurine, pancuronium, or alcuronium was augmented (P less than 0.01). Dose-response study showed that 2.5% CO2 shifted the dose-response curves for d-Tc and vecuronium to the right (P less than 0.01) from those with 5% CO2, whereas 7.5% CO2 shifted them to the left (P less than 0.05). In contrast, neither 2.5% CO2 or 7.5% CO2 significantly shifted the dose-response curves for metocurine or pancuronium from those with 5% CO2. Their dose-response curves with 2.5% CO2 were to the left, instead of to the right, of those with 7.5% CO2 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis, Respiratory↗
PubMed1978

Synthesis and comparative skeletal muscle relaxant activity of some 2,4-imidazolidinediones and their corresponding 5-hydroxy-2,4-imidazolidinediones.

A series of 5-hydroxy substitution products of 2,4-imidazolidinediones, including the 5-hydroxy metabolite of the skeletal muscle contraction antagonist, dantrolene sodium, has been synthesized and evaluated for skeletal muscle relaxant activity. Most of these analogues are active in vivo with iv administration and in vitro. While two analogues are also active by oral and ip administration, only 1-[[[5-(3,4-dichlorophenyl)-2-furanyl]methylene]amino]-5-hydroxy-2,4-imidazolidinedione is sufficiently active in inhibiting the Straub tail in mice. However, none of these analogues has a muscle relaxant efficacy index greater than 1, comparable to dantrolene.

Animals↗
PubMed2001

The interaction of AR-A008055 and its enantiomers with the GABA(A) receptor complex and their sedative, muscle relaxant and anticonvulsant activity.

AR-A008055 [(+/-)-1-(4-methyl-5-thiazolyl)-1-phenylmethylamine] is structurally related to clomethiazole and has been used to probe the mechanism of the neuroprotective effect of clomethiazole. Clomethiazole, (+/-)-AR-A008055 and (S)-(-)-AR-A008055 all displaced [35S]-t-butyl-bicyclophosphorothionate ([35S]TBPS) from rat cerebral cortex tissue (IC50 values: GABA, 8.1+/-0.04 microM; clomethiazole, 130+/-30 microM; (+/-)-AR-A008055, 494+/-7 microM; (S)-(-)-AR-A008055, 221+/-14 microM. (R)-(+)-AR-A008055 was without significant effect (IC50>1000 microM). None of the compounds interacted with NMDA or AMPA receptors or with sodium or calcium (N, P/Q) channels. Brain penetration of both enantiomers following their i.p. administration was excellent, with brain and plasma concentrations being similar. Clomethiazole dose-dependently inhibited spontaneous locomotor activity in rats and was approximately 10 times more sedative than either enantiomer of AR-A008055. Clomethiazole was more potent than (S)-(-)-AR-A008055 in the "pull-up" test (muscle relaxation) and in producing loss of righting reflex, while (R)-(+)-AR-A008055 had little effect. The time animals remained on a Rota-rod was of the order: clomethiazole<(S)-(-)-AR-A008055<(R)-(+)-AR-A008055. (S)-(-)-AR-A008055 (210 micromol/kg) raised seizure threshold to pentylenetetrazole (i.v.) by 119+/-21%. The (R)-(+)- enantiomer was not anticonvulsant. Overall, (S)-(-)-AR-A008055 exhibited a similar pharmacology to clomethiazole. However, its sedative and muscle relaxant effects were substantially less than clomethiazole, emphasising that these properties are not directly related to neuroprotective efficacy. The current data suggest that the proposed GABA uptake inhibitory property of (R)-(+)-AR-A008055 fails to produce significant sedative, myorelaxant or anticonvulsant activity.

Animals↗