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PubMed1975

A clinical comparison of AH8165 and pancuronium as muscle relaxants in patients undergoing cardiac surgery.

The non-depolarizing muscle relaxant AH8165 has been compared at two doses (0.5 and 1.0 mg/kg) with pancuronium (0.1 mg/kg) during induction of anaesthesia for patients having major cardiac surgery. After barbiturate-opiate premedication and thiopentone induction, administration of pancuronium was followed by no significant alteration in heart rate or arterial pressure. Both doses of AH8165 werr followed by significant tachycardia, and the higher dose by arterial hypotension. The lower dose of AH8165 was unsatisfactory for tracheal intubation, but the AH8165 1 mg/kg gave intubating conditions similar to those with pancuronium 0.1 mg/kg.

Adult↗
PubMed1997

Are plasma concentration values necessary for pharmacodynamic modeling of muscle relaxants?

BACKGROUND: The traditional approach to pharmacokinetic/ pharmacodynamic modeling of muscle relaxants requires sampling of plasma to determine drug concentrations. The authors recently proposed that certain pharmacodynamic characteristics (IR50, the steady-state infusion rate to maintain 50% twitch depression; keo, the rate constant for equilibration between plasma concentration and effect; and gamma, the Hill factor describing sigmoidicity of the concentration-effect relation) could be estimated without plasma concentration data. Here estimates for IR50, keo, and gamma determined with and without plasma concentration data are compared. METHODS: Six volunteers were given 15-60 micrograms/kg vecuronium on each of two occasions during anesthesia with propofol. Mechanical responses to train-of-four stimulation were measured at the adductor pollicis and at the laryngeal adductors. Various pharmacokinetic models accounting for the presence and potency of vecuronium's 3-desacetyl metabolite and a sigmoid e-max pharmacodynamic model were fit to the resulting plasma concentration and effect (adductor pollicis and laryngeal adductors) data to determine IR50 keo, and gamma for each effect. One model related dose to effect without plasma concentration data. RESULTS: Values for IR50(adductor pollicis), IR50(laryngeal adductors), gamma (adductor pollicis), and gamma (laryngeal adductors) were similar when determined with and without plasma concentration values. Values for keo (adductor pollicis) and keo (laryngeal adductors) were larger when determined without plasma concentration values compared with those determined with these values; however, the ratio of keo (adductor pollicis) to keo(laryngeal adductors) was similar when determined with and without plasma concentration values. CONCLUSIONS: Certain pharmacodynamic parameters were estimated accurately in the absence of plasma concentration values. This suggests limited utility for plasma concentration data under conditions similar to those of the present study.

Body Fluid Compartments↗
PubMed1980

Effects of nonspecific smooth muscle relaxants and Ca-blocker on Ca-release and Ca-binding in microsomal fractions from rabbit taenia coli.

Effects of nonspecific smooth muscle relaxants, papaverine (10(-4) M) and Aspaminol (1,1-diphenyl-3-piperidinobutanol hydrochloride, 10(-4) M), and Ca-blocker, D-600 (10(-6) M) on Ca-release and Ca-binding in the microsomal fractions of rabbit taenia coli were determined. The doses necessary to relax the K-depolarized taenia coli were determined. The doses necessary to relax the K-depolarized taenia coli maximally were used. Ca-binding in the microsomal fractions was inhibited by Aspaminol and D-600 and increased by papaverine in the concentration used. On the other hand, Ca-release from the Ca-incorporated microsomal fractions was inhibited by papaverine and Aspaminol but was not influenced by D-600. Changes observed in Ca-transfer may be related to relaxation of smooth muscle induced by the test drugs.

Animals↗
PubMed2002

Anaphylaxis to muscle relaxants: rational for skin tests.

IgE-dependent allergy to muscle relaxants (MR) has an estimated prevalence of 1 out of 6500 General Anesthesias (GA). 62% of anaphylaxis during surgery are due to MR anaphylaxis. All the molecules are divalent, carrying two NH4+ epitopes (quaternary ammonium ions), either structurally or after rapid in vivo protonization (vecuronium). The excellent overall performance of skin test makes them the golden standard for the diagnosis of anaphylactoid reactions. Techniques include intradermal tests and prick-tests. The current localizations are the forearm and the back. Positivity criteria are 3 mm for prick-tests. For IDTs, the criterium is the doubling of the size of the injection papula, when 0.02 to 0.04 ml is injected: 8 mm. The recommended concentrations are not falsely negative. Commercial concentrations can be tested by prick tests, except for mivacurium and atracurium tested of 1:10 dilution. A scale of concentrations is advised for IDT starting with 1:10,000, up to a normally non reactive concentration that is: 100 micrograms/ml (succinylcholine), 200 micrograms/ml (gallamine), 10 micrograms/ml (atracurium), 2 micrograms/ml (mivacurium), 200 micrograms/ml (pancuronium), 400 micrograms/ml (vecuronium), 1,000 micrograms/ml (rocuronium), 200 micrograms/ml (cis atracurium). The specificity and sensitivity of the skin tests to MRs are greater than 95%. The reproducibility over years is 88%. The overall concordance of PT and IDR is 97%. Both types of tests can be used for the diagnosis. IDT have to be carried out for the search of the cross sensitization. 84% of patients do have cross sensitization to MRs but only 16% react to all MRs. The further use of MRs selected by negative IDTs has been proved to be safe.

Anaphylaxis↗
PubMed1991

Surgical muscle relaxation with Norcuron injection.

Norcuron, a new, non-depolarizing muscle relaxant has been used for anaesthesia of 48 obstetrical and gynaecological operations. The product could assure the required neuromuscular blockade in all discussed operation types when given either in single or repeated doses. It's action developed rapidly and, if required, it could be antagonized within a short period. The drug had no unfavourable circulation influencing side-effect and could be combined with the used anaesthetics. In newborns delivered by Caesarean section pathological changes were observed nor in Apgar scores, neither in the cardiorespiratory adaptation.

Adult↗
PubMed2001

Advanced glycation end-products are responsible for the impairment of corpus cavernosal smooth muscle relaxation seen in diabetes.

OBJECTIVE: To determine if advanced glycation end-products (AGEs) are responsible for the lower neuronal and endothelial-derived nitric oxide (NO)-mediated relaxation of corpus cavernosum in tissue in diabetic rats than in control rats. MATERIALS AND METHODS: Diabetes was induced in male Wistar rats by an intraperitoneal injection with streptozotocin (60 mg/kg). One group of diabetic rats was given free access to water and standard diet. A second group was given standard diet and aminoguanidine with their water (50 mg/100 mL) from the initiation of diabetes. Two groups of rats that were not diabetic acted as age-matched controls. After 8 weeks animals were killed by cervical dislocation, corpus cavernosal tissue strips harvested and mounted in an organ bath to measure isometric tension. After 90 min of equilibration at optimal resting tension and contraction with 1 micromol/L noradrenaline, the response to either acetylcholine or electrical field stimulation (EFS) after adding guanethidine (5 micromol/L) and atropine (1 micromol/L) was determined for each group. RESULTS: There was no difference between the baseline characteristics of all the experimental groups. After 8 weeks the mean body mass and glycosylated haemoglobin (HbA1c) were significantly greater in the diabetic than in control animals. Aminoguanidine had no effect on the recorded body mass or HbA1c. The in vitro relaxation response to the application of acetylcholine or EFS of tissue strips from age-matched control animals fed a standard diet and those supplemented with aminoguanidine were the same. The administration of aminoguanidine to diabetic animals for 8 weeks reversed the expected impaired relaxation response to acetylcholine; the response to EFS was similar. CONCLUSION: AGEs are more prevalent in erectile tissue from diabetic than in control animals. Aminoguanidine reversed the impairment in neuronal and endothelial NO-mediated penile smooth muscle relaxation seen in diabetes. As aminoguanidine prevents AGE formation, erectile dysfunction in diabetes is probably caused partly by the generation of AGEs.

Animals↗
PubMed1983

[Influence of a muscle relaxant, tizanidine, on gastric acid secretion and gastric ulcer in rats].

Effects of tizanidine, a centrally acting muscle relaxant, on gastric acid secretion and gastric ulcers were studied in the rat. Tizanidine (5 mg/kg, s.c.) did not influence basal acid secretion, but inhibited the centrally stimulated acid secretion in anesthetized rats. Intraduodenal administration of tizanidine (10 mg/kg) also inhibited the centrally stimulated acid secretion. The compound potentiated bethanechol-induced acid secretion at 10 mg/kg, s.c. Clonidine was found to have similar effects to tizanidine at the lower dose. Both tizanidine and clonidine inhibited basal acid secretion at a relatively low dose in conscious rats. Tizanidine (5 mg/kg, s.c.) did not modify indomethacin- and stress-induced ulcers, but Shay ulcers were slightly inhibited by the drug. Indomethacin ulcers were significantly inhibited by 10 mg/kg, s.c., 10 mg/kg, p.o. or 20 mg/kg, p.o. of tizanidine. Clonidine also was found to be a strong inhibitory agent of indomethacin-, stress- and Shay-ulcers. These results suggest that similar to clonidine, a high dosage of tizanidine influences gastric acid secretion and gastric ulcers, although the activity is lower than that of clonidine.

Anesthesia↗
PubMed1992

Inhibitory effect of inaperisone hydrochloride (inaperisone), a new centrally acting muscle relaxant, on the micturition reflex.

We examined the effects of inaperisone hydrochloride (inaperisone), a new centrally acting muscle relaxant, on bladder function in anesthetized rats and isolated rat tissues. We also investigated its mechanism of action. When a balloon inserted into the bladder was expanded, rhythmic bladder contractions were observed; inaperisone (4 mg/kg i.v.) abolished these contractions, in both normal and decerebrated rats. The bladder tonus or bladder contraction induced by peripheral stimulation of the pelvic nerve was barely inhibited by inaperisone (4 mg/kg i.v.), but this dose of inaperisone abolished the efferent discharge from the pelvic nerve that accompanied the rhythmic bladder contractions. The doses of intracerebroventricularly (i.c.v.) and intrathecally injected inaperisone which abolished the rhythmic bladder contractions were 10 and 100 micrograms, respectively. The inhibitory effects of inaperisone (4 mg/kg i.v.) were not diminished by naloxone (1 mg/kg i.v.) or by bicuculline (0.5 mg/kg i.v.), but were diminished by phaclofen (30 mg/kg i.v. or 300 micrograms i.c.v.). The specific binding of [3H]baclofen to rat brain synaptosomal membranes was barely inhibited by inaperisone (up to 1 mM). From these results, it is speculated that, among other possible mechanisms, inaperisone inhibits the micturition reflex by acting indirectly on GABAB receptors in the brainstem.

Anesthesia↗
PubMed1996

The effects of the muscle relaxant, CS-722, on synaptic activity of cultured neurones.

1. The pharmacological properties of the centrally acting muscle relaxant, CS-722, were studied in cultured hippocampal cells and dorsal root ganglion cells of the rat using the whole-cell variation of the patch clamp technique. 2. CS-722 inhibited the occurrence of spontaneous excitatory and inhibitory postsynaptic currents in hippocampal neurones at concentrations of 100-300 microM, but had no effect on postsynaptic currents evoked by the application of glycine, gamma-aminobutyric acid, glutamate or N-methyl-D-aspartate. 3. CS-722 reduced voltage-gated sodium currents, while shifting the sodium channel inactivation curve to more negative membrane potentials. This effect is similar to that reported for local anaesthetics. Voltage-gated potassium currents were decreased by CS-722 by approximately 20%, whereas voltage-activated calcium currents were inhibited by about 25%. 4. CS-722 inhibited evoked inhibitory postsynaptic currents. However, the spontaneous quantal release of inhibitory transmitter was not affected. 5. The inhibitory effect of CS-722 on spontaneous inhibitory postsynaptic currents and excitatory postsynaptic currents in hippocampal cultures probably results from an inhibition of both sodium and calcium currents. This inhibitory effect is likely to be amplified in polysynaptic neuronal circuits.

Anesthetics↗
PubMed1993

Effect of vascular smooth muscle relaxants on the protein kinase C-mediated contraction in the rat pulmonary artery.

In the rat pulmonary artery, phorbol 12,13-dibutyrate induces a contraction due to the activation of the protein kinase C. We investigated the sensitivity of this protein kinase C-mediated contraction to a variety of vascular smooth muscle relaxants. Pretreatment of rat pulmonary artery with relaxant compounds altered the subsequent concentration-response curve to phorbol 12,13-dibutyrate (0.05-2 microM) in a variable manner. Isoprenaline (0.1-10 microM), nifedipine (0.01-1 microM) and cromakalim (0.1-10 microM) had no effect, whereas vasoactive intestinal peptide (VIP, 1-10 nM), forskolin (0.1-2 microM), theophylline (0.1-2.5 mM), 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (RO 20-1724, 2-20 microM), dipyridamole (10-100 microM), 8 bromo-cyclic GMP (8-br-cGMP, 5-500 microM) and dibutyryl cyclic AMP (db-cAMP, 100-500 microM) shifted the concentration-response curve to phorbol 12,13-dibutyrate to the right and decreased the maximal response. When cumulative concentrations of relaxants were applied on the plateau of the contraction induced by 0.2 or 2 microM phorbol 12,13-dibutyrate, again, isoprenaline, nifedipine and cromakalim failed to decrease the protein kinase C-mediated contraction, whereas the other agents produced concentration-dependent relaxation. From their inhibitory effect on the 0.2 microM phorbol 12,13-dibutyrate-induced contraction, the rank order of potency of these relaxants was: VIP >> forskolin > RO 20-1724 > 8-br-cGMP > theophylline > dipyridamole > db-cAMP. In chemically (beta escin) skinned preparations, cGMP (5-500 microM) and cAMP (50-1000 microM) antagonized in a concentration dependent manner the contraction induced by phorbol 12,13-dibutyrate at constant Ca2+ concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Stimulatory effects of chlorzoxazone, a centrally acting muscle relaxant, on large conductance calcium-activated potassium channels in pituitary GH3 cells.

Chlorzoxazone, a centrally acting muscle relaxant, has been used as a marker for hepatic CYP2E1 activity. However, little is known about the mechanism of chlorzoxazone actions on ion currents in neurons or neuroendocrine cells. We thus investigated its effects on ion currents in GH(3) lactotrophs. Chlorzoxazone reversibly increased Ca(2+)-activated K(+) current (I(K(Ca))) in a concentration-dependent manner with an EC(50) value of 30 microM. The chlorzoxazone-stimulated I(K(Ca)) was inhibited by iberitoxin (200 nM) or clotrimazole (10 microM), but not by glibenclamide (10 microM) or apamin (200 nM). Chlorzoxazone (30 microM) suppressed voltage-dependent L-type Ca(2+) current. In the inside-out configuration, chlorzoxazone applied to the intracellular side of the patch did not modify single-channel conductance of large conductance Ca(2+)-activated K(+) (BK(Ca)) channels, but did increase channel activity by increasing mean open time and decreasing mean closed time. Chlorzoxazone also caused a left shift in the activation curve of BK(Ca) channels. However, Ca(2+)-sensitivity of these channels was unaffected by chlorzoxazone. 1-Ethyl-2-benzimidazolinone (30 microM), 2-amino-5-chlorobenzoxazole (30 microM) or chlormezanone (30 microM) enhanced BK(Ca) channel activity, while 6-hydroxychlorzoxazone (30 microM) slightly increased it; however, chlorphenesin carbamate (30 microM) had no effect on it. Under the current-clamp condition, chlorzoxazone (10 microM) reduced the firing rate of action potentials. In neuroblastoma IMR-32 cells, chlorzoxazone (30 microM) also stimulated BK(Ca) channel activity. The stimulatory effects of chlorzoxazone on these channels may be responsible for the underlying mechanism of chlorzoxazone actions on neurons and neuroendocrine cells.

Adenoma↗
PubMed1984

The process of muscle relaxation by the combined action of MgAMPPNP and ethylene glycol.

Insect flight muscle fibres were relaxed by the combined action of MgAMPPNP and ethylene glycol, as measured by the stiffness of the fibres. Relaxation occurred over a small range of glycol concentration. Addition of Ca2+ raised the glycol required for relaxation. The speed at which the stiffness measurement was made did not influence the glycol concentration at which relaxation occurred. Glycol in excess of that needed to relax the muscle caused a slight rise in high-frequency stiffness. Removal of the glycol restored the rigor stiffness. Under glycol-relaxed conditions, much of the AMPPNP bound in muscle fibres was retained during cold-chase (elution of [3H] AMPPNP by nonradioactive AMPPNP); the intensity ratio of the inner equatorial X-ray diffraction peaks rose upon glycol relaxation to a value slightly below that characteristic of natural relaxation. The results are interpreted in terms of cooperative attachment of the crossbridges to actin.

Adenosine Triphosphate↗
PubMed1977

Smooth muscle relaxant properties and vasomotor actions of 2-amino-1-p-nitrophenylpropane-1,3-diol.

Experiments with the guinea pig ileum, trachea, and vas deferens, the rat fundal strip, the rabbit jejunum and aortic strip, and the toad heart indicated that 2-amino-1-p-nitrophenylpropane-1,3-diol, the hydrolytic product of chloramphenicol, inhibited smooth muscles. Its action was direct and not through any mediators. After intravenous administration, the compound produced vasodepression followed by an overshooting rise of blood pressure. Vasodepression was not mediated by adrenergic, cholinergic, or histaminergic mechanisms. Hypertension was a sympathomimetic effect. Muscle relaxant and cardiovascular effects of the compound were similar to those of chloramphenicol, although it had no antibacterial effect.

Animals↗
PubMed1977

Comparison of muscle relaxants in clinical use.

A prospective clinical comparison of d-tubocurarine, alcuronium, gallamine and pancuronium was performed in 400 surgical patients. Various parameters usually followed during clinical anaesthesia were recorded from the beginning of, to the recovery from anaesthesia. Endotracheal intubation was performed with or without suxamethonium. Intubation was always possible in 1-3 min when different muscle relaxants were used in the following initial doses: d-tubocurarine 0.4 mg/kg, alcuronium 0.3 mg/kg, gallamine 1.8 mg/kg, and suxamethonium 0.8 mg/kg. However, there was a statistically significant inferiority of the d-tubocurarine and gallamine groups. The use of suxamethonium seemed to shorten the duration of the initial dose of the nondepolarising agents and also to increase especially the dose of gallamine when calculated as mg/kg/h. It should be mentioned that the non-depolarising agents were given soon after suxamethonium without waiting for the return of spontaneous respiration. Pancuronium and alcuronium caused least changes in the cardiovascular parameters. Erythematous skin reactions were seen mostly after the use of d-tubocurarine and suxamethonium. This could depend on histamine liberating potency of these muscle relaxants.

Adjuvants, Anesthesia↗
PubMed2002

Involvement of cyclic nucleotides in renal artery smooth muscle relaxation.

The elevation of vascular smooth muscle tone in the renal arteries during kidney transplantation and nephron-sparing surgery plays a major role in postsurgical organ dysfunction. Therefore, a better understanding of the intracellular mechanisms of contraction and relaxation is of fundamental interest to improve urological treatment. The present study was designed to investigate the complex intracellular system of cyclic nucleotides involved in the regulation of smooth muscle relaxation by using swine renal artery rings in the Schuler organ bath. Phenylephrine (PE) induced dose-dependent and fully reversible isometric contractions with a threshold concentration of 10 nM and an EC(50) of 804 nM. The receptor was identified as alpha(1A)-subtype by the selective antagonist WB4101. Increasing the intracellular concentration of cyclic 3':5'-adenosine monophosphate (cAMP) by dibutyryl-cAMP (5 mM) and forskolin (5 micro M) resulted in a decreased contractiltity of 48.0% and 76.3%, respectively. Elevation of the cytosolic content of cyclic 3':5'-guanosine monophosphate (cGMP) using dibutyryl-cGMP (1 mM), sodium nitroprusside (100 micro M) and SIN-1 (100 micro M) decreased the average PE-induced contraction by 16.4%, 41.9% and 62.4%, respectively. The unselective phosphodiesterase inhibitors theophylline (1 mM), papaverine (100 micro M) and IBMX (5 mM) reduced the PE-induced contraction by 37.3%, 93.1% and 95.5%, respectively. Furthermore, selective inhibition of phosphodiesterases by milrinone (PDE(3)-selective) resulted in a decreased contractility by 1.3% (50 micro M), 29.5% (100 micro M) and 93.5% (5 mM), and using rolipram (PDE(4) selective), the PE-induced contraction was inhibited by 57.9% (50 micro M) and 81.9% (100 micro M). The results suggest the involvement of cAMP and cGMP in the relaxation of renal artery smooth muscle cells. Moreover, phosphodiesterases, especially PDE(3) and PDE(4), seem to play a critical role in the regulation of renal artery smooth muscle tone.

Animals↗
PubMed1982

Pharmacological studies on 6-amino-2-fluoromethyl-3-(O-tolyl)-4(3H)-quinazolinone (afloqualone), a new centrally acting muscle relaxant. (II) Effects on the spinal reflex potential and the rigidity.

Effects of afloqualone on mono- (MSR) and poly-synaptic reflex (PSR) potentials and alpha- and gamma-rigidities were studied in experimental animals. Afloqualone dose dependently inhibited both MSR and PSR potentials in spinalized cats though afloqualone had no inhibitory effect on the patellar reflex in cats as reported in the previous paper. Afloqualone, like tolperisone, more selectively inhibited the PSR potential than MSR potential, whereas baclofen inhibited them in reverse order. However, the selectivity towards the PSR potential was higher with afloqualone than with tolperisone. In rats and cats, afloqualone dose dependently relaxed both alpha- and gamma-rigidity when administered p.o. as well as i.v. Its 50% inhibitory dose for alpha-rigidity was 1.5-2 times larger than that for gamma-rigidity. Tolperisone also relaxed both rigidities in i.v. administration, but had little effect when given p.o. Only mephenesin relaxed the post-ischaemic spinal rigidity in cats. These results suggest that afloqualone, like other well known centrally acting muscle relaxants except for baclofen, more strongly inhibits the polysynaptic pathway than the mono-synaptic pathway of the spinal cord as well as more strongly the gamma-system than the alpha-system.

Animals↗