Preclinical Pharmacology in the Rhesus Monkey of CW 1759-50, a New Ultra-short Acting Nondepolarizing Neuromuscular Blocking Agent, Degraded and Antagonized by L-Cysteine.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Structure-activity studies were performed to identify a new neuromuscular blocking agent retaining the ultra-short acting characteristics of gantacurium, including degradation and reversal by L-cysteine, but lacking its histaminoid properties in man. CW 1759-50 has emerged from this program. METHODS: Adduction of CW 1759-50 with L-cysteine was studied by high-performance liquid chromatography and mass spectrometry. Institutional Animal Care and Use Committee-approved comparisons of CW 1759-50 to gantacurium were performed in rhesus monkeys. ED95 for neuromuscular blockade was established. Spontaneous recovery was compared to reversal by L-cysteine in paired studies of boluses or infusions. In addition, changes in mean arterial pressure and heart rate after very large doses of 15 to 60 × ED95 were compared. RESULTS: The half-time of adduction of L-cysteine to CW 1759-50 in vitro was 2.3 min. The ED95 of CW 1759-50 was 0.069 ± 0.02 mg/kg; ED95 of gantacurium was 0.081 ± 0.05 mg/kg (P = 0.006). Duration of action (recovery to 95% twitch height after 98 to 99% blockade) was as follows: CW 1759-50, 8.2 ± 1.5 min; and gantacurium, 7.4 ± 1.9 min; (n = 8 and 9, P = 0.355). Administration of L-cysteine (30 mg/kg) shortened recovery (i.e., induced reversal) from CW 1759-50 after boluses or infusions (P always less than 0.0001). Recovery intervals (5 to 95% twitch) ranged from 6.1 to 6.7 min (and did not differ significantly) after boluses of 0.10 to 0.50 mg/kg, as well as control infusions (P = 0.426 by analysis of variance). Dose ratios comparing changes of 30% in mean arterial pressure or heart rate to ED95 for neuromuscular blockade (ED 30% Δ [mean arterial pressure or heart rate]/ED95) were higher for CW 1759-50 than for gantacurium. CONCLUSIONS: CW 1759-50, similar to gantacurium, is an ultra-short acting neuromuscular blocking agent, antagonized by L-cysteine, in the monkey. The circulatory effects, however, are much reduced in comparison with gantacurium, suggesting a trial in humans.

Pancuronium enhances isoflurane anesthesia in rats via inhibition of cerebral nicotinic acetylcholine receptors.

PURPOSE: This study was conducted to elucidate the mechanism of enhancement of volatile anesthetics by neuromuscular blocking agents in rats and to consider the relevance of this enhancement to clinical anesthesia. METHODS: Male Sprague-Dawley rats were used. After confirming a movement in response to tail clamping under 1.1 % isoflurane anesthesia, response was determined when the tail clamp was applied at several points after microinjection of pancuronium into the lateral ventricle. Arousal responses to microinjection of nicotine into the lateral ventricle were assessed with or without pretreatment with intraventricular pancuronium. The intravenous 50 % effective dose (ED50) and 95 % effective dose (ED95) for neuromuscular blockade with pancuronium administered in a cumulative fashion at 1.1 % isoflurane were calculated. RESULTS: Intraventricular pancuronium dose-dependently reduced the response to tail clamping, and the dose required to show immobilization of 50 % of rats (intraventricular ED50) was 1.62 µg/kg. Pretreatment with pancuronium at 6 µg/kg significantly reduced the effect of awakening by nicotine under isoflurane anesthesia (P = 0.044). The intravenous ED50 and ED95 for neuromuscular blockade were 63 µg/kg (90 % confidence interval [CI] 52-75 µg/kg) and 133 µg/kg (90 % CI 109-158 µg/kg), respectively. The ratio of intraventricular ED50 to intravenous ED50 was 0.026. CONCLUSION: Pancuronium microinjection into the lateral ventricle dose-dependently enhances the depth of isoflurane anesthesia, which might be caused by inhibition of neuronal nicotinic acetylcholine receptor transmission in the cerebrum. Intravenous injection of pancuronium at high doses might increase the cerebrospinal concentration to a level at which an effect can be observed.

Cysteine reversal of the novel neuromuscular blocking drug CW002 in dogs: pharmacodynamics, acute cardiovascular effects, and preliminary toxicology.

BACKGROUND: CW002 is a neuromuscular blocking drug that is inactivated by endogenous L-cysteine. This study determined the exogenous L-cysteine dose-response relationship for CW002 reversal along with acute cardiovascular effects and organ toxicity in dogs. METHODS: Six dogs were each studied four times during isoflurane-nitrous oxide anesthesia and recording of muscle twitch, arterial pressure, and heart rate. CW002 (0.08 mg/kg or 9 x ED95) was injected, and the time to spontaneous muscle recovery was determined. CW002 was then administered again followed 1 min later by 10, 20, 50, or 100 mg/kg L-cysteine (1 dose/experiment). After twitch recovery, CW002 was given a third time to determine whether residual L-cysteine influenced duration. Preliminary toxicology was performed in an additional group of dogs that received CW002 followed by vehicle (n = 8) or 200 mg/kg L-cysteine (n = 8). Animals were awakened and observed for 2 or 14 days before sacrificing and anatomic, biochemical, and histopathologic analyses. RESULTS: L-cysteine at all doses accelerated recovery from CW002, with both 50 and 100 mg/kg decreasing median duration from more than 70 min to less than 5 min. After reversal, duration of a subsequent CW002 dose was also decreased in a dose-dependent manner. Over the studied dose range, L-cysteine had less than 10% effect on blood pressure and heart rate. Animals receiving a single 200-mg/kg dose of L-cysteine showed no clinical, anatomic, biochemical, or histologic evidence of organ toxicity. CONCLUSION: The optimal L-cysteine dose for rapidly reversing the neuromuscular blockade produced by a large dose of CW002 in dogs is approximately 50 mg/kg, which has no concomitant hemodynamic effect. A dose of 200 mg/kg had no evident organ toxicity.

Gene expression analysis of human middle ear cholesteatoma using complementary DNA arrays.

OBJECTIVE: To identify genes regulated in human cholesteatoma compared with normal skin tissue using complementary DNA arrays. STUDY DESIGN: In vitro analysis. METHODS: Eight cholesteatoma and retroauricular skin samples were obtained from the same patients during surgery. Upregulated and downregulated genes were highlighted using complementary DNA arrays for screening. Reverse transcriptase-polymerase chain reaction and immunohistochemical staining were performed to confirm the results of the complementary DNA array. RESULTS: Twelve genes were found to be induced or upregulated in cholesteatoma compared with skin samples. These included genes involved in cell proliferation and differentiation (eg, calgranulin A, calgranulin B, psoriasin, thymosin beta-10) and cell invasion (eg, cathepsin C, cathepsin D, cathepsin H). Analyses by means of reverse transcription-polymerase chain reaction showed enhanced expression of several genes including calgranulin A, calgranulin B, psoriasin, thymosin beta-10, cathepsin C, cathepsin D, and cathepsin H in cholesteatoma, supporting the findings from the gene array. In addition, it was verified by immunohistochemical analysis that the expressions of Calgranulin A, Calgranulin B, and Cathepsin D were mainly located in cholesteatoma epithelium. CONCLUSION: The observed alteration in gene expression may play a role in various mechanisms of pathogenesis in cholesteatoma.