On the relationship between inhibition and receptor occupancy by nondepolarizing neuromuscular blocking drugs

Background Nondepolarizing neuromuscular blocking drugs (NDNBs) are clinically used to produce muscle relaxation during general anesthesia. To better understand clinical properties of NDNBs, comparative in vitro pharmacologic studies have been performed. In these studies, a receptor binding model, which relies on the assumption that the inhibition, i.e., the effect of an NDNB, is proportional to the receptor occupancy by the drug, has been effectively used to describe obtained experimental data. However, it has not been studied in literature under which conditions the above assumption can be justified nor the assumption still holds in vivo. The purpose of this study is to explore the in vivo relationship between the inhibition and the receptor occupancy by an NDNB and to draw implications on how in vitro experimental results can be used to discuss the in vivo properties of NDNBs. Methods An ordinary differential equation model is employed to simulate physiologic processes of the activation of receptors by acetylcholine (ACh) as well as inhibition by an NDNB. With this model, the degree of inhibition is quantified by the fractional amount of receptors that are not activated by ACh due to the presence of an NDNB. The results are visualized by plotting the fractional amounts of the activated receptors as a function of the receptor occupancy. Results Numerical investigations reflecting in vivo conditions show that the degree of inhibition is not proportional to the receptor occupancy, i.e., there is a nonlinear relationship between the inhibition and the receptor occupancy. However, under a setting of high concentration of ACh reflecting a typical situation of in vitro experiments, the relationship between the inhibition and the receptor occupancy becomes linear, suggesting the validity of the receptor binding model. Also, it is found that the extent of nonlinearity depends on the selectivity of NDNBs for the two binding sites of the receptors. Conclusions While the receptor binding model may be effective for estimating affinity of an NDNB through in vitro experiments, these models do not directly describe in vivo properties of NDNBs, because the nonlinearity between the inhibition and the receptor occupancy causes the modulation of the resultant concentration-effect relationships of NDNBs.

A case of anaphylactic shock induced by sugammadex in China

Sugammadex, an antagonist of neuromuscular blocking drugs, was used to rapidly reverse rocuronium induced neuromuscular blockade by encapsulating free rocuronium molecules as inclusion complexes. Because it can enhance the rapid recovery after surgery, summadex is gradually used in clinical. There are relatively few reports about anaphylactic reaction to it. We will present a case of severe anaphylactic shock induced by summadex, as the first in China. Author biography: At present, Wei pan is a junior doctor in Shuguang Hospital Affiliated to Shanghai University of traditional Chinese medicine. She graduated from the anesthesia College of Xuzhou Medical University with a master's degree at the age of 27.

On the Relationship between Inhibition and Receptor Occupancy by Nondepolarizing Neuromuscular Blocking Drugs

Background: Nondepolarizing neuromuscular blocking drugs (NDNBs) are clinically used to produce muscle relaxation during general anesthesia. To better understand clinical properties of NDNBs, comparative in vitro pharmacologic studies have been performed. In these studies, a receptor binding model, which relies on the assumption that the inhibition, i.e., the e ect of an NDNB, is proportional to the receptor occupancy by the drug, has been effectively used to describe obtained experimental data. However, it has not been studied in literature under which conditions the above assumption can be justified nor the assumption still holds in vivo. The purpose of this study is to explore the in vivo relationship between the inhibition and the receptor occupancy by an NDNB and to draw implications on how in vitro experimental results can be used to discuss the in vivo properties of NDNBs. Methods: An ordinary di erential equation model is employed to simulate physiologic processes of the activation of receptors by acetylcholine (ACh) as well as inhibition by an NDNB. With this model, the degree of inhibition is quantified by the fractional amount of receptors that are not activated by ACh due to the presence of an NDNB. The results are visualized by plotting the fractional amounts of the activated receptors as a function of the receptor occupancy. Results: Numerical investigations reflecting in vivo conditions show that the degree of inhibition is not proportional to the receptor occupancy, i.e., there is a nonlinear relationship between the inhibition and the receptor occupancy. However, under a setting of high concentration of ACh reflecting a typical situation of in vitro experiments, the relationship between the inhibition and the receptor occupancy becomes linear, suggesting the validity of the receptor binding model. Also, it is found that the extent of nonlinearity depends on the selectivity of NDNBs for the two binding sites of the receptors. Conclusions: While the receptor binding model may be effective for estimating affinity of an NDNB through in vitro experiments, these models do not directly describe in vivo properties of NDNBs, because the nonlinearity between the inhibition and the receptor occupancy causes the modulation of the resultant concentration-effect relationships of NDNBs.

Fentanyl not an Exception to Anaphylaxis

Intraoperative anaphylaxis can lead to significant morbidity and mortality but rarely occurs. Vascular collapse and bronchospasm are the hallmarks of this condition. numerous agents have been identified as triggers of intraoperative anaphylaxis, the most common being neuromuscular blocking drugs and latex. But opioids rarely cause anaphylaxis. We report an unusual case of intraoperative anaphylaxis with pulmonary edema during a routine plastic surgery procedure was due to iv fentanyl.

Pseudocholinesterase Deficiency Considerations: A Case Study

Pseudocholinesterase deficiency, sometimes called butyrylcholinesterase deficiency, is a rare disorder in which the neuromuscular blocking drugs succinylcholine and mivacurium cannot be metabolized properly in the blood plasma. This disorder can either be acquired as a result of certain comorbidities or it can be inherited genetically. Anesthesia providers must understand the pathophysiology of pseudocholinesterase deficiency and be prepared to safely and effectively manage patients who show signs and symptoms consistent with the disorder after the use of the indicated neuromuscular blocking drugs. This article summarizes the pharmacologic and physiologic data relevant to understanding the basic pathophysiology associated with pseudocholinesterase deficiency and illustrates a case study of a young woman suspected of having the disorder after a prolonged delay in emergence from general anesthesia.