A muscle relaxant is a drug that affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers act by interfering with transmission at the neuromuscular end plate and have no central nervous system (CNS) activity. They are often used during surgical procedures and in intensive care and emergency medicine to cause temporary paralysis. Spasmolytics, also known as "centrally acting" muscle relaxant, are used to alleviate musculoskeletal pain and spasms and to reduce spasticity in a variety of neurological conditions. While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxant, the term is commonly used to refer to spasmolytics only.
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of receptor proteins. They are sometimes called blockers; examples include alpha blockers, beta blockers, and calcium channel blockers. In pharmacology, antagonists have affinity but no efficacy for their cognate receptors, and binding will disrupt the interaction and inhibit the function of an agonist or inverse agonist at receptors. Antagonists mediate their effects by binding to the active site or to the allosteric site on a receptor, or they may interact at unique binding sites not normally involved in the biological regulation of the receptor's activity. Antagonist activity may be reversible or irreversible depending on the longevity of the antagonist–receptor complex, which, in turn, depends on the nature of antagonist–receptor binding. The majority of drug antagonists achieve their potency by competing with endogenous ligands or substrates at structurally defined binding sites on receptors.
Chlorphenamine, also known as chlorpheniramine, is an antihistamine used to treat the symptoms of allergic conditions such as allergic rhinitis. It is taken orally. The medication takes effect within two hours and lasts for about 4-6 hours.
Curare is a common name for various alkaloid arrow poisons originating from plant extracts. Used as a paralyzing agent by indigenous peoples in Central and South America for hunting and for therapeutic purposes, curare only becomes active when it contaminates a wound or is introduced directly to the bloodstream; it is not active when ingested orally. These poisons cause weakness of the skeletal muscles and, when administered in a sufficient dose, eventual death by asphyxiation due to paralysis of the diaphragm. Curare is prepared by boiling the bark of one of the dozens of plant sources, leaving a dark, heavy paste that can be applied to arrow or dart heads. In medicine, curare has been used as a treatment for tetanus and strychnine poisoning and as a paralyzing agent for surgical procedures.
Tubocurarine is a toxic benzylisoquinoline alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or mechanical ventilation. Safer alternatives, such as cisatracurium and rocuronium, have largely replaced it as an adjunct for clinical anesthesia and it is now rarely used.
Neuromuscular-blocking drugs, or Neuromuscular blocking agents (NMBAs), block transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished via their action on the post-synaptic acetylcholine (Nm) receptors.
Rocuronium bromide is an aminosteroid non-depolarizing neuromuscular blocker or muscle relaxant used in modern anaesthesia to facilitate tracheal intubation by providing skeletal muscle relaxation, most commonly required for surgery or mechanical ventilation. It is used for standard endotracheal intubation, as well as for rapid sequence induction (RSI).
Atracurium besilate, also known as atracurium besylate, is a medication used in addition to other medications to provide skeletal muscle relaxation during surgery or mechanical ventilation. It can also be used to help with endotracheal intubation but suxamethonium (succinylcholine) is generally preferred if this needs to be done quickly. It is given by injection into a vein. Effects are greatest at about 4 minutes and last for up to an hour.
Mivacurium chloride is a short-duration non-depolarizing neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation.
Doxacurium chloride is a neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to provide skeletal muscle relaxation during surgery or mechanical ventilation. Unlike a number of other related skeletal muscle relaxants, it is rarely used adjunctively to facilitate endotracheal intubation.
A muscarinic receptor antagonist (MRA) is a type of anticholinergic agent that blocks the activity of the muscarinic acetylcholine receptor. The muscarinic receptor is a protein involved in the transmission of signals through certain parts of the nervous system, and muscarinic receptor antagonists work to prevent this transmission from occurring. Notably, muscarinic antagonists reduce the activation of the parasympathetic nervous system. The normal function of the parasympathetic system is often summarised as "rest-and-digest", and includes slowing of the heart, an increased rate of digestion, narrowing of the airways, promotion of urination, and sexual arousal. Muscarinic antagonists counter this parasympathetic "rest-and-digest" response, and also work elsewhere in both the central and peripheral nervous systems.
A nicotinic antagonist is a type of anticholinergic drug that inhibits the action of acetylcholine (ACh) at nicotinic acetylcholine receptors. These compounds are mainly used for peripheral muscle paralysis in surgery, the classical agent of this type being tubocurarine, but some centrally acting compounds such as bupropion, mecamylamine, and 18-methoxycoronaridine block nicotinic acetylcholine receptors in the brain and have been proposed for treating nicotine addiction.
Receptor theory is the application of receptor models to explain drug behavior. Pharmacological receptor models preceded accurate knowledge of receptors by many years. John Newport Langley and Paul Ehrlich introduced the concept that receptors can mediate drug action at the beginning of the 20th century. Alfred Joseph Clark was the first to quantify drug-induced biological responses. So far, nearly all of the quantitative theoretical modelling of receptor function has centred on ligand-gated ion channels and G protein-coupled receptors.
Gantacurium chloride is a new experimental neuromuscular blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in surgical anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation. Gantacurium is not yet available for widespread clinical use: it is currently undergoing Phase III clinical development.
Laudexium metilsulfate is a neuromuscular blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in surgical anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation.
Candocuronium iodide is a aminosteroid neuromuscular-blocking drug. Its use within anesthesia for endotracheal intubation and for providing skeletal muscle relaxation during surgery or mechanical ventilation was briefly evaluated in clinical studies in India, though further development was discontinued due to attendant cardiovascular effects, primarily tachycardia that was about the same as the clinically established pancuronium bromide. Candocuronium demonstrated a short duration in the body, but a rapid onset of action. It had little to no ganglion blocking activity, with a greater potency than pancuronium.
The alpha-3 beta-2 nicotinic receptor, also known as the α3β2 receptor, is a type of nicotinic acetylcholine receptor, consisting of α3 and β2 subunits.
Cholinergic blocking drugs are a group of drugs that block the action of acetylcholine (ACh), a neurotransmitter, in synapses of the cholinergic nervous system. They block acetylcholine from binding to cholinergic receptors, namely the nicotinic and muscarinic receptors.
Neuromuscular drugs are chemical agents that are used to alter the transmission of nerve impulses to muscles, causing effects such as temporary paralysis of targeted skeletal muscles. Most neuromuscular drugs are available as quaternary ammonium compounds which are derived from acetylcholine (ACh). This allows neuromuscular drugs to act on multiple sites at neuromuscular junctions, mainly as antagonists or agonists of post-junctional nicotinic receptors. Neuromuscular drugs are classified into four main groups, depolarizing neuromuscular blockers, non-depolarizing neuromuscular blockers, acetylcholinesterase inhibitors, and butyrylcholinesterase inhibitors.
(what is this?) (verify) 
