Directly acting muscle relaxants like dantrolene and botulinum toxin (BoNT) have distinct mechanisms and applications. Dantrolene, a hydantoin derivative, acts on the ryanodine receptor (RYR1) in skeletal muscle cells. RYR1 are calcium channels present at the sarcoplasmic reticulum membrane. In response to excitation, they release calcium ions from the sarcoplasmic reticulum to the cytosol. Calcium promotes actin-myosin-mediated contraction of muscles.
The binding of dantrolene to the RYR1...

Skeletal muscle relaxants are used to relax muscle tone and alleviate painful muscle contractions. However, the choice of skeletal muscle relaxants depends on the duration of the surgical procedure in order to minimize potential side effects. Skeletal muscle relaxants like neuromuscular blocking agents [NMBAs] are commonly employed as adjuvants alongside general anesthetics in clinical settings. NMBAs are also used to maintain controlled ventilation during surgery of the larynx or pharynx...

Depolarizing blockers are administered through intravenous injection. Succinylcholine is the most common choice of depolarizing blockers in emergency clinical practices. Although they have a rapid onset, they readily diffuse away from the motor end plate into the extracellular fluid. They are metabolized by enzymes such as liver butyrylcholinesterase and plasma pseudocholinesterases. This produces a short duration of action, typically 5-10 minutes long, unlike nondepolarizing blockers, which...

Skeletal muscle relaxants are widely used for muscle paralysis and relieving pain following any muscle injury or stiffness. However, depending on the drug type, they can have adverse effects that range from mild to severe. Usually, nondepolarizing neuromuscular blockers have minimal side effects. For example, drugs like d-tubocurarine, cisatracurium, and rocuronium cause hypotension, whereas drugs like baclofen, when stopped abruptly, can lead to the recurrence of spastic conditions.
Unlike...

Nondepolarizing neuromuscular blockers prevent the membrane depolarization of muscle cells and inhibit muscle contraction. These are usually administered with anesthetics to achieve complete muscle relaxation. Upon administration, these drugs first block the small, rapidly contracting muscles of the face and hands, followed by the larger muscles of the trunk and the intercostal muscles. The diaphragm is the last muscle to be affected.
Although all competitive neuromuscular blockers are designed...

Indirect-acting cholinergic agonists, also known as anticholinesterases, exert their pharmacological effects by enhancing cholinergic transmission in various body parts, including the neuromuscular junction, autonomic cholinergic synapses, and the brain.
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...