Skeletal Muscle Relaxants, Myasthenia Gravis and Glaucoma

Skeletal muscle relaxants are important drugs in pharmacology and are frequently tested in GPAT, NIPER, UPSC Drug Inspector, AIIMS Pharmacist, Railway Pharmacist, SSC, ESIC and State Pharmacist examinations. These drugs reduce skeletal muscle tone or produce temporary muscle paralysis and are broadly classified into peripheral and central muscle relaxants. Peripheral agents act at the neuromuscular junction or directly on skeletal muscle. Succinylcholine is the major depolarising neuromuscular blocker, whereas drugs such as rocuronium, vecuronium and atracurium are non-depolarising neuromuscular blockers. Dantrolene acts directly on skeletal muscle by reducing calcium release from the sarcoplasmic reticulum and is particularly important in the treatment of malignant hyperthermia. Central muscle relaxants such as baclofen and tizanidine reduce muscle spasticity mainly through actions in the central nervous system. Baclofen acts as a GABA-B receptor agonist, while tizanidine is an α₂-adrenergic agonist.

Myasthenia gravis is an autoimmune disorder of neuromuscular transmission characterised by fatigable skeletal muscle weakness. In the common form, antibodies interfere with postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction. Acetylcholinesterase inhibitors, particularly pyridostigmine, improve muscle strength by increasing the availability of acetylcholine. Neostigmine may also be used, while immunosuppressive and other immune-directed therapies are important in long-term management. A key examination concept is the distinction between myasthenic crisis and cholinergic crisis.

Glaucoma involves progressive optic nerve damage and is commonly associated with elevated intraocular pressure. Pharmacological treatment aims to reduce intraocular pressure either by decreasing aqueous humor production or increasing its outflow. Timolol reduces aqueous humor production, latanoprost increases uveoscleral outflow, pilocarpine increases trabecular outflow, and dorzolamide inhibits carbonic anhydrase. Understanding the mechanism, therapeutic use, and adverse effects of these drugs is essential for success in pharmacy competitive examinations.

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