G-Neostigmine0.5 mg/ml

G-Neostigmine is a reversible acetylcholinesterase inhibitor with the following clinically established uses:

• Reversal of non-depolarizing neuromuscular blockade: FDA-approved for reversing the effects of non-depolarizing neuromuscular blocking agents after surgical procedures, always given together with an anticholinergic agent (atropine or glycopyrrolate).
• Myasthenia gravis: Guideline-supported symptomatic treatment (parenteral use) when oral therapy is not feasible, such as in the immediate postoperative period or during a myasthenic crisis under close monitoring.
• Postoperative/postpartum non-obstructive urinary retention: Established adjunct use to stimulate bladder detrusor tone in the absence of mechanical obstruction.
• Postoperative abdominal distension (paralytic ileus): Established use to stimulate gastrointestinal motility in non-obstructive ileus.

G-Neostigmine is administered only by trained healthcare personnel with appropriate monitoring equipment available.

Each ml of injection contains Neostigmine Methyl Sulphate BP/USP equivalent to 0.5 mg or 1 mg of neostigmine methylsulfate, as a sterile aqueous solution for injection.

G-Neostigmine is a synthetic, reversible cholinesterase inhibitor (parasympathomimetic agent) belonging to the carbamate class. It is used parenterally to reverse the effects of non-depolarizing neuromuscular blocking agents, to treat myasthenia gravis when oral therapy is impractical, and to stimulate bladder and bowel motility in non-obstructive postoperative retention/distension.

Because G-Neostigmine does not readily cross the blood-brain barrier at usual doses, its clinical effects are largely confined to the peripheral cholinergic system.

Anticholinesterase agent / Parasympathomimetic (reversible cholinesterase inhibitor); antimyasthenic and neuromuscular blockade reversal agent.

Neostigmine Methyl Sulphate reversibly inhibits acetylcholinesterase, the enzyme responsible for breaking down acetylcholine at cholinergic synapses. This inhibition increases the concentration and duration of action of acetylcholine at the neuromuscular junction and at muscarinic receptor sites, leading to:

• Enhanced neuromuscular transmission, which competitively antagonizes and reverses the effect of non-depolarizing neuromuscular blocking agents.
• Increased skeletal muscle strength in myasthenia gravis by prolonging acetylcholine availability at the diminished number of functional receptors.
• Increased tone and motility of gastrointestinal and urinary smooth muscle (muscarinic effect).

Neostigmine Methyl Sulphate is a quaternary ammonium compound and does not readily cross the blood-brain barrier, so central nervous system effects are minimal at therapeutic doses. It is administered parenterally (IV, IM, or SC) because oral bioavailability is poor and unreliable; onset after IV administration is rapid (within minutes), with a duration of action of approximately 1 to 2 hours, and it is metabolized by plasma esterases and hepatic microsomal enzymes with renal elimination of metabolites and unchanged drug.

G-Neostigmine has the following well-established clinically significant interactions:

• Depolarizing neuromuscular blockers (e.g., succinylcholine): G-Neostigmine does not antagonize and may prolong or intensify the neuromuscular blockade of depolarizing agents; it is not recommended for reversing these drugs.
• Aminoglycoside antibiotics (neomycin, streptomycin, kanamycin, gentamicin): These have intrinsic neuromuscular blocking activity and can antagonize the effect of G-Neostigmine, potentially requiring dose adjustment.
• Other anticholinesterase agents: Concurrent use increases the risk of cholinergic toxicity/crisis (see Overdose).
• Corticosteroids: May reduce the anticholinesterase effect of G-Neostigmine in myasthenia gravis; abrupt steroid withdrawal during concurrent anticholinesterase therapy has been associated with severe weakness.
• Anticholinergic drugs (e.g., atropine, glycopyrrolate): Co-administered deliberately to block unwanted muscarinic effects, but can also mask early signs of cholinergic overdose.

Side effects of G-Neostigmine arise mainly from excessive cholinergic (muscarinic and nicotinic) stimulation:

• Most common: Bradycardia, nausea, and vomiting.
• Cardiovascular: Arrhythmias, hypotension, tachycardia, syncope, and rarely cardiac arrest.
• Gastrointestinal: Increased salivation, abdominal cramps, diarrhea, dry mouth, flatulence.
• Respiratory: Increased bronchial and pharyngeal secretions, bronchospasm, dyspnea, respiratory depression.
• Neuromuscular/CNS: Muscle weakness, muscle cramps/fasciculations, dizziness, drowsiness, headache, convulsions (rare).
• Dermatologic: Sweating, flushing, rash, urticaria.
• Allergic: Hypersensitivity reactions including anaphylaxis (rare but serious).

Excessive dosing can precipitate a cholinergic crisis (see Overdose).

Pregnancy: There are no adequate and well-controlled studies of G-Neostigmine in pregnant women. Anticholinesterase drugs, including G-Neostigmine, may cause uterine irritability and induce premature labor when given near term. G-Neostigmine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus, and only under close medical supervision.

Lactation: It is not known whether G-Neostigmine is excreted in human breast milk. Because many drugs are excreted in breast milk, caution should be exercised, and a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother, in consultation with a physician.

Use G-Neostigmine with caution in the following situations:

• Bronchial asthma: Cholinergic stimulation can worsen bronchoconstriction and increase bronchial secretions.
• Bradycardia or cardiac arrhythmia/recent coronary event: Muscarinic cardiac effects can worsen bradycardia and precipitate arrhythmias or hypotension; an anticholinergic agent (atropine or glycopyrrolate) should be given before or with G-Neostigmine to mitigate these effects, and resuscitation equipment should be readily available.
• Parkinson's disease: Symptoms may be exacerbated.
• Peptic ulcer disease: Increased gastric acid secretion and motility may aggravate ulcer symptoms.
• Epilepsy: May theoretically lower seizure threshold in susceptible individuals.
• Hyperthyroidism: May increase sensitivity to cardiac effects.
• Hypersensitivity/anaphylaxis risk: Facilities for managing an acute allergic reaction must be available.

Overdosage can cause a cholinergic crisis, which may be difficult to distinguish from a myasthenic crisis; edrophonium testing and clinical judgment under specialist supervision may be needed to differentiate the two, as their management is opposite (see Overdose).

Overdosage of G-Neostigmine produces a cholinergic crisis characterized by excessive muscarinic effects (nausea, vomiting, diarrhea, excessive salivation and sweating, increased bronchial secretions, bradycardia, miosis) and nicotinic effects (progressive muscle weakness that can involve the respiratory muscles, potentially leading to respiratory failure).

Suspected overdose or a cholinergic crisis is a medical emergency: seek immediate medical attention or contact emergency services. Management, which must be carried out by trained medical personnel, generally involves immediate withdrawal of G-Neostigmine, administration of atropine to control muscarinic symptoms, and supportive care including airway management and ventilatory support if needed. Do not attempt to manage a suspected overdose at home.

Store at room temperature (below 30°C), away from light and moisture. Do not freeze. Keep out of reach of children. Discard any unused portion of opened ampoules; do not use if the solution is discolored or contains particulate matter.

Pediatric patients: G-Neostigmine has been used in all pediatric age groups for reversal of neuromuscular blockade using the same weight-based dosing as adults (0.03–0.07 mg/kg IV). Infants and small children may be at greater risk from incomplete reversal due to decreased respiratory reserve and require close monitoring for bradycardia and hypotension. Use for other indications (myasthenia gravis, urinary retention) in children should be individualized and supervised by a specialist, as controlled pediatric data for these uses are limited.

Elderly patients: Renal function decline may prolong elimination half-life, but spontaneous recovery from neuromuscular blockade is also slower in this group; specific dose adjustment is generally not required, but a longer period of postoperative monitoring is recommended.

Renal impairment: Elimination half-life is prolonged; no fixed dose reduction is established, but extended monitoring after administration is advised.

Hepatic impairment: Pharmacokinetics have not been formally studied; as hepatic metabolism contributes to clearance, extended monitoring is advised.

For reversal of neuromuscular blockade, G-Neostigmine is given as a single dose (with additional doses as needed) at the end of a surgical procedure. For myasthenia gravis, parenteral G-Neostigmine is used only for the shortest duration necessary (e.g., perioperatively or during a crisis) before transitioning back to oral anticholinesterase therapy, with the dosing schedule individualized and adjusted by the treating physician based on response. For urinary retention/ileus, treatment is generally continued only until normal bladder/bowel function resumes, per physician assessment.

Cholinesterase inhibitor; parasympathomimetic agent; carbamate-class anticholinesterase.

Neostigmine Methyl Sulphate reversibly binds to and inhibits acetylcholinesterase, preventing the breakdown of acetylcholine at cholinergic synapses. This increases acetylcholine concentration and prolongs its action at nicotinic receptors of the neuromuscular junction (improving muscle strength and reversing non-depolarizing neuromuscular blockade) and at muscarinic receptors of smooth muscle and exocrine glands (increasing gastrointestinal and urinary tract motility and secretions).

Category C

G-Neostigmine is used in pediatric patients of all ages for reversal of non-depolarizing neuromuscular blockade, using the same weight-based dosing recommendations as adults (0.03–0.07 mg/kg IV, given with an appropriate anticholinergic agent). Because infants and small children have decreased respiratory reserve, they may be at greater risk of complications from incomplete reversal and require close monitoring of respiratory and cardiovascular status, including watchfulness for bradycardia and hypotension given the sensitivity of pediatric blood pressure to heart rate changes. Use of G-Neostigmine for myasthenia gravis or urinary retention/ileus in children should be undertaken only under specialist supervision, with dosing individualized, as formal safety and efficacy data for these specific pediatric indications are limited.