PRONEO INJECTION

Indications

• Myasthenia gravis
• Lambert-Eaton myasthenic syndrome
• Reversal of neuromuscular blockade from muscle relaxants (e.g., gallamine, tubocurarine)

Dosage

Children: Child 1 month–5 years

Adults: Initially, 1-2 mg, then 1-5 mg every 4 hours, given 30 minutes before meals.

Mechanism of action

Neostigmine acts as a reversible inhibitor of acetylcholinesterase, leading to increased concentrations of acetylcholine at the neuromuscular junction. This inhibition promotes increased stimulation of both nicotinic and muscarinic receptors, facilitating enhanced muscle contraction. The accumulation of acetylcholine occurs at sites of cholinergic transmission, thereby improving neuromuscular transmission in conditions like myasthenia gravis.

Pharmacodynamics

The pharmacological effects of neostigmine are attributed to the prevention of hydrolysis of acetylcholine by acetylcholinesterase at cholinergic synapses. This results in enhanced neuromuscular transmission, improved muscle strength, and reversal of neuromuscular blockade caused by certain competitive neuromuscular relaxants. Neostigmine is particularly effective in conditions where there is a deficiency of acetylcholine at the neuromuscular junction, such as myasthenia gravis.

Pharmacokinetics

Neostigmine is administered via oral or parenteral routes and displays a rapid onset of action. The drug is not significantly metabolized in the liver and is primarily excreted unchanged in the urine. Its duration of action generally lasts from 2 to 4 hours, necessitating multiple doses throughout the day for sustained therapeutic effect. Neostigmine's poor penetration across the blood-brain barrier limits its central effects, focusing its action mainly on peripheral sites.

Contra-indications

• Intestinal obstruction
• Urinary obstruction

Adverse effects

• Abdominal cramps
• Diarrhoea
• Excessive tearing
• Hypersalivation
• Nausea
• Vomiting
• Bronchoconstriction
• Increased bronchial secretions
• Lacrimation
• Excessive sweating
• Involuntary defaecation
• Involuntary micturition
• Miosis
• Nystagmus
• Bradycardia
• Heart block
• Arrhythmias
• Hypotension
• Agitation
• Excessive dreaming
• Weakness
• Fasciculation
• Paralysis

Interactions

• Aminoglycosides may decrease the effects of neostigmine

Precautions

• Caution in patients with arrhythmias
• Asthma (extreme caution)
• Epilepsy
• Hyperthyroidism
• Hypotension
• Parkinsonism
• Peptic ulceration
• Recent myocardial infarction
• Vagotonia
• Elderly patients may be at increased risk of adverse effects
• Close monitoring in renal impairment

Pregnancy

Manufacturer advises to avoid use due to potential toxicity in animal studies.

Breast-feeding

Amount probably too small to be harmful, but avoid use.

Storage

Store in a refrigerator (2–8 °C); may be stored (in the original carton, protected from light) at or below 30 °C for up to 14 days.

Formulations

• Neostigmine methylsulfate injection
• Oral tablets

Mechanism of action

Neostigmine is a parasympathomimetic, specifically, a reversible cholinesterase inhibitor. The drug inhibits acetylcholinesterase which is responsible for the degredation of acetylcholine. So, with acetylcholinesterase inhibited, more acetylcholine is present By interfering with the breakdown of acetylcholine, neostigmine indirectly stimulates both nicotinic and muscarinic receptors which are involved in muscle contraction.. It does not cross the blood-brain barrier. ...PHARMACOLOGICAL EFFECTS OF ANTICHOLINESTERASE AGENTS ARE DUE PRIMARILY TO PREVENTION OF HYDROLYSIS OF ACH /ACETYLCHOLINE/ BY ACHE /ACETYLCHOLINESTERASE/ AT SITES OF CHOLINERGIC TRANSMISSION. TRANSMITTER THUS ACCUMULATES, AND THE ACTION OF ACH /ACETYLCHOLINESTERASE/ THAT IS LIBERATED BY CHOLINERGIC IMPULSES OR THAT LEAKS FROM THE NERVE ENDING IS ENHANCED. Neostigmine increased both miniature end-plate potential and end-plate potential amplitudes but did not affect quantal content in isolated frog sciatic nerve-Sartorius muscle prepn. This suggests that cholinesterase inhibition was the only effect. Long term (24-96 hr) treatment of a mouse-derived myogenic cell line (G8) with neostigmine markedly reduced binding of alpha-bungarotoxin (alpha-BuTx) to these cells. Protein synthesis in these cultures was markedly reduced and cell morphology degenerated. Myotubes maintained slightly hyperpolarized resting membrane potentials, and were able to respond to iontophoretic acetylcholine (Ach) application with overshooting action potentials. Degenerative changes at the neuromuscular junction associated with chronic neostigmine treatment in vivo are probably due to a direct action of the anticholinesterase on the muscle, rather than to altered intracleft ACh levels or to presynaptic effects of the anticholinesterase. The intraluminal probe mounted with 2 electrode-strain gauge pairs, 4 cm apart, was used to study the effect of a neutral interview, a stressful interview, a meal (478.7 cal) and neostigmine (0.5 mg, im) on the contractile electrical complex, continuous electrical response activity and their associated contractions in 17 normal subjects. Neostigmine resulted in an incr in contractile electric complex & continuous electric response activity indexes 5-10 and 25-30 min after the injection, respectively. Both the meal and neostigmine incr the percentage of propagated contractile electric complexes during all of the recording periods.

Pharmacodynamics

Neostigmine is a cholinesterase inhibitor used in the treatment of myasthenia gravis and to reverse the effects of muscle relaxants such as gallamine and tubocurarine. Neostigmine, unlike physostigmine, does not cross the blood-brain barrier. By inhibiting acetylcholinesterase, more acetylcholine is available in the synapse, therefore, more of it can bind to the fewer receptors present in myasthenia gravis and can better trigger muscular contraction.