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Neostigmine (Neostigmine Methylsulfate) - Description and Clinical Pharmacology

 
 



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DESCRIPTION:

Neostigmine Methylsulfate Injection, USP is the dimethylcarbamate of (m-hydroxyphenyl) trimethylammonium methylsulfate.

The structural formula is:

Neostigmine Methylsulfate, an anticholinesterase agent, is a bitter tasting, white crystalline powder and is very soluble in water and soluble in alcohol. Neostigmine Methylsulfate Injection, USP is a sterile, nonpyrogenic solution intended for intramuscular, subcutaneous or slow intravenous use.

Each mL of the 1:1000 concentration contains Neostigmine Methylsulfate 1 mg, Methylparaben 1.8 mg and Propylparaben 0.2 mg (used as preservatives), in Water for Injection q.s. pH (range 5.0 - 6.5) adjusted, when necessary, with Sodium Hydroxide.

Each mL of the 1:2000 concentration contains Neostigmine Methylsulfate 0.5 mg, Methylparaben 1.8 mg and Propylparaben 0.2 mg (used as preservatives), in Water for Injection q.s. pH (range 5.0 - 6.5) adjusted, when necessary, with Sodium Hydroxide.

CLINICAL PHARMACOLOGY

Neostigmine inhibits the hydrolysis of acetylcholine by competing with acetylcholine for attachment to acetylcholinesterase at sites of cholinergic transmission. It enhances cholinergic action by facilitating the transmission of impulses across neuromuscular junctions. It also has a direct cholinomimetic effect on skeletal muscle and possibly on autonomic ganglion cells and neurons of the central nervous system. Neostigmine undergoes hydrolysis by cholinesterase and is also metabolized by microsomal enzymes in the liver. Protein binding to human serum albumin ranges from 15 to 25 percent.

Following intramuscular administration, Neostigmine is rapidly absorbed and eliminated. In a study of five patients with myasthenia gravis, peak plasma levels were observed at 30 minutes, and the half-life ranged from 51 to 90 minutes. Approximately 80 percent of the drug was eliminated in urine within 24 hours; approximately 50% as the unchanged drug and 30 percent as metabolites. Following intravenous administration, plasma half-life ranges from 47 to 60 minutes have been reported with a mean half-life of 53 minutes.

The clinical effects of Neostigmine usually begin within 20 to 30 minutes after intramuscular injection and last from 2.5 to 4 hours.

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