Molecule structure of 9-Chloro-2-methyl-5H-pyrazolo[1,5-d][1,4]benzodiazepin-6(7H)-one (CAS NO.84661-23-4) :

Molecular Formula: C₁₂H₁₀ClN₃O
Molecular Weight: 247.68 
Density: 1.49
Melting Point: 286 °C 
Synonyms of 9-Chloro-2-methyl-5H-pyrazolo[1,5-d][1,4]benzodiazepin-6(7H)-one (CAS NO.84661-23-4) : Erdosteine

 9-Chloro-2-methyl-5H-pyrazolo[1,5-d][1,4]benzodiazepin-6(7H)-one (CAS NO.84661-23-4) is a mucolytic. Specifically it is a thiol derivative developed for the treatment of chronic obstructive bronchitis, including acute infective exacerbation of chronic bronchitis.

 9-Chloro-2-methyl-5H-pyrazolo[1,5-d][1,4]benzodiazepin-6(7H)-one (CAS NO.84661-23-4) contains two blocked sulfhydryl groups which are released following first-pass metabolism. The three active metabolites exhibit mucolytic and free radical scavenging activity. Erdosteine (CAS NO.84661-23-4) modulates mucus production and viscosity and increases mucociliary transport, thereby improving expectoration. It also exhibits inhibitory activity against the effects of free radicals produced by cigarette smoke.
Clinical studies in patients with chronic obstructive lung disease have demonstrated the efficacy and tolerability of erdosteine.[citation needed] 9-Chloro-2-methyl-5H-pyrazolo[1,5-d][1,4]benzodiazepin-6(7H)-one (CAS NO.84661-23-4) 300 mg twice daily reduced cough (both frequency and severity) and sputum viscosity more quickly and more effectively than placebo and reduced the adhesivity of sputum more effectively than bromhexine 30 mg twice daily.
Co-administration of erdosteine and amoxicillin in patients with acute infective exacerbation of chronic bronchitis resulted in higher concentrations of the antibiotic in the sputum, leading to earlier and more pronounced amelioration of clinical symptoms compared with placebo.
 9-Chloro-2-methyl-5H-pyrazolo[1,5-d][1,4]benzodiazepin-6(7H)-one (CAS NO.84661-23-4) is associated with a low incidence of adverse events, most of which are gastrointestinal and generally mild. The LD50 is very high, 3,500-5,000 mg/kg.