Stability condition

Purity

(area%)

2-hydroxy-5-methylpyridine

(area%)

Iodobenzene

(area%)

Single maximum

impurity (area%)

Total impurities

(area%)

Pirfenidone @

5 N HCl-RT after 24 hours

99.91

ND

ND

0.01

0.09

Pirfenidone @

5 N NaOH-RT 24 hours

99.90

ND

ND

0.03

0.07