RT Journal Article
SR Electronic
T1 Effect of Sodium Thiosulfate on the Photolysis of Phenobarbital: Evidence of Complex Formation
JF PDA Journal of Pharmaceutical Science and Technology
JO PDA J Pharm Sci Technol
FD Parenteral Drug Association (PDA)
SP 205
OP 210
VO 48
IS 4
A1 Asker, Ahmed F.
A1 Islam, Mohammad S.
YR 1994
UL http://journal.pda.org/content/48/4/205.abstract
AB Photodegradation of phenobarbital in aqueous solutions exposed to short-wave ultraviolet light was studied in presence and in absence of sodium thiosulfate. The degradation process appeared to follow first-order kinetics and was found to be dependent on pH, buffer system and sodium thiosulfate concentration. Ionic strength did not have any appreciable effect. The rate of photodegradation was found to be inversely proportional to phenobarbital concentration, especially below 8 × 10−4 M. Solutions of phenobarbital containing alcohol, propylene glycol and benzyl alcohol as cosolvents showed markedly improved stability under UV irradiation in absence of sodium thiosulfate. Complex formation between the thiosulfate anion and phenobarbital appeared to be primarily responsible for the photostabilization of the drug. The equilibrium constant for this complex was calculated to be 36.23 M−1.