In Vitro Sustained Release of Pyridostigmin Bromide from Injectable Thermosensitive Chitosan Hydrogel

Somanis one of the strongest nerve agents and treatment of poisoning with Soman is difficult and time-critical.Pyridostigmine bromide is an inhibitor of cholinesterase used for protecting against toxicity by Soman. The approved dose used forpretreatment to protect against Soman is a30 mg tablet using every 4 h, while the sustained release dosage formof pyridostigmine bromide has twice daily oral administration. Because of this short schedule of pyridostigmine bromide under the stressing conditions,modification of dosage and administration period of pyridostigmine bromide is essential. In this study, a new injectable thermosensitive sustained release dosage form of pyridostigmine bromide was achieved by chitosan/glycerolphosphate solution. In this study, thermosensitivity and rheological properties of chitosan solution (2% w/v) in aqueous hydrochloric acid (0.1 molar) with different percent of glycerolphosphate salt as well as the release profile of pyridostigmine bromide have been investigated. Effect of glycerolphosphate salt concentration on turbidity, gelation time and pH of chitosan solution was also studied. The presented results indicated that hydrogel containing 2% w/v of chitosan and 16% w/v of glycerolphosphate salt could sustain the delivery of pyridostigmine bromide up to four days.