Cell: 1mm.

Solution— Place a volume of Oral Solution,equivalent to about 200mg of amantadine hydrochloride,in a vessel,dissolve in 0.1Nhydrochloric acid,and filter.Transfer the filtrate to a separator,add 10mLof 0.5Nsodium hydroxide,and extract with 5mLof methylene chloride.Filter the extract through anhydrous sodium sulfate,and rinse the anhydrous sodium sulfate with 2mLof methylene chloride.

Internal standard solution,Standard preparation,andChromatographic system— Proceed as directed in the Assayunder Amantadine Hydrochloride Capsules.

Assay preparation— Pipet 5.0mLof the Oral Solution into a 250-mLconical flask,and add 45mLof 1.0Nsodium hydroxide and 50.0mLof Internal standard solution.Shake for 60minutes,and collect the hexane layer (Assay preparation).

Procedure— Proceed as directed in the Assayunder Amantadine Hydrochloride Capsules.Calculate the quantity,in mg,of amantadine hydrochloride (C10H17N·HCl)in the portion of Oral Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Amantadine Hydrochloride RSin the Standard preparation;and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.