Baclofen Oral Suspension
Baclofen Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of baclofen (C10H12ClNO2).
Prepare Baclofen Oral Suspension 5 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 795).
Baclofen 500 mg
Vehicle: a mixture of Vehicle for Oral Solution (regular or sugar-free), NF, and Vehicle for Oral Suspension, NF (1:1), a sufficient quantity to make 100 mL
If using Baclofen Tablets, place the Tablets in a suitable mortar and comminute to a fine powder, or add Baclofen powder. Add 5 mL of the Vehicle to wet the powder, and triturate the powder to form a fine paste. Add the Vehicle in small portions almost to volume, and mix thoroughly after each addition. Transfer, stepwise and quantitatively, the contents of the mortar to a calibrated bottle. Add sufficient Vehicle to bring to final volume, and mix well.
•  Procedure
Mobile phase:  Acetonitrile and 0.05 M monobasic sodium phosphate (20:80). Adjust with phosphoric acid to a pH of 3.5.
Standard solution:  5 µg/mL of USP Baclofen RS in water
Sample solution:  Shake thoroughly by hand each bottle of Oral Suspension. Pipet 0.5 mL of Oral Suspension from each bottle to a 500-mL volumetric flask, dilute with water to volume to obtain a concentration of 5 µg/mL, and pass through a 0.22-µm polyvinylidenefluoride (PVDF) filter.
Chromatographic system 
Mode:  LC
Detector:  UV 220 nm
Column:  4.6-mm × 25-cm; 5-µm packing L1
Flow rate:  1 mL/min
Injection size:  15 µL
System suitability 
Sample:  Standard solution
[Note—The retention time of baclofen is about 5.5 min. ]
Suitability requirements 
Relative standard deviation:  NMT 2.0% for replicate injections
Samples:  Standard solution and Sample solution
Calculate the percentage of the labeled amount of baclofen (C10H12ClNO2) in the portion of Oral Suspension taken:
Result = (rU/rS) × (CS/CU) × 100
rU== peak response from the Sample solution
rS== peak response from the Standard solution
CS== concentration of baclofen in the Standard solution (µg/mL)
CU== nominal concentration of baclofen in the Sample solution (µg/mL)
Acceptance criteria:  90.0%–110.0%
•  pH 791: 4.2–5.2
•  Packaging and Storage: Package in tight, light-resistant containers. Store in a cold place.
•  Labeling: Label it to state that it is to be well shaken, and to state the Beyond-Use Date.
•  Beyond-Use Date: NMT 35 days after the day on which it was compounded
•  USP Reference Standards 11
USP Baclofen RS Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Jeanne H. Sun
Assistant Scientific Liaison
(CMP2010) Compounding
Reference Standards RS Technical Services
USP35–NF30 Page 2300
Pharmacopeial Forum: Volume No. 32(1) Page 51