Sildenafil Compounded Oral Suspension

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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Sildenafil Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of Sildenafil (C₂₂H₃₀N₆O₄S). 

Prepare Sildenafil Compounded Oral Suspension containing 2.5 mg/mL of Sildenafil as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉). 

a Viagra 25-mg tablets, Pfizer Inc., New York, NY. 

b Paddock Laboratories, Minneapolis, MN. 

Calculate the required quantity of each ingredient for the total amount to be prepared. Place the required number of Sildenafil Citrate tablets in a suitable mortar, and comminute to a fine powder with a pestle. Add the Vehicle in small portions, and triturate to make a smooth paste. Add increasing volumes of the Vehicle to make a Sildenafil liquid that is pourable. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough of the Vehicle to bring to nal volume, and mix well. 

1 ASSAY 

Procedure 

Mobile phase: Acetonitrile and 0.2 M ammonium acetate (50:50). Pass through a nylon 66 filter of 0.45-µm pore size, and degas. Standard stock solution: 2.5 mg/mL of Sildenafil prepared from USP Sildenafil Citrate RS in Mobile phase 

Standard solution: 0.25 mg/mL of Sildenafil prepared from Standard stock solution and Mobile phase 

Sample solution: Shake thoroughly by hand each bottle of Oral Suspension. Prepare 0.25 mg/mL of Sildenafil from Oral Suspension and Mobile phase, and centrifuge. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 245 nm 

Column: 3.0-mm × 15-cm; 5-µm packing L1 

Column temperature: 25° 

Flow rate: 0.5 mL/min 

Injection volume: 10 µL 

System suitability 

Sample: Standard solution 

[Note—The retention time for Sildenafil is about 7.1 min.] 

Suitability requirements 

Relative standard deviation: NMT 2.0% for replicate injections 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of the labeled amount of Sildenafil (C₂₂H₃₀N₆O₄S) in the portion of Oral Suspension taken:

Calculate the percentage of Sildenafil citrate (C₂₂H₃₀N₆O₄S .C₆H₈O₇) in the portion of the sample taken: 

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = peak response from the Sample solution

r_S = peak response from the Standard solution  

C_S = concentration of sildenafil in the Standard solution (mg/mL)

C_U = nominal concentration of sildenafil in the Sample solution (mg/mL) 

Acceptance criteria: 90.0%–110.0% 

2 SPECIFIC TESTS 

pH 〈791〉: 3.9–4.9 

3 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Package in tight, light-resistant containers. Store in a refrigerator or at controlled room temperature. Beyond-Use Date: NMT 90 days after the date on which it was compounded, when stored in a refrigerator or at controlled room temperature Labeling: Label it to indicate that it is to be well shaken before use, and to state the Beyond-Use Date. 

USP Reference Standards 〈11〉 

USP Sildenafil Citrate RS