Pentoxifylline 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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1 DEFINITION

Pentoxifylline Compounded Oral Suspension contains NLT 90.0% and NMT 110.0% of the labeled amount of pentoxifylline (C₁₃H₁₈N₄O₃). 

Prepare Pentoxifylline Compounded Oral Suspension 20 mg/mL as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

^a Trental 400-mg tablets, sano-aventis, Somerville, NJ. 

Calculate the required quantity of each ingredient for the total amount to be prepared. Place the required number of Pentoxifylline extended release tablets in a suitable mortar, add Purified Water in small portions, and triturate to make a smooth paste. Add increasing volumes of Purified Water to make a pentoxifylline liquid that is pourable. Transfer the contents of the mortar, stepwise and quantitatively, to a calibrated bottle. Add enough Purifier Water to bring to final volume, and mix well.

2 ASSAY

Procedure

Solution A: 50 mM monobasic potassium phosphate buffer, adjusted with phosphoric acid to a pH of 3.2

Mobile phase: Acetonitrile and Solution A (20:80). Pass through a filter of 0.45-µm pore size, and degas.

Internal standard solution: 100 µg/mL of caffeine in Mobile phase

Standard stock solution: 20 mg/mL of USP Pentoxifylline RS in Mobile phase

Standard solution: Pipet 1.0 mL of Standard stock solution into a 15-mL conical centrifuge tube, and add 9 mL of deionized water. Mix the sample for 30 s in a vortex mixer, and centrifuge for 30 min at 1250 × g. Pipet 50 µL of the supernatant into a separate borosilicate culture tube, dilute with 575 µL of Mobile phase, and add 625 µL of Internal standard solution to obtain a solution having a nominal concentration of 80 µg/mL of pentoxifylline and 50 µg/mL of caffeine.

Sample solution: Shake thoroughly by hand each bottle of Oral Suspension. Pipet 1.0 mL of Oral Suspension into a 15-mL conical centrifuge tube, and add 9 mL of deionized water. Mix the sample for 30 s in a vortex mixer, and centrifuge for 30 min at 1250 × g. Pipet 50 µL of the supernatant into a separate borosilicate culture tube, dilute with 575 µL of Mobile phase, and add 625 µL of Internal standard solution to obtain a solution having a nominal concentration of 80 µg/mL of pentoxifylline and 50 µg/mL of caffeine.

2.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: UV 280 nm

Column: 4.6-mm × 25-cm; 5-µm packing L1

Flow rate: 1.0 mL/min

Injection volume: 10 µL

2.2 System suitability

Sample: Standard solution

[Note—The relative retention times for caffeine and pentoxifylline are about 0.42 and 1.0, respectively.]

Suitability requirements

Resolution: NLT 10.0 between pentoxifylline and caffeine

Column efficiency: NLT 10,000 theoretical plates

Tailing factor: NMT 2.0 for the pentoxifylline peak

Relative standard deviation: NMT 2.0% for replicate injections

2.3 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of the labeled amount of pentoxifylline (C₁₃H₁₈N₄O₃) in the portion of Oral Suspension taken:

Result = (R_U /R_S ) × (C_S /C_U ) × 100

R_U = peak response ratio of pentoxifylline to the internal standard from the Sample solution

R_S = peak response ratio of pentoxifylline to the internal standard from the Standard solution

C_S = concentration of USP Pentoxifylline RS in the Standard solution (µg/mL)

C_U = nominal concentration of pentoxifylline in the Sample solution (µg/mL)

Acceptance criteria: 90.0%–110.0%

3 SPECIFIC TESTS

pH 〈791〉: 5.9–7.7

4 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 Pentoxifylline RS