Gabapentin Compounded Cream

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

Gabapentin Compounded Cream contains NLT 90.0% and NMT 110.0% of the labeled amount of gabapentin (C₉H₁₇NO₂).

Prepare Gabapentin Compounded Cream, 20 mg/g and 100 mg/g as follows (see Pharmaceutical Compounding—Nonsterile Preparations 〈795〉).

To Prepare a Gabapentin Compounded Cream containing 20 mg/g of gabapentin:

^a PCCA, Houston, TX.

To Prepare a Gabapentin Compounded Cream containing 100 mg/g of gabapentin:

^a PCCA, Houston, TX.

In an appropriately sized electronic mortar and pestle container, add 50 g of Lipoderm, then place the Gabapentin and Propylene Glycol on top, then add sufficient Lipoderm to bring to final weight. Mix the mixture with an electronic mortar and pestle for 5 min on a speed of about 1500 rpm. Process through an ointment mill once at the middle setting and once at the nest setting to reduce the particle size of the active ingredient and reduce air content of the preparation. Return the mixture to the electronic mortar and pestle container and mix again for 3–5 min on a speed of about 1100 rpm.

2 ASSAY

Procedure

Solution A: A solution of 1.44 g/L of ammonium acetate in water, adjusted using glacial acetic acid to a pH of 4.0. Pass through a polyvinyl difluoride filter of 0.22-µm pore size.

Mobile phase: Solution A and acetonitrile (15:85)

Standard stock solution: 2 mg/mL of USP Gabapentin RS in methanol. Sonicate for 2 min and vortex.

Standard solutions: Prepare ve calibration standard solutions having the concentrations of gabapentin in Table 1, by diluting Standard stock solution with methanol.

Table 1

Sample solution of 20 mg/g Gabapentin Cream: Collect about 2 mL of Cream into a 3-mL syringe, avoiding air gaps. Transfer the Cream from a 3-mL syringe into a 1-mL syringe until fully filled. Insert the piston and move to about 5 mm above the 1-mL mark. Wipe excess Cream off the outside of syringe. Weigh the full syringe and record the weight. Fill a 50-mL volumetric ask with 25 mL of methanol (wet the neck of the ask with methanol) and transfer the Cream into the ask. Weigh the empty syringe (the difference between the original and nal weight should be between 900 and 1100 mg). Vortex the ask for 3 min, sonicate for 5 min, and then vortex for 2 min. Bring the ask to volume with methanol. Vortex for 2 min (the solution should be partially cloudy). Pass through a 0.45-µm polyvinylidene fluoride (PVDF) filter, discard the first 3 mL, and then transfer into an HPLC vial.

Sample solution of 100 mg/g Gabapentin Cream: Collect about 2 mL of Cream into a 3-mL syringe, avoiding air gaps. Transfer the Cream from a 3-mL syringe into a 1-mL syringe until fully filled. Insert the piston and move to about 5 mm above the 1-mL mark. Wipe excess Cream off the outside of the syringe. Weigh the full syringe and record the weight. Fill a 250-mL volumetric ask with 25 mL of methanol (wet the neck of the ask with methanol) and transfer Cream into the ask. Weigh the empty syringe (the difference between the original and nal weight should be between 900 and 1100 mg). Vortex the ask for 3 min, sonicate for 5 min, and then vortex for 2 min. Bring ask to volume with methanol. Vortex for 2 min (the solution should be partially cloudy). Pass through a 0.45-µm PVDF filter, discard the first 3 mL, and then transfer into an HPLC vial.

2.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: LC

Detector: Evaporative light-scattering

Drift tube temperature: 50°

Gain: 8

Offset: 0 mV

Sampling rate: 100 ms

Filter: 5 s

Gas: 3.5 bar

Column: 4.6-mm × 15-cm; 3.5-µm packing L68

Temperatures

Autosampler: 10°

Column: 50°

Flow rate: 1.0 mL/min

Injection volume: 10 μL

2.2 System suitability

Sample: 100% calibration Standard solution (0.40 mg/mL)

Suitability requirements

Tailing factor: NMT 2.0

Relative standard deviation: NMT 3.5% for six standard injections

2.3 Analysis

Samples: Each of the Standard solutions and Sample solution in triplicate

Identify the gabapentin peaks in the chromatogram of the Sample solution by comparison with the chromatograms obtained from the Standard solutions. Measure the areas of the gabapentin peaks. Plot the logarithms of the average peak area versus the logarithms of the concentrations, in mg/mL, of gabapentin obtained from the Standard solutions and determine the linear regression line using a least-squares analysis. The correlation coefficient for the linear regression line is NLT 0.995. From the graphs so obtained, determine the concentration, C, in mg/mL, of the gabapentin in the Sample solution.

Calculate the percentage of the labeled amount of gabapentin (C₉H₁₇NO₂) in the portion of Cream taken:

Result = (CV/W) × 100

C = concentration of Gabapentin in the Sample solution (mg/mL)

V = volume of Gabapentin in the Sample solution (mL)

W = weight of Cream in the Sample solution (mg)

Acceptance criteria: 90.0%–110.0%

3 SPECIFIC TESTS

pH 〈791〉

For 20 mg/g Cream: 5.8–6.8

For 100 mg/g Cream: 6.0–7.0

Appearance: Opaque, white cream

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Package in a metered-dose, plastic container. Store at controlled room temperature.

Beyond-Use Date: NMT 90 days from the date on which it was compounded when stored at controlled room temperature. Preparations have passed Antimicrobial Effectiveness Testing 〈51〉.

Labeling: Label it for external use only and to state the Beyond-Use Date.

USP Reference Standards 〈11〉

USP Gabapentin RS _{(USP 1-Dec-2023)}