Famciclovir Tablets USP Monograph Method Using a Purospher™ STAR RP-8 endcapped HPLC Column and UV Detection

Sonal Shinde, Application Specialist

Article from Analytix Reporter - Issue 6

Famciclovir is an antiviral drug indicated for the treatment of herpes zoster, herpes simplex virus 2 (genital herpes), herpes labialis (cold sores), etc. It is a guanosine analogue, a prodrug form of penciclovir, and marketed by Novartis under the trade name Famvir. Generics are produced by TEVA and Mylan, among others. Purospher™ STAR RP-8 endcapped HPLC columns can be used to monitor organic impurities in tablet formulations following the new USP monograph for Famciclovir Tablets. The method suitability requirements are defined by the relative standard deviation (NMT 5.0% for Famciclovir standard solution) and the chromatographic resolution between propionyl famciclovir and 6-chloro famciclovir (NLT 1.2 using the system suitability solution).

Experimental Conditions
Column	Purospher™ STAR RP-8 endcapped (5 µm) 250x4.6 mm (1.51454)
Mobile Phase	[A] 2.72 g/L of monobasic potassium phosphate in water. Adjust with 1 M phosphoric acid to a pH of 4.0 ±0.05.
	[B] Acetonitrile
Gradient	See table
Flow Rate	1 mL/min
Pressure Drop	132-147 bar (1914-2131 psi)
Detection	UV @ 220 nm (analytical flow cell; 10 µL)
Temperatures	Column: 50 °C; Autosampler: 8 °C
Injection Volume	20 µL
Samples
Standard Solution	1 μg/mL of USP Famciclovir RS in Mobile Phase A (Figure 1)
SST Solution	0.5 mg/mL of USP Famciclovir System Suitability Mixture RS in Mobile Phase A (Figure 2)
Test Solution	Nominally 1 mg/mL of Famciclovir in Mobile Phase A prepared as follows. Transfer an amount equivalent to 250 mg of Famciclovir, from not less than (NLT) 10 finely powdered tablets, to a 250-mL volumetric flask. Add about 125 mL of mobile phase A and sonicate for 30 min with intermittent shaking. Dilute with mobile phase A to volume. (Figure 3)
	Other samples in monograph method (not shown here)
Peak ID Solution	4 μg/mL of USP Famciclovir Related Compound A RS and 10 μg/mL of USP Famciclovir Related Compound B RS in Mobile Phase A

The method acceptance criteria are defined by the relative retention times for Famciclovir related compound A, Famciclovir related compound B, Famciclovir, 6-Chloro famciclovir, and Propionyl famciclovir and are about 0.2, 0.5, 1.0, 1.32, and 1.35, respectively. This application note illustrates with required analytical data that the method meets USP41-NF36 guidelines.

Gradient
Time	A (%)	B (%)
0	95	5
50	75	25
60	75	25
65	95	5
75	95	5

Figure 1. Chromatographic data – blank & standard solution.

Figure 2. Chromatographic data - system suitability test (SST) solution.

Peaks	Compound	Retention Time (min)	RRT	Resolution	Tailing Factor
1	Famciclovir Related compound B	15.8	0.51	-	0.99
2	Famciclovir	30.8	1.00	47.9	1.02
3	6-Chloro famciclovir	40.7	1.32	25.7	0.98
4	Propionyl famciclovir	41.4	1.34	1.7	0.98

Figure 3. Chromatographic data - test solution.

Peaks	Compound	Retention Time (min)	RRT	Resolution	Tailing Factor
1	Famciclovir Related compound B	15.8	0.51	0	0.99
2	Famciclovir	30.8	1.00	47.5	1.02
3	6-Chloro famciclovir	40.7	1.32	8.9	0.98
4	Propionyl famciclovir	41.4	1.34	7.7	0.98

Validation and verification

1. Specificity

Inject solution and determine the retention time of desired analyte in the presence of other components such as impurities and excipients.

2. Standard Repeatability (1 ppm)

Sample	Area Units
STD 1	214,771
STD 2	213,539
STD 3	214,102
STD 4	214,935
STD 5	214,216
Mean	214,313
Standard Deviation	559
RSD (%)	0.3

3. Linearity, LOD & LOQ

Famciclovir Concentration (μg/mL)	Area Units
0.5	59,951
1	98,532
5	478,367
12.5	1,190,770
25	2,360,140
40	3,757,032
50	4,687,957
60	5,618,958
75	7,007,616
LOD (ppm)	0.3
LOQ (ppm)	0.9

Figure 4. Area / Concentration in ppm