INTRODUCTION:

Fenofibrate (CAS 49562-28-9) is an oral medication of fibrate class used to treat abnormal lipid levels which is approved by FDA for the treatment of patients with hypertriglyceridemia, primary hypercholesterolemia etc. It is chemically propan-2-yl 2-[4-(4-chlorobenzoyl) phenoxy]-2-methylpropanoate¹ and available as white, crystalline powder with molecular formula C₂₀H₂₁ClO₄ and molecular weight 360.83g/mol.

Spectrophotometric methods^2-5, liquid chromatographic methods, LC-MS methods etc were developed for the assay of Fenofibrate in pharmaceutical dosage forms and biological fluids. Similar type of methods were developed for different drug molecules in the literature^6-10. The authors have proposed new spectrophotometric technique for the assay of Fenofibrate in pharmaceutical dosage form and validated as per ICH guidelines.

Figure 1: Chemical structure of Fenofibrate

MATERIALS AND METHODS:

Shimadzu Model No. UV-1800 double beam UV-VIS spectrophotometer with quartz cells is used for the entire study and all the solutions were scanned 200-400nm. Solutions such as acetate buffer (pH 4.0), phosphate buffer (pH 7.8), phosphate buffer (pH 5.8), 0.1M sodium hydroxide solutions were prepared as per IP 2022. Fenofibrate stock solution was prepared by dissolving 25mg of Fenofibrate in 25mL volumetric flask with methanol (1000µg/mL) from which working standard solution (100µg/mL) was also prepared in methanol and further dilutions were prepared on dilution with different solutions in the present study and the methods were validated as per ICH guidelines. Fenofibrate is available as tablets with brand names LIPICARD (USV Private Ltd; Label claim 160mg), FINOBRATE (Knoll Health Care Pvt Ltd; Label claim 145mg). FINATE (Franco-Indian Pharmaceuicals Pvt Ltd.; Label claim 160mg) and as FENOBATE capsules (East West Pharma Private Ltd; 200mg) in India.

Method validation¹¹

A series of Fenofibrate solutions 0.5-40µg/mL were prepared from working standard on dilution with acetate buffer (pH 4.0) (Method I), phosphate buffer (pH 7.8) (Method II), 0.1M sodium hydroxide buffer (Method III), and 1-40µg/mL were prepared from working standard on dilution with phosphate buffer (pH 5.8) (Method IV), distilled water (Method V), and scanned (200-400nm) against their reagent blanks. The spectra so obtained has shown maximum absorbance (λ_max) at 292 nm (Method I), 291.20nm (Method II), 291.60nm (Method III), 293.60nm (Method IV) and 290.20nm (Method V). The absorbance of all these solutions was noted at λ_max,and a calibration curve was drawn by taking the concentration on the X-axis and the corresponding absorbance on the Y-axis. Precision studies were performed by calculating the percentage relative standard deviation of independent assays of six determinations on the same day and on three consecutive days (Day1, Day 2 and Day 3) whereas accuracy studies were carried out by standard addition method.

Assay of Fenofibrate tablets:

Twenty tablets of Fenofibrate were powdered with the help of motor and pestle and tablet powder equivalent to 10mg of Fenofibrate was weighed and dissolved in 10mL volumetric flask containing methanol (1000 µg/mL), the solution was sonicated and filtered. Working standard solution was prepared in methanol (100µg/mL), further series of dilutions were prepared on dilution with acetate buffer (pH 4.0), phosphate buffer (pH 7.8), 0.1M Sodium Hydroxide, phosphate buffer (pH 5.8), distilled water for Method I, II, III, IV and V respectively and the percentage recovery was calculated from the linear regression equations obtained.

RESULTS AND DISCUSSION:

New spectrophotometric methods have been developed for the determination of Fenofibrate tablets using acetate buffer (pH 4.0), phosphate buffer (pH 7.8), 0.1M sodium hydroxide buffer, phosphate buffer (pH 5.8) and distilled water. A review of previously published spectrophotometric methods was given in Table 1.

Table 1: Spectrophotometric methods in literature

Reagent	Linearity (μg/mL)	λ_max (nm)	Reference
Methanol	0-60	287.5	2
Methanol + DW	2-12	285	3
Methanol	3-30	285.5	4
4M sodium acetate and 1.25M sodium citrate	5-35	296	5
Acetate buffer (pH 4.0),	0.5-40	292	Present method
Phosphate buffer (pH 7.8)		291.20
0.1M Sodium hydroxide		291.60
Phosphate buffer (pH 5.8)	1-40	293.60
Distilled water	1-40	290.20

Fenofibrate has shown absorption maxima at 292 nm (Method I), 291.20 nm (Method II), 291.60 nm (Method III), 293.60 nm (Method IV), 290.20 nm (Method V). It obeys Beer-Lambert’s law over the concentration range 0.5-40 µg/mL in acetate buffer (pH 4.0), phosphate buffer (pH 7.8), 0.1M Sodium hydroxide buffer, and concentration range 1-40 µg/mL in phosphate buffer (pH 5.8), distilled water (Table 2). The linear regression equations were found to be y=0.0519x-0.0174 (0.9993), y=0.0505x-0.0124 (0.9996), y=0.053x-0.0143 (0.9993), y=0.0494x-0.014 (0.9998), y=0.0499x-0.01 (0.9999) for acetate buffer, phosphate buffer (pH 7.8), 0.1M Sodium hydroxide, phosphate buffer (pH 5.8) and distilled water respectively.

The percentage RSD in accuracy (Table 3) and precision studies (Table 4) for all the methods was found to be less than 2 in indicating that the methods are precise and accurate. The assay was performed for tablets and the percentage recovery was calculated (Table 5). The optical characteristics of the method were shown in Table 6.

Table 2: Linearity of Fenofibrate

Conc. (µg/mL)	Absorbance
Methods	I	II	III	IV	V
0.5	0.0300	0.0277	0.0313	-	-
1	0.0468	0.0455	0.0553	0.0382	0.0452
2	0.0837	0.0987	0.0923	0.0865	0.0884
5	0.2217	0.2177	0.2348	0.2285	0.2218
10	0.4752	0.4720	0.4838	0.4655	0.4897
20	0.9843	0.9698	1.0053	0.9643	0.9885
30	1.5691	1.5171	1.6129	1.4795	1.4934
40	2.0625	2.0144	2.1102	1.9659	1.9842


Method I (Acetate buffer pH 4.0)	Method II (Phosphate buffer pH 7.8)

Method III (0.1M Sodium hydroxide)	Method IV (Phosphate buffer pH 5.8)

Method V (Distilled water)

Figure 2: Absorption spectra of Fenofibrate (30 µg/mL)

Table 3: Accuracy of Fenofibrate Tablet

Spiked Conc. (µg/mL)

Formulation

(µg/mL)

Total Conc.

(µg/mL)

Conc. obtained (μg/mL) [% Recovery] (RSD)

Method I

Method II

Method III

Method IV

Method V

0.5 (50%)

96.64

[0.037]

0.0391

94.96

[0.304]

0.3202

99.28

[0.327]

0.3295

98.00

[0.011]

0.0117

97.35

[0.026]

0.0271

1 (100%)

97.84

[0.145]

0.1482

98.03

[0.035]

0.0358

97.26

[0.453]

0.4666

99.01

[0.01]

0.0100

99.05

[0.047]

0.0477

1.5 (150%)

97.21

[0.02]

0.0205

98.50

[0.137]

0.1400

98.94

[0.140]

0.1416

99.20

[0.122]

0.1231

99.61

[0.015]

0.0153

*Mean of three replicates

Table 4: Precision study of Fenofibrate Tablet

Intraday precision
Conc. (µg/mL)	Absorbance
Conc. (µg/mL)	Method I	Method II	Method III	Method IV	Method V
10	0.4752	0.4720	0.4838	0.4655	0.4897
10	0.4753	0.4722	0.4835	0.4653	0.4892
10	0.4751	0.4721	0.4832	0.4649	0.4895
10	0.4760	0.4728	0.4842	0.4654	0.4893
10	0.4754	0.4731	0.4845	0.4659	0.4890
10	0.4755	0.4726	0.4839	0.4662	0.4896
Mean ± S.D (% RSD)	0.4754±0.0003 (0.067)	0.4724±0.0004 (0.092)	0.4838±0.0004 (0.096)	0.4655±0.0004 (0.098)	0.4893±0.0002 (0.053)
Interday precision
Conc. (µg/mL)	Absorbance
Conc. (µg/mL)	Method I	Method II	Method III	Method IV	Method V
10	0.4752	0.4720	0.4838	0.4655	0.4897
10	0.4762	0.4725	0.4842	0.4657	0.4893
10	0.4749	0.4723	0.4847	0.4661	0.4899
Mean ± S.D (% RSD)	0.4754±0.0006(0.143)	0.4722±0.0002(0.053)	0.4842±0.0004(0.093)	0.4657±0.0003(0.065)	0.4896±0.0003(0.0624)

*Mean of three replicates

Table 5: Assay of Fenofibrate tablets

Brand	Method I		Method II		Method III		Method IV		Method V
Brand	Observed (mg)	% Recovery	Observed (mg)	% Recovery	Observed (mg)	% Recovery	Observed (mg)	% Recovery	Observed (mg)	% Recovery
I	9.95	99.5	9.32	93.2	9.98	99.8	9.93	99.3	9.96	99.6
II	9.9	99	9.53	95.3	9.99	99.9	9.86	98.6	9.99	99.9

Table 6: Optical characteristics

Parameters		Method I	Method II	Method III	Method IV	Method V
Linearity range (µg/mL)		0.5-40	0.5-40	0.5-40	1-40	1-40
λ_max(nm)		292	291.20	291.60	293.60	290.20
Molar extinction coefficient (litre/mole/cm^-1)		1.8727 x 10⁴	1.8221 x 10⁴	1.9123 x 10⁴	1.7824 x 10⁴	1.8005 x 10⁴
Sandell’s sensitivity (µg/cm²/0.001 absorbance unit)		0.31599	0.22574	0.25094	0.26315	0.18036
Slope		0.0519	0.0505	0.053	0.0494	0.0499
Intercept		0.0174	0.0124	0.0143	0.014	0.01
Correlation coefficient		0.9993	0.9996	0.9993	0.9998	0.9999
Precision (%RSD)	Intraday	0.0670	0.0924	0.0967	0.0985	0.0539
Precision (%RSD)	Interday	0.1432	0.0533	0.0931	0.0656	0.0624
Accuracy (% RSD)		0.02-0.14	0.03-0.32	0.14-0.46	0.01-0.12	0.01-0.04
Assay (%)		99.5	93.2	99.8	99.3	99.6