A stability indicating LC method for felodipine

Development and Validation of RP-HPLC and an Ecofriendly HPTLC Method for Simultaneous Determination of Felodipine and Metoprolol Succinate, and their Major Metabolites in Human Spiked Plasma

BACKGROUND

Felodipine is a calcium channel blocker used together with metoprolol succinate for treatment of hypertension.

OBJECTIVE

Two chromatographic methods were developed for simultaneous determination of felodipine (FEL) and metoprolol succinate (MET), and their major metabolites, dehydrofelodipine and metoprolol acid, respectively.

METHODS

The first method was RP-HPLC which comprised separation of the studied components by gradient elution using a Phenomenex C8 column and a mobile phase composed of water (adjusted to pH 3.5 with o-phosphoric acid)-acetonitrile - methanol (45:40:15, by volume) for the first 6 min and (30:60:10, by volume) for the next 4 min at a flow rate of 1 mL/min followed by UV detection of the eluted peaks at 225 nm. The second method was an HPTLC method where separation was achieved using a mobile phase consisting of toluene-ethyl acetate-methanol-ammonia-formic acid (10:5:2.5:0.3:0.1, by volume) and scanning of the separated bands at 225 nm.

RESULTS

Validation of the developed methods was done according to ICH guidelines. Successful application of the developed methods was carried out for determination of the studied drugs in human spiked plasma and in Logimax® tablets.

CONCLUSIONS

The developed RP-HPLC and HPTLC methods can be further applied for quality control testing of the studied drugs.

HIGHLIGHTS

RP-HPLC and HPTLC methods for determination of FEL, MET and their major metabolites. The developed methods were successfully applied for determination of FEL and MET in Logimax® tablets.

Micronization and microencapsulation of felodipine by supercritical carbon dioxide

Felodipine (FLD) is a poorly water-soluble drug. To improve its dissolution rate, the rapid expansion of supercritical solutions (RESS) technique was used to prepare micronized FLD drug particles, which were encapsulated in poly-(ethylene glycol) 4000 (PEG 4000). The physical properties of the encapsulated drug particles were characterized by a variety of analytical methods, including optical light microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and powder X-ray diffraction (powder-XRD) and the dissolution behaviour of FLD was studied in the microparticles. The supercritical condition of micronized FLD occurred at a relatively high pressure and moderate temperature. FLD-PEG 4000 microparticles compared well with micronized FLD. RESS was effective in reducing the particle size of FLD; spot-shaped micronized FLD and popcorn-shaped FLD-PEG 4000 microparticles were observed. The particulate properties of the microparticles included a narrow distribution and uniform size. Thermodynamic analysis showed an implantation interaction between FLD and PEG 4000 molecules, but no polymorphism in the micronized FLD or FLD-PEG 4000 microparticles. FLD-PEG 4000 microparticles had a significantly faster drug dissolution rate than micronized FLD. These data show that RESS can be used to prepare FLD-PEG 4000 microparticles with small particle size (2-6 microm) and enhanced dissolution rate.

A capillary zone electrophoresis method for the quantitative determination of hypoxoside in commercial formulations of African potato (Hypoxis hemerocallidea)

Hypoxoside is a norlignan diglucoside present in the corms of African potato, Hypoxis hemerocallidea, used as a popular African traditional medicine for its nutritional and immune boosting properties. A specific analytical method employing capillary zone electrophoresis has been developed and validated for the quantitative determination of this analyte. Sulfafurazole was used as internal standard, and electrophoretic separation of both analytes could be achieved within 12 min. Linearity of the method was established within the range 5-60 microg/mL and provided a high degree of accuracy (100 +/- 3%). The recovery of the method was found to be 100 +/- 5% and the RSDs of the intra- and inter-day precision were better than 5.19 and 2.52%, respectively. The limits of detection and quantification were calculated to be 0.5 and 2 microg/mL, respectively. The described method was used for the analysis and quality control of two commercially available products containing African potato. The method can also be used to determine product stability since it could separate the hypoxoside peak from its degraded products obtained from degradation studies.

Titrimetric and spectrophotometric assay of felodipine in tablets using bromate–bromide, Methyl Orange and Indigo Carmine reagents

Three new methods based on titrimetric and spectrophotometric techniques are described for the determination of felodipine (FLD) in the bulk drug and in tablets using a bromate?bromide mixture and two dyes, Methyl Orange and Indigo Carmine. In the titrimetric method (method A), the drug solution was treated with a measured excess of the bromate?bromide mixture in acid medium and after the reaction was judged to be complete, the unreacted bromine was determined iodometrically. The two spectrophotometric methods are based on the bromination of the drug with a known excess of the bromate?bromide mixture under acidic conditions followed by the estimation of the surplus bromine by reaction with either Methyl Orange (Method B) or Indigo Carmine (Method C) and measuring the absorbance at 520 nm or 610 nm, respectively. In all the methods, the amount of reacted bromine corresponds to the drug content. The titrimetric procedure is applicable for between 6?15 mg and the reaction stoichiometry was found to be 1:1 (drug: BrO3?). The systems obey Beer?s law between 0.12 ? 0.87 ?gml-1 and 0.5 ? 6.0 ?gml-1 formethods B and C respectively. The limits of detection and quantification are reported for both the spectrophotometric methods. The methods could usefully be applied to routine quality control of pharmaceutical formulations containing FLD. Statistical comparison of the results with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision.