Development and validation of a spectrofluorimetric method for the analysis of tolfenamic acid in pure and tablet dosage form

Photolysis of tolfenamic acid in aqueous and organic solvents: a kinetic study

Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug that was studied for its photodegradation in aqueous (pH 2.0-12.0) and organic solvents (acetonitrile, methanol, ethanol, 1-propanol, 1-butanol). TA follows first-order kinetics for its photodegradation, and the apparent first-order rate constants (k obs) are in the range of 0.65 (pH 12.0) to 6.94 × 10-2 (pH 3.0) min-1 in aqueous solution and 3.28 (1-butanol) to 7.69 × 10-4 (acetonitrile) min-1 in organic solvents. The rate-pH profile for TA photodegradation is an inverted V (∧) or V-top shape, indicating that the cationic form is more susceptible to acid hydrolysis than the anionic form of TA, which is less susceptible to alkaline hydrolysis. The fluorescence behavior of TA also exhibits a V-top-shaped curve, indicating maximum fluorescence intensity at pH 3.0. TA is highly stable at a pH range of 5.0-7.0, making it suitable for formulation development. In organic solvents, the photodegradation rate of TA increases with the solvent's dielectric constant and solvent acceptor number, indicating solute-solvent interactions. The values of k obs decreased with increased viscosity of the solvents due to diffusion-controlled processes. The correlation between k obs versus ionization potential and solvent density has also been established. A total of 17 photoproducts have been identified through LC-MS, of which nine have been reported for the first time. It has been confirmed through electron spin resonance (ESR) spectrometry that the excited singlet state of TA is converted into an excited triplet state through intersystem crossing, which results in an increased rate of photodegradation in acetonitrile.

Analysis of Tolfenamic Acid using a Simple, Rapid, and Stability-indicating Validated HPLC Method

BACKGROUND

Tolfenamic acid (TA) belongs to the fenamates class of nonsteroidal anti-inflammatory drugs. Insufficient information is available regarding the availability of a reliable and validated stability-indicating method for the assay of TA.

OBJECTIVE

A relatively simple, rapid, accurate, precise, economical, robust, and stabilityindicating RP-HPLC method has been developed to determine TA in pure and tablet dosage forms.

METHODS

The method was validated according to the ICH guideline, and parameters like linearity, range, selectivity, accuracy, precision, robustness, specificity, and solution stability were determined. TLC and FTIR spectrometry were used to ascertain the purity of TA. The specificity was determined with known impurities and after performing forced degradation, while the robustness was established by Plackett-Burman's experimental design. The mobile phase used for the analysis was acetonitrile and water (90:10, v/v) at pH 2.5. The detection of the active drug was made at 280 nm using a C18 column (tR = 4.3 min.). The method's applicability was also checked for the yellow polymorphic form of TA.

RESULTS

The results indicated that the method is highly accurate (99.39-100.80%), precise (<1.5% RSD), robust (<2% RSD), and statistically comparable to the British Pharmacopoeia method with better sensitivity and specificity.

CONCLUSION

It was observed that the stress degradation studies do not affect the method's accuracy and specificity. Hence the proposed method can be used to assay TA and its tablet dosage form.

A new fluorescence-based method for rapid and specific quantification of rotigotine in chitosan nanoparticles

A new, simple, rapid and sensitive fluorescence-based method has been developed and validated for the estimation of rotigotine (RTG) in bulk and nanoformulations. RTG is a dopamine agonist approved by both the United States Food and Drug Administration and the European Medicines Agency for the treatment of Parkinson's disease and restless leg syndrome. To date, no fluorescence-based analytical method has been reported for the estimation of RTG in any pharmaceutical dosage forms. The developed method is validated as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use guidelines. A solution of the pure drug in phosphate buffer pH 6.4 exhibited strong fluorescence emission (λ_em) at a wavelength of 298 nm when excited (λ_ex) at a wavelength of 277 nm. The developed method demonstrated good linearity over a range of 250-2500 ng/mL. Limit of detection and limit of quantitation values were found to be 36.25 ng/mL and 109.85 ng/mL respectively. The developed method was found to be accurate, precise, specific and robust. The validated method was successfully applied for the estimation of entrapment efficiency and drug loading of in-house intranasal RTG-loaded chitosan nanoparticles.