Stress Degradation Studies on Tadalafil and Development of a Validated Stability-Indicating LC Assay for Bulk Drug and Pharmaceutical Dosage Form

Integrated Quality by Design (QbD) Approach for Stability Indicating RPHPLC Method for the Estimation of Tadalafil Hydrochloride in Bulk Drug and Pharmaceutical Formulations

Background:

In view of the current FDA standardization and product quality control criteria, Quality by design approach for analytical methods is gaining importance to develop a robust analytical method. A new Quality by Design approach by RP-HPLC was developed and validated for the quantification and purification of Tadalafil hydrochloride and its tablet formulations.

Objective:

The objective of the study was to develop and validate a simple, robust, and accurate method by QbD approach for detection Tadalafil hydrochloride and its degradation products in bulk drug and tablet formulation.

Methods:

The chromatographic separation was performed on JASCO Crest Pack RPC18 column (250mm×4.6mm, 5μm) with mobile phase A consisting of a mixture of Acetonitrile: Methanol (40:20 v/v); and mobile phase B: 0.01M Ammonium acetate in water pH adjusted to 3.50± 0.05 with glacial acetic acid with 1.0ml/min flow rate at 285nm. Box-Behnken's three-level, 3-factorial design was employed to create and analyze a "Design Space" (DoE). This design was statistically analyzed by ANOVA, counter-plot, and 3D response surfaces plots, which demonstrated that the model was statistically significant. The developed method was validated as per the ICH guidelines Q2 (R1).

Results and Discussion:

The tadalafil hydrochloride showed good regression (R2>0.9995) within tested ranges, and the percent recovery was found to be 98% in the marketed formulation.

Conclusion:

The method was found to be highly specific without the interference of impurities and degradation products of tadalafil hydrochloride. For quantification and routine quality control of tadalafil and its marketed formulation, the stability-indicating the RP-HPLC method could thus be extended.

UHPLC for quality evaluation of genuine and illegal medicines containing sildenafil citrate and tadalafil

One of the highest incidences of illegal drug products is related to phosphodiesterase-5 inhibitors, used in treatment of erectile dysfunction, including those containing sildenafil citrate and tadalafil. In this context, comprehensive evaluation of the quality of genuine and illegal medicines was performed. A simple and rapid ultra-high performance liquid chromatography (UHPLC-UV) method to quantify sildenafil and tadalafil in the presence of six degradation products was developed and validated. Sildenafil and tadalafil were submitted to forced degradation. The separation was carried out on a Kinetex C18 (50 × 2.1 mm; 1.7 μm) column with mobile phase composed of acetonitrile and aqueous triethylamine solution. The calibration curves were linear in the range of 14-126 μg mL-1 for sildenafil citrate and 4-36 μg mL-1 for tadalafil and the method proved to be selective, precise, accurate and robust. Sildenafil degraded in oxidative media, whereas tadalafil degraded in acidic, alkaline and oxidative environment. The chemical structures and the mechanisms for the formation of the main degradation products were proposed by UHPLC coupled to tandem mass spectrometry. The UHPLC-UV method was applied in the pharmaceutical analysis of genuine and seized medicines. Some of them did not meet quality standards, mainly due to contents below specifications and the large variation on contents between units within a batch.

D-optimal design as a useful tool response surface methodology for the optimization of signals from synchronous fluorescence prior to simultaneous determination of avanafil and tadalafil

A rapid, smart and sensitive first derivative spectrofluorimetric method has been carried out for the simultaneous estimation of avanafil and tadalafil either in their pure form, tablet dosage form or spiked human plasma. The measurements of normal emission spectra or synchronous fluorescence intensity of both drugs show severe overlap which hindered their determination using normal fluorescence or synchronous intensity. Therefore, a highly sensitive first derivative synchronous fluorescence procedure was used to resolve this overlap. The method is based upon measurement of the amplitude of the first derivative of synchronous fluorescence intensity of both drugs at Δλ = 70 nm and at suitable wavelength of 396 nm and 364 nm for avanafil and tadalafil, respectively. Under the optimum conditions, the linear determination ranges are 50-1800 and 5-400 ng mL^-1 with a detection limit of 12.93 and 1.46 ng mL^-1 for avanafil and tadalafil, respectively. A response surface methodology was used for optimization using D-optimal design which can be used for determination of the exact optimum parameters specifically designed for this method. In addition; it is a good way to graphically clarify the relationship between various experimental variables and the synchronous fluorescence intensity.

A simple and sensitive HPLC fluorescence method for determination of tadalafil in mouse plasma

A simple and sensitive high-performance liquid chromatographic (HPLC) method utilizing fluorescence detection was developed for the determination of the phosphodiesterase type 5 inhibitor tadalafil in mouse plasma. This method utilizes a simple sample preparation (protein precipitation) with high recovery of tadalafil (∼98%), which eliminates the need for an internal standard. For constituent separation, the method utilized a monolithic C(18) column and a flow rate of 1.0mL/min with a mobile phase gradient consisting of aqueous trifluoroacetic acid (0.1% TFA in deionized water pH 2.2, v/v) and acetonitrile. The method calibration was linear for tadalafil in mouse plasma from 100 to 2000ng/mL (r>0.999) with a detection limit of approximately 40ng/mL. Component fluorescence detection was achieved using an excitation wavelength of 275nm with monitoring of the emission wavelength at 335nm. The intra-day and inter-day precision (relative standard deviation, RSD) values for tadalafil in mouse plasma were less than 14%, and the accuracy (percent error) was within -14% of the nominal concentration. The method was utilized on mouse plasma samples from research evaluating the potential cardioprotective effects of tadalafil on mouse heart tissue exposed to doxorubicin, a chemotherapeutic drug with reported cardiotoxic effects.