Quality by Design Yields Stability-Indicating HPLC Method for Diabetes Drug Pair

Researchers in India have developed and validated a reverse-phase high-performance liquid chromatography method that can simultaneously measure dapagliflozin propanediol monohydrate and telmisartan in a single chromatographic run, applying a Quality by Design framework to make the optimization systematic rather than trial-and-error. The work, published as open access research in Discover Pharmaceutical Sciences, addresses a practical gap: according to the authors, no liquid chromatographic technique for the simultaneous quantification of these two drugs in the same dosage form had been reported, even as a fixed-dose combination of the two molecules moves through late-stage clinical development in India.

The two analytes make an awkward chromatographic pair. Dapagliflozin propanediol monohydrate, the first approved sodium-glucose cotransporter 2 inhibitor, is used with diet and exercise to improve glycemic control in adults with type 2 diabetes by blocking glucose reabsorption in the nephron’s proximal tubules. Telmisartan, an angiotensin receptor blocker, treats hypertension by selectively binding angiotensin II type 1 receptors with high affinity, preventing angiotensin II from acting on vascular smooth muscle. The authors note that dapagliflozin is relatively polar while telmisartan is highly lipophilic, a physicochemical contrast that makes achieving adequate retention and resolution for both compounds in one run a genuine challenge.

Preliminary experiments illustrated that difficulty. Early trials on C18 ODS columns with simple binary mobile phases such as methanol-water and acetonitrile-water produced inadequate separation: dapagliflozin eluted near the solvent front while telmisartan showed excessively long retention times exceeding ten minutes, and telmisartan exhibited significant peak tailing attributed to its acidic nature and interaction with residual silanol groups on the stationary phase. Introducing buffered systems helped. At a pH around 4, telmisartan showed improved peak symmetry due to suppression of ionization, while dapagliflozin maintained adequate retention, leading the team to select potassium dihydrogen phosphate buffer adjusted to pH 4 with orthophosphoric acid.

The systematic core of the study was a Box-Behnken response surface design, chosen over a central composite design because it required fewer runs while still capturing interaction and quadratic effects across three factors at three levels. The three critical method parameters examined were the percentage of organic modifier in the mobile phase, the flow rate, and the detection wavelength. Using Design Expert software, the team constructed a design matrix of seventeen experimental runs, with retention time, resolution, and tailing factor for both drugs serving as the measured responses from which second-order polynomial models with interaction terms were fitted.

The fitted equations revealed how each parameter shaped the separation. Negative coefficients for mobile phase composition, flow rate, and wavelength in the dapagliflozin retention time model indicated that increasing any of these shortened its retention, while the resolution model showed that wavelength increases reduced resolution, whereas mobile phase composition and flow rate positively influenced it. Based on desirability optimization, the final conditions settled on acetonitrile, 0.01 M potassium dihydrogen phosphate buffer, and methanol in a 70:20:10 v/v/v ratio at pH 4, delivered at 1.0 mL/min with ultraviolet detection at 236 nm, a wavelength at which both drugs showed considerable absorption without interference in scans from 200 to 400 nm.

Under these optimized conditions the method achieved baseline separation with a resolution of 2.09, above the greater-than-2.0 criterion, with retention times of 3.1 minutes for dapagliflozin and 5.1 minutes for telmisartan. Tailing factors were 1.66 and 1.28 respectively, and theoretical plate counts reached 2307 and 2933, satisfying system suitability expectations that include more than 2000 plates and asymmetry factors close to 1. Validation followed International Council for Harmonization guidelines and covered linearity, range, precision, accuracy, specificity, and robustness across calibration ranges of 0.01 to 10 µg/mL for dapagliflozin and 0.04 to 40 µg/mL for telmisartan.

The quantitative performance was tight. Correlation coefficients were 0.9992 for dapagliflozin and 0.9995 for telmisartan in the results reported from the calibration analysis. Injection repeatability produced %RSD values of 0.88 for dapagliflozin and 0.85 for telmisartan, and all robustness checks, which deliberately shifted the wavelength to 234 and 238 nm, the flow rate to 0.9 and 1.1 mL/min, and the temperature to 20 and 30 °C, returned %RSD values below 2%. Standard-addition accuracy gave recoveries of 99.11 to 101.84% w/w for dapagliflozin and 99.17 to 101.42% w/w for telmisartan, and the limits of detection and quantification were reported as 0.01 and 0.001 µg/mL for dapagliflozin and 0.04 and 0.004 µg/mL for telmisartan.

Forced degradation testing probed the method’s stability-indicating claim. Both drugs were stressed with 0.01 N hydrochloric acid and 0.01 N sodium hydroxide at 70 °C for one hour, 3% hydrogen peroxide at 70 °C for one hour, dry heat in a hot air oven, and 254 nm ultraviolet light for 24 hours. Under these conditions the method showed roughly 10 to 20% degradation for both compounds, visible as decreased peak areas relative to non-degraded controls. Notably, no new degradant peaks appeared in the chromatograms; the authors attribute this to the possible absence of a chromophore or insufficient ultraviolet absorbance of the degradation products at the selected wavelength. They emphasize that the retention times of the intact drug peaks remained consistent across all stress conditions with no co-eluting peaks, which they present as evidence of specificity, while reporting only intact-drug retention times in the degradation table to avoid misinterpretation.

The method also performed on real products. Applied to powdered marketed tablets, Dapavel 10 containing 10 mg of dapagliflozin propanediol monohydrate and Aquris Telartam 40 containing 40 mg of telmisartan, the assay returned drug contents of 101.49% for dapagliflozin and 101.13% for telmisartan. Solution stability checks at room temperature over 0, 18, 42, and 48 hours supported routine use. The authors frame the clinical relevance of the combination through complementary mechanisms, with telmisartan’s angiotensin II receptor blockade offering antihypertensive and renoprotective effects alongside dapagliflozin’s SGLT2 inhibition, and they note that as of March 14, 2024, the combination was in Phase III clinical trials with Erias Lifesciences Limited according to the Central Drugs Standard Control Organization.

The team is candid about the boundaries of the work. The optimization was restricted to three critical parameters, and adding variables such as column temperature, a wider buffer pH range, or alternative stationary phases could further strengthen robustness. The forced degradation studies covered laboratory-controlled stress conditions only and may not capture every degradation pathway that long-term stability studies would reveal, and the method was demonstrated at laboratory scale, with inter-laboratory validation suggested as the next step toward industrial transfer. Within those limits, the study offers a documented example of how a designed experiment can compress what might otherwise be months of manual chromatographic scouting into seventeen structured runs, yielding a validated, stability-indicating assay ready for quality-control laboratories working with this emerging combination.

Subject of Research: Development and validation of a Quality by Design-based stability-indicating RP-HPLC method for simultaneous estimation of dapagliflozin propanediol monohydrate and telmisartan

Article Title: Stability-indicating RP-LC method for simultaneous estimation of dapagliflozin propanediol monohydrate and telmisartan based on QbD approach

Article References: Patel, K. P., Chhalotiya, U. K., Shah, D. A., Tandel, J. N., Kachhiya, H. M., Parmar, M. S., Solanki, K. H., Ahir, K. B., & Vohra, S. (2026). Stability-indicating RP-LC method for simultaneous estimation of dapagliflozin propanediol monohydrate and telmisartan based on QbD approach. Discover Pharmaceutical Sciences, 2(1), Article 10. https://doi.org/10.1007/s44395-026-00046-4

Image Credits: AI Generated

DOI: 10.1007/s44395-026-00046-4

Keywords: RP-HPLC, Quality by Design, Box-Behnken design, dapagliflozin, telmisartan, forced degradation, method validation, pharmaceutical analysis, chromatography, stability-indicating method, ICH guidelines, fixed-dose combination