(W1030-02-12) Crystal Defects Cause Nitrosamine Formation in Ranitidine under Accelerate Storage Condition

Purpose: The purpose of this research is to determine how nitrosamines are formed in the solid state due to the presence of Solid-state reactive species in drug substances, including crystal defects produced via milling, grinding, tableting, and crystallization, as well as potentially amorphous material in the drug substance and drug product.

Methods: Ranitidine hydrochloride samples with varying crystal qualities were prepared through cryogenic milling for different durations. The cryomilled samples were characterized using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) to confirm the crystallinity, while the surface area of the cryomilled samples was measured with Brunauer-Emmet-Teller (BET) theory. The scanning electron microscope (SEM) images were obtained to demonstrate the surface features of the cryomilled samples. The cryomilled samples (50% w/w) were blended with microcrystalline cellulose (49.5%, w/w) and magnesium stearate (0.5%, w/w) using a Turbula 3D shaker mixer. The powder blend (150 mg) was compressed into standard concave bisect tablets using a 6 mm die under a compression force of 1000 lbs. The bulk sample and cryomilled samples containing SSRS along with the tablets compressed from these samples were stored under accelerated conditions (60 °C, sealed) for several days and then analyzed using liquid chromatography coupled with tandem mass spectrometry (LC/MS-MS) to quantify N-nitrosodimethylamine (NDMA), the primary degradation impurity in ranitidine hydrochloride.

Results: The PXRD patterns show no evidence of a significant amorphous component, and the DSC thermograms show no glass transition peak, indicating that the solid form remains stable during the grinding process, with no amorphous content present in the cryomilled samples. The surface area of the cryomilled 5-minute sample was 1.88 m²/g. This increased to 2.71 m²/g after 10 minutes of cryogrinding, and further to 4.17 m²/g after 15 minutes of cryogrinding. After cryogrinding for 30 minutes, the surface area increased to 4.79 m²/g. The BET surface area indicates a significant increase in surface area for the 5-15 minutes cryogrinding times, there is only a minor change in surface area for the 15-30 minutes cryogrinding time. The SEM images for the bulk sample, cryogrinding 10-minute sample, and 30-minute sample are shown in Figure 1. After even brief cryogrinding, the 10-minute cryoground sample shows that the particles have a much different morphology than prior to cryogrinding. In particular, the single-crystal particle size is much smaller than the material prior to cryogrinding. Further grinding resulted in even smaller particle sizes, as is shown for the 20-minute and 30-minute cryoground material. Overall, the particle size has not changed dramatically upon cryogrinding, in that the particle size before and after cryogrinding is similar (at least in these images). However, the particles themselves are much different. The increase in BET surface area is attributed to a higher number of crystal defects. Figure 2 shows stability data for the cryoground ranitidine hydrochloride that was stored at 60 °C, 0% RH for several days. The same dataset was plotted with a logarithmic y-axis (a) and a linear y-axis (b). The bulk sample (CM 0Min) contained 1.5 ppm (μg/g) NDMA at T=0 days. The cryomilled samples contained higher NDMA levels with increased cryomilling time, which indicated that the cryomilling process contributed to ranitidine hydrochloride degradation. Cryomilling 30 minutes (CM 30Min) sample degraded to approximately 46 ppm within 6 days, whereas the cryomilling 25 minutes (CM 25Min) sample required 12 days, and the cryomilling 15 minutes (CM 15Min) sample took 24 days to reach the same level. Furthermore, the sample cryomilled for less than 15 minutes did not exceed 40 ppm of degradation after storage for 24 days. Ranitidine hydrochloride stored for 24 days had 300 ppm NDMA for the sample that was cryoground for 30 minutes. The data is very clear that cryogrinding results in degradation of ranitidine hydrochloride due to the formation of solid-state reactive species (SSRS). The stability data for tablets that contained ranitidine hydrochloride that was unground, and had been cryoground for 10 and 30 minutes, and then stored at 60 °C at 0% RH for several days, shows a similar trend compared to the cryoground powder data. The tablets made by the 30-minute cryoground ranitidine hydrochloride had the fastest degradation rate. The tablet stability results are also shown in Figure 2. The same dataset was plotted with a logarithmic y-axis (c) and a linear y-axis (d). Since NDMA is a yellow, oily liquid, the tablets with higher NDMA content appeared visibly darker after the stability test. The picture of tablets after storage is shown in Figure 3. The obvious color change emphasizes the dramatic difference between materials that do and do not contain a significant number of SSRS.

Conclusion: Solid-state reactive species (SSRS) can be produced through the grinding or milling of materials. Ranitidine Hydrochloride degradation in drug substance and drug product is influenced by SSRS. A higher amount of SSRS in the sample leads to faster degradation in the solid state.

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Acknowledgements: The authors would like to thank the Center for Pharmaceutical Processing Research for their financial support of this work. Disclosure: The authors declare the following competing financial interests: EJM is a partial owner of Kansas Analytical Services, which provides solid-state NMR services to the pharmaceutical industry. EJM and NJH are partial owners of Spectral NMR Technologies, which provides specialized NMR equipment for non-destructive testing of pharmaceutical products. The results presented here are from academic work at Purdue University, and no data from either Kansas Analytical Services or Spectral NMR Technologies are presented.


Figure 1. Scanning Electron Microscopy images of cryoground ranitidine hydrochloride.


Figure 2. Stability data for cryomilled ranitidine hydrochloride powder (a), (b) and tablets (c), (d) that were stored at 60°C, 0% RH after cryogrinding.


Figure 3. 150mg tablets contained 50% ranitidine hydrochloride (unground, cryomilled 10 minutes, or cryomilled 30 minutes), 49.5% microcrystalline cellulose, and 0.5% magnesium stearate stored at 60°C, 0% RH.