(M1230-12-80) Formulation Development and Characterization of Parenteral Nicardipine HCl Product for Intrathecal Administration

Purpose: Nontraumatic subarachnoid hemorrhage (SAH) is an uncommon but often devastating cause of stroke that causes high mortality. One common catastrophic neurological effect of SAH in patients is angiographic (cerebral) vasospasm. I.V administration of Nicardipine HCl (NHCl) reduces angiographic vasospasm but causes hypotension. One strategy to avoid systemic side effects is intrathecal administration of NHCl. Currently, available I.V NHCl products contain buffer solutions with acidic pH of < 3.5, which induces inflammation at the injection site and has poor patient compliance. Also, lower strength of < 2.5 mg/ml makes it unfeasible to administer a higher dose using a higher volume. The goal is to develop higher strength NHCl, but there are several challenges to overcome, i.e., poor solubility (0.1mg/ml in water) and drug stability. We developed strategies to enhance the solubility and pH of > 3.5. The intrathecal products limit the use of excipients, buffers, or co-solvents. We have used only dextrose, which not only enhances the solubility, pH > 3.5, but also acts as a baricity agent. We hypothesized that the development of parenteral NHCl with higher strength (5 mg/ml) in dextrose solution with a pH of > 4.5 will be significantly effective, minimize the irritation at the site of injection, lowers the required injection volume, and improve patient compliance. The aim of the research work is to formulate and characterize parenteral NHCl product for intrathecal administration to treat vasospasm and overcome systemic side effects.

Methods: The Thermo Scientific Ultimate 3000 HPLC was used in method development and validation. Isocratic method, C18 Column 250x4.6mm, was used and maintained at 40°C with a flow rate of 0.9 mL/min, retention time of 3.125 min, and absorption wavelength of 254nm. For solubility determination, to the 1ml of respective dextrose solution (5%, 6%, 7%, and 8%), an excess of NHCl was added and placed on a shaker at 200rpm overnight at RT. Next day, centrifuged at 13,450 rpm for 15 min. The supernatant was collected and analyzed by HPLC. For the formulation development of NHCl, to 5% dextrose in MilliQ water, (5mg/ml) was added gradually at 700rpm and 37^oC for 90min, and pH was measured. For the NHCl assay, a validated HPLC method was used. For stability testing,3ml of product (n=3) stored at ICH conditions (long term stability: 25^oC ± 2^oC/60% RH ± 5% RH, intermediate stability: 30^oC ± 2^oC/65% RH ± 5% RH, accelerated stability: 40^oC ± 2^oC/75% RH ± 5% RH, also, 2-8^oC). At specific time points (day 0, 2^nd week, 1^st, 3^rd month), visual observations were made, and 400µl of samples were collected and analyzed. 6^th and 12th-month samples will be collected and analyzed.

Results: The linearity range of 0.1-25µg/mL was established after a series of concentrations (0.1, 0.25, 0.5, 1, 2.5, 5, 10, 25 µg/mL) were analyzed with a validated method. A standard curve was plotted, and the linearity curve obtained using the developed method possesses an R² of 0.9998 ((R²) ≥ 0.998 for acceptance) (Figure 1A). For precision, 7 injections of each concentration from the linear standard curve (0.1-25µg/mL) were used to find the % RSD. For all the standards, the %RSD was found to be ≤ 5% (ICH guideline accepted %) (Table 1A). In accuracy, by using the equation found in the linearity graph, the concentrations of the known standards of concentrations from 0.1-25µg/mL were calculated from their AUC. From the graph, the slope of the curve was 1.000, and the intercept was 0.000, which shows the accuracy of the method (Figure 1B). In solubility, it was observed that with increasing conc. of dextrose, the solubility of NHCl was increased (Table 1B). From the HPLC analysis of NHCl product (5mg/ml in 5% dextrose), it was observed that the stock concentration assay of NHCl was 102.75±2.94% (USP: 100±10%). pH of the final formulation was 4.54. After 3 months, samples stored at 30^oC±2^oC/RH 65±5% showed assay concentration above the acceptable limit (123.04±6.58%). All other samples stored at different storage conditions showed the assay concentration of NHCl within the USP limits (Figure 2). At 0 day, all the samples appeared clear light yellowish in color. After 2 weeks, the sample stored at 40^oC±2^oC/RH 75± 5%, and after 1 month, the sample stored at 30^oC±2^oC/RH 65±5%, and after 3 months sample stored at 25^oC± 2^oC/RH 60± 5% showed fine particles, but the sample stored at 2-8^oC were clear at all time points (Table 2).

Conclusion: NHCl solubility in 5% w/v dextrose solution was 6.53mg/ml. The higher strength NHCl solution (5 mg/ml) product was developed using the 5 % w/v dextrose solution, and pH was 4.5. After 3 months all the samples passed assay except samples stored at 30^oC±2^oC/65% RH ± 5%, but only samples stored at 2-8^oC passed in visual observation test up to 3 months. We are continuing the stability studies and developing further strategies to enhance the stability of NHCl product.

Acknowledgements: This work is supported by EMORY University Hospital, Atlanta. Grant number: GR00538.

Figure 1A: Linearity Curve of Nicardipine HCl using the developed HPLC method.
Figure 1B: A plot of calculated concentrations as a function of stock solution-based concentrations.

Table 1A: Nicardipine HCL HPLC method validation using HPLC method
Table 1B: Solubility of Nicardipine HCl in different concentrations of dextrose

Table 2: Assay and visual observations of Nicardipine HCl product at different stability conditions
Figure 2: Assay of the stability studies samples of Nicardipine HCl (5mg/ml) in 5 % Dextrose solution (n=3)