JUDE ISESELE

Background: The selection of suspending agents in pharmaceutical formulations is often guided
by trial-and-error or historical precedent, rather than systematic rheological characterization. This approach can lead to suboptimal formulations, resulting in issues such as sedimentation, poor redispersibility, or excessive viscosity, which compromise therapeutic efficacy and patient
acceptability. This study evaluates and ranks selected natural gums and starches based on their
rheological properties in magnesium trisilicate suspension to identify locally sourced efficient
and stable suspending agents that could be used for preparing stable pharmaceutical formulations. Method: Natural suspending agents obtained from starches extracted from their tubers and
grains along with other selected natural gums were compounded at varying concentrations (1–
5% w/v) into magnesium trisilicate suspensions. Formulations were assessed for organoleptic
properties, pH stability (using a digital pH meter), viscosity (using Brookfield viscometer), and
sedimentation volume over 4 weeks (for pH and viscosity) and 7 days (for sedimentation
volume). A control without suspending agent served as baseline. Results: All natural suspending agents utilized improved the viscosity and sedimentation
volume (4.76-5.01 mPa·s and 0.48-0.98 respectively) when compared to the magnesium
trisilicate without any suspending agent which served as control (viscosity: 4.12 mPa·s;
sedimentation: 0.48 by day 7). Tragacanth gum (2% w/v) showed highest viscosity (7.52 mPa·s)
and sedimentation volume (0.92 by day 7), followed by acacia gum and gelatin. Starches (e.g., potato, cocoyam) provided moderate stability but exhibited greater pH decline (to ~4.0 after 4
weeks) due to potential degradation. Conclusions: Tragacanth, acacia, and gelatin were identified as the most effective natural
suspending agents in magnesium trisilicate suspensions. Starches provided moderate but
consistent results. The study establishes that locally sourced natural polymers can serve as cost- effective, biodegradable alternatives for pharmaceutical suspension formulations.

Background: The stability of pharmaceutical suspensions depends on their rheological properties, which are influenced by the type and concentration of suspending agents. This study evaluated and compared the rheological properties and performance of various suspending agents in ibuprofen suspension formulations. Methodology: Ten suspending agents Chitosan, Sodium Alginate, NaCMC, HPMC, HEC, Carbopol, CMEC, MC, Eudragit L-100, and PVP, were prepared using appropriate solvents. Eudragit L-100 was dissolved in ethanol, HEC, HPMC, and Carbopol in hot water, Chitosan in 1% H₂SO₄, while others were dispersed in distilled water. Each was evaluated for pH,
density, and viscosity. Six agents (NaCMC, CMEC, Sodium Alginate, MC, HPMC, and Carbopol) were selected to formulate ibuprofen suspensions, assessed for pH, viscosity, and sedimentation rate at ambient temperature. Results: All suspending agents produced formulations with acceptable pH (4.1–5.9). Viscosity increased with polymer concentration; Carbopol and NaCMC at 1.0% formed gel like systems, while0.5%gave smooth, pourable suspensions. Sedimentation tests showed the control settled rapidly, whereas Carbopol and NaCMC formulations exhibited the highest stability with uniform sedimentation over seven days. Conclusion: All agents improved suspension stability, though performance varied with concentration. Carbopol and NaCMC at 0.5% provided the best balance between viscosity and pourability, making them most suitable for ibuprofen suspensions