Metronidazole Suspension

Metronidazole Suspension: Formulation, Evaluation, and Clinical Implications

Introduction to Metronidazole Suspension

Metronidazole is a widely used antibacterial and antiprotozoal agent, often formulated as a suspension for ease of administration, especially in pediatric and geriatric patients. This article synthesizes recent research on the preparation, evaluation, and clinical implications of metronidazole suspensions.

Formulation and Stability of Metronidazole Suspensions

Challenges in Formulation

One of the primary challenges in formulating metronidazole suspensions is preventing caking or claying, which is often due to the flocculation behavior of the dispersed phase. Studies have explored various suspending agents to address this issue. For instance, the use of Abelmoschus esculentus (Okra) mucilage, both alone and in combination with sodium sesquicarbonate, has shown promise in achieving desirable flocculation patterns and improving suspension stability .

Suspending Agents and Stability

Research has identified several effective suspending agents for metronidazole suspensions. Xanthan gum and Avicel® RC-591, a combination of microcrystalline cellulose and carboxymethylcellulose sodium, have been found to provide optimal formulation properties, preventing monohydrate formation and ensuring stability. Additionally, Parkia biglobosa mucilage has demonstrated potential as a suspending agent, offering comparable performance to traditional agents like tragacanth and gelatin.

Stability Studies

Stability studies have shown that metronidazole suspensions can remain stable for extended periods. For example, suspensions prepared with Ora-Blend or simple syrup and stored in amber polyvinyl chloride bottles were stable for up to 93 days at both room temperature and under refrigeration. Similarly, suspensions in PCCA SuspendIt maintained stability for 180 days, with no significant changes in drug concentration, pH, or viscosity, and no microbial growth.

Clinical Evaluation and Efficacy

In Vivo Efficacy

The efficacy of metronidazole suspensions has been evaluated in various clinical settings. For instance, a study comparing metronidazole-loaded alginate beads to a suspension form in H. pylori-infected mice found that the bead formulation provided superior eradication rates. Specifically, a 15 mg/kg dose of the bead formulation achieved a 100% clearance rate, compared to only 33.33% for the suspension at a 20 mg/kg dose.

Impact on Food Intake

In chinchillas, the administration of commercial metronidazole and metronidazole benzoate suspensions resulted in a dose-dependent reduction in food intake. This effect was more pronounced at higher doses, indicating the need for careful monitoring of food intake during treatment.

Metabolism and Absorption

The metabolism of metronidazole following oral administration of benzoylmetronidazole suspension in children with giardiasis showed sustained plasma concentrations and a prolonged elimination phase. This suggests that the benzoyl ester form may slow the rate of absorption, potentially enhancing therapeutic efficacy.

Quality Assessment of Commercial Suspensions

A study assessing the quality of different brands of metronidazole benzoate oral suspensions available in Jimma Town, Ethiopia, found significant variability in drug content among brands. Despite all brands meeting pharmacopoeial specifications, the variability highlights the importance of quality control in ensuring therapeutic efficacy.

Conclusion

Metronidazole suspensions are a critical dosage form for various patient populations. Advances in formulation techniques, particularly the use of novel suspending agents, have improved the stability and efficacy of these suspensions. However, clinical evaluations and quality assessments underscore the need for ongoing research and stringent quality control to ensure optimal therapeutic outcomes.

Summary

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