Category: Formulation and Quality
Purpose: Jawbone infections are usually caused when a dental cavity remains untreated or there is an accumulation of bacteria in the side of the teeth or around an implant leading to peri-implantitis. If it is not treated immediately, the infection can cause serious health issues like endocarditis. The jawbone infections such as dental abscess, peri-implantitis, dry socket, and pockets are usually treated by incision and drainage, root canal treatment or extraction in combination with a prolonged course of antibiotic. However, antibiotics given orally have poor bioavailability in the bone which creates major therapeutic challenges. Metronidazole is highly active against many gram-negative and gram-positive anaerobic bacteria found in the dental infections. The goal of this study is to develop an injectable in situ gelling system to deliver effectively metronidazole at the site of jawbone infections. This study aims at the development and characterization of in situ gelling formulation containing metronidazole.
Methods: A HPLC method was developed and validated for the quantitation of metronidazole. Ranitidine was used as an internal standard. Standard stock solution of metronidazole was prepared by dissolving 1 mg/mL in mobile phase consisting of 0.1% acetic acid and acetonitrile in the ratio of 85:15. Standard solutions in the range of 1.6-205 µg/ml were prepared from stock solution with appropriate dilution. Ten µL aliquot of these solutions were used for determining metronidazole content by a HPLC method using C-18 column (Phenomenex, 250mm×4.6mm, 5µm), isocratic elution at flow rate of 1.5 mL/min, and detection at 319 nm after 4.5 min run time. The method developed was validated by determining parameters such as specificity, linearity, accuracy, and precision where in general relative standard deviation (RSD) of ≤ 10% is accepted as per USP guidelines. The in situ gelling system was prepared by adding 15 and 25% (w/v) poly(DL-lactide) (RESOMER R Type 203 S ) (PLA) to benzyl benzoate (BB) which was maintained at 370C on a magnetic stirrer to dissolve it. Metronidazole (0.5% w/v) was dissolved in PLA solution by sonicating for 20 seconds at 40W. Metronidazole-PLA (Metro-PLA) solution was characterized by Differential Scanning Calorimetry (DSC) to check its miscibility. Metro-PLA solution was injected into PBS (pH 7.4) which resulted into formation of a gel immediately. In vitro release of metronidazole was determined by withdrawing specific amount of PBS at specific time points by using the method described above. All the experiments were carried out in triplicates and P< 0.05 was used as level of significance.
Results: The standard curve was linear (R2 >0.99) for the concentration range (1.6-205 µg/ml) of metronidazole studied. The retention times for metronidazole and ranitidine (internal standard) were 4 min and 1.4 min, respectively. The relative standard deviation of accuracy and precision for intra- and inter-day repetitions were found to be less than 10% . PLA solution containing metronidazole was injectable. The release study indicated that 90±5 and 75±4% of metronidazole released from the formulation consisted of 15 and 25% (w/v) PLA in 4 and 24 hours, respectively. The DSC thermogram of metro-PLA solution did not exhibit any endothermic peak indicating the non-crystalline nature of the drug in the gel.
Conclusion: The HPLC method for quantitation of metronidazole was validated as per USP guidelines. In situ gelling formulations studied can deliver metronidazole at the target site, is an efficient treatment for jaw-bone infections. However, the period of release needs to be extended in any future studies by using approaches such as combination of polymers or loading metronidazole in PCL microparticle which can be easily incorporated in an in situ gelling system.