Effect of sodium bicarbonate on the properties of metronidazole floating matrix tablets.
The effect of sodium bicarbonate (SB) on the swelling behavior and the sustained release of floating systems was studied with varied proportions of this excipient and metronidazole. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. Under in vitro dissolution conditions, the addition of SB to metronidazole sustained-release tablets modifies the matrix hydration volume, increasing at the beginning, reaching a maximum, and then declining. Pure Carbopol matrices show a rapid hydration with a limited further effect of the SB and metronidazole loads. Methocel show a significant increase of the apparent hydration volume due to SB addition with no further notable change due to metronidazole load. Increasing the metronidazole load reduces the floating time of Carbopol matrices while no effect on Methocel matrices could be observed within 8 hours dissolution. Matrices show increasing release constant values (k) as the metronidazole load increases. Methocel matrices release the drug 10% to 15% faster than Carbopol matrices. SB increases the cumulative amount of drug released from Methocel but not that releasing from Carbopol. These results are attributed to the intrinsic polymer properties, the barrier effect of CO(2) bubbles, and the matrix volume expansion produced after addition of SB.
Gutiérrez-Sánchez
Pablo Emilio
PE
Department of Pharmacy of the National School of Biological Sciences, National Polytechnic Institute of Mexico, Distrito Federal, México.
Hernández-León
Alejandra
A
Villafuerte-Robles
Leopoldo
L
D000179:Acrylates / Q000737:chemistry*; D003692:Delayed-Action Preparations; D004305:Dose-Response Relationship, Drug; D065347:Hypromellose Derivatives; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D008795:Metronidazole / Q000008:administration & dosage / Q000737:chemistry*; D017693:Sodium Bicarbonate / Q000737:chemistry*; D012995:Solubility; D013607:Tablets
D000179:Acrylates; D003692:Delayed-Action Preparations; D013607:Tablets; C492577:carbopol 971P; D008795:Metronidazole; D065347:Hypromellose Derivatives; D017693:Sodium Bicarbonate; D008747:Methylcellulose