Do you think that the inclusion of water in the preparation of a suspension for enteric coating containing Eudragit L100 and PEG for the core tablets containing aspirin could be the cause for the degradation of aspirin into salicylic acid and acetic acid on long storage (as manifested by s.a. crystals on the tablet surface, with acetic acid odour and damage to the coat material while the tablets are still inside the blister sheet)? The aforementioned tablets failed the Q.C. tests.
If the coating suspension is changed into a solution in organic solvent (no water is used), can we get a better coating with no problems of aspirin degradation or damage to the coat? Do you suggest other causes for the aspirin degradation?
you can try isopropyl alcohol and ethanol for preparing coating solution
probably the coating is applied to fast. Or PEG retains water in the coating and standard drying conditions aren't enough. If crystal nucleations are wisible on the surface there is way to much water. It is difficult to explain it only with usage of water based dispersion.
Organic coating can be helpful, but residual solvent analysis have to be done afterwards.
Hello,
Compression of aspirin (crystalline) by tablet machine converts crystalline aspirin into amorphous form which is thermodynamically less stable than crystalline counterpart. So, further manufacturing processes should be controlled like good storage conditions in a well controlled humid conditions before enteric coating. Also, if you use NaoH as aid for crosslinking of Eudragit, the stochiometric ratio must be determined carefully to avoid hydrolysis of aspirin by residual NaOH. Incorporation of film coating layer as a barrier can be helpful to stability enhancement. Not to use PVP as a binder in the direct compression process or as plasticizer in the barrier film coating. This is due to the very hygroscopic nature of PVP that can acclerate the rate of reaction. Also, PEG has hygroscopic nature particularly with low molecular weights. So, incorporation in the coat can carry stability problems.
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