We have enteric-coated tablets with a dissolution requirement of 30 minutes. After coating, the tablets disintegrated at 33 minutes and failed dissolution. Further investigation showed that reducing the enteric coating weight gain improved dissolution.
Would it be feasible to rework the coated tablets by briefly rinsing them with ethanol, drying, weighing, and repeating the process until the desired coating weight gain is achieved?
The tablets would not be re-compressed; the goal is only to partially remove the Eudragit L100 coating.
Has anyone had experience with this approach or any references/technical guidance on such a rework process?
Step-by-Step Reworking Strategies should be followed as given below,
- Film Stripping & Washing (For Intact Non-Acid-Sensitive Cores)
If the enteric polymer layer is heavily blistered, peeling, or uneven, the existing coat must be stripped down to the core tablet. [1,
Solvent Stripping: If the core contains an API that can tolerate brief liquid exposure, wash the tablets with an appropriate solvent (often a water-alcohol mixture) inside the coating pan to dissolve the failing enteric layer.
Controlled Drying: Immediately apply high-efficiency drying air to prevent the moisture or solvent from penetrating and softening the tablet cores.
Core Inspection: Test a sample of the stripped cores for hardness, friability, and active content. If they pass, re-coat the batch normally.
- Crushing and Re-granulation (For Severe, Unsalvageable Defects)
When structural defects like severe twinning, sticking, or deep core erosion make re-coating impossible, you must salvage the raw material.
Milling: Crush the defective tablets into a coarse powder or granular form.
Polymer Separation (Optional): Use air-classification or sifting systems to separate and blow away the lightweight, flaky enteric film fragments from the heavier core granulate.
Assay & Compensation: Test the recovered powder to determine the exact active ingredient concentration per gram, as the remaining enteric polymer will dilute the mixture. Add fresh uncoated granules or excipients to compensate and hit the exact target specification.
Re-compression & Re-coating: Re-compress the blend into fresh core tablets, test them, and submit them to a brand-new coating cycle.
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How exactly do you wash the tablets? Are there any tips or tricks to ensure that the tablets are uniformly washed after the process?
Please follow the following procedure for washing and drying tablets,
- Prepare a mixture of purified water (20%) and Alcohol (Ethanol) or a suitable solvent (80%) in which the enteric coating material is soluble. You can change the % composition of the mixture as per the solubility of the enteric coating material.
- Transfer the tablets in a suitable-size coating pan and start rotations.
- Transfer the solvent mixture into the coating pan till the tablets are completely embeded in the solvents.
- Start coating pan rotations. Rotate the pan at slow speed so that tablets are not damaged and broken.
- Rotate the pan untill outer enteric coating is completely removed from the surface of tablets. Check this by stopping the pan intermitantly, removing a few tablets and observe visually for absence of coating material.
- Stop the rotations of pan when tablets are free of enteric coated material. Rmove the tablets from pan on a wire mesh / perforated (coarse) sieve and allow the solvent to drain off.
- Rinse the tablets with fresh mixture of solvents to get rid of the coating material completely.
- Now dry the tablets with a hot air current until they become dry.
- Draw a sample of tablets and check for % loss on drying (LOD). The LOD should be within the limit of core tablets. Check for other physical parameters of core tablets, such as dimensions (diameter, thickness) and friability, hardness, etc. Also, check for dissolution test and Residual solvents test by Gas Chromatography. It should meet the in-process QC specification.
- If the washed and dried core tablets meet the specification, then take the tablets for the routine enteric coating process.
- Document the entire re-working process in the Batch Manufacturing Record (BMR).