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Rglax Pharma

Comparison

Aqueous vs non-aqueous tablet coating

Water or solvent. The choice sets your process time, your plant requirements and what cores you can coat.

Written by Rglax Pharma, who manufacture coating material · Reviewed 25 August 2026

This is the first decision on a coating project and the hardest to reverse, because it decides what plant you need rather than what film you get. Both routes reach the same finish. They do not carry the same cost, the same cycle time or the same regulatory burden, and one of them will not touch a moisture sensitive core at all.

CriterionAqueousNon-aqueous (solvent)
VehiclePurified waterIPA, acetone, dichloromethane or a blend
Plant neededStandard coating suiteedgeFlameproof area and solvent recovery
Residual solvent testingNot requirededgeRequired against ICH Q3C limits
Process timeLonger, water carries less solids per passShorter, faster build-upedge
Typical solids12 to 20% w/w5 to 12% w/w
Moisture sensitive coresOften unsuitableThe reason the route existsedge
Effervescent coresNot possibleStandard routeedge
Metallic and pearl finishesLimitedWhere these finishes liveedge
Bed temperature35 to 40 °CCooler, solvent takes less heat to drive off
Humidity sensitivityHigh, a monsoon problemLowedge
Operator exposureNone beyond dustedgeSolvent handling controls required
Environmental costLowedgeRecovery and emissions to manage
Grades we hold615

Our verdict

If the core tolerates water, coat aqueous. It removes a whole category of plant, testing and operator exposure, and it is where regulators and new lines have been heading for two decades. Go solvent when the core forces you to, not to save cycle time.

Choose Aqueous when

Your core is stable to water, you are specifying a new line, or you would rather not hold a flameproof area and a recovery system.

Choose Non-aqueous (solvent) when

The core is hygroscopic or effervescent, the active hydrolyses, you need a metallic or pearl finish, or the dossier already names a solvent process you cannot reopen.

How to decide

Work it out from your own product.

Start from the core, not from the coating. Run a short water challenge on the active and the compressed core, hold it at your worst expected condition, and look at assay, related substances and hardness. If nothing moves, you are an aqueous project and the rest of the decision is cost and cycle time. If something does move, no amount of process tuning will make a water based film safe and you are a solvent project regardless of what it costs to run. The mistake we see most is a team that decides on cycle time first and then spends six months trying to stabilise a core that was never going to hold.

Where this goes wrong

  1. 01Choosing solvent for speed aloneYou take on a flameproof area, a recovery system, ICH Q3C residual solvent testing and operator exposure controls to save perhaps forty minutes a batch. That trade almost never pays back.
  2. 02Choosing aqueous without a water challengeThe core looks fine leaving the pan and fails at the six month stability pull, by which point the filing is written and the shade is approved.
  3. 03Scaling an aqueous process without checking ambient humidityA process validated in February at 30% RH has far less drying capacity in July at 80%. The formulation did not change; the air did.
  4. 04Assuming a solvent grade can simply be dispersed in waterThe polymer, plasticiser and pigment system are selected for the vehicle. Swapping the vehicle is a reformulation, not a substitution.

Questions about Aqueous and Non-aqueous (solvent)

Often yes, but they are two different grades and two different process windows, not one grade run two ways. Our methacrylic enteric base is the one polymer family we hold that genuinely serves both routes, which is why it carries most of the enteric range.

Usually, because water carries less solids per pass and takes more energy to drive off. How much longer depends on your drying capacity rather than on the film. Where the air handling is generous the gap narrows considerably.

Neither is preferred as such, but aqueous removes the residual solvent question entirely, and a dossier without an ICH Q3C section is a shorter dossier. New lines have been specified aqueous by default for two decades for that reason.

Solvent, without exception. An effervescent core reacts with the water in an aqueous dispersion as it lands, and there is no process window that avoids it.

Grades either way

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