Shellac for Pharmaceutical Tablet Coating — Enteric & Moisture-Barrier Films

Why formulators use shellac

In a tablet plant, shellac is a film-forming resin, not a confectionery shine. Dewaxed grades are dissolved in ethanol or made into an aqueous ammoniated solution and sprayed as a thin film that keeps moisture out, masks taste or delays release. Shellac is insoluble in gastric acid and dissolves as pH rises in the intestine, which is why it is used in selected delayed-release systems.

Shellac is not a universal replacement for synthetic enteric polymers such as methacrylic copolymers — release behaviour must be validated for each product. Wood-finishing flakes do not belong in a pharmaceutical file.

Pharmacopoeia grades

Pharma buyers specify shellac against a named monograph — USP-NF, Ph. Eur. or JP — not a generic "pharma grade". USP-NF recognises four types, most easily told apart by wax and loss-on-drying limits:

Acid value and other limits differ by type — always check the current monograph. For coating work, the dewaxed (refined) types are the usual choice because they give clearer, more consistent films. In the US, check the FDA Inactive Ingredient Database for the route and dosage form; in the EU, food-additive E 904 status does not by itself satisfy a pharmaceutical quality agreement.

How coating plants apply it

• Alcoholic solutions — dry dewaxed flake cut in pharmaceutical-grade ethanol; the traditional seal-coat and glaze system.
• Aqueous ammoniated solutions — water-based systems that avoid organic solvents, used for barrier and delayed-release films.

The solution is sprayed in a perforated pan or fluid-bed coater. Plasticisers and solids content are set by the formulator. Two raw-material problems show up on the line: residual wax gives haze and weak adhesion, and heat-aged bags dissolve poorly. Trial a 100–500 g sample from the same process family as the bulk lot, and ask for solubility data on the lot you are evaluating.

Stability and ageing

Shellac is a natural polymer that slowly continues to polymerise, especially in heat. Aged or heat-exposed material can dissolve more slowly and change film performance — which matters for enteric release. Store it cool and dry, use lots first-in first-out, and include stability data in the validation plan. See why shellac blocks in storage.

The pharma quality file

There is no single worldwide "pharmaceutical shellac licence". Buyers file an in-house specification aligned to USP-NF and/or Ph. Eur. limits, backed by batch data and a quality agreement. Food-additive E 904 status is not a substitute for a pharmaceutical specification.

• Batch COA against the named monograph, stating which USP-NF type (or Ph. Eur. grade) the lot is, with method references
• Microbiological results and residual-solvent data (ICH Q3C) where applicable
• TSE/BSE statement — insect origin, still commonly requested
• Safety data sheet, certificate of origin and lot traceability from seedlac to finished bag
• Change-notification commitment covering crop, bleaching route and site
• Kosher or Halal certificates where the product requires them

Checklist: choosing dewaxed shellac for tablet coating

1. Name the monograph and type: for example USP-NF refined bleached, or Ph. Eur. dewaxed bleached shellac.
2. Choose colour by the coat's job: refined bleached for a near-colourless seal or polish, refined orange where colour does not matter.
3. Pick the solvent system: alcoholic solution, or aqueous ammoniated for solvent-free lines.
4. Ask for lot data: acid value, wax, loss on drying, heavy metals and insolubles on the batch COA, plus microbiology and residual solvents where your file needs them.
5. Trial a sample from the same lot family and check solubility and film clarity before the first commercial batch.
6. Plan storage: cool, dry, first-in first-out, with stability data in the validation plan.

Purchase order language

How we supply pharmaceutical buyers

Our lac comes from the Jharkhand lac belt. Dewaxed and bleached coating grades are produced by specialist solvent processors in the Purulia–Kolkata belt and released under our documentation with a batch COA from a NABL-accredited laboratory. We supply dewaxed shellac for pharmaceutical and nutraceutical coating from a 25 kg MOQ, FOB Kolkata, CFR or CIF. For tablet binding and controlled-release matrices we also supply pharma-grade guar gum to the USP or BP monograph, and aleuritic acid as an intermediate for medicinal-chemistry and custom-synthesis work.

Pharmaceutical supply depends on the monograph and documents your quality agreement requires — tell us the pharmacopoeia, type, solvent system and volume when you request a quote, and we will confirm what can be supplied and documented before we price it. Samples of 100–500 g are available before the first order.

Quick answers

Which USP-NF shellac type is used for tablet coating? Usually a dewaxed (refined) type — refined bleached or refined orange — because the low wax content gives clearer, more consistent films. The formulator chooses based on colour and release requirements.

How does shellac work as an enteric coating? Shellac is insoluble in stomach acid and dissolves as pH rises in the intestine, so the film protects the active until it passes the stomach. Release behaviour must be validated for each product — shellac is not a universal replacement for synthetic enteric polymers.

Does E904 food status cover pharmaceutical use? No. Pharmaceutical buyers specify shellac against USP-NF, Ph. Eur. or JP. A lot can be dual-released to both food and pharmacopoeia specifications if it is tested against both.

This guide summarises publicly available regulations and industry practice as of September 2026. Verify the current rules for your market and your own quality agreement before ordering. It is not legal advice.