WBCIL Secures Patent for Revolutionary Solvent-Free Ferric Citrate Process

West Bengal Chemical Industries Limited (WBCIL) had achieved a significant breakthrough in India’s patent history. The Indian Patent Office had officially granted Patent No. 356552 to the company. This patent protects a solvent-free iron citrate process for manufacturing pharmaceutical-grade API. This innovation changes how we approach renal drug manufacturing. It offers a cleaner, safer, and more cost-effective solution for the industry.

The patent is titled “Solvent Free, Cost-Effective Process for Preparation of Ferric Citrate. It addresses major challenges in the current supply chain. The invention focuses on high purity and specific physical properties. These properties are vital for treating Hyperphosphatemia effectively.

Key Takeaways:

WBCIL’s patented process (Patent No. 356552) sets a new industry standard by using water as the sole solvent, eliminating hazardous organic residues and embracing “Green Chemistry” for pharmaceutical-grade Ferric Citrate.

The innovation significantly enhances therapeutic efficacy for CKD patients by engineering a specific particle size (20–50 microns) and high surface area that maximizes phosphate-binding capacity in the gastrointestinal tract.

By utilizing cost-effective raw materials like iron powder and streamlined spray-drying technology, this process offers a scalable, sustainable, and high-purity solution that reduces production costs while meeting strict global regulatory standards.

The Clinical Need: Treating Hyperphosphatemia

To understand the value of this patent, we must look at the disease. Hyperphosphatemia is a condition defined by high serum phosphorus levels. It commonly affects patients with chronic kidney disease (CKD) on dialysis.

The body cannot filter excess phosphate naturally in these cases. Patients require medication known as phosphate binders. Ferric Citrate is a potent phosphate binder approved by the US FDA. It works in the gastrointestinal tract.

The mechanism is simple yet precise. Ferric iron (Fe+3) binds with dietary phosphate. This reaction forms an insoluble ferric phosphate complex. The body cannot absorb this complex. It is excreted safely in the stool. This reduces the patient’s serum phosphorus levels.
However, the efficacy depends on the quality of the drug. The particle size and surface area matter immensely. This is where WBCIL’s ferric citrate patent makes a difference.

The Problem with Old Methods

The patent document outlines the flaws in previous technologies. Producing Ferric Citrate was not always efficient or “green.”
Known methods often involve complex steps.

• US Patent 6903235: This method mixes solid Citric Acid with solid Ferric salt. It requires adding alcohol to the mixture. Alcohol handling adds safety risks and costs.
• US Patent 7767851: This process uses alkaline metal hydroxides and Ferric Chloride. It involves forming a precipitate and heating it. It also requires an organic solvent to precipitate the solid Ferric Citrate.
• WO2016162888: This method uses alkali metal carbonates and coagulating agents. Coagulating agents introduce impurities. These must be washed away, wasting water and time.

These older processes share common downsides. They use organic solvents. They require multiple purification steps. They use expensive iron salts as starting materials.

The WBCIL Solution: A Solvent Free Iron Citrate Process

WBCIL’s invention eliminates these issues altogether. The patent describes a process that uses water as the only solvent.

The method is defined by its simplicity and precision.
It involves a direct reaction between Iron Powder and Citric Acid Monohydrate. There are no coagulating agents17. No organic solvents are used for precipitation.

This is a true “Green Chemistry” approach. It reduces hazardous waste. It lowers the cost of production significantly. It makes the ferric citrate manufacturing process sustainable.

Step-by-Step: The Ferric Citrate API Manufacturing Process

The patent provides a detailed recipe for this breakthrough. Let us break down the technical steps revealed in the document.

1. Preparation of the Reactant Mix

The process starts with a reactor vessel. Water is the medium. Citric Acid Monohydrate is added to the water. The mix is stirred until the acid dissolves completely.

Then, Iron Powder is added gradually. The molar ratio is critical here. The ratio of Citric Acid to Iron Powder is between 0.8 and 1.5. This ensures there is enough acid to react with the metal.

2. Controlling the Reaction Environment

Chemistry requires strict control of the environment. The patent specifies exact parameters.

Temperature: The reaction mass is kept between 30°C and 35°C.
Pressure: The vessel operates at atmospheric pressure.
pH Level: The acidity is strictly controlled. The pH must remain between 4 and 4.5.
Maintaining the pH is vital. It ensures the correct ionic form of the citrate is produced.

3. The Oxidation Process

Iron powder is elemental iron Fe. To become Ferric Citrate, it must oxidize to the Fe3+ state.
The process achieves this by purging air into the reactor. Air is bubbled through the liquid mixture. This is done at a pressure of 0.25 to 0.5 kg/m²28.
This step continues until a specific endpoint is reached. The Ferric content must reach 21% to 22%. Simultaneously, the Ferrous content Fe2+ must be less than 1%. This ensures high purity. It limits the presence of unreacted or partially reacted iron.

4. Isolation via Spray Drying

Once the reaction is complete, the product must be dried. The patent uses spray drying to isolate the solid drug.
First, the solution is filtered to remove any unreacted particles32. The patent mentions using a Sparkler Filter. The clear filtrate then goes to the dryer.
Inlet Temperature: The dryer air enters at 275°C.
Outlet Temperature: The air exits at 105°C.

This rapid drying creates a fine powder. It sets the particle size and surface area.

Technical Specifications: Pharmaceutical-Grade Ferric Citrate

The result of this process is a high-grade API. The patent lists specific quality standards.

Chemical Purity:

The product typically achieves a purity of 98.21%. This is exceptionally high for an industrial process.

Elemental Composition:

Ferric Iron: 21% to 22%.
Ferrous Iron: Less than 1%.

Physical Properties:

The patent claims a specific BET surface area. The area ranges from 12 to 16.5 m²/gm
The particle size is controlled between 20 and 50 microns.
These numbers are not random. They are engineered for performance.

The Science of Surface Area and Binding

The patent document provides fascinating data on surface area. The “BET Active Surface Area” indicates how well the drug binds to its target.
Ferric Citrate works by contact. The iron must “touch” the phosphate to bind it. A larger surface area means more contact points. This leads to higher phosphate binding capacity. Check out our patent pdf file to know more about it.

The patent shows the link between size and area.

A 261-micron particle has a surface area of only 0.39 m²/gm.
A 45-micron particle has a surface area of 15.77 m²/gm.
A 22-micron particle has a surface area of 16.12 m²/gm.

As the particle gets smaller, the active area explodes. This is why the patent targets the 20-50 micron range.

The patent correlates this area to binding power.

At 15.77 m²/gm, the drug binds 19.16 mg of Phosphate per gram of ferric citrate.
At 16.12 m²/gm, binding jumps to 19.84 mg of Phosphate per gram of ferric citrate.

The prior art failed to achieve this specific balance consistently. WBCIL’s process maximises this binding efficiency. The target range of 19.1 to 19.8 mg P/gm is optimal.

Industrial Scalability and Cost

A major claim of this patent is “Cost Effectiveness”.
In pharma, lab success does not always mean factory success. However, this process is proven to be scalable.

Example 1 from the Patent:
The document details a large-scale batch.

Water: 2000 Litres.
Citric Acid: 375 kg.
Iron Powder: 130 kg.

This single batch yielded 500 kg of Ferric Citrate. This proves the method works at an industrial scale. It is not just a theoretical concept.

The cost savings come from two sources. First, Raw Materials. Iron powder is generally cheaper than specialised ferric salts.
Second, Process Time. Avoiding organic solvents skips expensive recovery steps. There is no need to distil and recycle alcohol.

Ferric Citrate Dosage Forms

The patent is not limited to the powder alone. It covers the use of this API in various forms. The high dissolution rate (2-4 mg/cm²-min) aids formulation.

Manufacturers can process this API into:
Tablets
Capsules
Granules
Powders

Why High Purity Ferric Citrate Matters?

Purity is a safety issue. Chronic kidney disease patients are vulnerable. Their kidneys cannot filter toxins well.
Low-quality iron salts can contain heavy metals. They can also contain unreacted reagents.
WBCIL’s process ensures a “Pharmaceutical Grade” product.
By keeping Ferrous content below 1%, they reduce side effects. Ferrous iron behaves differently from ferric iron. Consistency is key for long-term dosing.
Also, the absence of organic solvents is critical. Regulatory bodies such as the US FDA closely monitor residual solvents. A “solvent-free” process guarantees zero organic residue. This simplifies regulatory compliance for the buyer.

Regulatory Impact of Patent No. 356552

Intellectual property is a key asset. This patent grants WBCIL exclusive rights in India. The term lasts for 20 years from the filing date, August 8, 2017.

This protection allows WBCIL to license the technology. It also allows them to be a sole supplier of this specific grade.
Global pharma companies look for such clear IP situations. It assures them of a stable, legally protected supply chain.

Conclusion: A New Standard

The granting of this Ferric Citrate patent is a major win. It validates Indian innovation in chemical engineering.
WBCIL has proven that “simpler is better.” By removing solvents, they improved the product. By using basic raw materials, they lowered the cost.
This solvent free iron citrate process delivers on all fronts.

It is environmentally friendly.
It creates a potent phosphate binder.
It is safe for the patient.
It is profitable for the manufacturer.

For the pharmaceutical industry, this is the future. Sustainable, high-purity manufacturing is no longer optional. It is the new standard.