Carboxymethylcellulose Calcium
[CAS# 9050-04-8]

Identification

• Classification: Food additive >> Thickener
• Name: Carboxymethylcellulose Calcium
• Synonyms: Carboxymethyl cellulose
• Molecular Formula: C₂₃H₃₀ClN₃O
• Molecular Weight: 399.96
• CAS Registry Number: 9050-04-8
• EC Number: 618-566-8
• SMILES: Clc1cc2c(nc3c(c2NC(CCCN(CC)CC)C)cc(cc3)OC)cc1

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*
• Boiling point: 557.1±50.0 °C 760 mmHg (Calc.)^*
• Flash point: 290.7±30.1 °C (Calc.)^*
• Index of refraction: 1.623 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS08 Danger
• Risk Statements: H317-H334
• Safety Statements: P261-P272-P280-P285-P302+P352-P304+P341-P333+P313-P342+P311-P363-P501

Discovery and Applications

Carboxymethylcellulose calcium is the calcium salt form of carboxymethylcellulose (CMC), a water-soluble anionic polysaccharide derived from cellulose. In this compound, some of the carboxymethyl groups (–CH₂COO⁻) introduced onto the cellulose backbone during synthesis are present in the form of calcium carboxylates (–COO⁻Ca²⁺). It is generally supplied as an off-white to white powder that is odorless and tasteless, and it exhibits swelling properties in water but is not freely soluble, unlike its sodium counterpart.

Carboxymethylcellulose calcium was developed as part of efforts to create derivatives of CMC with modified solubility and ion exchange characteristics. While sodium carboxymethylcellulose (NaCMC) is highly water-soluble, the calcium salt form is only slightly soluble in water and instead swells to form a gel-like dispersion. This property makes it especially useful in controlled-release pharmaceutical formulations, where a slower rate of hydration and erosion is desired.

One of the primary applications of carboxymethylcellulose calcium is as a matrix-forming agent in oral controlled-release drug delivery systems. In tablet formulations, it functions as a hydrophilic matrix that swells upon contact with gastrointestinal fluids, forming a gel layer that controls the diffusion of the active pharmaceutical ingredient. The gel barrier maintains its integrity over time and provides extended or sustained drug release. Its low solubility compared to sodium CMC reduces the risk of dose dumping and enables better control over drug release kinetics.

In addition to its matrix-forming properties, carboxymethylcellulose calcium offers good tablet-binding characteristics and contributes to mechanical strength. It can be used alone or in combination with other polymers to fine-tune the release profile of drugs. It is compatible with a wide range of pharmaceutical excipients and active ingredients and is generally considered inert, non-toxic, and non-allergenic.

Carboxymethylcellulose calcium is included in pharmacopeias such as the European Pharmacopoeia and the Japanese Pharmacopoeia, where it is recognized for its use as a pharmaceutical excipient. Its physicochemical properties—such as degree of substitution, viscosity, and particle size—can be adjusted during manufacturing to suit specific formulation requirements.

The compound is typically produced by partial neutralization of sodium carboxymethylcellulose with a soluble calcium salt, such as calcium chloride. The resulting product contains calcium ions bound to carboxylate groups along the polymer chain. The material retains many of the desirable properties of the cellulose backbone, such as film-forming capability, biocompatibility, and biodegradability.

Outside of pharmaceutical uses, carboxymethylcellulose calcium may also be employed in specialized food, cosmetic, and biomedical applications where swelling and gel-forming properties are beneficial. In some oral care products, it contributes to the viscosity and texture of toothpaste or mouthwash formulations. However, its usage is more limited in non-pharmaceutical fields compared to sodium carboxymethylcellulose.

In summary, carboxymethylcellulose calcium is a calcium salt derivative of carboxymethylcellulose valued for its swelling behavior, gel formation, and utility in controlled-release pharmaceutical formulations. It is recognized for its safety, compatibility, and ability to provide sustained drug delivery through matrix formation, making it a useful component in modern drug formulation technologies.

References

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