Alginates as Pharmaceutical Excipients

Alginate excipients are versatile biopolymers derived from various natural sources, primarily seaweed, and have gained significant prominence in the pharmaceutical industry due to their diverse applications. The pharmaceutical industry relies on alginates for their exceptional properties, which include gelling ability, controlled drug release, and biocompatibility. As pharmaceutical excipients, alginates play a pivotal role in various drug formulations, including tablets, capsules, gels, and wound dressings. This article provides an overview of alginates used in the pharmaceutical sector, covering their sources, manufacturing process, and their use. Additionally, it will list the relevant monographs from the United States Pharmacopeia-National Formulary (USP-NF) and the European Pharmacopoeia (EP) for alginates, along with the Chemical Abstracts Service (CAS) number for identification.

Manufacturing of Alginates

The manufacturing process, characterized by meticulous harvesting, washing, chemical treatment, and purification, ensures that pharmaceutical-grade alginates meet stringent quality and safety standards, making them a trusted component in the development of pharmaceutical products.
Alginates are extracted from various species of brown seaweed, such as Laminaria hyperborea and Ascophyllum nodosum. These seaweeds are rich in alginate content, making them the primary sources for pharmaceutical-grade alginates. The extraction process involves harvesting the seaweed, washing, and chopping it into small pieces. The alginate-rich seaweed is then treated with alkali, usually sodium hydroxide, to break down the seaweed’s cell walls and release the alginates. Following this, the alginates are precipitated, purified, and dried to create the final pharmaceutical-grade product.

Function of Alginates as Excipients

Alginate excipients perform several important functions in the tableting process, including:

  • Oral Drug Delivery: Alginates are used to encapsulate pharmaceutical compounds for oral delivery, offering controlled release and improved bioavailability.
  • Wound Dressings: Alginate-based wound dressings promote wound healing by maintaining a moist environment, absorbing excess exudate, and protecting against infections.
  • Dental Impressions: Alginate-based dental impression materials are widely used for making molds of patients’ teeth and oral tissues.
  • Gastrointestinal Drug Delivery: Alginates are used in the development of gastroretentive drug delivery systems, ensuring prolonged drug release in the stomach.
  • Controlled Release Systems: Alginate microspheres and beads are employed in controlled drug release systems, allowing for sustained drug delivery.
  • Anti-Reflux Suspension: Alginate-based anti-reflux preparations form a protective lay in the stomach respectively a mechanical barrier preventing reflux into the esophagus.



Factors to consider when selecting Alginate Excipients

When selecting a alginate excipient, several factors should be considered, including:

  • Type of Alginate: Different types of alginates are available, including sodium alginate, calcium alginate, and potassium alginate, each with distinct properties. The selection should be based on the compatibility with the formulation and the intended application. For example, sodium alginate is commonly used in controlled-release formulations, while calcium alginate is employed for its gelling and wound-healing properties.
  • Viscosity and Gel Strength: The viscosity and gel strength of alginates can vary significantly. Consider the desired consistency of the formulation, as higher viscosity and gel strength may be required for some applications, such as gels or controlled-release tablets.
  • Particle Size: The particle size of alginate powders can affect the flowability and compressibility of the excipient in tablet formulations. The choice of particle size should align with the manufacturing process and the intended dosage form.
  • Purity and Quality: The quality of the alginate is paramount. Look for high-purity alginates that meet relevant pharmacopeial standards to ensure the safety and efficacy of the final pharmaceutical product.
  • Source and Origin: The source of the seaweed used to extract alginates can impact the properties of the excipient. Different species of brown seaweeds and the location of cultivation can lead to variations in alginate properties.
  • Biocompatibility: Consider the biocompatibility of the selected alginate with the human body, especially for applications like wound dressings or oral pharmaceuticals.
  • Drug Compatibility: Ensure that the alginate excipient is compatible with the active pharmaceutical ingredient (API). Compatibility issues can affect drug stability and release, so it’s essential to perform compatibility studies.
  • Regulatory Compliance: Check that the chosen alginate complies with relevant regulatory standards and pharmacopeial monographs, such as the United States Pharmacopeia (USP) or the European Pharmacopoeia (EP), to ensure safety and quality.
  • Solubility and Swelling Characteristics: Consider the solubility and swelling characteristics of the alginate in the intended medium, as these properties can impact drug release and formulation performance.
  • pH Sensitivity: Some alginates are pH-sensitive and may form gels or change properties in response to pH variations. This can be advantageous in specific formulations but should be considered carefully.
  • Manufacturability: Evaluate how easily the chosen alginate can be incorporated into the manufacturing process. Factors such as powder flow, blending properties, and compressibility are crucial for solid dosage forms.
  • Cost and Availability: Cost considerations and the availability of the selected alginate excipient may impact the overall formulation’s feasibility.
  • Intended Application: The specific application of the pharmaceutical formulation, whether it’s a tablet, capsule, gel, wound dressing, or another dosage form, will significantly influence the choice of alginate and its associated properties.

By carefully evaluating these factors, pharmaceutical formulators can select the most appropriate alginate excipient for their specific formulation, ensuring that it meets both quality and performance requirements. Additionally, conducting compatibility studies with the API and thorough testing can help verify that the chosen alginate excipient performs as intended in the final product.

Alginates pharmaceutical excipients
Alginates pharmaceutical excipients

Definitions according to the European Pharmacopeia and USP/NF

The United States Pharmacopeia-National Formulary (USP-NF) and the European Pharmacopoeia (EP) have established standards for alginates to ensure their quality and safety in pharmaceutical applications.

USP-NF Monograph for Sodium Alginate:

  • CAS Number: 9005-38-3
  • Description: A white to yellowish-white, almost odorless powder.
  • Identification: Complies with the tests for sodium.
  • Assay: Contains not less than 90.0% and not more than 106.0% of C6H7NaO6, calculated on the dried basis.

EP Monograph for Sodium Alginate:

  • CAS Number: 9005-38-3
  • Description: A white to pale yellowish-brown or pale greyish-brown, fibrous, unbranched, cylindrical, filiform or ribbon-like, tough, elastic, brittle, readily breaking in fragments.
  • Identification: Complies with the test for sodium.
  • Content: Contains not less than 90.0% and not more than 106.0% of C6H7NaO6, calculated with reference to the dried substance.

Alginate Excipients

Common alginate excipients used in the pharmaceutical industry include:

  • Alginic Acid: Alginic acid is a natural polysaccharide derived from brown seaweed, primarily composed of linear chains of alternating guluronic and mannuronic acid residues. It is used as a swelling agent with high water binding capacity and is mainly applied for tablet disintegration. Also, it is the precursor to various alginates, which are salts and derivatives of alginic acid and are used as binders, disintegrants, thickeners, gelling agents, and film formers in various formulations.
  • Sodium Alginate: Sodium alginate is perhaps the most widely used alginate in the pharmaceutical industry. It is used in various applications, including controlled-release tablets, wound dressings, and gastroretentive formulations.
  • Calcium Alginate: Calcium alginate is often employed for its gelling properties. It is used in wound care products, such as alginate dressings, due to its ability to form a gel when it comes into contact with wound exudate.
  • Potassium Alginate: Potassium alginate is used in some pharmaceutical applications, particularly in dental impression materials, where it helps create accurate molds of the oral cavity.
  • Ammonium Alginate: Ammonium alginate is another variant that finds occasional use in pharmaceutical applications, especially in dental and oral care products.
  • Micro- and Nano-sized Alginate Particles: Alginate particles can be used to encapsulate drugs, allowing for controlled release and targeted delivery.

Alginate Excipients on – in alphabetical order

PROTANAL PH 6160(Kelcosol NF)IFF
VIVAPHARM® Alginates – Alginic AcidJRS Pharma
VIVAPHARM® Alginates – Calcium AlginateJRS Pharma
VIVAPHARM® Alginates – Sodium AlginateJRS Pharma


In conclusion, alginates play a vital role in the pharmaceutical industry due to their diverse applications, including controlled drug release, wound healing, gastrointestinal therapies, dental impressions, and topical formulations. The standardized monographs in USP-NF and EP ensure the quality and safety of pharmaceutical alginates, making them a valuable ingredient in various pharmaceutical products.