A Review on Sustainable and Eco-Friendly Excipients Used in Drug Formulation

Pharmaceutical excipients are substances other than the active pharmaceutical ingredient (API) that are incorporated into dosage forms to facilitate manufacturing, maintain product stability, control drug release, and improve patient compliance (Rowe et al.; Ansel and Allen). From a formulation perspective, excipients influence critical quality attributes such as compressibility, disintegration time, viscosity, spreadability, and bioavailability (Ansel and Allen). Traditionally, excipient selection has been guided primarily by functional performance, cost, and availability, with comparatively little attention given to the origin or environmental impact of these materials (Mounika & Vudikala, 2025). However, increasing regulatory expectations, heightened environmental awareness, and the growing complexity of modern drug delivery systems have prompted formulators to reconsider conventional excipient selection strategies (Mounika & Vudikala, 2025). Sustainable and eco-friendly excipients – generally derived from renewable, biodegradable, or naturally occurring sources – have therefore gained importance as formulation components that can provide acceptable performance while offering improved safety and environmental compatibility (Beneke et al., 2009). Rather than replacing conventional excipients solely for ecological reasons, these materials are increasingly evaluated based on their functional equivalence, compatibility with APIs, and suitability for dosage-form design. Accordingly, this review examines sustainable excipients primarily as formulation tools that contribute directly to pharmaceutical performance and product quality.

Role     of Sustainability in Pharmaceutical Formulations

Sustainability in pharmaceutical formulation extends beyond environmental considerations and is increasingly integrated alongside performance, safety, and regulatory compliance (Mounika & Vudikala, 2025). Excipients obtained from renewable or natural sources often exhibit physicochemical properties – such as swelling behaviour, gel formation, viscosity enhancement, and muco-adhesion – that are directly relevant to dosage-form functionality (Reddy & Yang, 2015). From a formulation standpoint, the use of sustainable excipients can support improved biocompatibility, reduce the accumulation of persistent materials, simplify waste management during manufacturing, and align with regulatory expectations for excipient safety (Rowe et al.; Beneke et al., 2009). Consequently, sustainability should be regarded as a supportive formulation attribute that complements, rather than replaces, performance-based excipient selection (Ansel & Allen).

Characteristics of Ideal Sustainable Excipients

An ideal sustainable excipient should fulfil both formulation performance requirements and safety expectations (Rowe et al.). In addition to being derived from renewable or biodegradable sources, such excipients must demonstrate consistent functional behaviour within pharmaceutical formulations (Mounika & Vudikala, 2025). Key characteristics include proven non-toxicity and biocompatibility (Beneke et al., 2009), functional effectiveness at practical concentrations (Rowe et al.), chemical and physical stability during processing and storage (Ansel & Allen), compatibility with APIs and other excipients (Rowe et al.), control of variability associated with natural raw materials (Mounika & Vudikala, 2025), and cost-effectiveness with scalability for industrial application (Mounika & Vudikala, 2025). The major sources of natural excipients and the associated formulation challenges, including variability, stability, and scalability, are schematically represented in Figure 1.

Note: This figure is meant to be used as a graphical abstract.

Key elements included:

• Sources: Plants, animals, microbes, minerals
• Core focus: Sustainable & eco-friendly excipients
• Applications: Solid, liquid, semisolid, novel drug delivery systems
• Outcomes: Performance, stability, patient safety, regulatory acceptance

Figure 1. Natural Excipients & Challenges Diagram | Major sources of natural pharmaceutical excipients and associated formulation challenges.

Sustainable excipients may be classified based on their source and primary pharmaceutical function, which highlights their relevance in dosage-form design (Rowe et al.).

Plant-based excipients, such as starch, cellulose, pectin, and guar gum, are commonly used as binders, disintegrants, and gelling agents.

Animal-based excipients, including gelatin and chitosan, are employed as capsule materials and bioadhesive polymers.

Microbial-based excipients, such as xanthan gum and dextran, function primarily as stabilisers and viscosity modifiers.

Mineral-based excipients, including talc and calcium carbonate, are used as glidants and fillers.

Functional and Case-Based Discussion Of Major Excipients

5.1 Starch

Starch is a naturally occurring polysaccharide composed of amylose and amylopectin and is widely used due to its multifunctional properties (Rowe et al.). It serves as a binder during granulation and as a disintegrant upon hydration (Ansel and Allen). Modified starches are frequently employed to improve flow and compressibility, making them suitable for modern tablet manufacturing processes.

5.2 Cellulose and Cellulose Derivatives

Cellulose and its derivatives represent some of the most extensively used natural polymers in pharmaceutical formulations (Rowe et al.). Microcrystalline cellulose (MCC) is commonly used as a diluent and dry binder because of its excellent compressibility, while cellulose derivatives such as hydroxypropyl methylcellulose (HPMC) and carboxymethyl cellulose (CMC) function as film-formers and matrix-forming agents in controlled-release systems (Reddy & Yang, 2015; A George, 2023).

5.3 Guar Gum

Guar gum is a galactomannan polysaccharide known for its high viscosity and swelling capacity (Reddy & Yang, 2015; Beneke et al., 2009). In sustained-release formulations, guar gum forms a gel barrier that controls drug diffusion and prolongs drug release.

5.4 Chitosan

Chitosan is a biodegradable polymer derived from chitin and exhibits mucoadhesive, permeation-enhancing, and antimicrobial properties (Reddy & Yang, 2015; Jain et al., 2024). These characteristics make it particularly suitable for mucoadhesive and targeted drug delivery systems.

5.5 Pectin

Pectin is obtained from citrus peels and apples and is widely used as a gelling agent (Rowe et al.; Beneke et al., 2009). Due to its susceptibility to enzymatic degradation by colonic microflora, pectin has gained importance in colon-targeted drug delivery systems (Reddy & Yang, 2015).

Applications in Pharmaceutical Dosage Forms

Sustainable excipients are utilized across a wide range of dosage forms depending on their functional performance (Ansel and Allen). These include solid dosage forms such as tablets and capsules, liquid dosage forms such as suspensions and emulsions, semisolid dosage forms including gels and ointments, and novel drug delivery systems designed for controlled or targeted drug release. The application-based roles of commonly used sustainable excipients across different dosage forms are summarised in Table 1.

Table 1. Application-Based Role of Major Sustainable Excipients

Advantages from A Formulation Perspective

From a formulation perspective, sustainable and eco-friendly excipients offer several advantages beyond basic functionality. Their inherent biocompatibility reduces the likelihood of adverse reactions, particularly during long-term therapy, thereby enhancing patient safety (Mounika & Vudikala, 2025). Owing to their natural origin, these excipients generally exhibit lower toxicity and immunogenicity, making them suitable for sensitive patient populations such as paediatric and geriatric groups (Nammas, 2024). Sustainable excipients also demonstrate considerable functional versatility. Plant-derived polysaccharides such as pectin, guar gum, and xanthan gum can act as binders, disintegrants, stabilisers, or release-modifying agents depending on formulation requirements (A George, 2023). Biodegradable polymers such as chitosan and poly (lactic-co-glycolic acid) (PLGA) enable sustained and targeted drug delivery while maintaining compatibility with sensitive APIs (Jain et al., 2024). Regulatory acceptance represents another significant advantage, provided that quality, purity, and consistency are adequately demonstrated. Many naturally derived excipients are classified as Generally Recognised as Safe (GRAS) and are included in major pharmacopeias such as the USP, EP, and IP, thereby facilitating regulatory submissions and product development (Rowe et al.). In addition, sustainable excipients may improve processing characteristics, such as tablet hardness and compressibility, while reducing reliance on synthetic additives and potentially lowering formulation complexity and manufacturing costs (Singh and Sharma, 2021). A comparative overview of sustainable and conventional synthetic excipients with respect to formulation performance, regulatory familiarity, and scalability is presented in Table 2.

Table 2. Comparison of Sustainable and Conventional Excipients from a Formulation Perspective