Department of Pharmaceutics, Shivnagar vidya prasarak mandal’s college of pharmacy, Malegaon, Baramati
Cardiovascular diseases (CVDs) remain the leading cause of global mortality, with effective pharmacotherapy often limited by poor aqueous solubility and low oral bioavailability of many drugs, particularly those belonging to BCS Class II and IV. Conventional oral formulations frequently exhibit inconsistent therapeutic outcomes due to dissolution-limited absorption, extensive first-pass metabolism, and variability in gastrointestinal conditions. In this context, lipid-based drug delivery systems, particularly self-emulsifying drug delivery systems (SEDDS) and their solid counterparts (S-SEDDS) have emerged as promising strategies to enhance the solubilization and absorption of poorly water-soluble cardiovascular drugs. SEDDS are isotropic mixtures of oils, surfactants, and co-surfactants that spontaneously form fine oil-in-water emulsions upon contact with gastrointestinal fluids, thereby increasing surface area and improving drug dissolution and permeability.The transformation of liquid SEDDS into S-SEDDS further improves formulation stability, ease of handling, and patient compliance while retaining self-emulsifying properties. Several cardiovascular drugs including simvastatin, carvedilol, amlodipine, and atorvastatin have demonstrated enhanced bioavailability and improved pharmacokinetic performance when formulated using S-SEDDS. Recent advancements such as nano-SEDDS and supersaturable systems have further improved formulation efficiency by reducing droplet size and preventing drug precipitation. Despite these advantages, challenges such as limited drug loading capacity, potential excipient-related toxicity, and regulatory complexities remain to be addressed. Overall, S-SEDDS represent a versatile and promising platform for improving the oral delivery of cardiovascular drugs, with significant potential for future clinical translation.
Cardiovascular diseases (CVDs) continue to be the leading cause of mortality worldwide, accounting for a substantial proportion of global deaths and posing a major public health challenge [1,3]. The increasing prevalence of risk factors such as sedentary lifestyle, unhealthy dietary habits, obesity, diabetes, and aging populations has significantly contributed to the rising burden of cardiovascular disorders [2, 3]. Major cardiovascular conditions, including hypertension, coronary artery disease, myocardial infarction, and heart failure, require long-term pharmacological intervention to prevent disease progression and improve patient outcomes [2,4].
Figure 1. Rising global burden of cardiovascular diseases (CVDs) from 1990-2025 [1, 3, 4].
Despite the availability of a wide range of therapeutic agents, the effective management of cardiovascular diseases remains challenging due to limitations associated with conventional drug delivery systems [6, 7]. One of the most critical issues is the poor aqueous solubility of many cardiovascular drugs, particularly those classified under the Biopharmaceutics Classification System (BCS) Class II and IV [5, 8]. These drugs exhibit dissolution-limited absorption, which results in low and variable oral bioavailability [6, 8]. Since oral administration is the most preferred route due to its convenience and patient compliance, poor solubility presents a significant barrier to achieving optimal therapeutic efficacy [7]. The dissolution behavior of poorly water-soluble drugs is often the rate-limiting step in their absorption process [7, 8]. Inadequate dissolution in gastrointestinal fluids leads to incomplete drug release and erratic absorption patterns, which can result in inconsistent plasma drug concentrations [6, 8]. This variability may compromise therapeutic outcomes and increase the risk of treatment failure or adverse effects [10, 11]. Drugs such as statins, beta-blockers, and calcium channel blockers are particularly affected by these limitations due to their lipophilic nature [45–49]. Another major factor influencing drug bioavailability is extensive first-pass metabolism in the liver [9, 10]. After oral administration, many cardiovascular drugs undergo significant hepatic metabolism before reaching systemic circulation, resulting in reduced bioavailability [9]. For instance, drugs like propranolol and verapamil are subject to high first-pass metabolism, which necessitates higher dosing to achieve therapeutic plasma levels [10, 11]. This can increase the likelihood of dose-related side effects and toxicity [11]. In addition to hepatic metabolism, intestinal metabolism and efflux mechanisms further limit drug absorption [12].Efflux transporters such as P-glycoprotein (P-gp) actively transport drugs back into the intestinal lumen, reducing their intracellular concentration and overall absorption [12].
The combined effect of metabolic enzymes and efflux transporters creates a significant barrier to effective oral drug delivery [12]. These biological challenges highlight the need for advanced formulation strategies to enhance drug absorption and bioavailability [21, 22]. Gastrointestinal physiology also plays a crucial role in determining drug absorption [13]. Variations in pH along the gastrointestinal tract can significantly affect drug solubility and stability [14]. Weakly basic drugs tend to dissolve in the acidic environment of the stomach but may precipitate in the more neutral pH of the intestine, while weakly acidic drugs may exhibit limited solubility in gastric conditions [14, 15]. Such pH-dependent solubility issues contribute to unpredictable pharmacokinetic profiles and therapeutic outcomes [15, 16]. Furthermore, factors such as gastric emptying time, intestinal motility, and the presence of food can influence drug absorption [15, 16]. Food intake, particularly high-fat meals, can either enhance or inhibit drug absorption depending on the drug’s physicochemical properties [16, 17]. Lipophilic drugs may show improved absorption in the presence of dietary lipids due to enhanced solubilization, whereas food may also delay gastric emptying and alter drug release profiles [16, 17]. These variations introduce complexity in dosing regimens and contribute to inter- and intra-patient variability [17]. Patient-related factors, including poor adherence to medication regimens, further complicate cardiovascular therapy [18, 19]. Chronic cardiovascular conditions often require long-term or lifelong treatment, which can lead to reduced compliance due to complex dosing schedules, side effects, and lack of immediate symptomatic relief [19, 20]. Poor adherence can result in suboptimal therapeutic outcomes, increased risk of complications, and higher healthcare costs [18–20]. Therefore, improving drug delivery systems to enhance efficacy and reduce dosing frequency is essential for better patient compliance [20].
To overcome these challenges, lipid-based drug delivery systems have emerged as a promising approach for improving the solubility and bioavailability of poorly water-soluble drugs [21–23]. These systems utilize lipids and surfactants to enhance drug solubilization and facilitate absorption through the gastrointestinal tract [22, 23]. By incorporating drugs into lipid matrices, these formulations improve dissolution behavior and promote transport across biological membranes [23, 24]. Additionally, lipid-based systems can stimulate lymphatic transport, thereby bypassing hepatic first-pass metabolism and increasing systemic drug availability [24, 25]. Among lipid-based systems, self-emulsifying drug delivery systems (SEDDS) have gained considerable attention due to their ability to spontaneously form fine emulsions upon contact with gastrointestinal fluids [26–28].
Figure 2. SEDDS as a promising strategy for improving oral drug delivery and therapeutics of cardiovascular drugs [21, 28, 45].
SEDDS are isotropic mixtures of oils, surfactants, and co-surfactants that, under mild agitation, produce oil-in-water emulsions with small droplet sizes [27, 28]. The formation of such emulsions significantly increases the surface area available for drug absorption, leading to enhanced dissolution and bioavailability [28, 29]. The performance of SEDDS is largely attributed to their ability to maintain drugs in a solubilized state during gastrointestinal transit [29, 30]. This prevents drug precipitation and ensures consistent absorption [30]. Furthermore, surfactants in the formulation may enhance intestinal permeability by interacting with biological membranes and modulating transport pathways [23, 30]. The presence of lipids also facilitates the formation of mixed micelles and chylomicrons, which play a key role in lymphatic drug transport [24, 25].
Despite their advantages, conventional liquid SEDDS formulations are associated with several limitations, including physical instability, leakage, and handling difficulties [31, 32]. Liquid formulations may undergo phase separation or drug precipitation during storage, which can affect their performance and shelf life [31]. Additionally, the incorporation of liquid formulations into solid dosage forms such as tablets and capsules presents significant challenges [32]. To address these limitations, solid self-emulsifying drug delivery systems (S-SEDDS) have been developed as an advanced alternative [31–33]. These systems involve the conversion of liquid SEDDS into solid dosage forms using techniques such as adsorption, spray drying, and melt granulation [32, 33]. S-SEDDS retain the advantages of lipid-based formulations while offering improved stability, ease of handling, and better patient compliance [33–35]. Upon contact with gastrointestinal fluids, S-SEDDS rapidly disperse to form fine emulsions similar to their liquid counterparts [32, 33]. This ensures that the drug remains in a solubilized state, enhancing dissolution and absorption [33, 34]. The solid nature of these formulations also improves dose uniformity and reduces the risk of leakage and degradation [34, 35]. These characteristics make S-SEDDS highly suitable for large-scale manufacturing and clinical application [35].
Recent advancements in formulation technologies have further enhanced the potential of S-SEDDS [50–54]. The development of nano-SEDDS has enabled the formation of ultra-fine droplets, which improve drug absorption and bioavailability [51–53]. Supersaturable SEDDS have been introduced to maintain drug super saturation and prevent precipitation, thereby enhancing absorption [52]. Additionally, the use of artificial intelligence and machine learning in formulation design has facilitated the optimization of excipient selection and process parameters [55, 56]. Despite these advancements, several challenges remain in the development and clinical translation of S-SEDDS [57]. Issues such as limited drug loading capacity, potential toxicity of surfactants, and lack of standardized regulatory guidelines need to be addressed [35,57]. Furthermore, establishing reliable in vitro–in vivo correlations for lipid-based formulations remains a complex task due to the dynamic nature of gastrointestinal processes [7, 57].
Cardiovascular therapy faces numerous pharmacokinetic and pharmacodynamic challenges that significantly affect the efficacy of treatment despite the availability of potent therapeutic agents [6, 7]. One of the most prominent challenges is the poor aqueous solubility of many cardiovascular drugs, particularly those belonging to the Biopharmaceutics Classification System (BCS) Class II and IV [5, 8]. These drugs exhibit dissolution-limited absorption, which results in low and variable bioavailability following oral administration [6, 8]. As oral delivery remains the most preferred route due to its convenience and patient compliance, poor solubility represents a major barrier to effective therapy [7]. The dissolution rate of poorly water-soluble drugs is often the rate-limiting step in their absorption process [7, 8]. Inadequate dissolution in gastrointestinal fluids leads to incomplete drug release and erratic absorption patterns, resulting in fluctuations in plasma drug concentrations [6, 8]. Such variability can compromise therapeutic outcomes and increase the risk of adverse effects [10, 11]. Lipophilic cardiovascular drugs, including statins and calcium channel blockers, are particularly susceptible to these limitations due to their low intrinsic solubility [45–49].
Another critical challenge in cardiovascular therapy is extensive first-pass metabolism, which significantly reduces the fraction of drug reaching systemic circulation [9, 10]. After oral administration, many drugs undergo substantial hepatic metabolism, leading to reduced bioavailability [9]. For example, drugs such as propranolol and verapamil exhibit high first-pass metabolism, requiring higher doses to achieve therapeutic plasma concentrations [10, 11]. This dose escalation may increase the risk of toxicity and side effects, thereby limiting clinical effectiveness [11]. In addition to hepatic metabolism, intestinal metabolism and efflux transport mechanisms further restrict drug absorption [12]. Efflux transporters such as P-glycoprotein (P-gp) actively pump drugs back into the intestinal lumen, thereby reducing their intracellular concentration and absorption [12]. The interplay between metabolic enzymes and efflux transporters creates a significant barrier to effective oral drug delivery [12]. These biological obstacles necessitate the development of advanced delivery systems capable of overcoming such limitations [21, 22]. Gastrointestinal (GI) physiological variability is another important factor influencing cardiovascular drug therapy [13]. The pH of the gastrointestinal tract varies from highly acidic in the stomach to near neutral in the intestine, which can significantly affect drug solubility and stability [14]. Weakly basic drugs may dissolve readily in the stomach but precipitate upon entering the intestine, whereas weakly acidic drugs may exhibit limited solubility in gastric conditions [14, 15]. Such pH-dependent solubility issues contribute to unpredictable drug absorption and therapeutic response [15, 16].
Figure 3. Major challenges associated with cardiovascular therapy [6, 8, 64, 65].
Gastrointestinal motility and transit time also play a crucial role in drug absorption [15]. Variations in gastric emptying and intestinal transit can influence the residence time of drugs in different regions of the GI tract, thereby affecting dissolution and absorption [15, 16]. Delayed gastric emptying may prolong drug exposure to acidic conditions, potentially affecting stability, while rapid intestinal transit may limit the time available for absorption [15, 16]. These factors contribute to variability in drug bioavailability among patients [16]. Food intake further complicates cardiovascular drug therapy by influencing drug absorption [16, 17]. High-fat meals can enhance the solubility of lipophilic drugs, leading to increased absorption, while also delaying gastric emptying and altering drug release profiles [16, 17]. Conversely, food may reduce the absorption of certain drugs by interfering with dissolution or transport processes [17]. This variability makes it difficult to establish consistent dosing regimens and may affect therapeutic outcomes [17]. Inter-individual variability among patients is another major challenge in cardiovascular therapy [10, 11]. Factors such as age, gender, genetic polymorphisms, and disease state can significantly influence drug metabolism and response [10]. Genetic variations in drug-metabolizing enzymes, particularly cytochrome P450 isoforms, can result in differences in drug clearance and efficacy [10, 11]. Additionally, comorbid conditions such as hepatic or renal impairment can alter pharmacokinetics, requiring dose adjustments [11].
Polypharmacy is common in cardiovascular patients and increases the risk of drug-drug interactions [18, 19]. Patients with cardiovascular diseases often require multiple medications, including antihypertensives, anticoagulants, and lipid-lowering agents [19]. The concurrent use of multiple drugs can lead to interactions that affect drug absorption, metabolism, or excretion [18, 19]. These interactions may reduce therapeutic efficacy or increase the risk of adverse effects, complicating treatment regimens [19, 20]. Another important limitation is the delayed onset of action of many orally administered cardiovascular drugs [7, 8]. In acute conditions such as myocardial infarction or hypertensive emergencies, rapid drug action is essential [4]. However, conventional oral formulations may not provide immediate therapeutic effects due to slow dissolution and absorption [7, 8]. This limitation necessitates the use of alternative delivery systems or routes of administration [4]. Poor patient adherence is a significant barrier to effective cardiovascular therapy [18–20]. Chronic cardiovascular conditions require long-term treatment, often involving complex dosing regimens [19]. Factors such as side effects, cost, and lack of immediate symptomatic relief can reduce patient compliance [18, 19]. Non-adherence to prescribed therapy can lead to disease progression, increased hospitalization, and higher healthcare costs [20]. Variability in plasma drug concentration is another challenge that affects therapeutic outcomes [7, 8]. Fluctuations in drug levels may result in periods of sub therapeutic exposure or toxicity [10, 11]. Maintaining drug concentrations within the therapeutic window is particularly critical for cardiovascular drugs, as both under dosing and overdosing can have serious consequences [10]. Controlled and predictable drug delivery systems are therefore essential for improving treatment outcomes [7]. Stability issues associated with conventional formulations also limit their effectiveness [31, 32]. Many drugs are sensitive to environmental factors such as temperature, light, and humidity, which can lead to degradation and reduced efficacy [31]. Additionally, poor wettability and crystallization tendencies can further limit drug dissolution and absorption [32]. These formulation-related challenges highlight the need for more robust delivery systems [32]. The limitations of conventional dosage forms underscore the need for innovative drug delivery strategies [21–23]. Lipid-based systems, including self-emulsifying drug delivery systems (SEDDS), have been developed to address these challenges by enhancing solubility and absorption [21, 22]. These systems improve drug dissolution and promote lymphatic transport, thereby bypassing first-pass metabolism [23–25]. As a result, they offer a promising approach for improving the bioavailability of poorly soluble cardiovascular drugs [22, 23]. Among these advanced systems, solid self-emulsifying drug delivery systems (S-SEDDS) have emerged as a particularly effective solution [31–33]. By converting liquid SEDDS into solid dosage forms, S-SEDDS improve stability, handling, and patient compliance while retaining the benefits of lipid-based formulations [32, 33]. These systems provide enhanced dissolution, reduced variability, and improved therapeutic outcomes [33–35]. In summary, cardiovascular therapy is associated with multiple challenges, including poor solubility, first-pass metabolism, gastrointestinal variability, and patient-related factors [6–8]. These limitations significantly affect drug bioavailability and therapeutic efficacy [10, 11]. The development of advanced drug delivery systems such as S-SEDDS offers a promising strategy to overcome these challenges and improve clinical outcomes [21–23].
Self-emulsifying drug delivery systems (SEDDS) are lipid-based formulations designed to enhance the oral bioavailability of poorly water-soluble drugs by improving their solubilization and absorption [21–23]. These systems consist of isotropic mixtures of oils, surfactants, and co-surfactants that spontaneously form fine oil-in-water emulsions upon contact with aqueous gastrointestinal fluids under mild agitation [26–28]. The unique ability of SEDDS to maintain drugs in a solubilized state during gastrointestinal transit makes them particularly suitable for lipophilic drugs exhibiting dissolution-limited absorption [6, 8]. The development of SEDDS is primarily driven by the need to overcome the limitations associated with conventional oral dosage forms, particularly for drugs belonging to BCS Class II and IV [5, 8]. Poor aqueous solubility leads to incomplete dissolution and erratic absorption, which in turn results in low and variable bioavailability [6, 8]. By incorporating drugs into lipid-based matrices, SEDDS enhance drug dissolution and facilitate transport across biological membranes [21–23]. This approach not only improves absorption but also reduces variability caused by gastrointestinal conditions [23, 24].
The mechanism of self-emulsification in SEDDS is governed by physicochemical and thermodynamic principles [30]. Unlike conventional emulsions that require external energy input, SEDDS form emulsions spontaneously due to favorable free energy changes and low interfacial tension [30, 37]. The presence of surfactants and co-surfactants reduces the energy required for droplet formation, enabling rapid emulsification upon dilution [37]. For spontaneous emulsification to occur, the change in free energy must be minimal or negative, which is achieved by the use of appropriate surfactants that significantly reduce interfacial tension [30, 37]. Upon oral administration, SEDDS are exposed to gastrointestinal fluids and mild agitation caused by gastric motility [13, 15]. This leads to rapid dispersion of the formulation and formation of fine droplets [27, 28].
Surfactant molecules orient themselves at the oil–water interface, forming a stabilizing interfacial film that prevents droplet coalescence [37]. Co-surfactants further enhance interfacial flexibility, allowing the formation of smaller droplets with improved stability [37]. The formation of nano- or micro-sized droplets plays a crucial role in enhancing drug absorption [27–29]. Smaller droplets provide a larger surface area, which facilitates faster drug release and dissolution [28, 29]. The increased surface area also promotes closer contact with the intestinal epithelium, enhancing drug permeability and absorption [23, 24]. As a result, SEDDS significantly improve the oral bioavailability of poorly soluble drugs [21–23]. Another key aspect of the SEDDS mechanism is lipid digestion and its role in drug absorption [24, 25]. After emulsification, lipid components undergo enzymatic digestion by pancreatic lipases, resulting in the formation of monoglycerides and free fatty acids [24]. These digestion products interact with bile salts and phospholipids to form mixed micelles, which serve as carriers for drug molecules [24, 25]. Drugs incorporated within these micelles remain solubilized and are transported to the intestinal epithelium for absorption [24]. Lymphatic transport is an important pathway associated with SEDDS that contributes to enhanced bioavailability [24, 25]. Lipophilic drugs incorporated into chylomicrons can be transported via the lymphatic system, thereby bypassing hepatic first-pass metabolism [25]. This mechanism significantly increases systemic drug availability and reduces metabolic degradation [24, 25]. The efficiency of lymphatic transport depends on factors such as drug lipophilicity and lipid composition of the formulation [25].
In addition to improving solubility and absorption, SEDDS may also modulate intestinal permeability [23]. Surfactants present in the formulation can interact with biological membranes, altering their fluidity and enhancing drug transport across the intestinal barrier [23]. Some surfactants may also inhibit efflux transporters such as P-glycoprotein, thereby increasing intracellular drug concentration and absorption [12, 23]. These combined effects contribute to the superior performance of SEDDS compared to conventional formulations [21–23].
Figure 4. Formulation and solidification approaches of solid self-emulsifying drug delivery system [31, 32, 52, 57].
The performance of SEDDS is highly dependent on the selection and optimization of its components, including oils, surfactants, and co-surfactants [21–23]. Each component plays a specific role in determining the solubilization capacity, emulsification efficiency, and stability of formulation [30].
Solid self-emulsifying drug delivery systems (S-SEDDS) are advanced lipid-based formulations developed by transforming liquid SEDDS into solid dosage forms while retaining their self-emulsifying properties [31–33]. These systems combine the solubilization advantages of lipid formulations with the stability, manufacturability, and patient compliance of solid dosage forms [33–35]. The transition from liquid to solid systems addresses key limitations such as leakage, poor stability, and handling difficulties associated with conventional SEDDS [31, 32]. The formulation of S-SEDDS involves incorporating optimized liquid SEDDS into solid carriers or converting them into solid matrices using suitable techniques [32, 33]. The choice of solid carrier is critical, as it influences drug loading capacity, flow properties, and reconstitution behavior [33]. Commonly used carriers include porous silica, microcrystalline cellulose, and magnesium aluminometasilicate, which possess high surface area and adsorption capacity [33–35]. These materials enable efficient conversion of liquid formulations into free-flowing powders suitable for further processing [33]. Among the various solidification techniques, adsorption onto solid carriers is one of the most widely used approaches [32, 33]. In this method, the liquid SEDDS is gradually added to a porous carrier until complete adsorption is achieved, resulting in a dry and free-flowing powder [32]. This technique is simple, cost-effective, and easily scalable, making it suitable for industrial applications [33]. However, the drug loading capacity may be limited by the adsorption efficiency of the carrier [35].
Spray drying is another important technique used to prepare S-SEDDS [32, 33]. This method involves atomizing the liquid formulation into a hot drying chamber, where rapid solvent evaporation leads to the formation of dry particles [32]. Spray drying allows the production of uniform particles with controlled size and improved dispersibility [33]. It also enhances formulation stability and enables large-scale manufacturing [32]. However, process parameters such as temperature and feed rate must be carefully optimized to prevent drug degradation [33].
Melt granulation is a solvent-free technique in which lipid components act as binders and are melted to form granules with solid excipients [33]. Upon cooling, the formulation solidifies into granules that can be compressed into tablets or filled into capsules [33]. This method is environmentally friendly and avoids the use of organic solvents [33–35]. However, it requires careful temperature control to ensure the stability of thermolabile drugs [35].
Freeze drying (lyophilization) is also employed to produce porous S-SEDDS with enhanced reconstitution properties [32]. In this process, the formulation is frozen and subjected to sublimation under vacuum conditions, resulting in highly porous structures [32]. These structures facilitate rapid emulsification upon contact with aqueous media [32, 33]. Despite its advantages, freeze drying is expensive and less suitable for large-scale production [33]. The selection of an appropriate solidification technique depends on multiple factors, including drug properties, excipient compatibility, scalability, and cost considerations [33–35]. Each method offers unique benefits and limitations, and the choice must be optimized based on the desired product characteristics [33].
Upon oral administration, S-SEDDS rapidly disperse in gastrointestinal fluids to form fine emulsions similar to their liquid counterparts [32, 33]. This ensures that the drug remains in a solubilized state, enhancing dissolution and absorption [33–35]. The solid nature of these systems improves stability, reduces variability, and enhances patient compliance [34, 35]. Recent advancements in S-SEDDS formulation have focused on improving performance and scalability [50–54]. Techniques such as nano-structuring and the incorporation of functional excipients have enhanced drug loading and stability [51–53]. Additionally, the integration of computational tools has enabled more efficient optimization of formulation variables [55, 56]. These developments highlight the growing importance of S-SEDDS in modern drug delivery systems [50–56].
S-SEDDS have emerged as a promising platform for improving the oral delivery of poorly water-soluble cardiovascular drugs [21–23]. These systems address key challenges such as low solubility, poor bioavailability, and high variability in drug absorption [6–8]. By enhancing solubilization and promoting lymphatic transport, S-SEDDS significantly improve therapeutic efficacy [24, 25]. One of the most extensively studied drugs in S-SEDDS formulations is simvastatin, a lipid-lowering agent used in the management of hyperlipidemia [45]. Simvastatin exhibits poor aqueous solubility and undergoes extensive first-pass metabolism, resulting in low bioavailability [45]. S-SEDDS formulations of simvastatin have demonstrated significant improvement in dissolution rate and systemic exposure [45]. Enhanced pharmacokinetic parameters, including increased peak plasma concentration and area under the curve, have been reported [45]. These improvements are attributed to better solubilization and absorption via lipid-mediated pathways [24, 25].
Carvedilol, a non-selective beta-blocker used in hypertension and heart failure, is another example of a drug benefiting from S-SEDDS formulation [46]. Carvedilol has low solubility and high first-pass metabolism, leading to variable bioavailability [46]. S-SEDDS formulations have shown improved dissolution behavior and more consistent absorption profiles [46]. Enhanced permeability and reduced variability contribute to improved therapeutic outcomes [46].
Amlodipine, a calcium channel blocker widely used for hypertension, has also been formulated using S-SEDDS [47]. Although amlodipine has moderate solubility, its absorption can be influenced by gastrointestinal variability [47]. S-SEDDS improve dissolution and provide more consistent drug release, leading to better control of blood pressure [47]. These formulations also reduce inter-patient variability and enhance therapeutic predictability [47].
Atorvastatin, another commonly prescribed statin, suffers from poor aqueous solubility and extensive metabolism [48]. Incorporation into S-SEDDS has resulted in improved solubilization and enhanced oral bioavailability [48]. The lipid-based nature of the formulation facilitates absorption and may promote lymphatic transport, thereby reducing first-pass metabolism [24, 25]. This leads to improved lipid-lowering efficacy and more consistent pharmacokinetic profiles [48].
Figure 5. Applications of SEDDS in cardiovascular drugs [45, 46, 52,57].
Nifedipine, a poorly soluble calcium channel blocker, has also been studied in S-SEDDS formulations [49]. Conventional formulations of nifedipine exhibit variable absorption due to solubility limitations and sensitivity to gastrointestinal conditions [49]. S-SEDDS improve dissolution rate and enable rapid drug release, which is particularly important in acute conditions such as hypertensive emergencies [49]. In addition to these drugs, other cardiovascular agents such as angiotensin receptor blockers and diuretics have shown improved performance when formulated as S-SEDDS [21–23]. These drugs often suffer from poor solubility and benefit significantly from lipid-based delivery systems [21, 22]. Improved dissolution, enhanced absorption, and reduced variability have been consistently observed [22, 23].
The clinical significance of S-SEDDS lies in their ability to provide more predictable pharmacokinetics and improved therapeutic outcomes [21–23]. By reducing variability associated with gastrointestinal conditions and food effects, these systems enhance drug efficacy and patient compliance [16, 17]. Furthermore, the potential to reduce dosing frequency and improve bioavailability makes S-SEDDS an attractive option for long-term cardiovascular therapy [18–20]. Recent advancements have further expanded the applications of S-SEDDS in cardiovascular drug delivery [50–54]. The development of nano-SEDDS has enabled the formation of ultra-fine droplets, improving drug absorption and bioavailability [51–53]. Supersaturable systems have been introduced to maintain drug solubility and prevent precipitation [52]. Additionally, the integration of artificial intelligence in formulation design has facilitated optimization and improved performance [55, 56].
Despite these advantages, challenges such as limited drug loading, potential excipient toxicity, and formulation complexity remain [35, 57]. Addressing these issues through continued research and innovation will be essential for the successful clinical translation of S-SEDDS [57]. Nevertheless, the growing body of evidence supports their potential as an effective platform for improving cardiovascular drug delivery [21–23].
Despite the considerable progress made in the development of self-emulsifying drug delivery systems (SEDDS) and their solid counterparts (S-SEDDS), several research gaps continue to limit their full clinical translation, particularly in the field of cardiovascular therapy [21–23]. While these systems have demonstrated significant improvements in the solubility and bioavailability of poorly water-soluble drugs, challenges related to mechanistic understanding, formulation optimization, scalability, and regulatory acceptance remain inadequately addressed [30,35]. One of the most critical research gaps is the lack of reliable and predictive in vitro–in vivo correlation (IVIVC) models for lipid-based formulations [7]. Unlike conventional dosage forms, the performance of SEDDS and S-SEDDS is highly dependent on dynamic gastrointestinal processes, including lipid digestion, bile salt interaction, and enzymatic activity [24, 25]. These processes are complex and difficult to replicate accurately under in vitro conditions, leading to poor predictability of in vivo drug behavior [7]. As a result, formulation development often relies on empirical approaches rather than mechanistic understanding [30]. Developing physiologically relevant in vitro models that simulate gastrointestinal conditions remains a major research priority [7, 24].
Another significant gap lies in the limited understanding of lipid digestion kinetics and its influence on drug absorption [24, 25]. Although it is well established that lipid digestion enhances drug solubilization through the formation of mixed micelles, the precise mechanisms governing this process are not fully understood [24]. Variability in factors such as bile salt concentration, pancreatic enzyme activity, and intestinal motility can significantly influence lipid digestion and drug absorption [13, 15]. This variability contributes to inconsistent pharmacokinetic profiles and poses challenges in predicting therapeutic outcomes [16]. Further mechanistic studies are required to elucidate the interplay between lipid digestion and drug transport [24, 25]. The issue of drug precipitation upon dilution remains another critical challenge in SEDDS and S-SEDDS formulations [30].
Although these systems are designed to maintain drugs in a solubilized state, dilution in gastrointestinal fluids can lead to supersaturation and subsequent precipitation [30, 52]. This reduces the concentration of drug available for absorption and compromises bioavailability [52]. While supersaturable SEDDS have been developed to address this limitation, further research is needed to identify more effective precipitation inhibitors and stabilization strategies [52, 53]. Limited drug loading capacity is another important limitation that requires attention [35]. The amount of drug that can be incorporated into SEDDS formulations is constrained by its solubility in the lipid components [21, 23]. This becomes particularly challenging for drugs requiring high therapeutic doses, as larger quantities of excipients may be needed, potentially increasing the risk of toxicity [35]. The development of novel lipid excipients with higher solubilization capacity and improved safety profiles is therefore an important area for future research [34, 35]. The safety and toxicity of excipients, particularly surfactants, represent another significant research gap [35]. Although non-ionic surfactants are generally considered safe, high concentrations may cause gastrointestinal irritation and alter membrane integrity [35]. Long-term safety data for many excipients used in lipid-based formulations are limited, especially for chronic therapies such as cardiovascular treatment [18–20]. Comprehensive toxicological studies are required to ensure the safety and acceptability of these systems for long-term use [35].
Scalability and manufacturing challenges also hinder the widespread adoption of S-SEDDS [33–35]. While techniques such as adsorption and spray drying are effective at the laboratory scale, their translation to industrial-scale production can be complex [32, 33]. Maintaining batch-to-batch consistency, controlling process parameters, and ensuring product stability are significant challenges [33]. The development of robust and scalable manufacturing processes is essential for the commercialization of S-SEDDS [33–35]. Regulatory challenges further complicate the development and approval of lipid-based drug delivery systems [57]. The lack of standardized guidelines for evaluating SEDDS and S-SEDDS makes it difficult to establish consistent quality and performance criteria [57]. Regulatory agencies require detailed characterization of excipients, formulation behavior, and stability, which can be challenging due to the complex nature of these systems [57]. Harmonization of regulatory frameworks and the development of standardized evaluation protocols are necessary to facilitate approval and commercialization [57].
Another important gap is the limited availability of clinical data supporting the efficacy of S-SEDDS formulations [21–23]. Although numerous preclinical studies have demonstrated improved bioavailability, relatively few clinical trials have been conducted to validate these findings in humans [21]. The translation of preclinical success into clinical outcomes remains a critical challenge [21–23]. More well-designed clinical studies are needed to establish the therapeutic benefits and safety of S-SEDDS in cardiovascular patients [21]. The potential application of personalized medicine in S-SEDDS development remains largely unexplored [10, 11]. Individual variability in gastrointestinal physiology, metabolism, and genetic factors can significantly influence drug response [10]. Tailoring formulations based on patient-specific characteristics could improve therapeutic outcomes and reduce variability [10, 11]. This approach aligns with the growing trend toward precision medicine and represents an important direction for future research [11].
Recent technological advancements offer promising opportunities to address these challenges [50–54]. The development of nano-SEDDS has enabled the production of ultra-fine droplets, which improve drug absorption and bioavailability [51–53]. These systems provide enhanced surface area and improved interaction with biological membranes, leading to better therapeutic performance [51]. Similarly, supersaturable SEDDS have been developed to maintain drug super saturation and prevent precipitation, thereby enhancing absorption while reducing surfactant concentration [52, 53]. The integration of artificial intelligence (AI) and machine learning (ML) in formulation development represents a significant advancement in the field [55, 56]. These technologies enable the prediction of optimal formulation compositions and process parameters based on physicochemical properties [55]. AI-driven approaches can reduce experimental workload, improve accuracy, and accelerate the development process [56]. However, their application in lipid-based drug delivery is still in its early stages and requires further validation [56].
Another promising area of research is the development of novel excipients and functional lipids [34, 35]. These materials are designed to enhance solubilization, stability, and absorption while minimizing toxicity [34]. The use of biodegradable and biocompatible excipients can improve the safety profile of S-SEDDS and facilitate regulatory approval [35]. Advances in material science are expected to play a key role in the future development of these systems [34]. Future research should also focus on improving in vitro models that better simulate gastrointestinal conditions [7, 24]. The development of bio relevant dissolution media and dynamic digestion models can enhance the predictability of formulation performance [7]. Such models will help bridge the gap between in vitro and in vivo studies, facilitating more efficient formulation development [7].
CONCLUSION
Self-emulsifying drug delivery systems (SEDDS) and their solid counterparts (S-SEDDS) represent effective strategies to overcome the limitations of poorly water-soluble cardiovascular drugs. By enhancing solubilization, dissolution, and intestinal absorption, these systems significantly improve oral bioavailability and therapeutic performance. The transformation of liquid SEDDS into solid forms further improves stability, manufacturability, and patient compliance. Despite these advantages, challenges such as limited drug loading, excipient safety concerns, and lack of predictive IVIVC models remain. Recent advancements including nano-SEDDS, supersaturable systems, and AI-driven formulation approaches offer promising solutions to these limitations. Overall, S-SEDDS provide a versatile and scalable platform with strong potential for improving cardiovascular drug delivery, although further research and clinical validation are essential for their widespread application.
REFERENCES
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