Overcoming the dissolution rate, gastrointestinal permeability and oral bioavailability of glimepiride and simvastatin co-delivered in the form of nanosuspension and solid self-nanoemulsifying drug delivery system: A comparative study

Enhancing the oral bioavailability of fisetin: polysaccharide-based self nano-emulsifying spheroids for colon-targeted delivery

Fisetin (FS) is a flavonoid that possesses antioxidant and anti-inflammatory properties against ulcerative colitis. FS shows poor dissolution rate and permeability. An attempt has been made to develop colon-targeted solid self-nanoemulsifying drug delivery systems (S-SNEDDS) of FS. Initially, liquid (L) SNEDDS were prepared by loading FS into isotropic mixture of L-SNEDDS was prepared using Labrafil M 1944 CS, Transcutol P, and Tween 80. These L-SNEDDS were further converted into solid (S) SNEDDS by mixing the isotropic mixture with 1:1:1 ratio of guar gum (GG), xanthan gum (XG) and pectin (PC) [GG:XG:PC (1:1:1)]. Aerosil-200 (A-200) was added to enhance their flow characteristics. Further, they were converted into spheroids by extrusion-spheronization technique. The solid-state characterization of S-SNEDDS was done by SEM, DSC, and PXRD, which revealed that the crystalline form of FS was converted into the amorphous form. In the dissolution study, S-SNEDDS spheroids [GG:XG:PC (1:1:1)] exhibited less than 20% drug release within the first 5 h, followed by rapid release of the drug between the 5th and 10th h, indicating its release at colonic site. The site-specific delivery of FS to colon via FS-S-SNEDDS spheroids was confirmed by conducting pharmacokinetic studies on rats. Wherein, results showed delay in absorption of FS loaded in spheroids up to 5 h and achievement of Cmax at 7h, whereas L-SNEDDS showed rapid absorption of FS. Furthermore, FS-L-SNEDDS and FS-S-SNEDDS spheroids [GG:XG:PC (1:1:1)] increased oral bioavailability of FS by 6.86-fold and 4.44-fold, respectively, as compared to unprocessed FS.

Application of quality by design in optimization of nanoformulations: Principle, perspectives and practices

Nanoparticulate drug delivery systems (NDDS) based nanoformulations have emerged as promising drug delivery systems. Various NDDS-based formulations have been reported such as polymeric nanoparticles (NPs), nanoliposomes, solid lipid NPs, nanocapsules, liposomes, self-nano emulsifying drug delivery systems, pro liposomes, nanospheres, microemulsion, nanoemulsion, gold NPs, silver NPs and nanostructured lipid carrier. They have shown numerous advantages such as enhanced bioavailability, aqueous solubility, permeability, controlled release profile, and blood-brain barrier (BBB) permeability. This advantage of NDDS can help to deliver pure drugs to the target site. However, the formulation of nanoparticles is a complex process that requires optimization to ensure product quality and efficacy. Quality by Design (QbD) is a systemic approach that has been implemented in the pharmaceutical industry to improve the quality and reliability of drug products. QbD involves the optimization of different parameters like zeta potential (ZP), particle size (PS), entrapment efficiency (EE), polydispersity index (PDI), and drug release using statistical experimental design. The present article discussed the detailed role of QbD in optimizing nanoformulations and their advantages, advancement, and applications from the industrial perspective. Various case studies of QbD in the optimization of nanoformulations are also discussed.

Nanosuspensions in ophthalmology: Overcoming challenges and enhancing drug delivery for eye diseases

This review article provides a comprehensive overview of the advancements in using nanosuspensions for controlled drug delivery in ophthalmology. It highlights the significance of ophthalmic drug delivery due to the prevalence of eye diseases and delves into various aspects of this field. The article explores molecular mechanisms, drugs used, and physiological factors affecting drug absorption. It also addresses challenges in treating both anterior and posterior eye segments and investigates the role of mucus in obstructing micro- and nanosuspensions. Nanosuspensions are presented as a promising approach to enhance drug solubility and absorption, covering formulation, stability, properties, and functionalization. The review discusses the pros and cons of using nanosuspensions for ocular drug delivery and covers their structure, preparation, characterization, and applications. Several graphical representations illustrate their role in treating various eye conditions. Specific drug categories like anti-inflammatory drugs, antihistamines, glucocorticoids, and more are discussed in detail, with relevant studies. The article also addresses current challenges and future directions, emphasizing the need for improved nanosuspension stability and exploring potential technologies. Nanosuspensions have shown substantial potential in advancing ophthalmic drug delivery by enhancing solubility and absorption. This article is a valuable resource for researchers, clinicians, and pharmaceutical professionals in this field, offering insights into recent developments, challenges, and future prospects in nanosuspension use for ocular drug delivery.

Nanosuspension-Based Drug Delivery Systems for Topical Applications

Nanosuspensions have garnered recent attention as a promising strategy for mitigating the bioavailability challenges of hydrophobic drugs, particularly those characterized by poor solubility in both aqueous and organic environments. Addressing solubility issues associated with poorly water-soluble drugs has largely resolved the need to enhance drug absorption and bioavailability. As mucosal formulations and topical administration progress in the future, nanosuspension drug delivery, straightforward formulation techniques, and versatile applications will continue to be subjects of interest. Nanosuspensions have undergone extensive scrutiny in preparation for topical applications, encompassing ocular, pulmonary, and dermal usage. Among the numerous methods aimed at improving cutaneous application, nanocrystals represent a relatively recent yet profoundly intriguing approach. Despite the increasing availability of various nanosuspension products, primarily designed for oral administration, only a limited number of studies have explored skin permeability and drug accumulation in the context of nanosuspensions. Nevertheless, the scant published research unequivocally underscores the potential of this approach for enhancing cutaneous bioavailability, particularly for active ingredients with low to medium solubility. Nanocrystals exhibit increased skin adhesiveness in addition to heightened saturation solubility and dissolution rate, thereby augmenting cutaneous distribution. The article provides a comprehensive overview of nanosuspensions for topical application. The methodology employed is robust, with a well-defined experimental design; however, the limited sample size raises concerns about the generalizability of the findings. While the results demonstrate promising outcomes in terms of enhanced drug delivery, the discussion falls short of addressing certain limitations. Additionally, the references largely focus on recent studies, but a more diverse inclusion of historical perspectives could offer a more holistic view of the subject.

Oral self-nanoemulsifying drug delivery systems for enhancing bioavailability and anticancer potential of fosfestrol: In vitro and in vivo characterization

PURPOSE

The objective of the current research work was to fabricate a fosfestrol (FST)-loaded self-nanoemulsifying drug delivery system (SNEDDS) to escalate the oral solubility and bioavailability and thereby the effectiveness of FST against prostate cancer.

METHODS

32 full factorial design was employed, and the effect of lipid and surfactant mixtures on percentage transmittance, time required for self-emulsification, and drug release were studied. The optimized solid FST-loaded SNEDDS (FSTNE) was characterized for in vitro anticancer activity and Caco-2 cell permeability, and in vivo pharmacokinetic parameters.

RESULTS

Using different ratios of surfactant and co-surfactant (Km) a pseudo ternary phase diagram was constructed. Thirteen liquid nano emulsion formulations (LNE-1 to LNE-13) were formulated at Km = 3:1. LNE-9 exhibited a higher % transmittance (99.25 ± 1.82 %) and a lower self-emulsification time (24 ± 0.32 s). No incompatibility was observed in FT-IR analysis. Within 20 min the solidified FST loaded LNE-9 (FSTNE) formulation showed almost complete drug release (98.20 ± 1.30 %) when compared to marketed formulation (40.36 ± 2.8 %), and pure FST (32 ± 3.3 %) in 0.1 N HCl. In pH 6.8 phosphate buffer, the release profiles are found moderately higher than in 0.1 N HCl. FSTNE significantly (P < 0.001) inhibited the PC-3 prostate cell proliferation and also caused apoptosis (P < 0.001) compared to FST. The in vitro Caco-2 cell permeability study results revealed 4.68-fold higher cell permeability of FSTNE than FST. Remarkably, 4.5-fold rise in bioavailability was observed after oral administration of FSTNE than plain FST.

CONCLUSIONS

FSTNE remarkably enhanced the in vitro anticancer activity and Caco-2 cell permeability, and in vivo bioavailability of FST. Thus, FST-SNEDDS could be utilized as a potential carrier for effective oral treatment of prostate cancer.

Liquid antisolvent crystallization of pharmaceutical compounds: current status and future perspectives

The present work reviews the liquid antisolvent crystallization (LASC) to prepare the nanoparticle of pharmaceutical compounds to enhance their solubility, dissolution rate, and bioavailability. The application of ultrasound and additives is discussed to prepare the particles with narrow size distribution. The use of ionic liquid as an alternative to conventional organic solvent is presented. Herbal compounds, also known for low aqueous solubility and limited clinical application, have been crystalized by LASC and discussed here. The particle characteristics such as particle size and particle size distribution are interpreted in terms of supersaturation, nucleation, and growth phenomena. To overcome the disadvantage of batch crystallization, the scientific literature on continuous flow reactors is also reviewed. LASC in a microfluidic device is emerging as a promising technique. The different design of the microfluidic device and their application in LASC are discussed. The combination of the LASC technique with traditional techniques such as high-pressure homogenization and spray drying is presented. A comparison of product characteristics prepared by LASC and the supercritical CO₂ antisolvent method is discussed to show that LASC is an attractive and inexpensive alternative for nanoparticle preparation. One of the major strengths of this paper is a discussion on less-explored applications of LASC in pharmaceutical research to attract the attention of future researchers.

Ritonavir nanosuspensions prepared by microfluidization with enhanced solubility and desirable immunological properties

The objective of this study was to develop ritonavir (RTV) nanosuspensions (NSs) by microfluidization method. Particle size (PS) measurements were performed by photon correlation spectroscopy. Amorphous properties of the particles were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dissolution studies were conducted in fed state simulated intestinal fluid (FeSSIF) medium. The flow cytometry was utilized to determine the lymphocyte sub-groups and immune response of NSs. RTV NSs were obtained with 400-500 nm PS. The crystal properties of RTV remain unchanged. The solubility of NS was enhanced five times. 57% and 18% of RTV were dissolved in FeSSIF medium for NSs and coarse powder. According to immunological studies, the prepared NSs did not significantly alter the ratio of CD4⁺/CD8⁺. Therefore, NSs may be a beneficial approach for the oral administration of RTV.

Amidated Pluronic Decorated Muco-Penetrating Self-Nano Emulsifying Drug Delivery System (SNEDDS) for Improved Anti-Salmonella typhi Potential

The enteric system residing notorious Salmonella typhimurium (S. typhi) is an intracellular, food-borne, and zoonotic pathogen causing typhoid fever. Typhoid fever is one of the leading causes of mortality and morbidity in developing and underdeveloped countries. It also increased the prevalence of multidrug resistance globally. Currently, available anti-bacterial modalities are unable to penetrate into the intracellular compartments effectively for eradicating S. typhi infection. Therefore, in this study, we developed nanostructured lipid-based carriers in the form of a self-nanoemulsifying drug delivery system (SNEDDS) for targeted delivery of ciprofloxacin (CIP) into the S. typhi intracellular reservoirs. Capryol 90, Tween 80, and Span 20 were finalized as suitable oil, surfactant, and co-surfactant, respectively, according to the pseudoternary phase diagram emulsifying region. Targeting capability and mucopenetration of the SNEDDS was attributed to the inclusion of amidated pluronic (NH2-F127). Developed NH2-F127 SNEDDS were characterized via physicochemical, in vitro, ex vivo, and in vivo evaluation parameters. The size of the SNEDDS was found to be 250 nm, having positively charged zeta potential. In vitro dissolution of SNEDDS showed 80% sustained release of CIP in 72 h with maximum entrapment efficiency up to 90% as well as good hemocompatibility by showing less than 0.2% hemolysis and 90% biocompatibility. The survival rate of S. typhi in macrophages (RAW 264.7) was minimal, i.e., only 2% in the case of NH2-F127 SNEDDS. Macrophage uptake assay via nanostructures confirmed the maximum cellular uptake as evidenced by the highest fluorescence. Biofilm dispersion assay showed rapid eradication of developed resistant biofilms on the gall bladder. In vivo pharmacokinetics showed improved bioavailability by showing an increased area under the curve (AUC) value. Taken together, NH2-F127-SNEDDS can be utilized as an alternative and efficient delivery system for the sustained release of therapeutic amounts of CIP for the treatment of S. typhi.

Quality by Design Based Formulation of Xanthohumol Loaded Solid Lipid Nanoparticles with Improved Bioavailability and Anticancer Effect against PC-3 Cells

Many natural products with greater therapeutic efficacy are limited to target several chronic diseases such as cancer, diabetes, and neurodegenerative diseases. Among the natural products from hops, i.e., Xanthohumol (XH), is a prenylated chalcone. The present research work focuses on the enhancement of the poor oral bioavailability and weak pharmacokinetic profile of XH. We exemplified the development of a Xanthohumol-loaded solid lipid nanoparticles (XH-SLNs) cargo system to overcome the limitations associated with its bioavailability. The XH-SLNs were prepared by a high-shear homogenization/ultrasonication method and graphical, numerical optimization was performed by using Box-Behnken Design. Optimized XH-SLNs showed PS (108.60 nm), PDI (0.22), ZP (-12.70 mV), %EE (80.20%) and an amorphous nature that was confirmed by DSC and PXRD. FE-SEM and HRTEM revealed the spherical morphology of XH-SLNs. The results of release studies were found to be 9.40% in 12 h for naive XH, whereas only 28.42% of XH was released from XH-SLNs. The slow release of drugs may be due to immobilization of XH in the lipid matrix. In vivo pharmacokinetic study was performed for the developed XH-SLNs to verify the enhancement in the bioavailability of XH than naive XH. The enhancement in the bioavailability of the XH was confirmed from an increase in Cmax (1.07-folds), AUC0-t (4.70-folds), t1/2 (6.47-folds) and MRT (6.13-folds) after loading into SLNs. The relative bioavailability of XH loaded in SLNs and naive XH was found to be 4791% and 20.80%, respectively. The cytotoxicity study of naive XH, XH-SLNs were performed using PC-3 cell lines by taking camptothecin as positive control. The results of cytotoxicity study revealed that XH-SLNs showed good cell inhibition in a sustained pattern. This work successfully demonstrated formulation of XH-SLNs with sustained release profile and improved oral bioavailability of XH with good anticancer properties against PC-3 cells.

Multivariate Data Analysis and Central Composite Design-Oriented Optimization of Solid Carriers for Formulation of Curcumin-Loaded Solid SNEDDS: Dissolution and Bioavailability Assessment

The study was initiated with two major purposes: investigating the role of isomalt (GIQ9) as a pharmaceutical carrier for solid self-nanoemulsifying drug delivery systems (S-SNEDDSs) and improving the oral bioavailability of lipophilic curcumin (CUN). GIQ9 has never been explored for solidification of liquid lipid-based nanoparticles such as a liquid isotropic mixture of a SNEDDS containing oil, surfactant and co-surfactant. The suitability of GIQ9 as a carrier was assessed by calculating the loading factor, flow and micromeritic properties. The S-SNEDDSs were prepared by surface adsorption technique. The formulation variables were optimized using central composite design (CCD). The optimized S-SNEDDS was evaluated for differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), microscopy, dissolution and pharmacokinetic studies. The S-SNEDDS showed a particle size, zeta potential and PDI of 97 nm, -26.8 mV and 0.354, respectively. The results of DSC, XRD, FTIR and microscopic studies revealed that the isotropic mixture was adsorbed onto the solid carrier. The L-SNEDDS and S-SNEDDS showed no significant difference in drug release, indicating no change upon solidification. The optimized S-SNEDDS showed 5.1-fold and 61.7-fold enhancement in dissolution rate and oral bioavailability as compared to the naïve curcumin. The overall outcomes of the study indicated the suitability of GIQ9 as a solid carrier for SNEDDSs.

Quality by design-based optimization of formulation and process parameters for berberine nanosuspension for enhancing its dissolution rate, bioavailability, and cardioprotective activity

Berberine (BER) possesses dissolution rate limited oral bioavailability. The present study deciphers the formulation of nanosuspension loaded with BER for enhancing its cardioprotective potential. The nanosuspension was prepared by a liquid antisolvent precipitation technique using sodium lauryl sulfate as a surfactant and polyvinyl pyrrolidone K30 (PVP K30) as a polymer. The optimized formulation showed a particle size of 251.32 ± 4.18 nm, zeta potential of -24.10 ± 1.16 mV, and drug loading capacity of 98.22 ± 2.24%. The results showed about 6.01-fold and 3.54-fold enhancement in the dissolution rate and permeability, respectively, upon loading berberine into nanosuspension. About 8.44-fold increase in C_max , 27.22-fold increase in AUC_0-t , and 27.38-fold increase in AUC_0-∞ were observed in the case of BER nanosuspension, compared to its naïve form. The results of particle size, zeta potential, and drug loading showed a nonsignificant change in the response of fresh and aged nanosuspension, which indicated that the formulation was stable. In vitro results on H9C2 cell line indicated a lower cellular proliferation rate after treatment with BER nanosuspension with decreased cytoplasmic expression of angiotensin converting enzyme (ACE) protein. Overall, the results indicated the successful development of BER nanosuspension with an enhanced dissolution rate, permeability, bioavailability, and cardioprotective activity. Practical applications The present study provides the evidence that the formulation of nanosuspension loaded with berberine enhance the cardioprotective activity of berberine. The results of the study supports the improved bioavailability of nanosuspension of berberine showed enhanced cardioprotective activity.

Expanding arsenal against diabetes mellitus through nanoformulations loaded with glimepiride and simvastatin: A comparative study

Type 2 diabetes mellitus is one of the most common and life-threatening diseases found across the globe. It occurs due to insulin resistance (IR). Major causes of IR include obesity, sedentary life style and hyperlipidemia. Glimepiride (GLM) is one of the most common oral sulphonyl ureas that is being used to treat diabetes and Simvastatin (SIM) is one of the most common statins that is used to treat hyperlipidaemia. However, both the drugs suffer from dissolution rate limited oral bioavailability. Hence, the aim of present study was to develop two different nanoformulations viz. nanosuspension and self-nanoemulsifying drug delivery systems (SNEDDS) and evaluate their potential in treating type 2 diabetes mellitus on streptozotocin (STZ) induced rats. In the present study two such drugs, GLM and SIM were co-formulated into nanosuspension (NS) as well as self-nanoemulsifying drug delivery systems (L-SNEDDS). Both formulations were spray dried for solidification and evaluated for their antidiabetic potential against high fat diet and streptozotocin induced rat model. The study showed significant (p < 0.05) decrease in lipid/cholesterol and blood glucose levels and significant increase in antioxidant levels in the rats treated with NS and SNEDDS containing the drugs alone as well as their combination as compared to their unprocessed forms. However, the efficacy was more prominent in case of combination possibly due to dual benefits i.e., decrease in IR due to statin and control of blood glucose level. Among NS and SNEDDS, NS was found more efficacious than that of the SNEDDS possibly due to higher enhancement of oral bioavailability in case of NS.

Improved neuroprotective activity of Fisetin through SNEDDS in ameliorating the behavioral alterations produced in rotenone-induced Parkinson's model

Fisetin is a polyphenolic flavonoid reported to have antioxidant, anti-inflammatory, and anti-cancer activities. However, it loses its importance as an effective phytochemical due to its poor water solubility and lower bioavailability. In the present study, the self-nanoemulsifying drug delivery system (SNEDDS) of fisetin was developed in order to improve its pharmacological activity. The developed SNEDDS of fisetin was evaluated for improving the rotenone-induced behavioral changes in the rats, and its efficacy was compared with naïve fisetin. It was noticed that fisetin loaded in the SNEDDS formulation significantly (p < 0.001) ameliorated the rotenone-induced alteration in the body weight, grip strength, beam walk, postural instability, etc., in rats when compared to the effect of naïve fisetin. Naïve fisetin significantly (p < 0.05) ameliorated the effect of rotenone on the level of dopamine only at a higher dose. Whereas, SNEDDS of fisetin produced a significant (p < 0.05) effect at both dose levels when compared with the diseased group as well as also produced a significant (p < 0.05) effect when compared with the naïve fisetin group. The results of histopathological examination revealed about the neuroprotective effect of SNEDDS loaded with fisetin as observed through the protection of neuronal damage. From this study, it was concluded that SNEDDS improved the anti-Parkinsonian activity of fisetin by improving the behavioral alteration produced by rotenone due to enhancement in its solubility and bioavailability.

Development and optimization of oral nanoemulsion of rutin for enhancing its dissolution rate, permeability, and oral bioavailability

Rutin-loaded nanoemulsion (NE-RU) formulation is the core research work in this report. Labrafil^® M 1944 CS was used as the oil phase, Tween 80 as the surfactant, and Transcutol P as the co-surfactant in the preparation of nanoemulsion. By utilizing a three-level central composite design (CCD), the composition was optimized. The optimized formulation showed a droplet size of 98.53 ± 3.22 nm, zeta potential -46.70 ± 4.78 mV, and drug loading 92.34 ± 3.87%. The results of dissolution, permeability, and oral bioavailability showed about 25.55 folds, 1.98 folds, and 33.68 folds, respectively, in the case of NE-RU as compared to its naïve form. The response of fresh and aged NE was non-significantly different in terms of particle size, zeta potential, and drug loading, indicating that the formulation was stable. The successful development of NE-RU with an improved bioavailability profile suggested that this formulation might be used to examine the pharmacodynamics of oxidative stress-related metabolic disorders.

A comprehensive study of the basic formulation of supersaturated self-nanoemulsifying drug delivery systems (SNEDDS) of albendazolum

Albendazolum (ABZ) is a BCS class II drug. It has challenging biopharmaceutical properties, which include poor solubility and dissolution rate. These properties have laid the ground for developing a supersaturated self-nanoemulsifying drug delivery system (S-SNEDDS) to form oil-in-water nanoemulsion in situ to improve the oral bioavailability of ABZ. Based on the ABZ solubility, emulsifying ability, and stability after dispersion in an aqueous phase, an optimal self-nanoemulsifying drug delivery system (SNEDDS) consisting of oleic acid, Tween^® 20, and PEG 600 (X:Y:Z, w/w) was identified, having 10% (w/w) hydroxypropyl methylcellulose (HPMC) E15 lv as its precipitation inhibitor. The optimized system possessed a small mean globule size value (89.2 nm), good dispersion properties (polydispersity index (PDI): 0.278), and preserved the supersaturated state of ABZ. S-SNEDDS was transformed into solid supersaturated self-nanoemulsifying drug delivery systems (SS-SNEDDS) using microcrystalline cellulose as a solid material. The developed S-SNEDDS were characterized for globule size, pH, turbidity, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and flow properties. The data obtained from the results suggest that this S-SNEDDS formulation can enhance the solubility and oral bioavailability of ABZ for appropriate clinical application.

Development and optimization of sitagliptin and dapagliflozin loaded oral self-nanoemulsifying formulation against type 2 diabetes mellitus

Control of hyperglycemia and prevention of glucose reabsorption (glucotoxicity) are important objectives in the management of type 2 diabetes. This study deals with an oral combined dosage form design for two anti-diabetic drugs, sitagliptin and dapagliflozin using self-nanoemulsifying drug delivery systems (SNEDDS). The SNEDDS were developed using naturally obtained bioactive medium-chain/long-chain triglycerides oil, mixed glycerides and nonionic surfactants, and droplet size was measured followed by the test for antioxidant activities. Equilibrium solubility and dynamic dispersion experiments were conducted to achieve the maximum drug loading. The in vitro digestion, in vivo bioavailability, and anti-diabetic effects were studied to compare the representative SNEDDS with marketed product Dapazin^®. The representative SNEDDS containing black seed oil showed excellent self-emulsification performance with transparent appearance. Characterization of the SNEDDS showed nanodroplets of around 50–66.57 nm in size (confirmed by TEM analysis), in addition to the high drug loading capacity without causing any precipitation in the gastro-intestinal tract. The SNEDDS provided higher antioxidant activity compared to the pure drugs. The in vivo pharmacokinetic parameters of SNEDDS showed significant increase in C_max (1.99 ± 0.21 µg mL⁻¹), AUC (17.94 ± 1.25 µg mL⁻¹), and oral absorption (2-fold) of dapagliflozin compared to the commercial product in the rat model. The anti-diabetic studies showed the significant inhibition of glucose level in treated diabetic mice by SNEDDS combined dose compared to the single drug therapy. The combined dose of sitagliptin-dapagliflozin using SNEDDS could be a potential oral pharmaceutical product for the improved treatment of type 2 diabetes mellitus.