The objective of the current work was to develop optimized self-nanoemulsifying drug delivery systems (SNEDDS) and evaluate their
Solubility, together with permeability, plays significant role in oral bioavailability of a drug [
Lipid based formulation represents a distinctive and relatively novel solution to delivery of poorly soluble compounds. A lipid dosage form usually consists of one or more drugs dissolved in a blend of lipophilic excipients such as triglycerides, partial glycerides, surfactants, or cosurfactants [
Hydrochlorothiazide (HCT) is a potent diuretic drug that is practically insoluble in water and has a solubility of only 250
Rapid disintegrating tablet strategy has been experimented for HCT using various carriers [
Hydrochlorothiazide was received as a gift sample from Torrent Pharmaceuticals Ltd., Ahmedabad, India. Maisine 35-1, Transcutol P, and Lauroglycol 90 were generously provided by Gattefosse, France. Cremophor RH 40 and Cremophor EL were received as gift sample from BASF, USA. Captex 355 EP/NF, Captex 300 EP/NF, and Capmul MCM NF were a generous gift from Abitec Corporation, USA. Polyethylene glycol 400 (PEG 400) was purchased from Merck Limited, Mumbai, India. Oleic acid was purchased from S. D. Fine Chemicals Limited, Mumbai. Propylene glycol and Tween 80 were purchased from Thomas Baker Chemicals Limited, Mumbai. Castor oil USP was purchased from Arora Pharmaceuticals Private Limited, New Delhi. Empty hard gelatin capsules were obtained from Associated Capsules Pvt. Ltd, Mumbai. Dialysis Tubing (seamless cellulose tubing, MWCO 12000) was purchased from Sigma Chemical Co., USA. All other chemicals used were of analytical grade.
These studies were performed to determine the solubility in individual vehicle (Table
Solubility studies of HCT in various vehicles.
Vehicle | Function in SNEDDS | Solubility (mg/mL) |
---|---|---|
Maisine 35-1 | Oil | 1.97 ± 0.7 |
Oleic acid | Oil | 2.65 ± 0.85 |
Capmul MCM | Oil | 3.43 ± 0.54 |
Castor oil | Oil | 1.68 ± 0.54 |
Captex 355 EP/NF | Oil | 2.26 ± 0.8 |
Tween 80 | Surfactant | 161.46 ± 2.54 |
Cremophor EL | Surfactant | 27.19 ± 1.15 |
Cremophor RH 40 | Surfactant | 13.15 ± 1.2 |
Span 20 | Surfactant | 1.49 ± 0.73 |
Lauroglycol 90 | Surfactant | 1.34 ± 0.74 |
PEG 400 | Cosurfactant | 357.14 ± 2.94 |
Propylene glycol | Cosurfactant | 53.60 ± 1.05 |
Transcutol P | Cosurfactant | 288.72 ± 2.56 |
Water titration method was used for construction of phase diagram using oil and surfactant/cosurfactant mix (Smix). Based on solubility studies, two sets of Smix (i.e., Tween 80: Transcutol P and PEG 400: Transcutol P) were investigated with Capmul MCM as the oil phase. Surfactant and cosurfactant were added in the ratios of 1 : 1, 2 : 1, 3 : 1, and 4 : 1 for both of the sets. Distilled water was added dropwise to the mixture of certain weight ratios (i.e., 9 : 1, 8 : 2, 7 : 3, 6 : 4, 5 : 5, 4 : 6, 3 : 7, 2 : 8, and 1 : 9) of oil and surfactant/cosurfactant (Smix). Mixtures were stirred using magnetic stirrer. Then each mixture was observed for phase clarity and flowability. Phase diagrams were constructed by using trial version of CHEMIX School 3.50 software (Minnesota, USA) (Figures
Pseudoternary phase diagrams with the following components: oil = Capmul MCM, surfactant = Tween 80, and cosurfactant = PEG 400. S/Cos ratio of A is 1 : 1, B is 2 : 1, C is 3 : 1, and D is 4 : 1. S/Cos indicates surfactant/cosurfactant. Area in grey shade indicates self-emulsifying region.
Pseudoternary phase diagrams with following components: oil = Capmul MCM, surfactant = Tween 80, and cosurfactant = Transcutol P. S/Cos ratio of A is 1 : 1, B is 2 : 1, C is 3 : 1, and D is 4 : 1. S/Cos indicates surfactant/cosurfactant. Area in grey shade indicates self-emulsifying region.
From the solubility study and ternary phase diagram studies, SNEDDS components were selected for drug incorporation and a series of SNEDDS were prepared (Table
Composition of developed formulations.
Formulation codes | Composition (%w/w) | |||
---|---|---|---|---|
Capmul MCM | Tween 80 | Transcutol P | Drug | |
F1 | 19.17 | 51.11 | 25.56 | 4.17 |
F2 | 19.17 | 57.50 | 19.17 | 4.17 |
F3 | 28.75 | 50.31 | 16.77 | 4.17 |
F4 | 28.75 | 44.72 | 22.36 | 4.17 |
F5 | 19.17 | 38.33 | 38.33 | 4.17 |
F6 | 28.75 | 33.54 | 33.54 | 4.17 |
The HCT-SNEDDS was prepared by dissolving drug into Smix in glass vials and accurately weighed oil was added. Components were mixed and heated (45–50°C) to form a homogenous mixture and stored at room temperature till further use.
SNEDDS formulation containing 25 mg of drug (1 part) was diluted 10 times with distilled water, 0.1 N HCl, and phosphate buffer of pH 6.8 and observed (Table
Observation of dilution test.
Formulation | Distilled water | 0.1 N HCl | Phosphate buffer pH 6.8 |
---|---|---|---|
F1 | Stable up to 6 hr | Stable up to 6 hr | Stable up to 6 hr |
F2 | Stable up to 6 hr | Stable up to 6 hr | Stable up to 6 hr |
F3 | Stable up to 6 hr | Stable up to 6 hr | Stable up to 6 hr |
F4 | Stable up to 6 hr | Stable up to 6 hr | Stable up to 6 hr |
F5 | Unclear within 30 min | Unclear within 30 min | Unclear within 30 min |
F6 | Unclear within 30 min | Unclear within 30 min | Unclear within 30 min |
Preweighted quantity of HCT containing SNEDDS was dissolved in 25 mL of methanol. HCT content was determined spectrophotometrically (UV-2202, Systronics, India) at 270 nm. Observations are shown in Table
Characterization of SNEDDS formulations.
Parameters | F1 | F2 | F3 | F4 | F5 | F6 |
---|---|---|---|---|---|---|
Drug content (%) | 96.78 ± 1.46 | 98.88 ± 1.53 | 98.46 ± 1.07 | 96.88 ± 1.86 | 102.34 ± 2.41 | 98.56 ± 1.97 |
Self-emulsification time (sec) | 15 ± 1 | 18 ± 2 | 14 ± 1 | 9 ± 1 | 8 ± 1 | 6 ± 2 |
Precipitation | Stable | Stable | Stable | Stable | Unstable | Unstable |
Clarity | Bluish | Bluish | Bluish | Bluish | Turbid | Turbid |
Viscosity (cps) | ||||||
0-time dilution | 353 | 364 | 326 | 324 | 321 | 302 |
10-time dilution | 1.17 | 1.16 | 1.15 | 1.13 | 1.12 | 1.08 |
100-time dilution | 0.888 | 0.883 | 0.88 | 0.863 | 0.857 | 0.843 |
% transmittance | 55.73 | 81.43 | 71.23 | 57.41 | 61.54 | 56.32 |
Droplet size (nm) | 98.48 ± 10.24 | 42.84 ± 13.78 | 151 ± 2.67 | 158.5 ± 15.32 | 117.5 ± 3.22 | 95.84 ± 5.42 |
Zeta potential (mV) | −10.8 ± 0.11 | −15.4 ± 0.09 | −11.7 ± 0.23 | −12.3 ± 0.15 | −12 ± 0.18 | −13.6 ± 0.21 |
The emulsification time of SNEDDS formulation was assessed on USP II dissolution apparatus (Dolphin, India) (Table
1 mL of SNEDDS formulation was diluted 100 times with distilled water. Percentage transmittance was measured spectrophotometrically (UV-2202, Systronics, India) at 560 nm using distilled water as a blank (Table
SNEDDS (1 mL) was diluted 10 times and 100 times with distilled water in a beaker with constant stirring on a magnetic stirrer. Viscosity of resulting nanoemulsion and initial SNEDDS was determined by using Brookfield R/S plus rheometer (Brookfield Engineering, Middleboro, MA) (Table
SNEDDS formulation (600 mg) containing 25 mg of HCT was diluted to 100 mL and mixed gently by inverting the flask. The size of droplet hence formed was measured by using Zetasizer (Malvern Instruments) (Table
SNEDDS was diluted 10 times and 100 times with distilled water by constant stirring on a magnetic stirrer. Zeta potential of the resulting emulsion was determined by using Zetasizer (Malvern Instruments) (Table
600 mg of each SNEDDS formulation (F1–F6) was filled in hard gelatin capsule (size 0) and used for dissolution studies; results were compared with plain HCT and marketed tablet of HCT (AQUAZIDE). 2 mL aliquots were withdrawn at 5, 10, 20, 30, 45, and 60 min intervals and filtered using 0.22
Permeation of drug through biological membrane was evaluated by
Group I: three rats for plain HCT drug suspension in 0.25% carboxymethyl cellulose (HCT). Group II: three rats for optimized SNEDDS formulation (F2) of HCT (SNEDDS). Group III: three rats for 0.25% carboxymethyl cellulose (control). Group IV: three rats for blank SNEDDS formulation (placebo).
Fifteen hours prior to each experiment food and water were withdrawn. Suspension of HCT (10 mg/kg) and optimized SNEDDS formulation F2 (equivalent to 10 mg of HCT) was administered to animals by gavage performing doses. The four groups of rats were allocated to one of four different treatments as summarized in Table
Oral administration of pure HCT and optimized SNEDDS formulation F2 compared to control and placebo in Wistar rats.
Treatment | HCT | SNEDDS | Control | Placebo |
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Period 1 | Group 1 | Group 2 | Group 3 | Group 4 |
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Washout period of 72 hours | ||||
Period 2 | Group 2 | Group 3 | Group 4 | Group 1 |
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Washout period of 72 hours | ||||
Period 3 | Group 3 | Group 4 | Group 1 | Group 2 |
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Washout period of 72 hours | ||||
Period 4 | Group 4 | Group 1 | Group 2 | Group 3 |
Cumulative urine output was recorded at 2, 4, 6, and 8 hours after oral administration of compounds. The urine volume was measured and a urine sample was taken for further analysis. Urinary sodium was determined in a flame photometer (F129, Systronics, India). Results were presented as mean ± S.E.M. (standard error of mean) and were analyzed by two-way analysis of variance followed by Bonferroni post hoc test. A
Chemical and physical stability of optimized HCT SNEDDS formulation was assessed at
Evaluation data of optimized SNEDDS formulation subjected to stability studies at 40 ± 2°C/75 ± 5% RH.
Sampling points (days) | % drug content |
|
% transmittance |
---|---|---|---|
0 | 98.88 ± 1.53 | <10 | 81.43 |
30 | 98.31 ± 1.86 | <10 | 82.03 |
60 | 97.86 ± 2.32 | <10 | 82.31 |
90 | 97.41 ± 2.82 | <10 | 82.28 |
Solubility of drug substance is a key criterion for selection of components for developing a SNEDDS formulation. The self-emulsifying formulations consisting of oil, surfactant, cosurfactant, and drug should be a clear and monophasic liquid at ambient temperature. Solubility studies were performed to identify suitable oils, surfactants, and cosurfactants that possess good solubilizing capacity for HCT (Table
Self-nanoemulsifying systems form fine oil-water emulsions with gentle agitation, upon their introduction into aqueous media. Surfactant gets preferentially adsorbed at the interface, reducing the interfacial energy as well as providing a mechanical barrier to coalescence. Figures
The objective of dilution study was to study the degree of emulsification and recrystallization of the drug, if any. Dilution may better mimic conditions in the stomach following oral administration of SNEDDS preconcentrate. Accurate mixture of emulsifier is necessary to form stable nanoemulsion, for the development of SNEDDS formulation, when one part of each SNEDDS formulation was diluted with 10 parts of distilled water, 0.1 HCl, and phosphate buffer (pH 6.8). It was observed that the formulations F1 to F4 were found to be most stable because they do not show any precipitation or phase separation on storage in various dilution media (Table
Drug content of the SNEDDS formulations is shown in Table
The rate of emulsification is an important parameter for the assessment of the efficiency or spontaneous emulsification of formulation without aid of any external thermal or mechanical energy source. Formulation should disperse completely and quickly when subjected to aqueous dilution under mild agitation of GIT due to peristaltic activity. It has been reported that self-emulsification mechanism involves the erosion of a fine cloud of small droplets from the monolayer around emulsion droplets, rather than progressive reduction in droplet size [
Below 44% concentration of surfactant, there was turbid and unstable dispersion (Table
The percentage transmittance of the six selected optimized formulations was determined. As the value closer to 100% is formulation which is isotropic in nature, optimized formulations of F2-F3 from Smix ratio of 3 : 1 gave maximum percentage transmittance (Table
Viscosity of SNEDDS without dilution was found to be in between 302 and 364 cP, which was suitable for filling in hard gelatin capsule without risk of leaking problem. As SNEDDS was diluted 10 and 100 times with water, viscosity of the system was decreased, which indicates that oral administration of SNEDDS formulation will be diluted with the stomach fluid and viscosity will be decreased and therefore absorption from the stomach will be fast (Table
The droplet size of the emulsion is an essential factor in self-emulsification performance because it determines the rate and extent of drug release as well as drug absorption. Also, it has been reported that the smaller particle size of the emulsion droplets may lead to more rapid absorption and improve the bioavailability [
Emulsion droplet polarity is also a very essential factor in characterizing emulsification efficiency [
Zeta potential analysis of optimized formulation (F2).
SNEDDS formulation F2 showed significantly higher drug release as compared to plain HCT and marketed HCT tablet (AQUAZIDE) (Figure
Conventional dissolution testing can only provide a measure of dispersibility of SNEDDS in the dissolution medium of SNEDDS. Alternatively,
This study was performed to evaluate the pharmacodynamic potential of an optimized formulation (F2) against plain HCT. Cumulative volumes of excreted urine after oral administration compounds are shown in Figure
Time course of (a) urine output and (b) sodium output in different groups. Values are reported as mean ± S.E.M. for twelve rats in each group.
Sodium and chloride ions quantification is one of the best methods to determine diuretic effect of drugs [
Diuretic activity data suggest that SNEDDS formulation increased the pharmacological effect of drug. The higher diuretic activity of the SNEDDS is due to complete dissolution of HCT in SNEDDS, which could have increased absorption. Solubility is a crucial characteristic for increasing the bioavailability of drugs according to the BCS [
Optimized SNEDDS formulation (F2) filled into hard gelatin capsules as the final dosage form. Liquid-filled hard gelatin capsules are prone to leakage and the entire system has a very limited shelf life owing to its liquid characteristics and the possibility of precipitation of the drug from the system. Thus, to evaluate its stability and the integrity of the dosage form, the optimized formulation (F2) was subjected to stability studies. No change in the physical parameters such as homogeneity and clarity was observed during the stability studies. There was no major change in the drug content, drug release (
SNEDDS was successfully emerged as appealing approach to improve the bioavailability of HCT. Increased dissolution rate, increased solubility, and ultimately increased pharmacodynamic effect of a poorly water-soluble drug, hydrochlorothiazide, were observed with an optimized SNEDDS formulation consisting of Capmul MCM (19.17% w/w), Tween 80 (57.5% w/w), Transcutol P (12.7% w/w), and HCT (4.17% w/w). The developed formulation showed higher pharmacodynamic potential as compared with plain HCT. Results from stability studies established the stability of the developed formulation.
The authors report no conflict of interests.
The authors are extremely thankful to Gattefosse (France), Abitec Corporation (USA), and BASF Chemicals (USA) for providing gift samples of various oils, surfactants, and cosurfactants. The authors are grateful to Dr. Vikas Kumar for his valuable suggestions and material support during research work.