Analysis of Binding Interactions of Ramipril and Quercetin on Human Serum Albumin: A Novel Method in Affinity Evaluation.

The aim of this study was to analyze the binding interactions between a common antihypertensive drug (ramipril, R) and the widely distributed plant flavonoid quercetin (Q), in the presence of human serum albumin (HSA). From the observed fluorescence spectra of the (HSA + R) system we can assume that ramipril is also one of the Site 3 ligands-similar to fusidic acid-the binding of which has been proven by RTG crystallography. Our claim is supported by near-UV CD spectroscopy, microscale themophoresis and molecular modeling. The presence of R slightly inhibited the subsequent binding of Q to HSA and, on the contrary, the pre-incubation of HSA with Q caused a stronger binding of R, most likely due to allosteric interactions. At high concentrations, R is also able to displace Q from its binding site. The dissociation constant KD for the binding of R is more than hundredfold larger than for Q, which means that R is a very weak binder to HSA. The knowledge of qualitative and quantitative parameters of R, as well as the methods used in this study, are important for future research into HSA binding. This study shows the importance of implementing other methods for KD determination. Microscale thermophoresis has proved to be a novel, practical and accurate method for KD determination on HSA, especially in cases when fluorescence spectroscopy is unable to produce usable results.

Valvejet Technology for the Production of a Personalised Fixed Dose Combination of Ramipril and Glimepiride: an Investigative Study on the Stability of Ramipril.

PURPOSE: To use valvejet technology for printing a fixed dose combination of ramipril and glimepiride, and to investigate the stability profile of ramipril, which is susceptible to a range of processing and storage conditions. METHODS: Inks of ramipril and glimepiride were formulated and printed on to HPMC film and the films were evaluated for the chemical and solid-state integrity of the APIs using HPLC and XRPD. The stability of the APIs in the inks and in the printed samples was investigated using Raman and NMR techniques. RESULTS: The printed samples demonstrated excellent precision and accuracy in the doses of APIs deposited. Both drugs were chemically intact in the freshly printed samples and ramipril was found to be in its amorphous form. Ramipril in the printed samples has transformed into ramipril diketopiperazine when stored at 40°C with 75% RH, but remained stable when stored in a desiccator. Results from the stability study of ramipril ink show that the API has undergone degradation when stored both at room temperature and at 40°C but remained stable when stored in a refrigerator. CONCLUSION: An FDC of ramipril and glimepiride was successfully printed using valvejet technology. The significance of inkjet printing in producing amorphous dosage forms from solution based inks and personalised dosage forms of drugs susceptible to processing conditions was demonstrated using ramipril. This study illustrates the significance of examining the stability of the APIs in the inks and the importance of appropriate storing of both the inks and printed samples.

Design, synthesis and evaluation of novel 2-butyl-4-chloroimidazole derived peptidomimetics as Angiotensin Converting Enzyme (ACE) inhibitors.

A series of novel 2-butyl-4-chloro-1-methylimidazole derived peptidomimetics were designed, synthesized and evaluated for their Angiotensin Converting Enzyme (ACE) inhibitor activity. 2-Butyl-4-chloro-1-methylimidazole-5-carboxylic acid 2 obtained after oxidation of respective carboxaldehyde 1, was condensed with various amino acid methyl esters 3a-k to give imidazole-amino acid conjugates 4a-k in very good yields. Ester hydrolysis of 4a-k with aqueous LiOH gave the desired peptidomimetics 5a-k. Screening all the new compounds 4a-k and 5a-k using ACE inhibition assay, resulted five compounds 4i, 4k, 5e, 5h and 5i as potent ACE inhibitors with IC50 of 0.647, 0.531, 1.12, 0.657 and 0.100µM with minimal toxicity. Among them, 5i emerged as most active ACE inhibitor with greater potency than marketed drugs Lisinopril, Ramipril and relatively equipotent to Benazepril, Quinapril and Enalapril.

Statistical optimization and in-vitro evaluation of hollow microcapsules of an anti-hypertensive agent.

The present work attempts to formulate and evaluate hollow microcapsules of an antihypertensive drug--ramipril, which will remain in vicinity of absorption site. The emulsion diffusion solvent evaporation method was employed for preparation of microspheres using Eudragit E100. Glycerol monostearate and sodium lauryl sulfate were used as surfactants, which showed good effect of film integrity. The different proportion of Eudragit E100 and ramipril at varying speed were employed for formulating hollow microspheres using 3(2) full factorial design. The formulated microspheres were subjected to evaluation of various parameters such as particle size analysis using motic microscope, drug loading efficiency and in vitro drug release. The main effect plot showed negative impact of polymer concentration and drug complex concentration, whereas positive impact of rotation speed on the % release of drug and drug encapsulation efficiency. The optimized batch of microcapsules was formulated as a hard gelatine capsule dosage form containing loading (plain drug) as well as sustained fraction of drug in form of microcapsules. It was found that dosage form also showed good in vitro release profile.

A quality by design approach using artificial intelligence techniques to control the critical quality attributes of ramipril tablets manufactured by wet granulation.

Quality by design (QbD) is an essential part of the modern approach to pharmaceutical quality. This study was conducted in the framework of a QbD project involving ramipril tablets. Preliminary work included identification of the critical quality attributes (CQAs) and critical process parameters (CPPs) based on the quality target product profiles (QTPPs) using the historical data and risk assessment method failure mode and effect analysis (FMEA). Compendial and in-house specifications were selected as QTPPs for ramipril tablets. CPPs that affected the product and process were used to establish an experimental design. The results thus obtained can be used to facilitate definition of the design space using tools such as design of experiments (DoE), the response surface method (RSM) and artificial neural networks (ANNs). The project was aimed at discovering hidden knowledge associated with the manufacture of ramipril tablets using a range of artificial intelligence-based software, with the intention of establishing a multi-dimensional design space that ensures consistent product quality. At the end of the study, a design space was developed based on the study data and specifications, and a new formulation was optimized. On the basis of this formulation, a new laboratory batch formulation was prepared and tested. It was confirmed that the explored formulation was within the design space.

Preparation and Evaluation of '3 Cap' Pulsatile Drug Delivery System of Ramipril.

BACKGROUND: Chronotherapeutics, the drug delivery based on circadian rhythm, is recently gaining much attention worldwide. Various diseases like asthma, hypertension, and arthritis show the circadian variation that demands time scheduled drug release for effective drug action. Therefore, the pulsatile drug delivery system has been designed to confer preprogrammed drug delivery. OBJECTIVE: In the present study, a '3 Cap' pulsatile drug delivery system has been developed, optimized, and characterized in order to achieve the floating and pulsatile release of ramipril. METHODS: An optimal response surface design was employed to investigate the effect of isopropanol: formaldehyde vapors for varying time on drug release from the capsules. '3 Cap' pulsatile drug delivery system was evaluated in terms of floating time, density, the effect of gastric flow rate, and type of dissolution apparatus on drug release. RESULTS: Independent variables exhibited a significant effect on the drug release of the prepared formulations. Results showed that time between the release of fractions of dose increased with an increase in formaldehyde: isopropanol ratio and duration of exposure to formaldehyde vapors with no effect of gastric flow rate. CONCLUSION: The results of the designed system revealed that an optimum exposure of 1:2 of isopropanol: formaldehyde vapors for sixty minutes resulted in the desired release of second pulse of dose after a predetermined lag time of 5 hours as desired. '3Cap' system was successful in achieving floating and pulsed release of hypertensive drug opening a 'new lease of life' to the existing drug molecule.

Sensitivity enhancement and matrix effect evaluation during summation of multiple transition pairs-case studies of clopidogrel and ramiprilat.

Sensitivity enhancement via summation of multiple MRM transition pairs is gaining popularity in tandem mass spectrometric assays. Numerous validation experiments describing the assays for two model substrates, clopidogrel and ramiprilat, were performed. The quantitation of clopidogrel was achieved by the summation of transition pairs m/z 322.2 to m/z 212.0 and m/z 322.2 to m/z 184.0, while that of ramiprilat was achieved by the summation of transition pairs m/z 389.2 to m/z 206.1 and m/z 389.2 to m/z156.1. The use of summation approach achieved sensitivities of >2 fold for both compounds as compared with the reported single MRM transition pair assays. The validation experiments addressed some important assay development issues, such as: (a) lack of impact of matrix effect; (b) unequivocal verification of the percentage contribution of each MRM transition pair towards sensitivity; (c) sensitivity enhancement factor achieved by summation approach of MRM transition pairs; and (d) accurate prediction of quality control samples using summation approach vs a single MRM transition pair. In summary, the appropriateness of using two MRM transition pairs for quantitation was demonstrated for both clopidogrel and ramiprilat. Additionally, pharmacokinetic application of the MRM transition pair assays using a summation approach was established for the two compounds.

The development and validation of a quality by design based process analytical tool for the inline quantification of Ramipril during hot-melt extrusion.

Continuous processing is superseding conventional batch processing as a means of manufacturing within the pharmaceutical research/industry. This paradigm shift has led to the implementation of Process Analytical Technology (PAT) as a semi-automatic, predictive tool offering real-time quality control that can be built into the production line. However, PAT tools have been mainly utilised to monitor a single process (e.g. powder blending, synthesis of biopharmaceuticals and small molecules) rather than a full continuous manufacturing process. In addition, there is a paucity of guidance documents that consider the continuous and dynamic conditions of real-time measurements for validation purposes. In this study, the feasibility of developing and validating a predictive and reliable Raman method based on quality by design (QbD) and PAT frameworks for the real-time quantification of Ramipril (RMP) during hot-melt extrusion (HME) were investigated. Through QbD, a design space elucidating the quality attributes of RMP stability was successfully identified based on offline HPLC measurements. Process temperature and powder feeding rate were the main quality attributes to affect the stability of RMP during HME. The optimum combination of process and formulation variables were extracted from the validated design space and used to extrude RMP at a concentration range of 2.5-12.5 %w/w. Three calibration models were established using PLS regression analysis. The developed PLS calibration models showed excellent linearity (R2 = 0.989, 0.995, 0.992), accuracy (RMSEcv = 0.31, 0.26, 0.30%) and specificity (PC1 = 81, 85, 89%) for models 1, 2 and 3, respectively. Furthermore, the developed QbD-PAT model was able to predict the quantity of RMP at varied process feed rate (10, 35 rpm) operating under long processing time (60 min). The output of this study allows in-process optimisation of formulation and process variables to control the quality and quantity of RMP during HME. Furthermore, it allows the implementation of PAT tools as routine methods of analysis within the laboratory.

Efficacy and tolerability of two formulations of ramipril in Korean adults with mild to moderate essential hypertension: an 8-week, multicenter, prospective, randomized, open-label, parallel-group noninferiority trial.

OBJECTIVE: This study was designed to compare the efficacy and tolerability of a new generic formulation of ramipril (test) and the branded formulation of ramipril (reference) to satisfy regulatory requirements for marketing of the generic product for use in Korean patients with mild to moderate hypertension. METHODS: This was an 8-week, multicenter, prospective, randomized, open-label, parallel-group non-inferiority trial in adult patients (age > 18 years) with mild to moderate essential hypertension (sitting dia-stolic blood pressure [SiDBP] 90-109 mm Hg). After a 2-week washout of previous antihypertensive medications, eligible patients were randomized to receive either ramipril 5 mg/d in the morning (low-dose group: baseline SiDBP 90-99 mm Hg) or ramipril 10 mg/d (high-dose group: baseline SiDBP 100-109 mm Hg) for the first 4 weeks. If SiDBP was > or = 90 mm Hg after 4 weeks of treatment, the dose was increased to 10 mg/d for the remaining 4 weeks in the low-dose group, and hydrochlorothiazide 12.5 mg was added to the regimen for the remaining 4 weeks in the high-dose group. The primary end point was the change in SiDBP from baseline to week 8. Secondary end points included a noninferiority analysis of the test and reference formulations with respect to the change in mean sitting systolic blood pressure (SiSBP) from baseline to week 8; SiDBP and SiSBP response rates (proportion of patients achieving an SiDBP < 90 mm Hg and SiSBP < 140 mm Hg, respectively) at 8 weeks; and changes from baseline in SiSBP, pulse wave velocity (PWV), exercise capacity, left-ventricular diastolic function (LVDF), and levels of brain natriuretic peptide (BNP) and high-sensitivity C-reactive protein (hs-CRP). Laboratory and clinical adverse events (AEs) were monitored at each study visit (4 and 8 weeks). RESULTS: The modified intent-to-treat population consisted of 89 patients (45 test, 44 reference; 60 men, 29 women; mean age, 49.7 years; mean weight, 69.9 kg). At week 8, mean (SD) SiSBP and SiDBP were significantly decreased from baseline in both groups (test: from 145.0 [9.7]/98.1 [5.3] mm Hg to 132.2 [11.1]/ 91.8 [7.1] mm Hg [P < 0.001]; reference: from 145.1 [11.4]/98.0 [5.7] mm Hg to 134.0 [14.6]/92.5 [7.9] mm Hg [P < 0.001]). The changes in blood pressure at week 8 did not differ significantly between the test and reference groups or between the low- and highdose groups in a subgroup analysis. Blood pressure response rates at 8 weeks did not differ significantly between the groups receiving the test and reference formulations (SiDBP: 26.7% and 31.8%, respectively; SiSBP: 37.8% and 40.9%). In addition, there were no significant between-group differences in the change in PWV (-63.8 and -38.7 cm/sec), LVDF at rest or after exercise, or levels of BNP or hs-CRP. The incidence of AEs was 64.4% in the test formulation group and 68.2% in the reference group formulation (P = NS). The most common AE in both groups was cough (10/45 [22.2%] and 10/44 [22.7%]). CONCLUSIONS: There were no significant differences in the efficacy and tolerability of the test and reference formulations of ramipril in these Korean adults with mild to moderate hypertension. The new generic formulation was noninferior to the reference formulation in terms of the change in SiDBP at week 8.

Quality and stability of ramipril generics/copies versus reference ramipril (Tritace): a 3-month stability comparative study.

OBJECTIVE: This study aimed to evaluate the quality and stability over time of marketed ramipril generics/copies, in terms of Sanofi-Aventis specifications, relative to that of the reference ramipril product Tritace. METHODS: The quality and dissolution profiles of 22 marketed generic/copy tablet formulations of ramipril (2.5 mg) were compared with the reference ramipril tablet (2.5 mg; Tritace). Samples were analysed for levels of ramipril and impurities (as determined by the level of the major metabolite ramipril-diketopiperazine) before and after storage under temperature-stressed conditions (40 degrees C and 75% relative humidity) for 1.5 and 3 months. Dissolution analyses were performed before and after 3 months' temperature-stressed storage. All analytical results were compared with Sanofi-Aventis specifications for the manufacture of the reference ramipril product. One batch per generic/copy drug was analysed. RESULTS: In terms of the level of ramipril, 24% (4/17) of generics/copies failed to meet reference ramipril specifications (90-105% of label claim) at baseline, increasing to 47% (8/17) after 3 months under stressed conditions. At baseline, the dissolution profiles of 24% (5/21) of generics/copies failed to meet the reference ramipril product specifications (>or=80% dissolved in 30 minutes), with the failure rate increasing to 57% (12/21) after storage for 3 months. Total levels of impurities were above reference ramipril product specifications (

Effect of Labrasol on self-nanoemulsification efficiency of ramipril nanoemulsion.

The purpose of the present investigation was to evaluate the capacity of Labrasol as surfactant for self-nanoemulsification efficiency of ramipril nanoemulsion formulation. Based on the solubility profile of ramipril, Sefsol-218, Labrasol and Carbitol were selected as oil phase, surfactant and cosurfactant, respectively. Based on the stability profile of ramipril, standard buffer solution of pH 5.0 was selected as an aqueous phase for the development of ramipril nanoemulsion formulation. Nanoemulsion formulations of ramipril were developed using an aqueous phase titration method. Pseudoternary phase diagrams were constructed to identify the nanoemulsion region. Selected formulations were subjected to different thermodynamic stability tests using centrifugation, heating cooling cycles and freeze thaw cycles. The formulations which were stable at thermodynamic stability tests were taken for self-nanoemulsification efficiency test. No creaming, cracking, coalescence or phase inversion was observed on most of the formulations upon thermodynamic stability tests. All the formulations passed self-nanoemulsification tests in grade C, D and E but not in grade A and B. Because none of the formulation passed self-nanoemulsification efficiency test in grade A and B, it was concluded that Labrasol is not suitable as surfactant for oral or self nanoemulsifying drug delivery system of ramipril.

The development of an inline Raman spectroscopic analysis method as a quality control tool for hot melt extruded ramipril fixed-dose combination products.

Currently in the pharmaceutical industry, continuous manufacturing is an area of significant interest. In particular, hot-melt extrusion (HME) offers many advantages and has been shown to significantly reduce the number of processing steps relative to a conventional product manufacturing line. To control product quality during HME without process interruption, integration of inline analytical technology is critical. Vibrational spectroscopy (Raman, NIR and FT-IR) is often employed and used for real-time measurements because of the non-destructive and rapid nature of these analytical techniques. However, the establishment of reliable Process Analytical Technology (PAT) tools for HME of thermolabile drugs is challenging. Indeed, the Raman effect is inherently weak and might be subject to interference. Moreover, during HME, heating and photodecomposition can occur and disrupt spectra acquisition. The aim of this research article was to explore the use of inline Raman spectroscopy to characterise a thermolabile drug, ramipril (RMP), during continuous HME processing. Offline measurements by HPLC, LC-MS and Raman spectroscopy were used to characterise RMP and its main degradation product, ramipril-diketopiperazine (RMP-DKP, impurity K). A set of HME experiments together with inline Raman spectroscopic analyses were performed. The feasibility of implementing inline Raman spectroscopic analysis to quantify the level of RMP and RMP-DKP in the extrudate was addressed. Two regions in the Raman spectrum were selected to differentiate RMP and RMP-DKP. When regions were combined, a principle component analysis (PCA) model defined by these two main components (PC 1 = 50.1% and PC 2 = 45%) was established. Using HPLC analyses, we were able to confirm that the PC 1 score was attributed to the level of RMP-DKP, and the PC 2 score was related to the RMP drug content. Investigation of the PCA scatterplot indicated that HME processing temperature was not the only factor causing RMP degradation. Additionally, the plasticiser content, feeding speed and screw rotating speed contributed to RMP degradation during HME processing.

Low temperature fused deposition modeling (FDM) 3D printing of thermolabile drugs.

Fused deposition modelling (FDM) is the most commonly investigated 3D printing technology for the manufacture of personalized medicines, however, the high temperatures used in the process limit its wider application. The objective of this study was to print low-melting and thermolabile drugs by reducing the FDM printing temperature. Two immediate release polymers, Kollidon VA64 and Kollidon 12PF were investigated as potential candidates for low-temperature FDM printing. Ramipril was used as the model low melting temperature drug (109 °C); to the authors' knowledge this is the lowest melting point drug investigated to date by FDM printing. Filaments loaded with 3% drug were obtained by hot melt extrusion at 70 °C and ramipril printlets with a dose equivalent of 8.8 mg were printed at 90 °C. HPLC analysis confirmed that the drug was stable with no signs of degradation and dissolution studies revealed that drug release from the printlets reached 100% within 20-30 min. Variable temperature Raman and solid state nuclear magnetic resonance (SSNMR) spectroscopy techniques were used to evaluate drug stability over the processing temperature range. These data indicated that ramipril did not undergo degradation below its melting point (which is above the processing temperature range: 70-90 °C) but it was transformed into the impurity diketopiperazine upon exposure to temperatures higher than its melting point. The use of the excipients Kollidon VA64 and Kollidon 12PF in FDM was further validated by printing with the drug 4-aminosalicylic acid (4-ASA), which in previous work was reported to undergo degradation in FDM printing, but here it was found to be stable. This work demonstrates that the selection and use of new excipients can overcome one of the major disadvantages in FDM printing, drug degradation due to thermal heating, making this technology suitable for drugs with lower melting temperatures.

A comparative study between hot-melt extrusion and spray-drying for the manufacture of anti-hypertension compatible monolithic fixed-dose combination products.

The purpose of this work was to investigate the application of different advanced continuous processing techniques (hot melt extrusion and spray drying) to the production of fixed-dose combination (FDC) monolithic systems comprising of hydrochlorothiazide and ramipril for the treatment of hypertension. Identical FDC formulations were manufactured by the two different methods and were characterised using powder X-ray diffraction (PXRD) and modulated differential scanning calorimetry (mDSC). Drug dissolution rates were investigated using a Wood's apparatus, while physical stability was assessed on storage under controlled temperature and humidity conditions. Interestingly both drugs were transformed into their amorphous forms when spray dried, however, hydrochlorothiazide was determined, by PXRD, to be partially crystalline when hot melt extruded with either polymer carrier (Kollidon® VA 64 or Soluplus®). Hot melt extrusion was found to result in significant degradation of ramipril, however, this could be mitigated by the inclusion of the plasticizer, polyethylene glycol 3350, in the formulation and appropriate adjustment of processing temperature. The results of intrinsic dissolution rate studies showed that hot-melt extruded samples were found to release both drugs faster than identical formulations produced via spray drying. However, the differences were attributable to the surface roughness of the compressed discs in the Wood's apparatus, rather than solid state differences between samples. After a 60-day stability study spray dried samples exhibited a greater physical stability than the equivalent hot melt extruded samples.

Liquid chromatography tandem mass spectrometry method for simultaneous determination of metoprolol tartrate and ramipril in human plasma.

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of metoprolol tartrate (MT) and ramipril, in human plasma. Both the drugs were extracted by liquid-liquid extraction with diethyl ether-dichloromethane (70:30, v/v). The chromatographic separation was performed on a reversed-phase C8 column with a mobile phase of 10 mM ammonium formate-methanol (3:97, v/v). The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The method was validated over the concentration range of 5-500 ng/ml for metoprolol and ramipril in human plasma. The precursor to product ion transitions of m/z 268.0-103.10 and m/z 417.20-117.20 were used to measure metoprolol and ramipril, respectively.

Development and bioavailability assessment of ramipril nanoemulsion formulation.

The objective of our investigation was to design a thermodynamically stable and dilutable nanoemulsion formulation of Ramipril, with minimum surfactant concentration that could improve its solubility, stability and oral bioavailability. Formulations were taken from the o/w nanoemulsion region of phase diagrams, which were subjected to thermodynamic stability and dispersibility tests. The composition of optimized formulation was Sefsol 218 (20% w/w), Tween 80 (18% w/w), Carbitol (18% w/w) and standard buffer solution pH 5 (44% w/w) as oil, surfactant, cosurfactant and aqueous phase, respectively, containing 5 mg of ramipril showing drug release (95%), droplet size (80.9 nm), polydispersity (0.271), viscosity (10.68 cP), and infinite dilution capability. In vitro drug release of the nanoemulsion formulations was highly significant (p<0.01) as compared to marketed capsule formulation and drug suspension. The relative bioavailability of ramipril nanoemulsion to that of conventional capsule form was found to be 229.62% whereas to that of drug suspension was 539.49%. The present study revealed that ramipril nanoemulsion could be used as a liquid formulation for pediatric and geriatric patients and can be formulated as self-nanoemulsifying drug delivery system (SNEDDS) as a unit dosage form.

Spectrophotometric and spectrofluorimetric methods for the determination of ramipril in its pure and dosage form.

This paper describes three sensitive spectrophotometric and spectrofluorimetric methods for determination of ramipril in its pure form and pharmaceutical tablets. The first method is based on the oxidation of the drug with 1-chlorobenzotriazole reagent (CBT) in strong alkaline medium followed by measuring the absorbance at 350 nm. The method obeys Beer's law over concentration range 15-50 microg ml(-1). For the second and third, both are non-extractive methods based on the formation of ternary complex between copper (II), eosin and ramipril in the presence of methylcellulose as surfactant. Spectrophotometrically, under the optimum condition, the ternary complex showed an absorption maximum at 543 nm. The method obeys Beer's law over concentration range of 20-80 microg ml(-1). A fluorescence quenching method for the determination of ramipril by forming this ternary complex was also investigated for the propose of enhance the sensitivity of the determination. The methods are simple, sensitive, and accurate. The results obtained are reproducible with a coefficient of variation less than 2%. The proposed have been successfully applied to the assay of ramipril in tablets. The results compare favorably with official method.

Poly (amidoamine) dendrimer-mediated hybrid formulation for combination therapy of ramipril and hydrochlorothiazide.

We present a dendrimer-based hybrid formulation strategy to explore the potential of poly (amidoamine) PAMAM dendrimers to be used as drug carriers for combination therapy of an anti-hypertensive drug ramipril (RAPL) and a diuretic hydrochlorothiazide (HCTZ). The drug-dendrimer complexes were prepared by phase-equilibration method. The results showed that the solubility of RAPL and HCTZ was dependent on dendrimer concentration and pH of dendrimer solution. The solubility profile of both RAPL and HCTZ dendrimer complexes illustrated a non-linear relationship with dendrimer concentration. At 0.8% (w/v) dendrimer concentration, solubility of RAPL was increased 4.91 folds with amine-terminated while for HCTZ, solubility enhancement was highest (3.72 folds) with carboxy-terminated. The complexes were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance analysis and high performance liquid chromatography. In-vitro drug dissolution performance of pure drugs, individual drug loaded dendrimer formulations and hybrid formulations was studied in USP dissolution medium (pH7.0) and in simulated gastric fluid (pH1.2). Dendrimer mediated formulations showed faster and complete dissolution compared to pure RAPL or HCTZ. Surprisingly, similar pattern of dissolution profile was established with hybrid formulations as compared to individual drug loaded dendrimers. The dendrimer-based hybrid formulations were found to be stable at dark and refrigerated conditions up to 5weeks. Conclusively, the proposed formulation strategy establishes a novel multitasking platform using dendrimer for simultaneous loading and delivery of multiple drugs for pharmaceutical applications.

Biowaiver Eligibility of a Lower Strength Ramipril/Hydrochlorothiazide Immediate Release Tablets Using a New Validated HPLC Analytical Method.

Bioequivalence studies are expensive, time consuming and invasive to humans. Accordingly, an alternative in vitro study (biowaivers) has been introduced for drugs which belong to BCS class I and III and for other strengths of already approved higher drug strength. The main objective of this study was to prove the biowaiver eligibility of a lower strength Ramipril/Hydrochlorothiazide (2.5/12.5 mg) tablets. Visual and pharmacopoeial quality tests were performed on the higher and lower generic and on the reference listed drug to determine whether they are pharmaceutically equivalent. All products were investigated using the biowaiver criteria. Dissolution profiles were conducted at pH values 1.2, 4.5 and 6.8. Difference factor (f1) and similarity factor (f2) were calculated. The tested products were successfully complied with pharmacopeial requirements. f1 was below 15 and f2 was above 50 in all dissolution conditions. Precisely, Ramipril showed release higher than 85% within 15 min. f1 and f2 for Hydrochlorothiazide were 8 and 61 respectively at the recommended discriminative pH media.These results suggest that the current biowaiver criteria could be a sufficient guarantee of bioequivalence of the lower strength of Ramizide assuming that the product is manufactured at the same site and contains same quality and grade of excipients and in a proportional amounts.

Stability of ramipril in the solvents of different pH.

The stability of ramipril in the buffer solution with different pH and the influence of acid, alkaline and oxidative medium on ramipril stability were studied. The ramipril degradation products were determined by high-performance liquid chromatography (HPLC) method. Acetonitrile:sodium perchlorate was used as the mobile phase, at a flow rate of 1.0 ml/min (linear gradient elution). A Nucleosil 100-S 5 microm C18, 250 mm x 4.6 mm i.d. was utilized as stationary phase. Detection was affected spectrophotometrically at 210 nm. The drug substance was dissolved in the ammonium phosphate buffer (pH 3, 5 and 8) and these solutions were stored at 90 degrees C for 1 h. The other series of test solutions were prepared from stock solution (drug substance dissolved in solvent A of the mobile phase) by dilution in acid (0.1M HCl), alkaline (0.1M NaOH) and oxidative (hydrogen peroxide solution) medium. More then 0.2% of impurity D (ramipril-diketopiperazine) was detected in the buffer of pH 3 and pH 5. In the buffer of pH 8 there was detected more then 1% of impurity E (ramipril-diacid). No peaks for degradation products appeared in the chromatograms above limit of quantification. The alkaline medium has the greatest effect on degradation of ramipril into impurity E (more than 50%).