Effect of Formulation Parameters on Enalapril Maleate Mucoadhesive Buccal Tablet Using Quality by Design (QbD) Approach.

The buccal route has great prospects and possible benefits for the administration of drugs systemically. The present study involves designing, developing and optimising the buccal tablet formulation of Enalapril Maleate (EM) by using the QbD approach. We prepared the EM buccal tablets using the dry granulation method. In the QTPP profile, the CQAs for EM buccal tablets are Mucoadhesive strength, swelling index and drug release (dependent variables); the CMAs identified for EM buccal tablets were Carbopol 934P, HPMC-K100M and chitosan (independent variables). Diluent quantity, blending time and compression force were selected as CPPs; the Box-Behnkentdesign was used to evaluate the relationship between the CMAs and CPPs. Based on the DoE, the composition of the optimised formulation of EM BT-18 consists of 20mg of EM, 15 mg of carbopol 934p, 17 mg of HPMC-K100M, 10mg of chitosan, 30 mg of PVP K-30, 1 mg of magnesium stearate, 16 mg of Mannitol, 1 mg of aspartame, and 50 mg of Ethyl cellulose. The optimised formulation of EM BT 18 was found to have a Mucoadhesive strength of 24.32±0.30g. The swelling index was 90.74±0.25% and drug release was sustained up to 10 hours 98.4±3.62% compared to the marketed product, whose release was up to 8 hours. We attempted to design a buccal tablet of Enalapril Maleate for sustained drug release in the treatment of hypertension. Patients who cannot take oral medication due to trauma or unconscious conditions could receive the formulation. Development of a newly P.ceutical product is very time-consuming, extremely costly and high-risk, with very little chance of a successful outcome. Hence, this study showed EM tablets are already available on the market but we have chosen a buccal drug delivery system using a novel approach using QbD tools to target the quality of the product accurately.

Studies on charge transfer of enalapril maleate: from solid-state to molecular dynamics.

INTRODUCTION: Enalapril maleate is an antihypertensive ethyl ester pro-drug with two crystalline forms. A network of hydrogen bonds in both polymorphs plays an important role on solid-state stability, charge transfer process and degradation reactions (when exposed to high humidity, temperature and/or pH changes). COMPUTATIONAL PROCEDURES: Supramolecular arrangement was proposed by Hirshfeld surface using the CrystalExplorer17 software and quantum theory of atoms in molecules. The electronic structure properties were calculated using the functional hybrid M06-2X with 6-311++G** base function employing diffuse and polarization functions to improve the description of hydrogen atoms on intermolecular interactions. Also, the H+ charge transfer between enalapril and maleate molecules was performed using Car-Parrinello molecular dynamics with the Verlet algorithm. In both simulations, the temperature of the ionic system was maintained around 300 K using the Nosé-Hoover thermostat and the electronic system evolved without the use of the thermostat. RESULTS: This work evaluates the effect of maleate on the structural stability of enalapril maleate solid state. The electronic structural analysis points out a partially covalent character for N1-H∙∙∙O7 interaction; and the molecular dynamic showed a decentralized hydrogen on maleate driving a decomposition by charge transfer process while a centered hydrogen driving the stabilization. The charge transfer process and the mobility of the proton (H+) between enalapril and maleate molecules was demonstrated using supramolecular modeling analyses and molecular dynamics calculations.

Evaluation of two novel co-processed excipients for direct compression of orodispersible tablets and mini-tablets.

Pediatric, geriatric, and other patients who suffer from swallowing difficulties represent a special patient group, where an increased need in appropriate formulation development is required. To overcome these mostly swallowability linked issues, orodispersible tablets (ODTs) and orodispersible mini-tablets (ODMTs) can be seen as a suitable alternative to improve compliance. Orodispersible tablets are oral solid dosage forms which rapidly disintegrate after contact with saliva, leaving a liquid dispersion, which can be easily swallowed. To fulfil the required quality criteria and optimize the formulations regarding tensile strength and disintegration time, co-processed excipients (CPE) based on mannitol are frequently used in the manufacturing of orodispersible tablets. This study aimed to systematically compare two new CPEs, namely Granfiller-D® and Hisorad® and evaluate their potential in future OD(M)T formulations with already marketed products. The performance of the CPEs was examined in combination with three different APIs. Disintegration time, sufficient mechanical strength and content uniformity for low dosed formulation were chosen as main quality aspects. Conventionally sized tablets (9 mm) with 50% drug load of ibuprofen and paracetamol were produced with each CPE. Low dosed OD(M)Ts with a drug load of 4% enalapril maleate were manufactured to study content uniformity. Large differences were visible in the formulations containing ibuprofen and only Hisorad® allowed to compress ODT fulfilling the specifications of Ph.Eur. and FDA regarding disintegration times (180 s and 30 s, respectively). For the poorly binding model drug paracetamol, none of the studied excipients showed a satisfactory performance, with maximum tensile strengths < 1 MPa. To reach content uniformity in low dosed ODMTs, Ludiflash® seems to be the most preferable alternative, as the formulation showed the lowest acceptance values (AV) according to Ph.Eur. (<4) as well as the smallest coefficient of variation (CV) in API content (CV < 2%). In conclusion, the study revealed that none CPE is the ideal choice for all approaches, but different CPEs should be selected dependent on different challenges during formulation development of OD(M)Ts.

Simulation and Assignment of the Terahertz Vibrational Spectra of Enalapril Maleate Cocrystal Polymorphs.

The identification of crystalline drug polymorphs using terahertz vibrational spectroscopy is a powerful approach for the nondestructive and noninvasive characterization of solid-state pharmaceuticals. However, a complete understanding of the terahertz spectra of molecular solids is challenging to obtain because of the complex nature of the low-frequency vibrational motions found in the sub-3 THz (sub-100 cm-1) range. Unambiguous assignments of the observed spectral features can be achieved through quantum mechanical solid-state simulations of crystal structures and lattice vibrations utilizing the periodic boundary condition approach. The terahertz spectra of two polymorphs of enalapril maleate are presented here to demonstrate that even large pharmaceuticals can be successfully modeled using solid-state density functional theory, including cocrystalline solids comprised of multiple distinct species. These simulations enable spectral assignments to be made, but also provide insights into the conformational and cohesion energies that contribute to the polymorph stabilities. The results reveal that the Form II polymorph of enalapril maleate is the more stable of the two under ambient conditions, and that this stability is driven by a greater intermolecular cohesion energy as compared to Form I.

Validated LC-MS/MS method for the simultaneous determination of enalapril maleate, nitrendipine, hydrochlorothiazide, and their major metabolites in human plasma.

Hypertension is a major risk factor for atherosclerosis and ischemic heart disease. Most hypertensive patients need a combination of antihypertensive agents to achieve therapeutic goals. A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometric method was developed and validated for simultaneous determination of enalapril maleate (ENA) and its major metabolite enalaprilat (ENAT), nitrendipine (NIT) and its major metabolite dehydronitrendipine (DNIT), and hydrochlorothiazide (HCT) in human plasma using felodipine as an internal standard (IS). The drugs were extracted from plasma using one-step protein precipitation. Chromatographic separation was performed on a Symmetry C18 column, with water and acetonitrile (10:90, v/v) as mobile phase. The detection was carried out using multiple reaction monitoring mode and coupled with electrospray ionization source. Multiple reaction monitoring transitions were m/z 377.1 → 234.1 for ENA, m/z 349.2 → 206.1 for ENAT, m/z 361.2 → 315.1 for NIT, m/z 359 → 331 for DNIT, m/z 295.9 → 205.1 for HCT, and m/z 384.1 → 338 for felodipine (IS). The method was linear over concentration ranges of 1-200, 20-500, 5-200, 2-100, and 5-200 ng/mL for ENA, ENAT, NIT, DNIT, and HCT, respectively, with r2 ≥ 0.99. Method validation was performed according to U.S. Food and Drug Administration guidelines. The validated method showed good sensitivity and selectivity and could be applied for therapeutic drug monitoring and bioequivalence studies.

New Orodispersible Mini Tablets of Enalapril Maleate by Direct Compression for Pediatric Patients.

BACKGROUND: In many countries, hypertension in the pediatric population is considered a serious risk of mortality and morbidity. In this respect, it is central to design and develop new pharmaceutical forms for pediatric patients with hypertension. The development of Orodispersible Mini-Tablets (ODMTs) for pediatric use has gained importance in recent years. Therefore, regulations for developing suitable and palatable dosage forms for pediatric patients have been established by WHO authorities. OBJECTIVE: This study aimed to design and develop orodispersible mini tablets of enalapril maleate (EnM ODMTs) for pediatric use. METHODS: Five pharmaceutical formulations (A, B, C, D and E, shown in Table 1) were designed. The effects of different co-processed excipients and active pharmaceutical ingredients at different doses were studied. Lactose co-processed excipients selected were the following: Tablettose® 80, Microce- Lac® 100 and StarLac®. The micromeritic properties for all the physical mixtures were examined. The mini tablets were obtained by direct compression. Quality control parameters were determined in accordance with US Pharmacopeia. RESULTS: Three OMDTs with StarLac® showed good results of hardness, flow ability and fast disintegration. The formulation with 0.1 mg of enalapril maleate presented the best results for the official parameters of hardness (4.0 kp), friability (< 1%), disintegration time (28 s), drug content uniformity (103.6 %), and wetting time (23 s). CONCLUSION: The three OMDTs with StarLac® showed good quality parameters, according to official requirements. Formulation A exhibited the best wetting time, complying with the dose recommended for pediatric patients. This formulation could be considered eligible for being manufactured at industrial scale.

Microwave assisted synthesis of polyacrylamide grafted polymeric blend of fenugreek seed mucilage-Polyvinyl alcohol (FSM-PVA-g-PAM) and its characterizations as tissue engineered scaffold and as a drug delivery device.

Microwave assisted synthesis of graft copolymer of polymeric blend of Fenugreek seed mucilage (FSM)-Polyvinyl alcohol (PVA) with acrylamide (AM) was done by free radical polymerization using ammonium per sulfate (APS) as initiator. Varying amount of AM and APS was used to optimize the best grade based on highest percentage grafting efficiency and investigated with intrinsic viscosity measurement, Fourier Transformation infrared spectroscopy (FTIR),13C NMR spectra, X-ray diffraction, elemental analysis, Thermogravimetric analysis, Scanning electron microscopy. The results of intrinsic viscosity indicate that the optimized sample GF4 has longer chain length than in comparison to the native mucilage and thus exhibits more swelling tendencies and thus can be used as very good controlled release matrix system. The thermal analysis and X-ray indicates that GF4 is more stable and possess more amorphous properties than the native FSM. The NMR and FT-IR studies reveal that in GF4 there is prominent presence of amide and the hydroxyl groups indicating that grafting mechanism has efficiently taken place. Histological studies & SEM image for optimized grade implanted on animals revealed sufficient tissue growth and exhibited biodegradability proving the material to be biocompatible and suitable to be used as tissue engineered scaffolds. The controlled release behavior of the optimized polymeric system GF4 was evidenced by 95% release of loaded drug Enalapril maleate for 16 h. Graphical abstract.

New orodispersible mini-tablets for paediatric use - A comparison of isomalt with a mannitol based co-processed excipient.

The development of orodispersible mini-tablets (ODMTs) for paediatric use has gained importance within recent years as European authorities set up regulations for developing suitable and palatable dosage forms for paediatric patients. Polyols like mannitol and isomalt are frequently used in the manufacture of tablets where sensory properties have to be taken into account. In literature, ODTMs based on a commercialized co-processed excipient based on mannitol (Ludiflash®) have been already described. Isomalt is known for its pleasant sensory properties and therefore appears to be a good candidate for ODMTs. The feasibility of the direct compression grade of isomalt for the manufacture of ODMTs was assessed and compared to Ludiflash®. Hydrochlorothiazide and enalapril maleate were chosen as model drugs and compressed to 2 mm mini-tablets. ODMTs could be obtained fulfilling the criteria of Ph.Eur. with disintegration times of 180 s or even the FDA limit of 30 s. Dissolution studies and mass variation were fulfilled for all mini-tablets. Acceptance values (AV) ≤ 15 were achieved for formulations based on both isomalt and Ludiflash®. Stability data showed the change of disintegration time and tensile strength as a function of storing time, condition and excipient. Both excipients showed their potential for ODMTs for paediatric use.

Continuous Flow Synthesis of ACE Inhibitors From N-Substituted l-Alanine Derivatives.

A strategy for the continuous flow synthesis of angiotensin converting enzyme (ACE) inhibitors is described. An optimization effort guided by in situ IR analysis resulted in a general amide coupling approach facilitated by N-carboxyanhydride (NCA) activation that was further characterized by reaction kinetics analysis in batch. The three-step continuous process was demonstrated by synthesizing 8 different ACE inhibitors in up to 88 % yield with throughputs in the range of ≈0.5 g h-1 , all while avoiding both isolation of reactive intermediates and process intensive reaction conditions. The process was further developed by preparing enalapril, a World Health Organization (WHO) essential medicine, in an industrially relevant flow platform that scaled throughput to ≈1 g h-1 .

Potential Angiotensin Converting Enzyme Inhibitors from Moringa oleifera.

BACKGROUND: Hypertension is the chronic medical condition and it affected billions of people worldwide. Natural medicines are the main alternatives to treatment for a majority of people suffering from hypertension. Niazicin-A, Niazimin-A, and Niaziminin-B compounds from Moringa oleifera ethanolic leave extract were reported to have potent antihypertensive activity. OBJECTIVE: These compounds were targeted with Angiotensin-converting enzyme [ACE] which is one of the main regulatory enzymes of the renin-angiotensin system. METHODS: Protein-ligand docking of these compounds with [ACE] [both domain N and C] was conceded out through Autodock vina and visualization was done by chimera. Pharmacokinetics study of these compounds was predicted by ADME-Toxicity Prediction. RESULTS: Niazicin-A, Niazimin-A, and Niaziminin-B showed high binding affinity with ACE and partially blocked the active sites of the enzyme. Niazicin-A, Niazimin-A and Niaziminin-B showed the estimated free binding energy of -7.6kcal/mol kcal/mol, -8.8kcal/mol and -8.0kcal/mol respectively with C-domain of ACE and -7.9kcal/mol, -8.5kcal/mol and -7.7kcal/mol respectively with N-domain of ACE. The compounds showed better binding energy with angiotensinconverting enzyme in comparison to Captopril -5.5kcal/mol and -5.6kcal/mol and Enalapril [standard] -8.4kcal/mol and -7.5kcal/mol with C and N domain, respectively. CONCLUSION: Computationally, the selected bioactive molecules have shown better binding energy to known standard drugs which have been already known for inhibition of ACE and can further act as a pharmacophore for in vitro and in vivo studies in the development of alternative medicine.

Taste Masking of Enalapril Maleate by the Precipitation Method.

BACKGROUND: Taste masking of bitter or unpleasant drugs is an important prerequisite to improve patient compliance, especially for children and elderly patients. We aimed at obtaining taste-masked microparticles intended for incorporation into orodispersible tablets (ODTs). We selected the precipitation method using enalapril maleate (ENA) as a model bitter-tasting drug and Eudragit EPO® as a pH sensitive polymer. AIM: The aim of this study was to obtain microparticles with enalapril maleate by the precipitation method in order to mask the bitter taste of the drug. MATERIALS AND METHODS: Nine models of enalapril maleate ­ Eudragit EPO® microparticles were prepared by the precipitation method at varied drug-polymer ratios. The models were characterized in terms of size, shape, production yield, drug content, encapsulation efficiency and moisture content. Fourier-transformed infrared spectroscopy, powder X-ray diffraction and differential scanning calorimetry were used to analyze possible interactions in the complex. In vitro drug release in simulated salivary fluid and in vivo taste evaluation in rats were realized to prove taste masking. RESULTS: The particle size distribution varied from 266.9 µm to 410.9 µm. The shape of the resulting particles was irregular. The production yield varied from 23.6% to 78.2%. The drug content ranged between 2.3% to 4.8%, encapsulation efficiency increased from 1.6% to 9.0%. In vitro drug release data indicated significant taste masking. CONCLUSION: Some of the obtained microparticles by the precipitation method showed satisfactory taste masking efficiency, which proved the taste masking feasibility of this method.

From 'fixed dose combinations' to 'a dynamic dose combiner': 3D printed bi-layer antihypertensive tablets.

There is an increased evidence for treating hypertension by a combination of two or more drugs. Increasing the number of daily intake of tablets has been reported to negatively affect the compliance of patients. Therefore, numerous fixed dose combinations (FDCs) have been introduced to the market. However, the inherent rigid nature of FDCs does not allow the titration of the dose of each single component for an individual patient's needs. In this work, flexible dose combinations of two anti-hypertensive drugs in a single bilayer tablet with a range of doses were fabricated using dual fused deposition modelling (FDM) 3D printer. Enalapril maleate (EM) and hydrochlorothiazide (HCT) loaded filaments were produced via hot-melt extrusion (HME). Computer software was utilised to design sets of oval bi-layer tablets of individualised doses. Thermal analysis and x-ray diffractometer (XRD) indicated that HCT remained crystalline in the polymeric matrix whilst EM appeared to be in an amorphous form. The interaction between anionic EM and cationic methacrylate polymer may have contributed to a drop in the glass transition temperature (Tg) of the filament and obviated the need for a plasticiser. Across all tablet sets, the methacrylate polymeric matrix provided immediate drug release profiles. This dynamic dosing system maintained the advantages of FDCs while providing a superior flexibility of dosing range, hence offering an optimal clinical solution to hypertension therapy in a patient-centric healthcare service.

Continuous inkjet printing of enalapril maleate onto orodispersible film formulations.

Piezoelectric inkjet printing onto orodispersible films (ODFs) was proven to be a successful technique applying flexible doses of active pharmaceutical ingredients (APIs) onto edible substrates. The reported API printing and ODF production was conducted in a non-continuous production approach. Within this study, drug-free and hydrochlorothiazide (HCT) containing ODFs should be imprinted in-line with enalapril maleate (EM) ink during continuous ODF production. Macrogol inks based on various solvents and solvent-water mixtures were developed providing dynamic viscosities from 7 to 17 mPa*s. Water based inks contained 1.25%, methanol based inks up to 10% EM. Both inks could be printed (500-1000 Hz) during continuous ODF production. No EM recrystallization was observed for water-based inks. Mechanical properties were not affected by drug printing using various firing frequencies. ODF imprinted with water-based EM inks contained 0.04 mg EM/6 cm2. EM amount can be increased to a paediatric therapeutic dose of 0.5 mg EM utilizing methanol-based inks. These inks were successfully printed onto HCT ODFs resulting in a therapeutically relevant fixed-dose combination. No EM migration into the HCT layer could be observed. In conclusion, it was feasible to print EM doses onto drug-free and HCT ODFs during an in-line continuous manufacturing process.

Continuous manufacturing and analytical characterization of fixed-dose, multilayer orodispersible films.

Various drug therapies require more than one active pharmaceutical ingredient (API) for an effective treatment. There are many advantages, e.g. to improve the compliance or pharmacodynamic response in comparison to a monotherapy or to increase the therapy safety. Until now, there are only a few products available for the paediatric population due to the lack of age appropriate dosage forms or studies proving the efficacy and safety of these products. This study aims to develop orodispersible films (ODFs) in a continuous solvent casting process as child appropriate dosage form containing both enalapril maleate (EM) and hydrochlorothiazide (HCT) separated in different film layers. Furthermore, they should be characterised and the API migration analysed by confocal Raman microscopy (CRM). ODFs were successfully produced in a continuous manufacturing process in form of double- and triple-layer formulations based on hydroxypropylcellulose (HPC) or a combination of HPC and polyvinyl alcohol (PVA). CRM revealed that both APIs migrate within the film layers shortly after manufacturing. PVA inhibits the migration inside the double-layer film, but is not able to prevent the API migration as an interlayer inside a triple-layer ODF. With increasing film layers, the content of residual solvents and the disintegration time increases (mono-layer films: <10 s, triple-layer films: 37 s). In conclusion, it was feasible to produce fixed-dose combinations in therapeutic doses up to 9 mg HCT and 3.5 mg EM for the double-layer film with adequate mechanical properties, which enable coiling up onto jumbo rolls directly after production. The best separation of the two APIs was achieved by casting a double-layer ODF consisting of different film forming polymers, which can be beneficial when processing two incompatible APIs.

A series of N-of-1 trials to assess the therapeutic interchangeability of two enalapril formulations in the treatment of hypertension in Addis Ababa, Ethiopia: study protocol for a randomized controlled trial.

BACKGROUND: Hypertension is one of the leading causes of morbidity and mortality in Ethiopia. Treatment usually involves lifelong medication use. Enalapril is a common drug for the treatment of hypertension in Ethiopia. However, the drug is expensive and, therefore, there is limited capacity for people to afford the treatment. Locally produced Enalapril is a cost-effective solution to treat the disease. However, as local medicines regulation does not include bioequivalence tests on locally produced drugs, physicians and patients need assurance about the effectiveness and safety of local generics. Evidence on therapeutic equivalence is needed on these untested local drugs. METHODS: This is a hospital-based, randomized, partially blinded, three-cycle crossover trial in single patients, comparing a locally produced version of enalapril with enalapril imported from Europe. Patients involved in this trial are not blinded, as there is no local facility to produce relatively small numbers of placebos or encapsulated drugs. To ensure blinding of study investigators and data analysts, study medications are prepared by an independent pharmacy unit using opaque medication packaging. The importance of maintaining blinding is also part of patient pre-trial education. Each N-of-1 trial will consist of three successive 14-day treatment pairs, each pair comprising 7 days of 5-20 mg local and 7 days of 5-20 mg imported enalapril taken once daily in the morning. The primary outcome will be the average difference in systolic blood pressure as measured by home blood pressure measurements. DISCUSSION: The number of locally produced products, such as enalapril, being approved without proof of bioequivalence is dramatically increasing. By bridging the information gap on bioequivalence, the trial will give rigorous evidence on therapeutic equivalence of locally produced enalapril in the treatment of hypertension. If there is no difference, the hypothesized result, then patients can take the local medicine with confidence. This trial will also will determine whether aggregated N-of-1 studies are feasible to evaluate untested generic drugs in resource-limited countries where bioequivalence testing centers are unavailable. TRIAL REGISTRATION NUMBER: Australian and New Zealand Clinical Trial Registry, ID: ACTRN12616001088437p . Registered on 12 August 2016.

User-Friendly HPLC Method Development and Validation for Determination of Enalapril Maleate and Its Impurities in Enalapril Tablets.

The official method for the determination of Enalapril Maleate and its related substances in European Pharmacopoeia (EP) is a gradient liquid chromatographic method. The method used styrene-divinylbenzene copolymer column, mobile phase buffer pH 6.8 and column oven temperature 70°C. In this method, the separation between main component Enalapril and Ph. Eur. Imp-A was not completed hence the achieving system suitability requirement is a tough task and it requires quite often adjustment in chromatographic parameters. Moreover, column oven temperature 70°C is not user friendly to HPLC instruments and users. In this study, several changes were introduced to the method in order to improve the separation, peak shapes and to overcome the column oven temperature. A new user-friendly stability-indicating RP-HPLC method was developed for Enalapril related substances analysis. The developed method uses a ZORBAX Eclipse XDB-C18 column with column oven temperature at 55°C and mobile phase containing acetonitrile and a phosphate buffer at pH 3.0. The method is capable of separating all the known impurities with resolution more than 3.5, which is much better than that obtained with the existing monograph methods. The optimized method was validated and demonstrated to have acceptable specificity, sensitivity, linearity, accuracy, precision, robustness, solution stability and equivalency to the EP method. The developed method proved to be applicable to a wide number of C18 reversed-phase columns. In addition, the Enalapril assay method also presented with 20 min run time.

Increased drug load and polymer compatibility of bilayered orodispersible films.

The addition of enalapril maleate to a casting solution for orodispersible films (ODFs) containing hypromellose and carbomer 974P as film forming agents (standard casting solution, SCS) caused a dose dependent reduction of the viscosity. This phenomenon was a serious problem in the preparation of ODFs with an increased enalapril load (>1mg per ODF) when using the solvent casting method. The aim of the present work was twofold. Firstly, the influence of enalapril on the viscosity of SCS was studied in more detail. Secondly, two methods for increasing the enalapril load of an ODF were investigated that did not negatively influence the properties of SCS. The casting height was increased and the preparation of bilayered ODF, using the double-casting method, was explored. In the framework of the bilayered ODFs the compatibility between the film forming agents hydroxypropyl cellulose (HPC), sodium alginate (SA), hydroxyethyl cellulose (HEC) and the combination hypromellose-carbomer 974P (SCS) was investigated. RESULTS AND CONCLUSIONS: We found that enalapril concentration dependently reduced the pH, thereby negatively influencing the gel formation and the viscosity of SCS. An increased casting height did not result in a proportionally increased enalapril load. The enalapril load could be doubled when a bilayered ODF containing two layers of SCS was produced. Finally, not all combinations of film forming agents could be used for the preparation of bilayered ODFs. Besides, the sequence in which the different polymer layers were casted affected the appearance of the ODFs. In conclusion, the best formulations were produced with the polymer combinations SCS/SCS and SCS/HPC.

Biowaiver Monographs for Immediate-Release Solid Oral Dosage Forms: Enalapril.

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence testing for the marketing authorization of immediate-release, solid oral dosage forms containing enalapril maleate are reviewed. Enalapril, a prodrug, is hydrolyzed by carboxylesterases to the active angiotensin-converting enzyme inhibitor enalaprilat. Enalapril as the maleate salt is shown to be highly soluble, but only 60%-70% of an orally administered dose of enalapril is absorbed from the gastrointestinal tract into the enterocytes. Consequently, enalapril maleate is a Biopharmaceutics Classification System class III substance. Because in situ conversion of the maleate salt to the sodium salt is sometimes used in production of the finished drug product, not every enalapril maleate-labeled finished product actually contains the maleate salt. Enalapril is not considered to have a narrow therapeutic index. With this background, a biowaiver-based approval procedure for new generic products or after major revisions to existing products is deemed acceptable, provided the in vitro dissolution of both test and reference preparation is very rapid (at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Additionally, the test and reference product must contain the identical active drug ingredient.

Rapid analysis of drug dissolution by paper spray ionization mass spectrometry.

With a great quantity of solid dosage tested by dissolution technology, developing a rapid and sensitive method to access the content of drug within dissolution media is highly desired by analysts and scientists. Traditionally, dissolution media is not compatible with mass spectrometry since the inorganic salts in the media might damage the mass spectrometer. Here, paper spray ionization mass spectrometry (PSI-MS), one of the ambient mass spectrometry technologies, is developed to characterize the content of drugs in dissolution media. The porous structure of paper can effectively retain salts from entering mass spectrometer. This makes the measurement of drug content within dissolution media by mass spectrometer possible. After the experimental parameters were optimized, calibration curves of model drugs - enalapril, quinapril and benazepril were established by using corresponding deuterated internal standards. PSI-MS was then deployed to characterize the content of enalapril from the dissolution testing of enalapril tablets. The results from PSI-MS are comparable to those from HPLC characterization. More importantly, the analysis time of 6 samples is shortened from 90min to 6min. Detection limit of enalapril maleate tablets by PSI-MS is 1/300 of LC. PSI-MS is rapid, sensitive and accurate in analyzing drug content from dissolution tests.

Development and validation of multivariate calibration methods for simultaneous estimation of Paracetamol, Enalapril maleate and hydrochlorothiazide in pharmaceutical dosage form.

Three multivariate calibration spectrophotometric methods were developed for simultaneous estimation of Paracetamol (PARA), Enalapril maleate (ENM) and Hydrochlorothiazide (HCTZ) in tablet dosage form; namely multi-linear regression calibration (MLRC), trilinear regression calibration method (TLRC) and classical least square (CLS) method. The selectivity of the proposed methods were studied by analyzing the laboratory prepared ternary mixture and successfully applied in their combined dosage form. The proposed methods were validated as per ICH guidelines and good accuracy; precision and specificity were confirmed within the concentration range of 5-35µgmL-1, 5-40µgmL-1 and 5-40µgmL-1of PARA, HCTZ and ENM, respectively. The results were statistically compared with reported HPLC method. Thus, the proposed methods can be effectively useful for the routine quality control analysis of these drugs in commercial tablet dosage form.