Drug delivery systems for treatment of systemic hypertension

Candesartan cilexetil loaded nanodelivery systems for improved oral bioavailability

Candesartan cilexetil (CC), an antihypertensive drug, has low oral bioavailability due to poor solubility and hepatic first-pass metabolism. These are major limitations in oral delivery of CC. Several approaches are known to reduce the problems of solubility and improve the bioavailability of CC. Among various approaches, nanotechnology-based delivery of CC has potential to overcome the challenges associated with the oral administration. This review focuses on various nano-based delivery systems available and tried for improving the aqueous solubility, dissolution and consequently bioavailability of CC upon oral administration. Of all, solid lipid nanoparticles appear to be promising delivery system, based on current reported results, for delivery of CC, as this system improved the oral bioavailability and possessed prolonged pharmacodynamic effect.

High-Throughput Excipient Discovery Enables Oral Delivery of Poorly Soluble Pharmaceuticals

Polymeric excipients are crucial ingredients in modern pills, increasing the therapeutic bioavailability, safety, stability, and accessibility of lifesaving products to combat diseases in developed and developing countries worldwide. Because many early-pipeline drugs are clinically intractable due to hydrophobicity and crystallinity, new solubilizing excipients can reposition successful and even failed compounds to more effective and inexpensive oral formulations. With assistance from high-throughput controlled polymerization and screening tools, we employed a strategic, molecular evolution approach to systematically modulate designer excipients based on the cyclic imide chemical groups of an important (yet relatively insoluble) drug phenytoin. In these acrylamide- and methacrylate-containing polymers, a synthon approach was employed: one monomer served as a precipitation inhibitor for phenytoin recrystallization, while the comonomer provided hydrophilicity. Systems that maintained drug supersaturation in amorphous solid dispersions were identified with molecular-level understanding of noncovalent interactions using NOESY and DOSY NMR spectroscopy. Poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(NIPAm-co-DMA)) at 70 mol % NIPAm exhibited the highest drug solubilization, in which phenytoin associated with inhibiting NIPAm units only with lowered diffusivity in solution. In vitro dissolution tests of select spray-dried dispersions corroborated the screening trends between polymer chemical composition and solubilization performance, where the best NIPAm/DMA polymer elevated the mean area-under-the-dissolution-curve by 21 times its crystalline state at 10 wt % drug loading. When administered to rats for pharmacokinetic evaluation, the same leading poly(NIPAm-co-DMA) formulation tripled the oral bioavailability compared to a leading commercial excipient, HPMCAS, and translated to a remarkable 23-fold improvement over crystalline phenytoin.

Nanotechnology Based Approaches for Enhancing Oral Bioavailability of Poorly Water Soluble Antihypertensive Drugs

Oral administration is the most convenient route among various routes of drug delivery as it offers high patient compliance. However, the poor aqueous solubility and poor enzymatic/metabolic stability of drugs are major limitations in successful oral drug delivery. There are several approaches to improve problems related to hydrophobic drugs. Among various approaches, nanotechnology based drug delivery system has potential to overcome the challenges associated with the oral route of administration. Novel drug delivery systems are available in many areas of medicine. The application of these systems in the treatment of hypertension continues to broaden. The present review focuses on various nanocarriers available in oral drug administration for improving solubility profile, dissolution, and consequently bioavailability of hydrophobic antihypertensive drugs.

Association between Total Daily Doses with duration of hospitalization among readmitted patients in a multi-ethnic Asian population

Increased length of stay (LOS) in the hospital incurs substantial financial costs on the healthcare system. Multiple factors are associated with LOS. However, few studies have been done to associate the impact of Total Daily Doses (TDD) and LOS. Hence, the aim of this study is to examine the association between patients’ LOS upon readmission and their TDD before readmission. A retrospective cross-sectional study of readmission cases occurring from 1st January to 31st March 2013 was conducted at a regional hospital. Demographics and clinical variables were collected using electronic medical databases. Univariable and multiple linear regressions were used. Confounders such as comorbidities and drug related problems (DRP) were controlled for in this study. There were 432 patients and 649 readmissions examined. The average TDD and LOS were 18.04 ± 8.16 and 7.63 days ± 7.08 respectively. In the univariable analysis, variables that were significantly associated with the LOS included age above 75 year-old, race, comorbidity, number of comorbidities, number of medications, TDD and thrombocytopenia as DRPs. In the multiple linear regression, there was a statistically significant association between TDD (β = 0.0733, p = 0.030) and LOS. Variables that were found significant were age above 75 year-old (β = 1.5477, p = 0.008), Malay (β = −1.5123, p = 0.033), other races (β = −2.6174, p = 0.007), depression (β = 2.1551, p = 0.031) and thrombocytopenia as a type of DRP (β = 7.5548, p = 0.027). When TDD was replaced with number of medications, number of medications (β = 0.1487, p = 0.021), age of 75 year-old (β = 1.5303, p = 0.009), Malay (β = −1.4687, p = 0.038), race of others (β = −2.6499, p = 0.007), depression (β = 2.1951, p = 0.028) and thrombocytopenia as a type of DRP (β = 7.5260, p = 0.028) were significant. In conclusion, a significant relationship between TDD and number of medications before readmission and the LOS upon readmission was established. This finding highlights the importance of optimizing patients’ TDD in the attempt of reducing their LOS.

Enhanced oral bioavailability of isradipine via proniosomal systems

The objective of the present research was to develop a proniosomal formulation of isradipine and to evaluate the influence of proniosomal systems on the oral bioavailability of the drug in albino Wistar rats. Proniosomes were prepared by film deposition on carrier's method using various molar ratios of nonionic surfactants such as span20, span40, span60, and span80 with cholesterol as membrane stabilizing agent and dicetylphosphate as a charge inducer. The formation of niosomes and surface morphology of proniosome formulations were studied by optical and scanning electron microscopy (SEM), respectively. The prepared proniosomes have shown higher dissolution of isradipine compared with pure drug powder. Fourier transform infrared spectroscopy, differential scanning calorimetry, and powder X-ray diffractometry studies were performed to understand the solid state properties of the drug. Ex vivo permeation enhancement assessed from flux, permeability coefficient, and enhancement ratio were significantly higher for proniosomes compared with control. The pharmacokinetic parameters were evaluated in male albino Wistar rats and a significant enhancement in the bioavailability (2.3-fold) was observed from optimized proniosome formulation compared with control (oral suspension). The stability study reveals that the proniosome formulations are stable when stored at 4°C.

Formulation, evaluation, and pharmacokinetics of isradipine proliposomes for oral delivery

Proliposomes loaded with isradipine were prepared successfully to enhance the oral bioavailability of isradipine. In this study, proliposomes were prepared by film deposition by the carrier method with varying ratios of hydrogenated soy phosphatidyl choline (HSPC) and cholesterol using spray-dried mannitol (Pearlitol SD 200) as the carrier. The formulation containing an equimolar ratio of HSPC and cholesterol showed smaller vesicle size, high surface charge, and entrapment efficiency. The formation of liposomes and surface morphology of optimized proliposome formulation was studied by optical and scanning electron microscopy, respectively. Fourier transform infrared, differential scanning calorimetry, and powder X-ray diffractometry studies were performed to assess the solid-state characteristics of the formulation. Ex vivo permeation enhancement assessed from flux, permeability coefficient, and enhancement ratio were significantly higher for proliposomes, compared to control. The pharmacokinetic parameters were evaluated in male albino Wistar rats, and a significant improvement in bioavailability (2.4-fold) was observed from the optimized proliposome formulation, compared to control (oral suspension). The stability study revealed that the formulations are stable when stored at 4°C.

Alginates: Existing and Potential Biotechnological and Medical Applications

The present chapter on alginates in biotechnology and medicine comprises a description of traditional uses where alginates have been used as devices in e.g. wound dressings, as well as an in-depth introduction to possible future applications. The latter area is based on new scientific information on the immunostimulating properties of certain alginate sequences, as well as on the popularity gained by the alginate as immobilization matrix for cells. The latter opens up the use of alginate encapsulated cells for specific cell transplantation provided that the properties of the capsules are properly understood and controlled.

Oral osmotically driven systems: 30 years of development and clinical use

The number of marketed oral osmotically driven systems (OODS) has doubled in the last 10 years. The main clinical benefits of OODS are their ability to improve treatment tolerability and patient compliance. These advantages are mainly driven by the capacity to deliver drugs in a sustained manner, independent of the drug chemical properties, of the patient's physiological factors or concomitant food intake. However, access to these technologies has been restricted by the crowded patent landscape and manufacturing challenges. In this review article, we intend to give an overview of the OODS development in the last 30 years, detailing the technologies, specific products and their clinical use. General guidance on technology selection is described in light of the recent advances in the field. The clinical performance of these technologies is also discussed, with a focus on food effects and the in vivo-in vitro correlation. Special attention is paid to safety given the controversial case study of Osmosin. Overall, oral osmotically driven systems appear to be a promising technology for product life-cycle strategies.

Quantification of isradipine in human plasma using LC-MS/MS for pharmacokinetic and bioequivalence study

A highly sensitive and rapid method for the analysis of isradipine in human plasma using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed. The procedure involves a simple liquid-liquid extraction of isradipine and amlodipine (IS, internal standard) with methyl-t-butyl ether after alkaline treatment and separation by RP-HPLC. Detection was performed by positive ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode, monitoring the transitions m/z 372.1-->m/z 312.2 and m/z 408.8-->m/z 237.9, for quantification of isradipine and IS, respectively. The standard calibration curves showed good linearity within the range of 10 to 5000 pg/mL (r(2)>or=0.9998). The lower limit of quantitation (LLOQ) was 10 pg/mL. The retention times of isradipine (0.81 min) and IS (0.65 min) suggested the potential for high throughput of the proposed method. In addition, no significant metabolic compounds were found to interfere with the analysis. This method offered good precision and accuracy and was successfully applied for the pharmacokinetic and bioequivalence studies of 5 mg of sustained-release isradipine in 24 healthy Korean volunteers.

Antihypertensive pharmacobezoar

Most antihypertensive drugs have known side effects that are elicited by the careful clinician taking care of hypertensive patients. However, many antihypertensive medications utilize drug delivery systems that prolong the duration of blood pressure reduction. The gastrointestinal therapeutic system that is used with nifedipine, isradipine, and verapamil has a unique side effect. Obstruction may occur at the site of a previous surgical repair (pyloric stenosis or gastroplasty) or stenosis of the esophagus, small intestine, or colon. The same delivery system is used with methylphenidate, oxybutynin, glipizide, and doxazosin. Although this complication is rare, physicians who prescribe and care for hypertensive patients should recognize this potential problem.

Oral pulsatile drug delivery systems

In the field of modified release, there has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable lag phase from the time of administration. In particular, the recent literature reports on a variety of pulsatile release systems intended for the oral route, which have been recognised as potentially beneficial to the chronotherapy of widespread diseases, such as bronchial asthma or angina pectoris, with mainly night or early morning symptoms. In addition, time-dependent colon delivery may also represent an appealing related application. The delayed liberation of orally administered drugs has been achieved through a range of formulation approaches, including single- or multiple-unit systems provided with release-controlling coatings, capsular devices and osmotic pumps. Based on these premises, the aim of this review is to outline the rational and prominent design strategies behind oral pulsatile delivery.

Strategies to improve oral drug bioavailability

Efforts to improve oral drug bioavailability have grown in parallel with the pharmaceutical industry. As the number and chemical diversity of drugs has increased, new strategies have been required to develop orally active therapeutics. The past two decades have been characterised by an increased understanding of the causes of low bioavailability and a great deal of innovation in oral drug delivery technologies, marked by an unprecedented growth of the drug delivery industry. The advent of biotechnology and consequent proliferation of biopharmaceuticals have brought new challenges to the drug delivery field. In spite of the difficulties associated with developing oral forms of this type of therapeutics, significant progress has been made in the past few years, with some oral proteins, peptides and other macromolecules currently advancing through clinical trials. This article reviews the approaches that have been successfully applied to improve oral drug bioavailability, primarily, prodrug strategies, lead optimisation through medicinal chemistry and formulation design. Specific strategies to improve the oral bioavailability of biopharmaceuticals are also discussed.

The rise and rise of drug delivery

Drug delivery has typically focused on optimizing marketed compounds, improving their effectiveness or tolerability, and simplifying their administration. This role now includes the first biopharmaceuticals as well as more conventional drugs. As drug-delivery technologies come into play earlier in the development cycle, however, they can also enhance the screening and evaluation of new compounds and 'rescue' failed compounds, such as those with low solubility. In this article, we look back at how the burgeoning field of drug delivery came into being and describe approaches for future discovery and development.

Calcium channel blocker class heterogeneity: select aspects of pharmacokinetics and pharmacodynamics

Calcium channel blockers (CCBs) comprise a heterogeneous group of compounds with unique structures and pharmacologic characteristics. These agents are employed in the treatment of hypertension, coronary ischemia, and/or supraventricular arrhythmias. CCBs are both substrates for, and in the instance of verapamil and diltiazem inhibitors of, cytochrome P450 3A4. In the case of verapamil and diltiazem, this inhibitory effect increases the likelihood of drug-drug interactions with other compounds similarly metabolized by cytochrome P450 3A4. Much of the debate with reference to a cardiovascular risk for CCBs has been quieted with the advent of sustained-release delivery systems that offer a more gradual rate of drug delivery. The most common side effects with CCBs are vasodilatory in nature and include peripheral edema, flushing, and headache. Despite the potential for side effects with CCBs, their potent blood pressure-lowering effect makes them a prerequisite for blood pressure control in many patients.

Dependence of copolymer composition, swelling history, and drug concentration on the loading of diltiazem hydrochloride (DIL.HCl) into poly[(N-isopropylacrylamide)-co-(methacrylic acid)] hydrogels and its release behaviour from hydrogel slabs

The loading of an antihypertensive cationic drug, diltiazem hydrochloride (DIL.HCl), into poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], and their poly[(N-isopropylacrylamide)-co-(methacrylic acid)] P[(N-iPAAm)-co-(MAA)] hydrogels as well as their release behaviour have been investigated. For this purpose, two series of hydrogels have been tested, one previously soaked under acidic pH (treated hydrogels) and the other from the synthesis and washed in deionized water (untreated hydrogels). For the drug loading, these two series of hydrogels have been soaked in drug solutions with different concentrations. DIL.HCl amounts loaded by the gels as well as swelling degrees as a function of both hydrogel composition and DL.HCl concentration in the loading solution have been analyzed. Due to the interactions among DIL.HCl and the MAA group, "untreated" enriched MAA copolymer hydrogels present the highest drug load and loading efficiency. A DIL.HCl concentration of 320 microm/mL has been employed to load copolymers for release experiments, because for this concentration, hydrogels reach relative high drug load with a still high efficiency of loading. Release has been tested in three media, namely, fresh water (Milli-Q grade, pH 7.0), 0.1 N hydrogen chloride (pH 1.2), and a phosphate buffer (pH 7.0). In general, release is lower in fresh water and acidic media than in phosphate buffer. To explain these results, the effect of temperature, medium, and composition on the pH and thermo sensitivity of the hydrogels as well as the diltiazem-polymer interactions have been taken into account.

Electron Cryo‐Microscopy Reveals Mechanism of Action of Propranolol on Artificial Membranes

The pharmacological activity of several amphiphilic drugs is often related to their ability to interact with biological membranes. Propranolol is an efficient multidrug resistance (MDR) modulator; it is a nonselective beta-blocker and is thought to reduce hypertension by decreasing the cardiac frequency and thus blood pressure. It is used in drug delivery studies in order to treat systemic hypertension. We are interested in the interaction of propranolol with artificial membranes, as liposomes of controllable size are used as biocompatible and protective structures to encapsulate labile molecules, such as proteins, nucleic acids or drugs, for pharmaceutical, cosmetic or chemical applications. We present here a study of the interaction of propranolol, a cationic surfactant, with pure egg phosphatidylcholine (EPC) vesicles. The gradual transition from liposome to micelle of EPC vesicles in the presence of propranolol was monitored by time-resolved electron cryo-microscopy (cryo-EM) under different experimental conditions. The liposome-drug interaction was studied with varying drug/lipid (D/L) ratios and different stages were captured by direct thin-film vitrification. The time-series cryo-EM data clearly illustrate the mechanism of action of propranolol on the liposome structure: the drug disrupts the lipid bilayer by perturbing the local organization of the phospholipids. This is followed by the formation of thread-like micelles, also called worm-like micelles (WLM), and ends with the formation of spherical (globular) micelles. The overall reaction is slow, with the process taking almost two hours to be completed. The effect of a monovalent salt was also investigated by repeating the lipid-surfactant interaction experiments in the presence of KCl as an additive to the lipid/drug suspension. When KCl was added in the presence of propranolol the overall reaction was the same but with slower kinetics, suggesting that this monovalent salt affects the general lipid-to-micelle transition by stabilizing the membrane, presumably by binding to the carbonyl chains of the phosphatidylcholine.

Chronotherapeutics:A surge of ideas

Chronotherapeutics is advancing hypertension treatments beyond once-daily dosing by synchronizing the maximum levels of medication during times when cardiovascular risk is highest. It has long been established that patients are at higher risk for cardiovascular events-including myocardial infarction, stroke, and sudden death-in the early morning hours. Using novel oral delivery methods, chronotherapeutic medication synchronizes the delivery of blood pressure drug within the period of rates risk, significantly reducing both absolute blood pressure numbers and, especially important, the rate of blood pressure increase. These therapies have also shown the ability to maintain adequate blood pressure levels during the trough period. Several blood pressure medications now have chronotherapeutic formulations including the calcium channel blockers verapamil and diltiazem and the beta-blocker propranolol.