A new chronotherapeutic oral drug absorption system for verapamil optimizes blood pressure control in the morning

Chrono-tailored drug delivery systems: recent advances and future directions

Circadian rhythms influence a range of biological processes within the body, with the central clock or suprachiasmatic nucleus (SCN) in the brain synchronising peripheral clocks around the body. These clocks are regulated by external cues, the most influential being the light/dark cycle, in order to synchronise with the external day. Chrono-tailored or circadian drug delivery systems (DDS) aim to optimise drug delivery by releasing drugs at specific times of day to align with circadian rhythms within the body. Although this approach is still relatively new, it has the potential to enhance drug efficacy, minimise side effects, and improve patient compliance. Chrono-tailored DDS have been explored and implemented in various conditions, including asthma, hypertension, and cancer. This review aims to introduce the biology of circadian rhythms and provide an overview of the current research on chrono-tailored DDS, with a particular focus on immunological applications and vaccination. Finally, we draw on some of the key challenges which need to be overcome for chrono-tailored DDS before they can be translated to more widespread use in clinical practice.

Circadian Variation in Efficacy of Medications

Although much has been learned about circadian clocks and rhythms over the past few decades, translation of this foundational science underlying the temporal regulation of physiology and behavior to clinical applications has been slow. Indeed, acceptance of the modern study of circadian rhythms has been blunted because the phenomenology of cyclic changes had to counteract the 20th century dogma of homeostasis in the biological sciences and medicine. We are providing this review of clinical data to highlight the emerging awareness of circadian variation in efficacy of medications for physicians, clinicians, and pharmacists. We are suggesting that gold-standard double-blind clinical studies should be conducted to determine the best time of day for optimal effectiveness of medications; also, we suggest that time of day should be tracked and reported as an important biological variable in ongoing clinical studies hereafter. Furthermore, we emphasize that time of day is, and should be considered, a key biological variable in research design similar to sex. In common with biomedical research data that have been historically strongly skewed toward the male sex, most pharmaceutical data have been skewed toward morning dosing without strong evidence that this is the optimal time of efficacy.

Complexities in cardiovascular rhythmicity: perspectives on circadian normality, ageing and disease

Biological rhythms exist in organisms at all levels of complexity, in most organs and at myriad time scales. Our own biological rhythms are driven by energy emitted by the sun, interacting via our retinas with brain stem centres, which then send out complex messages designed to synchronize the behaviour of peripheral non-light sensing organs, to ensure optimal physiological responsiveness and performance of the organism based on the time of day. Peripheral organs themselves have autonomous rhythmic behaviours that can act independently from central nervous system control but is entrainable. Dysregulation of biological rhythms either through environment or disease has far-reaching consequences on health that we are only now beginning to appreciate. In this review, we focus on cardiovascular rhythms in health, with ageing and under disease conditions.

Circadian Rhythm Influences the Promoting Role of Pulsed Electromagnetic Fields on Sciatic Nerve Regeneration in Rats

Circadian rhythm (CR) plays a critical role in the treatment of several diseases. However, the role of CR in the treatment of peripheral nerve defects has not been studied. It is also known that the pulsed electromagnetic fields (PEMF) can provide a beneficial microenvironment to quicken the process of nerve regeneration and to enhance the quality of reconstruction. In this study, we evaluate the impact of CR on the promoting effect of PEMF on peripheral nerve regeneration in rats. We used the self-made “collagen-chitosan” nerve conduits to bridge the 15-mm nerve gaps in Sprague-Dawley rats. Our results show that PEMF stimulation at daytime (DPEMF) has most effective outcome on nerve regeneration and rats with DPEMF treatment achieve quickly functional recovery after 12 weeks. These findings indicate that CR is an important factor that determines the promoting effect of PEMF on peripheral nerve regeneration. PEMF exposure in the daytime enhances the functional recovery of rats. Our study provides a helpful guideline for the effective use of PEMF mediations experimentally and clinically.

G. S. Design and development of a dual-drug loaded pulsatile capsule for treatment of hypertension – in vitro and ex vivo studies

The aim of the present study was to design and evaluate a pulsatile dosage form to program the release of dual antihypertensive drugs to mimic the circadian pattern of BP.

Development of a gastroretentive pulsatile drug delivery platform

Objectives

To develop a novel gastroretentive pulsatile drug delivery platform by combining the advantages of floating dosage forms for the stomach and pulsatile drug delivery systems.

Methods

A gastric fluid impermeable capsule body was used as a vessel to contain one or more drug layer(s) as well as one or more lag-time controlling layer(s). A controlled amount of air was sealed in the innermost portion of the capsule body to reduce the overall density of the drug delivery platform, enabling gastric floatation. An optimal mass fill inside the gastric fluid impermeable capsule body enabled buoyancy in a vertical orientation to provide a constant surface area for controlled erosion of the lag-time controlling layer. The lag-time controlling layer consisted of a swellable polymer, which rapidly formed a gel to seal the mouth of capsule body and act as a barrier to gastric fluid ingress.

Key findings

By varying the composition of the lag-time controlling layer, it was possible to selectively program the onset of the pulsatile delivery of a drug.

Conclusions

This new delivery platform offers a new method of delivery for a variety of suitable drugs targeted in chronopharmaceutical therapy. This strategy could ultimately improve drug efficacy and patient compliance, and reduce harmful side effects by scaling back doses of drug administered.

Evening versus morning dosing regimen drug therapy for hypertension

BACKGROUND

Variation in blood pressure levels display circadian rhythms. The morning surge in blood pressure is known to increase the risk of myocardial events in the first several hours post awakening. A systematic review of the administration-time-related-effects of evening versus morning dosing regimen of antihypertensive drugs in the management of patients with primary hypertension has not been conducted.

OBJECTIVES

To evaluate the administration-time-related-effects of antihypertensive drugs administered as once daily monotherapy in the evening versus morning administration regimen on all cause mortality, cardiovascular morbidity and reduction of blood pressure in patients with primary hypertension.

SEARCH STRATEGY

We searched Cochrane CENTRAL on Ovid (4th Quarter 2009), Ovid MEDLINE (1950 to October 2009), EMBASE (1974 to October 2009), the Chinese Biomedical literature database (1978 to 2009) and the reference lists of relevant articles. No language restrictions were applied.

SELECTION CRITERIA

Randomized controlled trials comparing the administration-time-related effects of evening with morning dosing monotherapy regimens in patients with primary hypertension were included. Patients with known secondary hypertension, shift workers or white coat hypertension were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed trial quality. Disagreements were resolved by discussion or a third reviewer. Data synthesis and analysis were done using RevMan 5.1. Random effects meta-analysis and sensitivity analysis were conducted.

MAIN RESULTS

21 randomized controlled trials (RCTs) in 1,993 patients with primary hypertension met the inclusion criteria for this review - ACEIs (5 trials), CCBs (7 trials), ARBs (6 trials), diuretics (2 trials), alpha-blockers (1 trial), and beta-blockers (1 trial). Meta-analysis showed significant heterogeneity across trials.No RCT reported on all cause mortality, cardiovascular mortality, cardiovascular morbidity and serious adverse events.There was no statistically significant difference for overall adverse events (RR=0.78, 95%CI: 0.37 to 1.65) and withdrawals due to adverse events (RR=0.53, 95%CI: 0.26 to 1.07).No significant differences were noted for morning SBP (-1.62 mm Hg, 95% CI: -4.19 to 0.95) and morning DBP (-1.21 mm Hg, 95% CI: -3.28 to 0.86); but 24-hour BP (SBP: -1.71 mm Hg, 95% CI: -2.78 to -0.65; DBP: -1.38 mm Hg, 95% CI: -2.13 to -0.62) showed a statistically significant difference.

AUTHORS' CONCLUSIONS

No RCT reported on clinically relevant outcome measures - all cause mortality, cardiovascular morbidity and morbidity. There were no significant differences in overall adverse events and withdrawals due to adverse events among the evening versus morning dosing regimens. In terms of BP lowering efficacy, for 24-hour SBP and DBP, the data suggests that better blood pressure control was achieved with bedtime dosing than morning administration of antihypertensive medication, the clinical significance of which is not known.

Formulation and evaluation of press coated tablets for pulsatile drug delivery using hydrophilic and hydrophobic polymers

The aim of present investigation was to develop press coated tablet for pulsatile drug delivery of ketoprofen using hydrophilic and hydrophobic polymers. The drug delivery system was designed to deliver the drug at such a time when it could be most needful to patient of rheumatoid arthritis. The press coated tablets containing ketoprofen in the inner core was formulated with an outer shell by different weight ratio of hydrophobic polymer (micronized ethyl cellulose powder) and hydrophilic polymers (glycinemax husk or sodium alginate). The release profile of press coated tablet exhibited a lag time followed by burst release, in which outer shell ruptured into two halves. Authors also investigated factors influencing on lag time such as particle size and viscosity of ethyl cellulose, outer coating weight and paddle rpm. The surface morphology of the tablet was examined by a scanning electron microscopy. Differential scanning calorimeter and Fourier transformed infrared spectroscopy study showed compatibility between ketoprofen and coating material.

Circadian Variation in Stroke Onset: Identical Temporal Pattern in Ischemic and Hemorrhagic Events

Stroke is the culmination of a heterogeneous group of cerebrovascular diseases that is manifested as ischemia or hemorrhage of one or more blood vessels of the brain. The occurrence of many acute cardiovascular events--such as myocardial infarction, sudden cardiac death, pulmonary embolism, critical limb ischemia, and aortic aneurysm rupture--exhibits prominent 24 h patterning, with a major morning peak and secondary early evening peak. The incidence of stroke exhibits the same 24 h pattern. Although ischemic and hemorrhagic strokes are different entities and are characterized by different pathophysiological mechanisms, they share an identical double-peak 24 h pattern. A constellation of endogenous circadian rhythms and exogenous cyclic factors are involved. The staging of the circadian rhythms in vascular tone, coagulative balance, and blood pressure plus temporal patterns in posture, physical activity, emotional stress, and medication effects play central and/or triggering roles. Features of the circadian rhythm of blood pressure, in terms of their chronic and acute effects on cerebral vessels, and of coagulation are especially important. Clinical medicine has been most concerned with the prevention of stroke in the morning, when population-based studies show it is of greatest risk during the 24 h; however, improved protection of at-risk patients against stroke in the early evening, the second most vulnerable time of cerebrovascular accidents, has received relatively little attention thus far.

Influence of the Circadian System on Disease Severity

The severity of many diseases varies across the day and night. For example, adverse cardiovascular incidents peak in the morning, asthma is often worse at night and temporal lobe epileptic seizures are most prevalent in the afternoon. These patterns may be due to the day/night rhythm in environment and behavior, and/or endogenous circadian rhythms in physiology. Furthermore, chronic misalignment between the endogenous circadian timing system and the behavioral cycles could be a cause of increased risk of diabetes, obesity, cardiovascular disease and certain cancers in shift workers. Here we describe the magnitude, relevance and potential biological basis of such daily changes in disease severity and of circadian/behavioral misalignment, and present how these insights may help in the development of appropriate chronotherapy.

Controlled Release by Permeability Alteration of Cationic Ammonio Methacrylate Copolymers Using Ionic Interactions

A multiparticulate drug delivery system was studied in which the drug release of a model drug theophylline could be modulated by interactions of ammonio methacrylate polymer and anions. The system consisted of a EUDRAGIT NE coated anionic core, layered with drug and further layered with EUDRAGIT RS. The effects of different anions like chloride, succinate, citrate, and acetate as well as the thickness of the polymer layers on the in vitro drug release were studied. It was seen that succinate and acetate anions had permeability enhancing effects and citrate and chloride anions had permeability retarding effects on the polymer. The results indicate that changing these variables would enable us to get a desired release profile and hence the proposed system could be a viable alternative to existing technologies for the development of a controlled drug delivery system.

Chronobiology and chronotherapy of ischemic heart disease

The occurrence of the clinical manifestations of ischemic heart disease (IHD)--myocardial ischemia and angina pectoris, acute myocardial infarction, and sudden cardiac death--is unevenly distributed during the 24 h with greater than expected events during the initial hours of the daily activity span and in the late afternoon or early evening. Such temporal patterns result from circadian rhythms in pathophysiological mechanisms plus cyclic environmental stressors that trigger ischemic events. Both the pharmacokinetics (PK) and pharmacodynamics (PD) of many, though not all, anti-ischemic oral nitrate, calcium channel blocker, and beta-adrenoceptor antagonist medications have been shown to be influenced by the circadian time of their administration. The requirement for preventive and therapeutic interventions varies predictably during the 24 h, and thus therapeutic strategies should also be tailored accordingly to optimize outcomes. During the past decade, two first generation calcium channel blocker chronotherapies have been developed, trialed, and marketed in North America for the improved treatment of IHD. Nonetheless, there has been relatively little investigation of the administration-time (circadian rhythm) dependencies of the PK and PD of conventional anti-ischemic medications, and there has been little progress in the development of new generation IHD chronotherapies. Available epidemiologic, pharmacologic, and clinico-therapeutic evidence demonstrates how the chronobiologic approach to IHD can contribute new insight and opportunities to improve drug design and drug delivery to enhance therapeutic outcomes.

Chronotherapy of hypertension: administration-time-dependent effects of treatment on the circadian pattern of blood pressure

Some specific features of the 24-hour blood pressure (BP) pattern are linked to the progressive injury of target tissues and the triggering of cardiac and cerebrovascular events. Thus, there is growing interest in how to best tailor the treatment of hypertensive patients according to the circadian BP pattern of each individual. Significant administration-time differences in the kinetics (i.e., chronokinetics) plus beneficial and adverse effects (i.e., chronodynamics) of antihypertensive medications are well known. Thus, bedtime dosing with nifedipine GITS is more effective than morning dosing, while also significantly reducing adverse effects. The dose-response curve, therapeutic coverage, and efficacy of doxazosin GITS are all markedly dependent on the circadian time of drug administration. Moreover, valsartan administration at bedtime, as opposed to upon wakening, results in an improved diurnal/nocturnal BP ratio, increased percentage of controlled patients, and significant reduction in urinary albumin excretion in hypertensive patients. Chronotherapy provides a means of individualizing the treatment of hypertension according to the circadian BP profile of each patient, and constitutes a new option to optimize BP control and to reduce the risk of cardiovascular disease (myocardial infarction and stroke) and of end-organ injury of the blood vessels and tissue of the heart, brain, kidney, eye, and other organs.

Chronobiology, drug delivery, and chronotherapeutics

Biological processes and functions are organized in space, as a physical anatomy, and time, as a biological time structure. The latter is expressed by short-, intermediate-, and long-period oscillations, i.e., biological rhythms. The circadian (24-h) time structure has been most studied and shows great importance to the practice of medicine and pharmacotherapy of patients. The phase and amplitude of key physiological and biochemical circadian rhythms contribute to the known predictable-in-time patterns in the occurrence of serious and life-threatening medical events, like myocardial infraction and stroke, and the manifestation and severity of symptoms of chronic diseases, like allergic rhinitis, asthma, and arthritis. Moreover, body rhythms can significantly affect responses of patients to diagnostic tests and, most important to the theme of this special issue, medications. Rhythmicity in the pathophysiology of disease is one basis for chronotherapeutics--purposeful variation in time of the concentration of medicines in synchrony with biological rhythm determinants of disease activity--to optimize treatment outcomes. A second basis is the control of undesired effects of medications, especially when the therapeutic range is narrow and the potential for adverse effects high, which is the case for cancer drugs. A third basis is to meet the biological requirements for frequency-modulated drug delivery, which is the case for certain neuroendocrine peptide analogues. Great progress has been realized with hydrogels, and they offer many advantages and opportunities in the design of chronotherapeutic systems for drug delivery via the oral, buccal, nasal, subcutaneous, transdermal, rectal, and vaginal routes. Nonetheless, innovative delivery systems will be necessary to ensure optimal application of chronotherapeutic interventions. Next generation drug-delivery systems must be configurable so they (i) require minimal volitional adherence, (ii) respond to sensitive biomarkers of disease activity that often vary in time as periodic (circadian rhythmic) and non-periodic (random) patterns to release medication to targeted tissue(s) on a real time as needed basis, and (iii) are cost-effective.

Chronotherapy in hypertensive patients: administration-time dependent effects of treatment on blood pressure regulation

Ambulatory blood pressure measurements (ABPM) correlate more closely with target organ damage and cardiovascular events than clinical cuff measurements. ABPM reveals the significant circadian variation in BP, which in most individuals presents a morning increase, small post-prandial decline, and more extensive lowering during nocturnal rest. However, under certain pathophysiological conditions, the nocturnal BP decline may be reduced (nondipper pattern) or even reversed (riser pattern). This is clinically relevant since the nondipper and riser circadian BP patterns constitute a risk factor for left ventricular hypertrophy, microalbuminuria, cerebrovascular disease, congestive heart failure, vascular dementia and myocardial infarction. Hence, there is growing interest in how to best tailor and individualize the treatment of hypertension according to the circadian BP pattern of each patient. Significant administration-time differences in the kinetics and in the beneficial and adverse effects of antihypertensive medications are well known. Thus, bedtime dosing with nifedipine gastrointestinal therapeutic system (GITS) is more effective than morning dosing, while also significantly reducing adverse effects. The therapeutic coverage and efficacy of doxazosin GITS are dependent on the circadian time of drug administration. Moreover, valsartan administration at bedtime, as opposed to upon wakening, results in an improved diurnal/nocturnal BP ratio, increased percentage of controlled patients, and significant reduction in urinary albumin excretion in hypertensive patients. Chronotherapy provides a means of individualizing the treatment of hypertension according to the circadian BP profile of each patient, and constitutes a new option to optimize BP control and reduce the risk of cardiovascular disease.

Modulated release metoprolol succinate formulation based on ionic interactions: In vivo proof of concept

A modulated release, multiunit oral drug delivery technology using a system based on ionic interactions of anions of salts with quaternary ammonium ions of the ammoniomethacrylate polymer is described. The system consisted of a drug layered, EUDRAGIT NE-coated salt core which was further coated with EUDRAGIT RS. The relative effects of different anions on the polymer permeability have been investigated by studying their influence on the in vitro drug release. A prototype formulation of metoprolol succinate using this technology was developed and the drug release from the formulation was adjusted to have a release profile which would match the circadian rhythm i.e. a higher amount of drug would be available after an initial lower release (accelerated type of release). The formulation was tested in vivo in 12 healthy human volunteers in an open label, randomized, two-treatment, two-period, single dose crossover bio-study with reference formulation Beloc-zok. The in vivo release demonstrated that compared to the reference, a higher amount of drug was available in the plasma from the 7th hour onwards. A higher AUC of the drug was also observed compared to the reference formulation. An in vitro-in vivo correlation was attempted to identify a bio-relevant in vitro dissolution medium for the formulation.

Emerging drugs in the management of hypertension

Hypertension is a global health problem, affecting developing and developed countries alike. Most patients with hypertension are undiagnosed, and most diagnosed patients are either untreated or inadequately treated. Randomised controlled trial evidence suggests diuretic therapy for hypertension is as effective as newer drugs in reducing cardiovascular events. There is good evidence for the use of specific classes of drugs in hypertensive patients with a variety of associated clinical conditions, but for uncomplicated cases, the current emphasis in hypertension management is on blood pressure lowering rather than drug class. Individual patients vary in their responses to different drug classes, and optimal therapy for the individual is determined by trial and error. Pharmacogenomics may assist in tailoring therapy for individuals in the future. Emerging drugs include newer members of classes already established in clinical practice, for example, angiotensin II receptor antagonists, aldosterone receptor antagonists, calcium antagonists and centrally acting drugs; newer fixed-dose combination therapies; and more novel therapies, for example, endothelin (ET) receptor antagonists, activators of nitric oxide (NO)-sensitive guanylyl cyclase and vasopeptidase inhibitors.

[Influence of circadian rhythms on cardiovascular function]

The clinical importance of circadian biological rhythms has been strengthened by a number of studies showing a circadian distribution of cardiovascular events like myocardial infarction, stroke, complex arrhythmia, or sudden cardiac death. Incidence of diseases showed a maximum during the early morning hours after awakening from sleep. In addition, a number of pathophysiological mechanisms has been identified to coincide with this peak including blood pressure and heart rate surges, decreased endothelial dilatory capacity of peripheral and coronary arteries, enhanced sympathetic activity, decreased cardiac electrical stability, and increased platelet aggregation. This time window of high risk for the incidence of cardiovascular events has been identified as a target for new treatment and prevention strategies including new release forms of antihypertensive and coronary-dilatory drugs. The use of melatonin as an antihypertensive drug has been successfully explored and opens new opportunities for the management of cardiovascular dysfunction and disease from a circadian perspective.

Biological Rhythms, Medication Safety, and Women's Health

Biological processes and functions in women are well organized in time, as evidenced by the expression of ultradian (high frequency), circadian ( approximately 24-hour), circamensual ( approximately monthly), and circannual ( approximately yearly) rhythms and by the changes that occur with menarche, reproduction, and menopause. Attributes of women's circamensual structure have been explored in depth, particularly with regard to fertility/infertility and birth control. However, the role of 24-hour and other rhythms in health, disease, and treatment has been little studied. The symptom intensity of a variety of chronic medical conditions is rhythmic, as is the risk of severe events, such as stroke and myocardial infarct (MI). Improving the safety, efficacy, and preventive qualities of medications requires the understanding of how rhythms impact drug pharmacokinetics and pharmacodynamics. The therapeutic and adverse effects of prescription and nonprescription medications widely used by women can vary markedly with the (circadian) time of administration. Circadian rhythm-dependent differences in the safety of medications are particularly relevant to pregnant women; laboratory animal studies show that the fetal toxicity of various treatments varies not only with developmental stage but also with circadian time. Rhythm-dependent differences in the actions of medications are also of great importance to perimenopausal and postmenopausal women, who are advised to ingest prescribed pharmacotherapy for osteopenia and osteoporosis in the morning to minimize the risk of adverse effects and, as a consequence, may elect to take other medications at times not recommended in the instructions for their use. Medication trials must be comprehensive and representative of women and men of different life stages, ethnicities, and likely times (morning vs. evening) of drug use.

Treatment of elderly hypertensive patients with a delayed-release verapamil formulation in a community-based trial

This report of a practice-based clinical trial describes an open-label, multicenter dose-titration study of an elderly (age >or=65 years) subset of patients (N=628) with systolic blood pressures between 140 and 179 mm Hg or diastolic blood pressures between 90 and 109 mm Hg, to assess the effects of the Chronotherapeutic Oral Drug Absorption System (CODAS) formulation of verapamil hydrochloride. After starting 200 mg/d at bedtime, dosing was titrated to a maximum of 400 mg/d at 4-week intervals to achieve a target blood pressure of <140/<90 mm Hg using morning blood pressure measurements. Target blood pressure was reached in 57.1% of the elderly patients with CODAS verapamil monotherapy. A diastolic response (<90 mm Hg or a 10 mm Hg reduction from baseline) was achieved in 89.5% of these subjects, and a systolic blood pressure response (<140 mm Hg or 10% reduction from baseline) was attained in 75.5%. The percentages of patients achieving target blood pressure or the diastolic and systolic blood pressure responses were comparable to those previously reported for younger patients. It is notable that although 359 of the 628 patients reached control on treatment, 182 of the remaining 269 noncontrolled patients were not titrated to higher doses, indicating that even with a well tolerated drug there may be reluctance among clinicians to increase doses. CODAS verapamil was found to be efficacious and well tolerated among elderly hypertensive patients in this community trial.

Chronopharmaceutics: gimmick or clinically relevant approach to drug delivery?

Due to advances in chronobiology, chronopharmacology, and global market constraints, the traditional goal of pharmaceutics (e.g. design drug delivery systems with a constant drug release rate) is becoming obsolete. However, the major bottleneck in the development of drug delivery systems that match the circadian rhythm (chronopharmaceutical drug delivery systems: ChrDDS) may be the availability of appropriate technology. The last decade has witnessed the emergence of ChrDDS against several diseases. The increasing research interest surrounding ChrDDS may lead to the creation of a new sub-discipline in pharmaceutics known as chronopharmaceutics. This review introduces the concept of chronopharmaceutics, addresses theoretical/formal approaches to this sub-discipline, underscores potential disease-targets, revisits existing technologies and examples of ChrDDS. Future development in chronopharmaceutics may be made at the interface of other emerging disciplines such as system biology and nanomedicine. Such novel and more biological approaches to drug delivery may lead to safer and more efficient disease therapy in the future.

Formulation design of double-layer in the outer shell of dry-coated tablet to modulate lag time and time-controlled dissolution function: studies on micronized ethylcellulose for dosage form design (VII)

The dry-coated tablet with optimal lag time was designed to simulate the dosing time of drug administration according to the physiological needs. Different compositions of ethylcellulose (EC) powder with a coarse particle (167.5 microm) and several fine particles (< 6 microm), respectively, were mixed to formulate the whole layer of the outer shell of dry-coated tablets. The formulations containing different weight ratios of coarse/fine particles of EC powders or 167.5 microm EC powder/excipient in the upper layer of the outer shell to influence the release behavior of sodium diclofenac from dry-coated tablet were also explored. The results indicate that sodium diclofenac released from all the dry-coated tablets exhibited an initial lag period, followed by a stage of rapid drug release. When the mixture of the coarse/fine particles of EC powders was incorporated into the whole layer, the lag time was almost the same. The outer shell broke into 2 halves to make a rapid drug release after the lag time, which belonged to the time-controlled disruption of release mechanism. When the lower layer in the outer shell was composed of 167.5 microm EC powder and the upper layer was formulated by mixing different weight ratios of 167.5 microm and 6 microm of EC powders, the drug release also exhibited a time-controlled disruption behavior. Its lag time might be freely modulated, depending on the amount of 6 microm EC powder added. Once different excipients were respectively incorporated into the upper layer of the outer shell, different release mechanisms were observed as follows: time-controlled explosion for Explotab, disruption for Avicel and spray-dried lactose, erosion for dibasic calcium phosphate anhydrate, and sigmoidal profile for hydroxypropyl methylcellulose.

Circadian rhythm in the cardiovascular system: chronocardiology

BACKGROUND

We reviewed recent progress in the study of the chronobiological aspects of the cardiovascular system.

METHODS

Medline was used as the main search tool, and the full texts of selected papers were obtained.

RESULTS

More than 300 references were found, and 52 of them, representing the major findings in this field, were included in the reference list. Results of these studies confirm that most cardiovascular physiological parameters (such as heart rate, blood pressure, electrocardiogram indices) and pathophysiological events (myocardial ischemia/infarction, sudden cardiac death) show circadian rhythms. Results also suggest that consideration of these rhythms is important for the diagnosis and treatment of cardiovascular disorders and that restoration of normal circadian rhythms may be associated with clinical improvement.

CONCLUSION

The study of circadian rhythms in the cardiovascular system is emerging as an important area of investigation because of its potential implications for patient management.

Chrono: a community-based hypertension trial of a chronotherapeutic formulation of verapamil

An open-label, multicenter, dose-titration study evaluated 2,556 patients with stage I or II essential hypertension (untreated or previously treated with one antihypertensive agent) to assess the effect of a chronotherapeutic formulation of verapamil (Verelan PM) designed to provide maximum plasma concentrations in the midmorning hours. After starting with 200 mg/d at bedtime, the dose of Verelan PM was titrated to a maximum of 400 mg/d at 4-week intervals to achieve a target blood pressure (BP) <140/90 mm Hg using morning BP measurements. In 85.3% of patients, a diastolic blood pressure (DBP) response to less than 90 mm Hg or a 10-mm Hg decline from baseline DBP was achieved. The systolic BP response (<140 mm Hg or 10% decline from baseline) was attained in 76.9% of patients. Blood pressure was controlled in 62.6% of patients with Verelan PM monotherapy. Upward titration of Verelan PM from 200 to 400 mg nearly doubled the DBP response rate (45.8% to 85.3%). This chronotherapeutic formulation of verapamil was well tolerated in this community trial.

Manufacturing factors affecting the drug delivery function of thermo-responsive membrane prepared by adsorption of binary liquid crystals

A binary mixture of cholesteric oleyl carbonate (COC) and cholesteryl nonanoate (CN) with a weight ratio of 36% and 64% was adsorbed onto the cellulose nitrate membrane to prepare a thermo-responsive membrane. The thermo-responsive function of these COC/CN-adsorbed membranes was evaluated by an in vitro penetration study via repeatedly exchanging the temperature cycle. The manufacturing factors for preparing these thermo-responsive membranes, such as the binary COC/CN concentration used, immersion temperature of binary COC/CN chloroform solution, immersion temperature and time period of distilled water, vacuum-drying or air-drying process, and vacuum drying temperature, have been explored. The results indicated that the immersion temperature at 23 degrees C for membrane in binary COC/CN chloroform solution with 10 min and in distilled water with 12 h was the optimal temperature for fabricating the on-off thermo-responsive membranes prepared either by 22% or 25% concentration of binary COC/CN mixture. A good thermo-responsive function was further evidenced for these COC/CN-adsorbed membranes via vacuum-drying at 65 degrees C for 1 h. A possible mechanism concerning the thermal-dependent molecular motion, orientation and/or alignment of binary COC/CN mixture entrapped into the membrane may play an important role for the thermo-responsive behavior.

Circadian rhythms in medicine

Circadian (24-hour) rhythms are important to the practice of medicine. The phasing and amplitude of key physiologic and biochemical circadian rhythms contribute to predictable-in-time patterns in the manifestation and exacerbation of most medical conditions. Moreover, body rhythms can significantly affect responses of patients to diagnostic tests and medications. Rhythmicity in the pathophysiology of medical conditions is the rationale for chronotherapeutics--the purposeful variance of the concentration of medicines in synchrony with biological rhythm--determinants of disease activity--to optimize treatment outcomes. This article discusses the concept of biological time structure and its relevance to the practice of medicine, with a focus on neurologic issues.