Concepts of circadian chronopharmacology

Controlled Drug Delivery Systems: Current Status and Future Directions

The drug delivery system enables the release of the active pharmaceutical ingredient to achieve a desired therapeutic response. Conventional drug delivery systems (tablets, capsules, syrups, ointments, etc.) suffer from poor bioavailability and fluctuations in plasma drug level and are unable to achieve sustained release. Without an efficient delivery mechanism, the whole therapeutic process can be rendered useless. Moreover, the drug has to be delivered at a specified controlled rate and at the target site as precisely as possible to achieve maximum efficacy and safety. Controlled drug delivery systems are developed to combat the problems associated with conventional drug delivery. There has been a tremendous evolution in controlled drug delivery systems from the past two decades ranging from macro scale and nano scale to intelligent targeted delivery. The initial part of this review provides a basic understanding of drug delivery systems with an emphasis on the pharmacokinetics of the drug. It also discusses the conventional drug delivery systems and their limitations. Further, controlled drug delivery systems are discussed in detail with the design considerations, classifications and drawings. In addition, nano-drug delivery, targeted and smart drug delivery using stimuli-responsive and intelligent biomaterials is discussed with recent key findings. The paper concludes with the challenges faced and future directions in controlled drug delivery.

Chronotherapeutics: Recognizing the Importance of Timing Factors in the Treatment of Disease and Sleep Disorders

This review describes the characteristics of a number of pathologies, which are considered from the point of view of chronobiology, that is, the way in which biological processes are expressed throughout the 24-hour day. This perspective is a relatively new way of thinking about disease and additionally about how to treat diseases. It has called attention to the importance of not only the quantity of a drug that is administered but also when it is administered. In addition, the review presents an overview of the emerging clinical strategies known as chronotherapeutics, that is, the effects of the daily scheduling of drug administration and the consequences of the activity and efficacy of therapies that are applied in this manner. This article also reviews innovative ways in which physicians are applying time-specified drug treatment (chronopharmacology) for sleep disorders. Here, we present a systematic description of chronopharmacology as well as definitions of key terms that, we believe, will be helpful for newcomers to the field. It is hoped that greater awareness of this new perspective on pharmacology will promote its adoption by researchers and clinicians.

Opening the Debate: How to Fulfill the Need for Physicians' Training in Circadian-Related Topics in a Full Medical School Curriculum

BACKGROUND

Circadian rhythms are daily changes in our physiology and behavior that are manifested as patterns of brain wave activity, periodic hormone production, recurring cell regeneration, and other oscillatory biological activities. Their importance to human health is becoming apparent; they are deranged by shift work and jet-lag and in disparate conditions such as insomnia, sleep syndromes, coronary heart attacks, and depression, and are endogenous factors that contribute to cancer development and progression.

DISCUSSION

As evidence of the circadian connection to human health has grown, so has the number of Americans experiencing disruption of circadian rhythms due to the demands of an industrialized society. Today, there is a growing work force that experiences night shift work and time-zone shifts shaping the demands on physicians to best meet the needs of patients exposed to chronic circadian disruptions. The diverse range of illness associated with altered rhythms suggests that physicians in various fields will see its impact in their patients. However, medical education, with an already full curriculum, struggles to address this issue.

SUMMARY

Here, we emphasize the need for incorporating the topic of circadian rhythms in the medical curriculum and propose strategies to accomplish this goal.

Therapeutic applications of circadian rhythms for the cardiovascular system

The cardiovascular system exhibits dramatic time-of-day dependent rhythms, for example the diurnal variation of heart rate, blood pressure, and timing of onset of adverse cardiovascular events such as heart attack and sudden cardiac death. Over the past decade, the circadian clock mechanism has emerged as a crucial factor regulating these daily fluctuations. Most recently, these studies have led to a growing clinical appreciation that targeting circadian biology offers a novel therapeutic approach toward cardiovascular (and other) diseases. Here we describe leading-edge therapeutic applications of circadian biology including (1) timing of therapy to maximize efficacy in treating heart disease (chronotherapy); (2) novel biomarkers discovered by testing for genomic, proteomic, metabolomic, or other factors at different times of day and night (chronobiomarkers); and (3) novel pharmacologic compounds that target the circadian mechanism with potential clinical applications (new chronobiology drugs). Cardiovascular disease remains a leading cause of death worldwide and new approaches in the management and treatment of heart disease are clearly warranted and can benefit patients 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.

Optimization studies on compression coated floating-pulsatile drug delivery of bisoprolol

The purpose of the present work was to design and optimize compression coated floating pulsatile drug delivery systems of bisoprolol. Floating pulsatile concept was applied to increase the gastric residence of the dosage form having lag phase followed by a burst release. The prepared system consisted of two parts: a core tablet containing the active ingredient and an erodible outer shell with gas generating agent. The rapid release core tablet (RRCT) was prepared by using superdisintegrants with active ingredient. Press coating of optimized RRCT was done by polymer. A 3² full factorial design was used for optimization. The amount of Polyox WSR205 and Polyox WSR N12K was selected as independent variables. Lag period, drug release, and swelling index were selected as dependent variables. Floating pulsatile release formulation (FPRT) F13 at level 0 (55 mg) for Polyox WSR205 and level +1 (65 mg) for Polyox WSR N12K showed lag time of 4 h with >90% drug release. The data were statistically analyzed using ANOVA, and P < 0.05 was statistically significant. Release kinetics of the optimized formulation best fitted the zero order model. In vivo study confirms burst effect at 4 h in indicating the optimization of the dosage form.

Timing is important in medication administration: a timely review of chronotherapy research

BACKGROUND

Chronotherapy involves altering the timing of medication administration to improve the overall control of a disease and to minimise treatment side-effects, and is an emerging concept in the field of therapeutics.

AIM

The aim of this review is to conduct an in-depth analysis of the recent literature in order to identify and evaluate the evidence base for drug chronotherapy.

METHOD

A literature search was conducted in three databases (Medline, Embase, International Pharmaceutical Abstracts) using the search terms "Chronotherapy", "Chronopharmacology", "Chronopharmacokinetics", "Chronopharmacodynamics", "Chronoefficacy", "Chronoformulation", "Morning and Evening", "Morning and Bedtime" and their combinations. The selection criteria for the inclusion of articles in the review included currency (years 2008-Aug 2011), publication in English language, studies done in Humans and non-review articles that pertained to 'drug' therapy.

RESULTS

Our search revealed a total of 192 journal articles, of which 41 articles were selected for review. The specific hypothesis for the effectiveness of chronotherapy that was tested in these 41 studies was chronoeffectiveness (n = 34), followed by chronopharmacokinetics (n = 5), chronomodulation (n = 3) and chronopharmacodynamics (n = 2). The findings from two-thirds (n = 27) of the reviewed studies, support the notion of chronotherapy.

CONCLUSION

The review presents the scope of chronotherapy in drug utilization. We believe that the knowledge of chronotherapy is growing and the current research for chronotherapy is promisingly in the conceptualization or early experimental phase. Going forward, chronotherapy studies should also explore genetic, gender and age related differences. Preliminary screening of new drugs for chronotherapeutic potential may be a way of enhancing quality use of medicines.

Circadian clock manipulation for cancer prevention and control and the relief of cancer symptoms

Life has evolved on this planet with regular daily spans of direct solar energy availability alternating with nocturnal spans of dark. Virtually every earth-borne life form has factored this circadian pattern into its biology to ensure the temporal coordination with its resonating environment, a task essential for its individual survival and that of its species. The first whole genome inspections of mutations in human colon and breast cancer have observed specific retained clock gene mutations. Single nucleotide polymorphisms within the genes of clock, clock-controlled, and melatonin pathways have been found to confer excess cancer risk or protection from cancer. Experimental studies have shown that specific core clock genes (Per2 and Per1) are tumor suppressors because their genetic absence doubles tumor numbers, and decreasing their expression in cancer cells doubles cancer growth rate, whereas their overexpression decreases cancer growth rate and diminishes tumor numbers. Experimental interference with circadian clock function increases cancer growth rate, and clinical circadian disruption is associated with higher cancer incidence, faster cancer progression, and shorter cancer patient survival. Patients with advanced lung cancer suffering greater circadian activity/sleep cycle disruption suffer greater interference with function, greater anxiety and depression, poorer nighttime sleep, greater daytime fatigue, and poorer quality of life than comparable patients who maintain good circadian integration. We must now determine whether strategies known to help synchronize the circadian clocks of normal individuals can do so in advanced cancer patients and whether doing so allows cancer patients to feel better and/or live longer. Several academic laboratories and at least 2 large pharmaceutical firms are screening for small molecules targeting the circadian clock to stabilize its phase and enhance its amplitude and thereby consolidate and coordinate circadian organization, which in turn is likely to help prevent and control human cancer. These drugs and strategies can, in turn, be used to make cancer patients with advanced disease feel and function more normally.

Influence of nocturnal asthma on chronotype

Individual differences in circadian rhythm have been studied since the past century. Chronotypes are a chronobiology classification based on the preferential times for beginning and ending activities throughout the day. Chronotypes can be classified as definitely morning, moderately morning, indifferent, moderately evening, and definitely evening. We aim to assess the distribution of chronotypes in asthmatics and the relationship of chronotype to the presence of nocturnal symptoms. Two hundred subjects were evaluated, 100 asthmatics and 100 non-asthmatics. The Morningness/Eveningness questionnaire was applied for chronotype determination. The asthmatics were subdivided according to the presence or absence of nocturnal symptoms. The chronotype distribution did not differ significantly between asthmatics and non-asthmatics. Thirty-five percent of the asthma group reported nocturnal symptoms. There was a significant difference in chronotype distribution between asthmatics with and without nocturnal worsening. The asthmatics with nocturnal symptoms had a lower prevalence of morning types and had a greater predominance of indifferent chronotype compared to asthmatics without nocturnal symptoms (p = 0.011). In conclusion, asthmatics with nocturnal symptoms present deviation from the chronotype distribution curve when compared to asthmatics without nocturnal symptoms. This is the first study to show the effect of a disease on chronotypes.

The Dosing-Time Dependent Effects of Intravenous Hypnotics in Mice

Chronobiology, which focuses on the biological rhythms that occur in the organization of living organisms, has been studied for several decades. Chronopharmacology, however, has received little attention until recently. We examined the hypnotic duration of intraperitoneally administered ketamine, pentobarbital, propofol, midazolam, and ethanol, to test whether they have obvious dosing-time dependent effects. Male C57BL/6 mice, which showed clear circadian rhythms of water-intake under a strict 12-h lighting cycle, were used. All tested drugs had significantly longer episodes of loss of righting reflex when administered at 22:00 (early active phase) than at 10:00 (early inactive phase). This dosing-time dependent hypnotic duration did not depend on the contents and activities of cytochrome P450 enzymes in the liver. These findings might be of clinical benefit in deciding the administration time and doses of anesthetics.

[Chronobiology, chronotherapy and vascular risk]

The importance of rhythmic activities in humans, and their influence on the diseases are underscored. Clinical chronology is fundamental in order to interpret the physiopathological basis of temporary variations. Knowing the variability of the biological processes also makes it possible improving the effect of drugs utilized and minimize their adverse effects. This is the objective of Chronotherapy. We apply chronology and Chronotherapy in cardiovascular diseases, since many of them adjust their prevalence for specific rhythms. One thinks about the mechanisms or factors that favor cardiovascular diseases, especially those related to the circadian variations of blood pressure. We also review the variations in the pharmacokinetics of the drugs used in the treatment of cardiovascular diseases, delving further into the analysis of its effects according to their administration schedule. We can conclude that the use of those drugs according to the chronological knowledge makes possible to achieve better results in the control of cardiovascular diseases, and a greater safety in its use.

Chronopharmacological studies of ketamine in normal and NMDA epsilon1 receptor knockout mice

BACKGROUND

The effectiveness and toxicity of many drugs depends on the dosing-time schedule, relative to the circadian rhythms of biochemical, physiological, and behavioural processes. Previous studies have found chronopharmacology of ketamine, which is a N-methyl-d-aspartate (NMDA) receptor antagonist. The in vivo contribution of the NMDA receptor epsilon1 subunit (NR2A) in this effect is unclear.

METHODS

In the present study, daily variations in the hypnotic effect of ketamine were determined in wild-type mice and NMDA epsilon1 knockout (KO) mice.

RESULTS

The effect of ketamine had a definite daily variation in wild-type mice. No significant difference in blood concentration was observed at different dosing times (10:00 and 22:00). In NMDA receptor epsilon1 KO mice, the hypnotic effect of ketamine was weaker than in wild-type mice and there was no dependence on the time of administration. Significant pharmacokinetic differences were not observed between wild-type and KO mice.

CONCLUSIONS

The enhanced hypnotic effect in the active phase of the circadian cycle is likely a result of changes with the time of day in the susceptibility of the central nervous system to ketamine. Knockout of the NMDA receptor epsilon1 subunit gene markedly reduced the effect of ketamine, and eliminated the time-dependent sensitivity to ketamine.

Biologic and molecular mechanisms for sex differences in pharmacokinetics, pharmacodynamics, and pharmacogenetics: Part II

There are specific pharmacology issues related to women's unique physiology, including the hormonal changes that occur throughout their life span. Studies have shown alterations in drug metabolism in relation to phase of menstrual cycle, during pregnancy, or after menopause. In the brain, hormones can alter the response to drugs through various mechanisms. Estrogen and other compounds can bind to the estrogen receptor and modulate a wide range of activities within the cell. In addition, animal studies have demonstrated sexual dimorphism in the brain in terms of both the type of response to estrogen and the response as related to timing of administration. Many normal physiological changes that occur during pregnancy can affect pharmacokinetics and pharmacodynamics. These changes during pregnancy are dramatic rises in levels of estrogen and progesterone, increases in maternal blood volume, altered protein binding resulting from a drop in albumin levels, and a rise in levels of other plasma proteins. The field of chronobiology offers a way to study these changes in biological functions. Chronopharmacology is the study of how biological rhythms, particularly 24-hour, menstrual cycle, and annual rhythms, impact the pharmacokinetics and pharmacodynamics of drugs as a function of their timing. Chronopharmacokinetics is the study of the absorption, distribution, metabolism, and elimination of medicines according to the time of day, menstrual cycle, or year. In addition to applying chronobiology to the study of drugs used in women, new technologies were addressed from computer modeling, pharmacogenetics (genetics of the response to drugs), and in vivo drug metabolism studies.

Timing treatment to the rhythm of disease. A short course in chronotherapeutics

The recognition of circadian rhythms in both normal human biologic function and disease has heightened the awareness that the timing of drug regimens may have an important impact on effectiveness of treatment. Outcomes in several diseases that have predictable circadian variations (e.g., arthritis, asthma, allergies, pepticulcer disease, dyslipidemia, cancer) have been improved by matching the timing of medication use to the circadian rhythm of the illness. Results of the ongoing CONVINCE study may provide evidence that chronotherapy for hypertension and angina pectoris may be more effective than traditional homeostatic treatment.

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.

A chronobiologic approach to the pharmacotherapy of hypertension and angina

OBJECTIVE

To review the chronobiology of hypertension and coronary artery disease and the application of chronotherapeutics to their treatment and prevention.

DATA SOURCES

Clinical trials and review articles (English-language) on the topic of chronotherapy and cardiovascular disease were identified via a MEDLINE search from 1990 to March 2000, using the search terms chronotherapy, circadian rhythm, cardiovascular disease, hypertension, and angina.

DATA EXTRACTION

Search and evaluation focused on published clinical trials and review articles of circadian variation associated with pharmacotherapy for cardiovascular disease.

DATA SYNTHESIS

The existence of circadian rhythm in cardiovascular disease is well established. Heart rate and blood pressure peak during the morning hours and reach a nadir at bedtime. The incidence of myocardial infarction, stroke, sudden cardiac death, and myocardial ischemia also increases during the early-morning hours. Based on these relationships, researchers have begun to apply the science of chronotherapeutics, or timing of drug effect with biologic need, to improve cardiovascular outcomes. This includes administering traditional agents at specific times throughout the day and developing new agents--chronotherapeutic formulations with special release mechanisms--targeted at inducing the greatest effect during the morning surges. Chronotherapeutic agents are specifically designed to provide peak plasma concentrations during the early-morning hours, when effect appears most needed; lowest concentrations occur at night, when heart rate and blood pressure are lowest and, consequently, cardiovascular events are least likely to occur.

CONCLUSIONS

Whether chronotherapy of cardiovascular disease offers an advantage in long-term outcomes over traditional therapy must be studied in clinical trials.

Clinical chronobiology and chronotherapeutics with applications to asthma

The concept of homeostasis (i.e., constancy of the milieu interne) has long dominated the teaching and practice of medicine. Concepts and findings from chronobiology, the scientific study of biological rhythms, challenge this construct. Biological processes and functions are not at all constant; rather, they are organized in time as rhythms with period lengths that range in duration from as short as a second or less to as long as a year. It is the body's circadian (24 h) rhythms that have been researched most intensely. The peak and trough of these rhythms are ordered rather precisely in time to support the biological requirements of activity during the day and sleep at night. The timing of the peak and trough plus the magnitude of variation (amplitude) of physiological and biochemical functions during the 24 h give rise to predictable-in-time, day-night patterns in the manifestation and exacerbation of many common medical conditions. Circadian rhythms also can influence the response of patients to diagnostic tests and therapeutic interventions according to their timing with reference to body rhythms. Rhythms in the pathophysiology of medical conditions and patient tolerance to medications constitute the basis for chronotherapeutics, the timing of treatment in relation to biological rhythm determinants as a means of optimizing beneficial effects and safety. The article discusses recent advances in medical chronobiology and chronotherapeutics and their relevance to clinical medicine in general and the management of asthma in particular. Indeed, since asthma is a disease that exhibits rather profound circadian rhythmicity, investigation of its pathophysiology and therapy necessitates a chronobiologic approach.

Chronopharmacology for deoxyspergualin: toxicity and efficacy in the rat

BACKGROUND

Deoxyspergualin (DSG), a potent immunosuppressive drug, has been clinically used as a rescue therapy for acute graft rejection. However, DSG has severe adverse effects that limits its use. Here, we examined the optimized therapeutic protocol for DSG using chronopharmacological profiles of it.

METHODS

First, a dosing time-dependent difference in the toxicity and efficacy of DSG was determined using a heterotopic heart transplantation model. Second, chronokinetics of DSG were examined to reveal the mechanism for dosing time-dependent differences in the effect.

RESULTS

In rats treated with DSG at the active period, bone marrow suppression and damage of small intestine were significantly severe. However, no significant difference was found in cardiac allograft survival and pharmacokinetics according to the timing of drug administration.

CONCLUSIONS

The toxicity of DSG varied with the dosing time, whereas its efficacy did not. The chronopharmacological approach may provide merits for immunosuppressive therapy with DSG in clinical organ transplantation.

Enhancement of tumor growth under short light/dark cycle in mouse lung

We examined whether a change in daily light/dark cycle affected DNA synthesis and tumor growth in mouse lung. Both CD-1 and A/J mice, which were treated with urethane and maintained under the short light/dark cycle (6 h light, 6 h dark), developed significantly larger sizes of lung tumors than the mice maintained under the standard light/dark cycle (12 h light, 12 h dark), indicating that short and frequent light/dark cycles enhanced tumor growth. When 3H-labeled thymidine was injected and incorporated radioactivity in the lung tissue was measured, two peaks of DNA synthesis in the lung were observed in a day under the short light/dark cycle, and both peaks were during light periods, while only one peak was observed during the dark period under the standard light/dark cycle. Although the level of [3H]thymidine incorporation into the lung tissue in the short light/dark cycle is lower than that in the standard cycle, frequent or unbalanced DNA synthesis may have promoted the growth of lung tumors.