A steady-state evaluation of the bioavailability of chronotherapeutic oral drug absorption system verapamil PM after nighttime dosing versus immediate-acting verapamil dosed every eight hours

The role of clock genes in pharmacology

The physiology of a wide variety of organisms is organized according to periodic environmental changes imposed by the earth's rotation. This way, a large number of physiological processes present diurnal rhythms regulated by an internal timing system called the circadian clock. As part of the rhythmicity in physiology, drug efficacy and toxicity can vary with time. Studies over the past four decades present diurnal oscillations in drug absorption, distribution, metabolism, and excretion. On the other hand, diurnal variations in the availability and sensitivity of drug targets have been correlated with time-dependent changes in drug effectiveness. In this review, we provide evidence supporting the regulation of drug kinetics and dynamics by the circadian clock. We also use the examples of hypertension and cancer to show current achievements and challenges in chronopharmacology.

Drug delivery technologies for chronotherapeutic applications

It has been proven that the body follows a 24-hour cycle called a circadian rhythm. This cycle is coordinated by the suprachiasmatic nucleus and controls nearly all bodily functions including those related to drug delivery. Knowledge of the body's circadian rhythm leads to an improved understanding of diseases and their treatment, known as chronotherapy, such that synchronizing drug application in accordance with the natural rhythm of the body leads to improved disease management and a greater patient therapeutic outcome. Chronotherapeutic diseases include asthma, cardiovascular diseases, glaucoma, rheumatoid arthritis and cancers. In order to treat these diseases numerous chronotherapeutic drug delivery systems have been developed, such that drug is released in the period when it is most needed. This review paper attempts to concisely explicate the role of circadian rhythms in various disease states and furthermore describes the various oral drug delivery technologies that have been employed for the treatment of chronotherapeutic diseases.

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.

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.

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.

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.

Drug delivery systems for treatment of systemic hypertension

Novel drug delivery systems are available in many areas of medicine. Their application in the treatment of hypertension continues to widen. Oral drug delivery systems permit antihypertensive agents that were previously administered two to four times daily to be administered once daily. Biotechnical use of chemical-dispensing systems has been applied to propranolol (polymer coated beads), clonidine (transdermal therapeutic system), nifedipine (osmotic pump and coat-core), isradipine (osmotic pump), verapamil (sodium alginate and spheroidal oral delivery absorption system), felodipine (coat-core), nisoldipine (coat-core) and diltiazem (polymer coated beads and Geomatrix. The initial goal was to lower blood pressure by a uniform amount throughout the entire day. Now, new drug delivery systems are being developed to target blood pressure in the early morning hours when most cardiovascular events occur. Two chronotherapeutic drug delivery systems are now available for verapamil (chronotherapeutic oral delivery absorption system and delayed coat osmotic pump). Disadvantages of sustained-release products include delayed achievement of pharmacodynamic effect, unpredictable bioavailability, enhanced first-pass hepatic metabolism, dose dumping, sustained toxicity, dosage inflexibility and increased cost. Potential advantages include reduced administration frequency, enhanced adherence and convenience, reduced toxicity, stable drug concentrations, uniform drug effect, decreased cost (occasionally) and decreased daily dosage.

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.

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.