The effect of food on the pharmacokinetics of nifedipine in two slow release formulations: pronounced lag-time after a high fat breakfast

Comparative Bioequivalence and Food Effect of Two Formulations of 30-mg Nifedipine Controlled-Release Tablets in Healthy Chinese Adults

Nifedipine is a potent antihypertensive medication classified as a dihydropyridine calcium channel blocker. The objective of this trial was to assess the bioequivalence of a 30-mg nifedipine controlled-release tablet and a reference drug in a cohort of healthy Chinese individuals. Two independent open-label, randomized, single-dose, crossover studies were conducted, 1 under fasting conditions (N = 44, with 1 participant dropping out midway) and the other under fed conditions (N = 44, with 4 participants dropping out midway). Plasma concentrations of nifedipine were determined using liquid chromatography-mass spectrometry, and pharmacokinetic (PK) parameters were calculated using noncompartmental analysis with Phoenix WinNonlin 8.0 software. In both fasting and fed studies, reasonable bioequivalence was observed for the PK parameters of both the test product and the reference drug. A good safety profile was demonstrated for both the test product and reference drug, with no serious adverse events reported, and both were similarly well tolerated. An important observation with food coadministration was that systemic exposure to nifedipine (based on area under the curve, AUC0-∞) was reduced by approximately 12%. The bioequivalence of the test product and reference drug under fasting/fed conditions in healthy subjects in China was demonstrated by the study results.

Food Interactions Observed in a Pharmacokinetic Investigation Comparing Two Marketed Cold Preparations (BNO1016 and ELOM-080) after Administration to Beagle Dogs - A Pilot Study

Sinupret extract (BNO 1016) and Gelomyrtol forte (ELOM-080) represent the two top-selling cold remedies in Germany nowadays. Whereas BNO 1016 is a typical immediate release coated tablet, ELOM-080 is an enteric-coated soft gelatin capsule. The latter formulation, however, is at risk of pharmacokinetic interactions affecting absorption, especially in cases of concomitant food intake. In the present pilot study, we investigated the risk of a possible food effect in three male beagle dogs. Single doses of BNO 1016 and ELOM-80 were administered under fasting and fed conditions. Blood was sampled up to 30 h post-administration and plasma concentrations of the characteristic ingredients of BNO 1016 as well as ELOM-080 analytes were determined. Pharmacokinetic parameters focusing on the rate and extent of absorption were derived. BNO 1016 analytes demonstrated a similar course in both the fasted and fed states. ELOM-080 analytes also showed a similar picture in the fasted state. However, lag times (time from administration to first quantifiable time point in plasma) of up to 2 h post-administration with corresponding time to reach maximum concentration (obtained directly from the measured concentration) values of 3 to 4 h were observed, reflecting a longer gastric residence time. In the fed state, ELOM-080 showed significant pharmacokinetic characteristics, suggesting a clear food effect. A major observation was a double peak phenomenon that could be observed in two of three dogs. Furthermore, lag times of some analytes, up to 3 - 4 h, and corresponding time to reach maximum concentration values, up to 6 - 8 h, occurred. In contrast to BNO 1016, these findings suggest that, as with other enteric-coated formulations, there may also be a significant risk for food effects with ELOM-080 in humans.

Nifedipine Release From Extended-Release Solid Oral Formulations Using In Vitro Dissolution Testing Under Simulated Gastrointestinal Compression

Drug release plays a critical role in defining bioavailability for an extended release solid oral drug products and predictive dissolution tests are desired to establish clinically relevant quality standards for batch release. The objective of this study focuses on exploring the possible impacts of 1 gastrointestinal (GI) parameter for 1 drug: simulated GI contractions on nifedipine release (in 2 extended release solid oral formulations). The 60 mg nifedipine osmotic pump product A, and polymer matrix-based products B and C were examined in the study. An in-house dissolution system was used to simulate various levels of GI contractions on tested samples, and to monitor changes of sample mechanical properties during dissolution testing. The results show that the polymer matrix-based formulation failed to provide controlled release when simulated GI contraction was above 100 g of force. The method may be useful for polymer matrix-based products to assess potential formulation-related interactions with the GI tract during in vivo drug dissolution.

The mechanisms of pharmacokinetic food-drug interactions - A perspective from the UNGAP group

The simultaneous intake of food and drugs can have a strong impact on drug release, absorption, distribution, metabolism and/or elimination and consequently, on the efficacy and safety of pharmacotherapy. As such, food-drug interactions are one of the main challenges in oral drug administration. Whereas pharmacokinetic (PK) food-drug interactions can have a variety of causes, pharmacodynamic (PD) food-drug interactions occur due to specific pharmacological interactions between a drug and particular drinks or food. In recent years, extensive efforts were made to elucidate the mechanisms that drive pharmacokinetic food-drug interactions. Their occurrence depends mainly on the properties of the drug substance, the formulation and a multitude of physiological factors. Every intake of food or drink changes the physiological conditions in the human gastrointestinal tract. Therefore, a precise understanding of how different foods and drinks affect the processes of drug absorption, distribution, metabolism and/or elimination as well as formulation performance is important in order to be able to predict and avoid such interactions. Furthermore, it must be considered that beverages such as milk, grapefruit juice and alcohol can also lead to specific food-drug interactions. In this regard, the growing use of food supplements and functional food requires urgent attention in oral pharmacotherapy. Recently, a new consortium in Understanding Gastrointestinal Absorption-related Processes (UNGAP) was established through COST, a funding organisation of the European Union supporting translational research across Europe. In this review of the UNGAP Working group "Food-Drug Interface", the different mechanisms that can lead to pharmacokinetic food-drug interactions are discussed and summarised from different expert perspectives.

Effects of Dissolution Medium pH and Simulated Gastrointestinal Contraction on Drug Release From Nifedipine Extended-Release Tablets

In contrast to nifedipine matrix-based extended-release dosage forms, the osmotic pump drug delivery systems have a zero-order drug release independent of external variables such as pH, agitation rate, and dissolution media. The objective of this study focuses on the in vitro evaluation of the mechanical properties of osmotic pump and polymer matrix-based formulations in dissolution media, and the potential impacts that media pH and simulated gastrointestinal contraction have on drug release. Two strengths of osmotic pump product A and polymer matrix-based product B were used in this study. An in-house system was developed with the capability of applying mechanical compression and monitoring mechanical properties of sample during dissolution testing. A United States Pharmacopeia or an in-house apparatus was used for dissolution testing under various conditions. Compared to the product A, the mechanical properties of the product B change significantly at various pHs and mechanical compressions. The results suggest that polymer matrix-based products bear a risk of formulation-related interactions with the gastrointestinal tract during in vivo drug dissolution, especially in the case of concomitant pH and gastric contractile changes. Modified dissolution testing devices may help formulation scientists in product development and provide regulatory agencies with an additional metric for quality assurance of drug products.

Physiological Considerations and In Vitro Strategies for Evaluating the Influence of Food on Drug Release from Extended-Release Formulations

Food effects on oral drug bioavailability are a consequence of the complex interplay between drug, formulation and human gastrointestinal (GI) physiology. Accordingly, the prediction of the direction and the extent of food effects is often difficult. With respect to novel formulations, biorelevant in vitro methods can be extremely powerful tools to simulate the effect of food-induced changes on the physiological GI conditions on drug release and absorption. However, the selection of suitable in vitro methods should be based on a thorough understanding not only of human GI physiology but also of the drug and formulation properties. This review focuses on in vitro methods that can be applied to evaluate the effect of food intake on drug release from extended release (ER) products during preclinical formulation development. With the aid of different examples, it will be demonstrated that the combined and targeted use of various biorelevant in vitro methods can be extremely useful for understanding drug release from ER products in the fed state and to be able to forecast formulation-associated risks such as dose dumping in early stages of formulation development.

The impact of food intake on the luminal environment and performance of oral drug products with a view to in vitro and in silico simulations: a PEARRL review

Objectives

Using the type of meal and dosing conditions suggested by regulatory agencies as a basis, this review has two specific objectives: first, to summarize our understanding on the impact of food intake on luminal environment and drug product performance and second, to summarize the usefulness and limitations of available in vitro and in silico methodologies for the evaluation of drug product performance after food intake.

Key findings

Characterization of the luminal environment and studies evaluating product performance in the lumen, under conditions suggested by regulatory agencies for simulating the fed state, are limited. Various in vitro methodologies have been proposed for evaluating drug product performance in the fed state, but systematic validation is lacking. Physiologically based pharmacokinetic (PBPK) modelling approaches require the use of in vitro biorelevant data and, to date, have been used primarily for investigating the mechanisms via which an already observed food effect is mediated.

Summary

Better understanding of the impact of changes induced by the meal administration conditions suggested by regulatory agencies on the luminal fate of the drug product is needed. Relevant information will be useful for optimizing the in vitro test methods and increasing the usefulness of PBPK modelling methodologies.

Robustness of barrier membrane coated metoprolol tartrate matrix tablets: Drug release evaluation under physiologically relevant in vitro conditions

Robust in vitro drug release behavior is an important feature of extended release (ER) hydrophilic matrix formulations for accurate prediction of in vivo drug release. In this study, ER hydrophilic matrix tablets of metoprolol tartrate were formulated using a high viscosity grade of hypromellose as a rate-limiting polymer. Expectedly, this formulation showed an undesirable initial burst release followed by controlled drug release. Application of a barrier membrane (BM) coating of ethylcellulose with a pore former (hypromellose) resulted in the elimination of the burst effect. The aim of this study was to investigate the robustness of in vitro metoprolol release from BM-coated hydrophilic matrix tablets by simulating the physicochemical properties of gastrointestinal fluids and mechanical stress in the fasted- and fed state human gastrointestinal (GI) tract. Uncoated and BM-coated matrices were subjected to various dissolution studies simulating the varying pH conditions and additional physicochemical parameters, and the mechanical stress that can be caused by GI motility during both fasted and fed state GI passage. The BM-coated formulation showed robust drug release without an initial burst in all test scenarios. BM-coated matrix formulations thus represent a very promising approach for obtaining a highly controlled and robust drug release from oral ER formulations.

Can dosage form-dependent food effects be predicted using biorelevant dissolution tests? Case example extended release nifedipine

AIMS

Food intake is known to have various effects on gastrointestinal luminal conditions in terms of transit times, hydrodynamic forces and/or luminal fluid composition and can therefore affect the dissolution behavior of solid oral dosage forms. The aim of this study was to investigate and detect the dosage form-dependent food effect that has been observed for two extended-release formulations of nifedipine using in vitro dissolution tests.

METHODS

Two monolithic extended release formulations, the osmotic pump Adalat® XL 60mg and matrix-type Adalat® Eins 30mg formulation, were investigated with biorelevant dissolution methods using the USP apparatus III and IV under both simulated prandial states, and their corresponding quality control dissolution method. In vitro data were compared to published and unpublished in vivo data using deconvolution-based in vitro - in vivo correlation (IVIVC) approaches.

RESULTS

Quality control dissolution methods tended to overestimate the dissolution rate due to the excessive solubilizing capabilities of the sodium dodecyl sulfate (SDS)-containing dissolution media. Using Level II biorelevant media the dosage form dependent food effect for nifedipine was described well when studied with the USP apparatus III, whereas the USP apparatus IV failed to detect the positive food effect for the matrix-type dosage form.

CONCLUSIONS

It was demonstrated that biorelevant methods can serve as a useful tool during formulation development as they were able to qualitatively reflect the in vivo data.

Applications of linking PBPK and PD models to predict the impact of genotypic variability, formulation differences, differences in target binding capacity and target site drug concentrations on drug responses and variability

This study aimed to demonstrate the added value of integrating prior in vitro data and knowledge-rich physiologically based pharmacokinetic (PBPK) models with pharmacodynamics (PDs) models. Four distinct applications that were developed and tested are presented here. PBPK models were developed for metoprolol using different CYP2D6 genotypes based on in vitro data. Application of the models for prediction of phenotypic differences in the pharmacokinetics (PKs) and PD compared favorably with clinical data, demonstrating that these differences can be predicted prior to the availability of such data from clinical trials. In the second case, PK and PD data for an immediate release formulation of nifedipine together with in vitro dissolution data for a controlled release (CR) formulation were used to predict the PK and PD of the CR. This approach can be useful to pharmaceutical scientists during formulation development. The operational model of agonism was used in the third application to describe the hypnotic effects of triazolam, and this was successfully extrapolated to zolpidem by changing only the drug related parameters from in vitro experiments. This PBPK modeling approach can be useful to developmental scientists who which to compare several drug candidates in the same therapeutic class. Finally, differences in QTc prolongation due to quinidine in Caucasian and Korean females were successfully predicted by the model using free heart concentrations as an input to the PD models. This PBPK linked PD model was used to demonstrate a higher sensitivity to free heart concentrations of quinidine in Caucasian females, thereby providing a mechanistic understanding of a clinical observation. In general, permutations of certain conditions which potentially change PK and hence PD may not be amenable to the conduct of clinical studies but linking PBPK with PD provides an alternative method of investigating the potential impact of PK changes on PD.

Quantitative prediction of formulation-specific food effects and their population variability from in vitro data with the physiologically-based ADAM model: a case study using the BCS/BDDCS Class II drug nifedipine

Quantitative prediction of food effects (FE) upon drug pharmacokinetics, including population variability, in advance of human trials may help with trial design by optimising the number of subjects and sampling times when a clinical study is warranted or by negating the need for conduct of clinical studies. Classification and rule-based systems such as the BCS and BDDCS and statistical QSARs are widely used to anticipate the nature of FE in early drug development. However, their qualitative rather than quantitative nature makes them less appropriate for assessing the magnitude of FE. Moreover, these approaches are based upon drug properties alone and are not appropriate for estimating potential formulation-specific FE on modified or controlled release products. In contrast, physiologically-based mechanistic models can consider the scope and interplay of a range of physiological changes after food intake and, in combination with appropriate in vitro drug- and formulation-specific data, can make quantitative predictions of formulation-specific FE including the inter-individual variability of such effects. Herein the Advanced Dissolution, Absorption and Metabolism (ADAM) model is applied to the prediction of formulation-specific FE for BCS/BDDCS Class II drug and CYP3A4 substrate nifedipine using as far as possible only in vitro data. Predicted plasma concentration profiles of all three studied formulations under fasted and fed states are within 2-fold of clinically observed profiles. The % prediction error (%PE) in fed-to-fasted ratio of Cmax and AUC were less than 5% for all formulations except for the Cmax of Nifedicron (%PE=-29.6%). This successful case study should help to improve confidence in the use of mechanistic physiologically-based models coupled with in vitro data for the anticipation of FE in advance of in vivo studies. However, it is acknowledged that further studies with drugs/formulations exhibiting a wide range of properties are required to further validate this methodology.

A review of the gastrointestinal therapeutic system (GITS) formulation and its effectiveness in the delivery of antihypertensive drug treatment (focus on nifedipine GITS)

Hypertension treatment guidelines do not discriminate within drug classes and, furthermore, do not consider whether or not all of the formulations of any given drug licensed for once-daily administration can be considered to be therapeutically interchangeable. This article focuses on this issue with respect to nifedipine and the development of the gastrointestinal therapeutic system (GITS) formulation. Nifedipine GITS is regarded as the gold standard once-daily formulation of nifedipine and, as such, it is anticipated that alternative formulations will be therapeutically equivalent to nifedipine GITS. In general, this depends on demonstrating pharmacokinetic bioequivalence. This article is intended to focus attention on generic substitution and, in particular, on aspects of the scientific basis for the substitution of generic products in place of branded products. Such substitution is required for cost-saving or cost-containment reasons and is justified on the basis that the generic (substitute) drug is “therapeutically” equivalent to the branded drug. Unfortunately, there are serious shortcomings in the current methods of assessment insofar as they are typically based on statistical comparisons of average pharmacokinetic parameter values, using arbitrary comparative criteria. This article illustrates the shortcomings of the current approaches to generic substitution and concludes that, in regulatory terms, either more rigorous pharmacokinetic criteria are required or pharmacodynamic indices should be added to reinforce the regulatory criteria. Generic substitution is a balancing act but, at the moment, the cost issue is dominant. To restore the balance, equivalent efficacy must be confirmed. At present, therefore, in the absence of such regulatory rigor, the obvious course is to prefer the branded product, the therapeutic efficacy of which (including outcome benefits) has been established.

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.

Formulation of long-acting nifedipine tablets influences the heart rate and sympathetic nervous system response in hypertensive patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Pharmacokinetic and pharmacodynamics studies are usually carried out separately with theoretical linking or interpretations. The pharmacokinetics of short- vs. long-acting formulations of nifedipine is well known, but the pharmacokinetics of different once-a-day formulations of nifedipine is generally not well known by the practising physician.

WHAT THIS STUDY ADDS

This study provides practical patient-based information linking pharmacokinetics to pharmacodynamics in one of the target populations of patients, those with hypertension, who might receive the two different drugs. AIMS The haemodynamic responses to nifedipine vary between short- and long-acting formulations. However, the latter have not been compared despite marked differences in their constitution. Our 1-month randomized, crossover study was designed to compare the 30-mg osmotic, constant-release nifedipine gastrointestinal therapeutic system (N-GITS) with an encapsulated mini-tablet Coracten XL.

METHODS

Forty-four hypertensive patients aged 63 +/- 7 years were studied. The formulation was changed on day 15 and (for a single dose) day 30. At days 0, 14, 15, 29 and 30, patients were monitored for 6 h after dosing, during which blood pressure (BP), heart rate (HR) and plasma levels of norepinephrine (NE) and nifedipine were measured. The primary outcome was the difference in plasma NE between formulations at the time of peak nifedipine level.

RESULTS

Systolic BP decreased rapidly after the first dose of Coracten, achieving nadir at 5 h. HR rose by 1.2 +/- 8.8 beats min(-1). After N-GITS HR fell by 2.4 +/- 7.7 beats min(-1) (P = 0.159). Plasma NE was higher in the Coracten- (480 +/- 38.3 pg ml(-1)) than N-GITS-treated patients (343 +/- 75.0 pg ml(-1)) at the time of peak nifedipine concentrations (4 and 5 h, respectively) and their change from baseline was significantly (P = 0.0046) different. A similar difference between the drugs was seen again at days 15 and 30, at 5 h after switching formulations.

CONCLUSIONS

This study suggests that two different formulations of once-daily nifedipine result in different BP and plasma NE responses, and that switching between formulations causes opposite effects upon the sympathetic nervous response to falling BP.

Modified-release nifedipine: a review of the use of modified-release formulations in the treatment of hypertension and angina pectoris

Nifedipine is a dihydropyridine calcium channel antagonist with predominantly vasodilatory activity. Modified-release formulations of nifedipine are effective antihypertensive and antianginal therapies and are generally well tolerated. Among the available formulations, those that produce a gradual increase in plasma nifedipine concentration, which is then sustained over a 24-hour period, are preferred, as they cause a gradual onset of vasodilatation and avoid baroreflex sympathetic activation (for example, nifedipine gastrointestinal therapeutic system [GITS] and a Japanese controlled-release formulation). Modified-release nifedipine had beneficial effects on a number of markers of vascular function, and nifedipine GITS reduced the need for coronary procedures in patients with coronary artery disease. In patients with hypertension, nifedipine GITS and nifedipine retard had beneficial effects on the overall incidence of major cardiovascular events, as did nifedipine retard in patients with concurrent hypertension and coronary artery disease.

Clinical spectrum of the osmotic-controlled release oral delivery system (OROS), an advanced oral delivery form

BACKGROUND

The osmotic-controlled release oral delivery system, OROS, is an advanced drug delivery technology that uses osmotic pressure as the driving force to deliver pharmacotherapy, usually once-daily, in several therapeutic areas.

OBJECTIVE

The purpose of this review is to discuss the evolution of OROS technology and examine the many therapeutic areas where OROS products are being used.

METHODS

A search of Medline and EMBASE were performed using the keywords 'OROS' and 'osmotic delivery' for the period January 1990 to June 2005. Data were also obtained from the manufacturers' websites and associated publications.

RESULTS

OROS technology has evolved over the last 30 years, resulting in four systems: the elementary osmotic pump; the two-layer osmotic push-pull tablet; the advanced longitudinally compressed tablet multilayer formulation; and, the L-OROS system. OROS technology is employed for drug delivery in many therapeutic areas including: cardiovascular medicine, endocrinology, urology, and central nervous system (CNS) therapeutics. Two calcium channel blockers utilizing OROS technology for the treatment of hypertension are nifedipine and verapamil. Glipizide extended-release is used for the treatment of type 2 diabetes. Doxazosin is used for the treatment of benign prostatic hyperplasia, and oxybutynin for overactive bladder. Most recent developments are with drugs that affect the CNS, including the use of methylphenidate for treatment of attention deficit hyperactivity disorder, paliperidone extended-release and OROS hydromorphone, which are under clinical development for schizophrenia and chronic pain, respectively.

CONCLUSIONS

Drug delivery using the various OROS products can result in an improved safety profile, stable drug concentrations, uniform drug effects, and reduced dosing frequency. OROS technology has also enabled the use of an effective starting dose, without the need for dose titration, which allows the achievement of symptom control much earlier than that observed with immediate-release preparations. Such attributes can enhance patient compliance and convenience, thereby ensuring efficacy and improving patient outcomes.

Impact of the intragastric location of extended release tablets on food interactions

Gastrointestinal motility and transport as well as concomitant food intake are factors that are known to influence pharmacokinetics derived after intake of extended release dosage forms. However, the mechanisms behind these influencing factors are mostly unknown. In this study the gastrointestinal transit and the in vivo drug release of magnetically labelled extended release tablets containing felodipine were monitored together with the drug absorption phase of pharmacokinetics under fasting and fed conditions in six healthy volunteers using Magnetic Marker Monitoring. It was found that the in vivo drug release profiles of the tablets compared well under fasting and fed conditions. However, the plasma concentration profiles were strongly influenced by concomitant food intake. This could be attributed to elongated residence of the tablets in proximal parts of the stomach, resulting in delayed drug absorption and the occurrence of late high plasma peak concentrations. The lag time until the first appearance of felodipine in plasma and the residence time of the tablets in the proximal stomach, were found to be directly correlated. The study shows that increased plasma peak drug concentrations after intake of extended release formulations together with food can be explained by poor mixing in the proximal part of the stomach and are not necessarily due to failure of the formulation to control drug release (dose dumping).

Dihydropyridine calcium channel blockers: basic pharmacological similarities but fundamental therapeutic differences

Recent trials indicate that treatment with calcium channel blockers (CCBs) reduces cardiovascular morbidity and mortality in hypertensive patients (including those with significant coronary artery disease). Since the fundamental mechanism of action of all CCBs is the same, it might be assumed that the findings of these outcome studies can be generalized to all types of CCB. However, in the light of the well-recognized clinical pharmacological differences between the 'rate-limiting' agents, verapamil and diltiazem, and the dihydropyridine group of CCBs, this must be considered to be a misconception. Less well-recognized, and often ignored, are the significant differences between agents within the dihydropyridine group. These differences translate to distinct differences in the therapeutic profiles and may well translate into differences in outcome during long-term treatment. Thus, the differences in pharmacokinetic, pharmacodynamic and therapeutic profiles make it clear that caution should be exercised in assuming that all dihydropyridine CCBs licensed for once-daily administration are equivalent in terms of their durations of action and overall antihypertensive efficacy.

Antihypertensive therapy: special focus on drug interactions

Today, the lifetime risk of patients aged 55-65 years to receive antihypertensive drugs approaches 60%. Yet, recent trials suggest that hypertension is not adequately controlled in the majority of patients. The prevalence of hypertension increases with advancing age, as does the prevalence of comorbid conditions and the total number of medications taken. Multi-drug therapy, advancing age and comorbid conditions are also key risk factors for adverse drug reactions and drug interactions. In this review, the authors evaluate the most frequently used antihypertensive drugs (diuretics, beta-adrenergic blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers, angiotensin II receptor Type 1 blockers and alpha-adrenergic blockers) with special reference to pharmacodynamic and pharmacokinetic drug interactions. As the spectrum of drugs prescribed is constantly changing, safety yesterday does not imply safety today and safety today does not imply safety tomorrow. Furthermore, therapeutic efficacy should not be neglected over concerns regarding drug interactions. Many patients are at risk of clinically relevant drug interactions involving antihypertensive drugs but, presently, even more patients may be at risk of suffering from the consequences of their inadequately treated hypertension. In this respect, the authors discuss controversial viewpoints on the overall clinical relevance of drug interactions occurring at the level of cytochrome P450 metabolism.

Bioavailability of modified-release methylphenidate: influence of high-fat breakfast when administered intact and when capsule content sprinkled on applesauce

Ritalin, an immediate release form of racemic methylphenidate hydrochloride, has been available in the USA since 1955 and is used for the treatment of ADHD. The objective of this study was to evaluate the pharmacokinetics of modified-release methylphenidate (highest single dose), Ritalin LA, when administered under fasting condition, with a high-fat breakfast, and when sprinkled on applesauce in healthy adult subjects. Blood samples were drawn for 24 h following a 40 mg oral administration. Most subjects appeared to produce a bimodal methylphenidate plasma concentration profile. In all three treatment groups, methylphenidate was rapidly absorbed with an initial average t(max(0-4)) of 1.3-2.4 h and an average peak plasma concentration [C(max(abs))] of 14.4-15.2 ng/ml. On average, both the rate [C(max(abs)) and t(max(abs))] and the extent of absorption (AUC(0- infinity)) of methylphenidate were similar when the capsule was given with a high fat breakfast and when the capsule contents were sprinkled onto applesauce, compared with the fasting state. No dose dumping was observed when the capsule was given with a high fat breakfast or when sprinkled onto applesauce. The dose was safe and generally well tolerated. Coadministration of a single oral dose of 40 mg methylphenidate capsule whether administered intact with a high-fat breakfast or sprinkled on applesauce did not affect the overall rate or extent of absorption of methylphenidate compared with the fasted condition.

Clinical use of nifedipine GITS in the treatment of hypertension: an overview

Given the major role of elevated blood pressure in the pathogenesis of both stroke and coronary heart disease, one of the biggest challenges facing public health authorities and medical practitioners is the control of hypertension worldwide, both in individual patients and at the population level. The prevalence of hypertension increases with age and is nearly 60% in people aged 65 - 74 years. With increasing age, polymorbidity and polypharmacy usually contribute to an increasingly complex approach to manage the respective clinical conditions, including the treatment of hypertension. All subgroups of calcium channel blockers are effective and well-tolerated in lowering blood pressure. They are of demonstrated benefit for the prevention of stroke in elderly patients with systolic hypertension. Calcium channel blockers are particularly recommended for elderly patients with systolic hypertension and for black patients. The nifedipine gastrointestinal therapeutic system (GITS) formulation provides a once-daily dosing regimen with a continuous and slow release of the drug, resulting in a smooth plasma concentration/time profile. The INSIGHT study established that nifedipine GITS decreased mortality and morbidity at the same level as standard diuretic treatment in hypertensive patients with additional risk factors. A subgroup analysis showed that the long-term protective effects of nifedipine GITS extended to hypertensive patients with diabetes mellitus and with previous myocardial infarction. Two substudies of INSIGHT showed that nifedipine slowed the progression of atherosclerosis in carotid arteries (intima-media thickness) and coronary arteries (coronary calcium) as compared to diuretic.

Formulation-dependent food effects demonstrated for nifedipine modified-release preparations marketed in the European Union

The objective of this study was a comparative investigation of the influence of concomitant food intake on the bioavailability of two nifedipine-containing controlled-release formulations. Adalat OROS and CORAL were compared in a randomised, non-blind, four-way crossover design in 24 healthy, male subjects after single dose administration following a high fat American breakfast or an overnight fast of 12 h, respectively. Plasma samples were withdrawn until 48 h post-dose. In the fasted state, the bioavailability (AUC and C(max) values) was lower for CORAL than for Adalat OROS. Under fed conditions, differences in bioavailability between both products were markedly increased. With respect to the therapeutic use of both products, the most important finding was the significant dose-dumping effect observed after fed administration of CORAL, resulting in nifedipine plasma concentrations of nearly three- to four-fold in 11 of 24 volunteers. The mean ratio of C(max) was 235% comparing CORAL with Adalat OROS under these conditions. The formulation-dependent food interaction observed in this study may be therapeutically relevant, especially in the case of changing administration conditions or switching from one product to the other.