Novel drug-delivery systems for hypertension

Mucosal absorption of antibody drugs enhanced by cell-penetrating peptides anchored to a platform of polysaccharides

Our previous studies demonstrated that L-octaarginine grafted onto hyaluronic acid via a tetraglycine spacer significantly enhanced intranasal absorption of protein drugs with a molecular weight (Mw) of 22 kDa or less. The present study focused on its potential as an absorption enhancer for antibody drugs with a larger Mw and the enhancement mechanism. When ranibizumab (48 kDa) alone was intranasally administered in mice, its absolute bioavailability was 0.67% on average. The mean bioavailability elevated to 6.2% under coadministration with tetraglycine-L-octaarginine-linked hyaluronic acid. A similar result was observed under substitution of ranibizumab with certolizumab pegol (91 kDa), although bioavailability itself decreased with the Mw increase, irrespective of coadministration with the hyaluronic acid derivative. Rat experiments also revealed that coadministration with the polysaccharide derivative resulted in significant enhancement of intranasal absorption of trastuzumab (148 kDa). In vitro studies using gene-knocked down cells indicated that syndecan-4-induced macropinocytosis played a crucial role on acceleration of antibody uptake into epithelial cells on the nasal mucosa, irrespective of their Mw. It appeared that neither clathrin heavy chain nor caveolin-1 involved in cellular uptake of antibodies. Tetraglycine-L-octaarginine-linked hyaluronic acid was concluded to be a promising delivery tool that possessed universal absorption-enhancing abilities independent to Mw of biologics.

Captopril Polyvinyl Alcohol/Sodium Alginate/Gelatin-Based Oral Dispersible Films (ODFs) with Modified Release and Advanced Oral Bioavailability for the Treatment of Pediatric Hypertension

Hypertension can begin in childhood; elevated blood pressure in children is known as pediatric hypertension. Contrary to adult hypertension, there is a scarcity of commercial medications suitable for the treatment of pediatric hypertension. The aim of this study was to develop orally dispersible films (ODFs) loaded with captopril for the treatment of hypertension in children. Captopril-loaded ODFs were composed of different blends of synthetic polymers, such as polyvinyl alcohol (PVA) and polyvinyl pyrrolidone, and natural polymers, such as sodium alginate (SA) and gelatin. The ODFs were characterized based on their mechanical and thermal properties, drug content, surface morphology, in vitro disintegration, in vitro release, and bioavailability. A novel HPLC method with precolumn derivatization was developed to precisely and selectively determine captopril levels in plasma. A low concentration of PVA and a high concentration of SA generated ODFs with faster hydration and disintegration rates. SA-based films exhibited fast disintegration properties (1-2 min). The optimized modified-release film (F2) showed significant (p < 0.05) enhancement in bioavailability (AUC = 1000 ng min/mL), with a value 1.43 times that of Capoten® tablets (701 ng min/mL). While the plasma concentration peaking was in favor of the immediate-release tablet, Tmax was significantly prolonged by 5.4 times for the optimized ODF (3.59 h) compared with that of the tablets (0.66 h). These findings indicate uniform and sustained plasma concentrations, as opposed to the pulsatile and rapid plasma peaking of captopril from the immediate-release tablets. These findings suggest that the modified release of oral films could offer more favorable plasma profiles and better control of hypertension than the conventional release tablets.

Microneedles for Extended Transdermal Therapeutics: A Route to Advanced Healthcare

Sustained release of drugs over a pre-determined period is required to maintain an effective therapeutic dose for variety of drug delivery applications. Transdermal devices such as polymeric microneedle patches and other microneedle-based devices have been utilized for sustained release of their payload. Swift clearing of drugs can be prevented either by designing a slow-degrading polymeric matrix or by providing physiochemical triggers to different microneedle-based devices for on-demand release. These long-acting transdermal devices prevent the burst release of drugs. This review highlights the recent advances of microneedle-based devices for sustained release of vaccines, hormones, and antiretrovirals with their prospective safe clinical translation.

Percutaneous Delivery of Antihypertensive Agents: Advances and Challenges

Hypertension remains a significant risk factor for several cardiovascular disorders including coronary artery disease and heart failure. Despite the large armamentarium of drugs available for the management of high blood pressure, low oral availability is an ongoing challenge. Researchers are constantly developing alternative drug delivery systems. This review focuses on the transcutaneous delivery of antihypertensive agents. The use of diverse technologies for the delivery of specific antihypertensive agents is emphasized. The advances made and the challenges encountered are highlighted. Several transdermal drug delivery strategies are employed for the transport of this group of therapeutic agents across the skin and the most widely used techniques include microneedles, iontophoresis, sonophoresis, and chemical penetration enhancers. Each of these methods has benefits and limitations, and there are ongoing attempts by scientists to address the shortcomings. For instance, skin irritation continues to be a major challenge with iontophoretic transport while the quantity of a medication that can be incorporated into dissolving microneedles is limited. With skin permeation enhancers, concerns relating to cytotoxicity and irritation are common. Even though the use of ultrasound is exciting, this mode of delivery is also accompanied by challenges such as the design of a battery system that is potent enough to drive a low-frequency sonophoretic cymbal array, while still being portable enough to function as a wearable device. Although most researchers report enhanced drug delivery with the aforementioned methods, it is important to deliver therapeutically useful doses of these medications.

Pharmaceutical applications of electrospinning

Development of tailor-made pharmaceutical nanofibers has gained vital prominence due to ease of fabrication and versatility of electrospinning (ES). ES is one of the flexible and, wonderful strategies for the fabrication of nanofibers. ES unit comprises a supplier of high voltage current, a syringe (pump), spinneret and a metal plate collector. The obtained nanofibers are optimized by manipulating process and formulation variables Viz: polymer/drug resolution (viscosity, concentration, physical phenomenon, molecular mass) and the environmental conditions (humidity, temperature). The electrospun nanofibers can be used for loading of the drug, amorphization of a crystalline API and an increase in its physical storage stability. ES technique enables mixing of two or more API and may facilitate or inhibit the burst release of a drug, along with attainment of modified release. Additionally, nanofibers demonstrate a reduction in overall dose needed for the therapeutic activity, by improving dissolution and bioavailability of the drugs. The current review is an attempt to focus on ES method, the optimization parameters, and pharmaceutical applications of the electrospun nanofibers.

1,4-Dihydropyridine: A Dependable Heterocyclic Ring with the Promising and the Most Anticipable Therapeutic Effects

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Nowadays, heterocyclic compounds act as a scaffold and are the backbone of medicinal chemistry. Among all of the heterocyclic scaffolds, 1,4-Dihydropyridine (1,4-DHP) is one of the most important heterocyclic rings that possess prominent therapeutic effects in a very versatile manner and plays an important role in synthetic, medicinal, and bioorganic chemistry. The main aim of the study is to review and encompass relevant studies related to 1,4-DHP and excellent therapeutic benefits of its derivatives. An extensive review of Pubmed-Medline, Embase and Lancet’s published articles was done to find all relevant studies on the activity of 1,4-DHP and its derivatives. 1,4-DHP is a potent Voltage-Gated Calcium Channel (VGCC) antagonist derivative which acts as an anti-hypertensive, anti- anginal, anti-tumor, anti-inflammatory, anti-tubercular, anti-cancer, anti-hyperplasia, anti-mutagenic, anti-dyslipidemic, and anti-ulcer agent. From the inferences of the study, it can be concluded that the basic nucleus, 1,4-DHP which is a voltage-gated calcium ion channel blocker, acts as a base for its derivatives that possess different important therapeutic effects. There is a need of further research of this basic nucleus as it is a multifunctional moiety, on which addition of different groups can yield a better drug for its other activities such as anti-convulsant, anti-oxidant, anti-mutagenic, and anti-microbial. This review would be significant for further researches in the development of several kinds of drugs by representing successful matrix for the medicinal agents.

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

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

Alginic acid cell entrapment: a novel method for measuring in vivo macrophage cholesterol homeostasis

Macrophage conversion to atherosclerotic foam cells is partly due to the balance of uptake and efflux of cholesterol. Cholesterol efflux from cells by HDL and its apoproteins for subsequent hepatic elimination is known as reverse cholesterol transport. Numerous methods have been developed to measure in vivo macrophage cholesterol efflux. Most methods do not allow for macrophage recovery for analysis of changes in cellular cholesterol status. We describe a novel method for measuring cellular cholesterol balance using the in vivo entrapment of macrophages in alginate, which retains incorporated cells while being permeable to lipoproteins. Recipient mice were injected subcutaneously with CaCl2 forming a bubble into which a macrophage/alginate suspension was injected, entrapping the macrophages. Cells were recovered after 24 h. Cellular free and esterified cholesterol mass were determined enzymatically and normalized to cellular protein. Both normal and cholesterol loaded macrophages undergo measureable changes in cell cholesterol when injected into WT and apoA-I-, LDL-receptor-, or apoE-deficient mice. Cellular cholesterol balance is dependent on initial cellular cholesterol status, macrophage cholesterol transporter expression, and apolipoprotein deficiency. Alginate entrapment allows for the in vivo measurement of macrophage cholesterol homeostasis and is a novel platform for investigating the role of genetics and therapeutic interventions in atherogenesis.

Programmed delivery of verapamil hydrochloride from tablet in a capsule device

The aim of the present work was to develop a programmed drug delivery system which would be able to release the drug after 6 h of lag time by use of hydrophilic polymers. The capsule body was made impermeable by use of formaldehyde vapor treatment, while the cap was untreated. The capsule was filled with two layered tablets (tablet-in-capsule), followed by a sodium bicarbonate:citric acid mixture (SBCM) and lactose as bulking agent. Sodium alginate, chitosan, HPMC K15 and chitosan:sodium alginate complex (CSAC) were used as the rate modulating layer. Through combined use of HPMC K15 and adjusting the ratio of CSAC, the desired lag time of 6 h was obtained. The effect of the bulking agents on the lag time were also studied and it was found that the lag time was decreased with higher amounts of lactose, and delayed dissolution and decreased lag time was observed at higher amount of effervescent mixture.

Alginates: Existing and Potential Biotechnological and Medical Applications

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

Antihypertensive pharmacobezoar

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

Transdermal clonidine: therapeutic considerations

Transdermal clonidine was approved by the US Food and Drug Administration in 1984 for the treatment of mild-to-moderate hypertension alone or in combination with a diuretic. Clonidine is released from the patch at a constant rate and thus displays a pharmacokinetic pattern not dissimilar to that of infusion therapy. Transdermal clonidine, like oral clonidine, is effective first- or second-line therapy for most forms of hypertension. More recently, transdermal clonidine has found alternative uses in the areas of smoking cessation, posttraumatic stress disorder, menopausal hot flashes, and alcohol and opiate withdrawal syndromes. The not infrequent development of a dermatitis, together with a substantially greater cost than oral clonidine, have been the major undoings for transdermal clonidine.

Extended-release Divalproex in Child and Adolescent Outpatients with Epilepsy

PURPOSE

To determine whether valproic acid [divalproex (DVP)] extended-release, administered at a higher proportionate once-daily dosage, can be safely substituted for delayed-release or sprinkle in pediatric patients with epilepsy.

METHODS

Patients between ages 6 and 17 years with stable epilepsy taking DVP were randomized to 7 days of either DVP delayed-release/sprinkle (at the usual daily dose taken before study entry) or extended-release DVP (daily dose, 8% to 25% higher than their usual dose), and then (crossed over to) 7 days of the comparator formulation. Patient's clinical status was evaluated at a screening visit and on days 8 and 15, and with telephone follow-up 1 month after study completion.

RESULTS

No statistically significant difference in mean plasma VPA levels measured at the end of treatment was observed: 99, 92, and 103 mug/ml with the delayed-release tablets (n = 4), the sprinkle formulation (n = 11), and the extended-release tablets (n = 16), respectively. Seizure-control rates were stable during patients' use of the extended-release formulation. None of the study patients experienced a treatment-related adverse event.

CONCLUSIONS

The total daily dose for patients taking the delayed-formulation may need to be increased by < or = 20% when they are switched to the extended-release formulation. When switching from sprinkles to the extended-release formulation, individual variability must be considered. In patients who have VPA levels near the very high end of the therapeutic range (>100 microg/ml), it may be more prudent to make only minor modifications to the total daily dose during conversion and then to individualize the DVP extended-release dose based on plasma levels.

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.

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.

Divalproex extended-release versus the original divalproex tablet: results of a randomized, crossover study of well-controlled epileptic patients with primary generalized seizures

PURPOSE

To compare the safety and efficacy of two formulations of divalproex, extended-release divalproex versus the original divalproex tablet, in adolescent and adult patients with epilepsy.

METHODS

Eligible patients were between the ages of 12 and 65 years with primary generalized epilepsy, which was controlled over the month prior to study enrollment with divalproex or valproic acid 1000 mg to 2000 mg/day. The patients were well-controlled; 39 of 43 (91%) had no seizures in the previous year. Patients were randomized to receive 84 days of either divalproex two times a day (b.i.d.)/three times a day (t.i.d.) or extended-release divalproex qd and then (crossed over to) 84 days of the comparator formulation. During the two treatment periods, patients received the same daily dose equivalent of divalproex as was taken during the month prior to study entry. The clinical status of patients was evaluated at a screening visit and at four subsequent visits conducted every 42 days.

RESULTS

There was no statistically significant difference between the formulation groups for seizure control rate (95% [41/43] for divalproex and 93% [40/43] for extended-release divalproex). Likewise, the formulation groups were similar based on the incidence of treatment-related adverse events. The most frequently reported (< or =11.4% for either formulation) treatment-related adverse events were asthenia, tremor, nausea, and dizziness.

CONCLUSIONS

Extended-release divalproex was similar to divalproex for the treatment of well-controlled, primary generalized epilepsy in terms of overall safety and efficacy parameters.

Transdermal clonidine skin reactions

The clonidine transdermal therapeutic system is being used as a therapy for blood pressure treatment. Systemic side effects seem to be fewer than with oral clonidine. However, localized skin reactions occur frequently and the incidence increases with the dose and duration of use. Common signs include erythema, scaling, vesiculation, excoriation, and induration. Allergic contact dermatitis is less frequent but common. Hyperpigmentation and depigmentation also occur. Pretreatment with 0.5% hydrocortisone is associated with less skin irritation and higher blood levels. Although oral clonidine is no longer widely used in the management of hypertension, awareness of these reactions to the transdermal delivery of this agent is important.

Verapamil revisited: a transition in novel drug delivery systems and outcomes

Verapamil, the oldest calcium-channel blocker, is now being rediscovered and reevaluated in the light of new novel drug delivery systems and new evidence-based trials. Verapamil, a phenylalkylamine, is useful in the treatment of hypertension, stable angina, and narrow QRS supraventricular arrhythmias. This calcium antagonist is effective in both young and old, and both black and white hypertensive patients, and is free of metabolic side effects. Verapamil has a well-documented history as an effective antianginal agent when directly compared with a beta-blocker, and is more effective in reducing myocardial ischemia compared with amlodipine monotherapy. Because of the short half-life of verapamil, drug delivery systems are used to prolong the duration of action. Novel drug delivery systems using encapsulated beads or a modified osmotic pump have been designed to be taken at nighttime to provide maximal blood pressure reduction in the early morning hours and effective 24-hour blood pressure control, and to avoid excessive blood pressure reduction during sleep. The Verapamil in Hypertension and Atherosclerosis Study has documented equivalent effectiveness of verapamil compared with chlorthalidone, but showed superior plaque regression and reduced events in subjects with the greatest plaques with verapamil treatment. The Angina Prognosis Study in Stockholm, comparing verapamil and metoprolol for stable angina, found no difference in total cardiovascular mortality or combined cardiovascular events. Other large ongoing randomized, multicenter trials, including Controlled-Onset Verapamil Investigation of Cardiovascular Endpoints and the International Verapamil-Trandolapril Study, will expand our knowledge of the role of verapamil in the treatment of hypertension.

Influence of pluronic F-68 on dissolution and bioavailability characteristics of multiple-layer pellets of nifedipine for controlled release delivery

A multiple-layer design of pellets for nifedipine was developed using pluronic F-68 to enhance dissolution rate. The influence of ratios of nifedipine in the inner layer to that in the outer layer, the ratios of pluronic F-68 to nifedipine in the solid dispersion, and the thickness of the control membrane on dissolution characteristics were investigated. With an increasing ratio of pluronic F-68 to nifedipine, the dissolution rate of nifedipine was gradually promoted and the extent of release was enhanced as well. DSC thermograms illustrate the gradual disappearance or broadening of the nifedipine melting peak with the presence of pluronic F-68. The decrease of the nifedipine ratio in the inner layer and the increase of the ratio of pluronic F-68 to nifedipine in the outer layer can enhance the release of nifedipine. With a fixed nifedipine ratio of 1.5 between the inner layer and the outer layer, increasing the ratio of pluronic F-68 to nifedipine in the outer layer significantly increased the initial release rate of nifedipine. By increasing the nifedipine ratio of the inner layer to the outer layer to 1:1, the increase of coating percentage referenced to the total weight decreased the release rate of nifedipine from the inner layer. The pharmacokinetic bioequivalence between the test product (Cardilate, N-6) and Coracten was found with a multiple-dose oral administration of 20 mg in 12 healthy, normal Chinese male volunteers.

Application of membrane-based dendrimer/DNA complexes for solid phase transfection in vitro and in vivo

In this study a general description of the use of solid support membranes as the device for DNA delivery mediated by PAMAM dendrimers is presented. In contrast to the other DNA carriers, dendrimer/DNA complexes retain the ability to transfect after drying, which enabled coating or incorporation of complexes into poly(DL-lactide-co-glycolide) or collagen-based bioerodable membranes. These studies provide support for the use of this technology for in vitro and in vivo transfection of skin cells. Expression of luciferase or green fluorescent protein from pCF1-Luc and pEGFP1 plasmids indicated that dendrimer/DNA complexes can mediate transfection after dissociation from the solid support and/or when retained on the surface of the membranes. Modification of the membranes by incorporation of an anionic lipid, phosphatidyl glycerol (PG) at 1-5% concentrations, resulted in more efficient in situ transfection, particularly with dendrimer/DNA complexes formed at the low charge ratios (1-5). We also report data supporting the feasibility of membrane-based dendrimer/DNA complexes, particularly formed at lower than neutralizing conditions, for topical in vivo delivery of DNA to hairless mouse skin.

[Compliance in antihypertensive therapy: analyses in scientific articles]

The aim of this study was to evaluate scientific articles published between 1991-1995, in order to identify the compliance in antihypertensive therapy, One hundred seven scientific articles were evaluated. The results showed that 68% were related to patient, 63% to pharmacological treatment, 62% general, 39% non pharmacological treatment, 34% organizational factors, and 8% related to disease. Compliance with antihypertensive therapy was the major challenge of hypertension management and to know how this aspect was focalized in scientific articles possible reduce non compliance in hypertension.

A new ternary polymeric matrix system for controlled drug delivery of highly soluble drugs: I. Diltiazem hydrochloride

PURPOSE

The purpose of this study was to develop a new ternary polymeric matrix system that is easy to manufacture and that delivers a highly soluble drug over long periods of time.

METHODS

Pectin, hydroxypropylmethylcellulose (HPMC), and diltiazem HCl granulated with gelatin at optimized ratios were blended at different loading doses and directly compressed. Swelling behavior, dissolution profiles and the effect of hydrodynamic stress on release kinetics were evaluated.

RESULTS

Diltiazem release kinetics from the ternary polymeric system was dependent on the different swelling behavior of the polymers and varied with the drug loading dose and hydrodynamic conditions. Drug release followed either non-Fickian or Case II transport kinetics. The relative influence of diffusion and relaxational/dissolution effects on release profiles for different drug loadings was calculated by a nonlinear regression approach. Photographs taken during swelling show that the anisotropic nature of the gel structure, drug loading dose, swelling capacity of polymers used, and the design of delivery system all play important roles in controlling the drug release and dissolution/erosion processes.

CONCLUSIONS

Zero-order delivery of diltiazem HCl from a simple tablet matrix was achieved. The ternary polymeric system developed in this study is suitable for controlled release of highly soluble drugs. It offers a number of advantages over existing systems, including ease of manufacturing and of release modulation, as well as reproducibility of release profiles under well defined hydrodynamic conditions. Our delivery system has the potential to fully release its drug content in a controlled manner over a long time period and to dissolve completely.

Clinicians and patients with hypertension: unsettled issues about compliance

Ambulatory treatment of hypertension depends largely on long-term oral medications to lower blood pressure and delay or prevent cardiovascular morbidity and mortality. Failure to achieve the therapeutic goal may reflect biologic, pharmacologic, or behavioral factors. Ignoring behavioral factors may result in unnecessary or even dangerous regimen escalation. More than half of patients with insufficient reductions in blood pressure display suboptimal medication compliance as assessed by pill count or bioassay. Once-daily dosing may be an important part of enhancing compliance, patient convenience, and regimen simplification; however, drug concentrations may be subtherapeutic when dosing delays or omissions occur. Electronic monitoring data in hypertension, glaucoma, seizure disorders, and other diseases indicate that 50% to 60% of patients adhere well to prescribed regiments, that 5% to 10% adhere poorly, and that the 30% to 45% adhere to an intermediate but markedly variable degree. A growing body of literature offers empirical support for focused and personalized interventions.

Controlled-release drug delivery systems in cardiovascular medicine

Controlled-release drug delivery technology has had a significant effect on the pharmacotherapy of cardiovascular diseases. Oral and transcutaneous controlled-release systems allow relatively short-acting drugs to be administered once or twice daily with comparable therapeutic efficacy and fewer adverse reactions compared with standard formulations. They can provide decreased fluctuations in drug concentrations in plasma while possibly reducing the total amount of drug necessary for a clinical response. Techniques include the diffusion, bioerosion or degradation, and generation of osmotic pressure in orally active and transcutaneous drug delivery systems. Calcium-channel blocking agents, nitrates, beta-blocking agents, antiarrhythmic agents, clonidine, and nicotinic acid can be administered by these techniques, which have greatly influenced the application of these drugs in clinical practice.

Transdermal clonidine as an adjunct to nifedipine-GITS therapy in patients with mild-to-moderate hypertension

Calcium channel blockers and central alpha-agonists are among the classes of antihypertensive drugs that yield the most favorable overall effects on risk factors for hypertension-related end-organ damage. An open-label prospective trial in 42 patients with a mean baseline blood pressure of 144/102 mm Hg sought to assess the usefulness of adjunctive treatment with transdermal clonidine (0.1 to 0.3 mg/day) in patients responding inadequately to nifedipine--gastrointestinal therapeutic system (GITS) (30 to 60 mg/day) monotherapy. Thirty-nine patients who failed to reach the goal of a seated mean diastolic blood pressure of < 90 mm Hg when treated only with once-a-day nifedipine-GITS entered a transdermal clonidine (once a week) titration phase followed by an 8-week maintenance course of the two drugs combined. The 35 patients completing this last phase responded with a mean seated diastolic blood pressure of 127/87 mm Hg. Only six patients required the highest dose of clonidine for control. A 97% compliance rate with the transdermal medication contrasted with a compliance rate of only 73% for the oral nifedipine. Two of three patients who had contact dermatitis after wearing a transdermal clonidine patch withdrew from the trial prematurely; other minor side effects required no interruption of therapy. The nifedipine-clonidine combination not only achieved blood pressure control in these patients but may prove advantageous in combining the protective effects of the two agents against complications of the hypertensive syndrome.