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At least 163 records · Page 9Linked to original sources
PubMed1990

Tissue distribution of a brain-enhanced chemical delivery system for estradiol.

Enhanced delivery and sustained release of estradiol (E2) in the brain could have potential clinical applications in the effective treatment of vasomotor "hot flushes" and prostatic cancer. We have, therefore, evaluated a brain-enhanced E2-chemical delivery system (E2-CDS), which is based upon the interconvertible dihydropyridine in equilibrium with pyridinium salt redox reaction. In this study, we evaluated the tissue distributions of E2-Q+ and E2--the inactive and active metabolites of the E2-CDS. Both E2-Q+ and E2 were detected in all tissues analyzed. In peripheral tissues, E2-Q+ and E2 were rapidly cleared, but in brain, concentrations of both compounds exhibited a slow decline with a t1/2 = 8 days. 14 Days after the E2-CDS administration, brain levels of E2-Q+ exceeded plasma levels by 170-fold, fat levels by 20-fold, and liver levels by 8-fold. Similarly, brain-E2 levels exceeded plasma levels by 38-fold, fat levels by 11-fold, and liver levels by 7-fold. Furthermore, levels of E2-Q+ In anterior pituitary, kidney, heart, and lung were initially 2- to 6-fold higher than brain levels, but 14 days after the E2-CDS administration, brain levels of E2-Q+ exceeded E2-Q+ levels in these peripheral tissues by 1.5- to 3-fold. The increased brain/peripheral tissues ratios of E2-Q+ and E2 in rats treated with the E2-CDS support brain-enhanced delivery and sustained release of E2 from this delivery system.

Animals↗
PubMed1989

Errors in low flow oxygen delivery systems.

Accurate delivery of low flow oxygen is essential for the management of infants with chronic respiratory failure. Twenty-seven examples of one low flow oxygen meter were tested. Measured flows were found to differ greatly from indicated settings, particularly at 250 mL/min settings. Knowledge of such errors as well as improved quality control are essential for appropriate management of oxygen therapy.

Oxygen Inhalation Therapy↗
PubMed1996

Oral immunization of rabbits against Pasteurella multocida with an alginate microsphere delivery system.

Oral delivery of microencapsulated antigens is a potential means to vaccinate rabbits against Pasteurella multocida, a common bacterial pathogen. Groups of five rabbits were dosed orally on days 0, 7, and 14 with alginate microspheres prepared to contain no added protein, 5 mg of a potassium thiocyanate extract of P. multocida (PTE), or 5 mg of PTE with 200 micrograms of cholera toxin (CT). In addition, groups were dosed orally with 5 mg of soluble PTE with or without 200 micrograms CT, intranasally (IN) with 1 mg of soluble PTE, or with saline. Serum and nasal lavage samples collected prior to initial immunization and 10, 16, and 21 days later were assayed by ELISA for anti-PTE IgG and IgA. Strong nasal lavage IgA and serum IgG activities were found in samples from rabbits immunized with PTE IN or orally when incorporated into microspheres. Addition of CT did not significantly enhance either response. To examine the development of protective immunity, groups were similarly immunized and challenge-exposed IN on day 16 with 10(6) CFU of P. multocida. One week later, rabbits were euthanized, and specimens from the lungs, nasopharynx, liver, and inner ear were cultured for P. multocida. Less severe infections of the lung and nasopharynx developed in rabbits immunized with PTE IN or orally in microspheres, with or without added CT. In addition, culture of liver and tympanic bullae samples from these rabbits yielded growth of P. multocida less frequently compared to other P. multocida-challenged rabbits. Coadministration of CT and PTE did not significantly improve protective immunity to challenge.

Adjuvants, Immunologic↗
PubMedDate not supplied

Drug delivery systems: avoiding the pitfalls.

Drug delivery systems are increasingly sophisticated, sometimes in ways that make it difficult to determine the regulatory and quality system requirements for the device component of these systems. This article discusses some important requirements and factors to consider when designing, developing and marketing drug delivery systems.

Drug Delivery Systems↗
PubMed2000

Long-term vaginal antibody delivery: delivery systems and biodistribution.

Topical delivery systems can provide prolonged delivery of antibodies to the vaginal mucosal surface for long-term protection against infectious diseases. We examined the biodistribution of antibodies during 30 days of vaginal antibody delivery in mice. Different antibody preparations (including monoclonal IgG and IgM, as well as several different (125)I-labeled IgGs) were administered by polymer vaginal rings, which were designed to provide continuous antibody delivery. Antibody concentrations remained high in the vaginal secretions for up to 30 days after disk insertion; radiolabeled antibody was also found, at approximately 100 times lower concentration, in the blood and other tissues. The measured concentrations agreed reasonably well with a simple pharmacokinetic model, which was used to calculate mucosal and systemic concentrations as a function of antibody delivery and elimination rates. Results from the model were consistent with previously reported antibody pharmacokinetic measurements: the half-life for antibody elimination for the vagina was approximately 3 h; the half-life for IgG(1) clearance from the blood was >1 day; and the overall permeability constant for vaginal uptake of IgG was approximately 0.01 to 0.03 h(-1). These results provide important information for the design of controlled antibody delivery devices for vaginal use, and suggest that high-dose, long-term vaginal administration of antibodies may be a reasonable approach for achieving sustained mucosal and systemic antibody levels.

Administration, Intravaginal↗
PubMed1975

Rural medical care: an experimental delivery system.

The experimental medical care delivery system has been operational since February, 1969. An average of over 200 patient visits per month were managed at the clinic during the past year. The average visit cost is $23.00, which is competitive with cost rates at neighborhood health centers. The average time per patient visit has been approximately 1 hr and 20 min. Of persons using the clinic, the largest number are women of childbearing age. Elderly patients have visited the clinic most frequently. Illness problems have accounted for the majority of patient visits. The program represents a cooperative effort between a rural community and a university to solve a problem of national interest. The implementation of this program has provided the opportunity to operationalize the family nurse practitioner concept in a system of medical care delivery. The feasibility of providing high quality medical care in a rural community by extending medical resources concentrated in an urban area has been demonstrated. This type of delivery system does provide a viable alternative for extending medical care to rural communities. A clinic manned by paramedical personnel offers the urban medical center along with concerned physicians the opportunity to extend their resources to rural areas which have been unable to attract and retain physicians.

Adolescent↗
PubMed2002

Evaluation of the System O2 Inc portable nonpressurized oxygen delivery system.

OBJECTIVE: To evaluate the performance of the System O2 portable non-pressurized delivery system (SysO2). This device produces oxygen through chemical reaction and might have utility for emergency/field use. METHODS: Performance was evaluated with 10 unmanned trials conducted under standard laboratory conditions. Measures included oxygen flow (mean and peak), total oxygen yield, and system weight-indexed yield. RESULTS: Oxygen flow peaked at 5.74 +/- 0.28 L x min(-1) (mean +/- SD) at 16.9 +/- 1.5 minutes before rapidly falling to zero. Mean flow was 2.98 +/- 1.52 L x min(-1) with a total yield of 62.9 +/- 6.6 L. Mean oxygen fraction was 0.96 +/- 0.15. The weight per unit of oxygen is substantially higher than for commercially available pressurized cylinders; e.g., 47.7 vs. 10.2 g x L(-1) for the small 246 L M9 cylinder. CONCLUSIONS: Given the limited flow rate and supply duration, we believe the SysO2 system does not offer significant advantage over the available pressurized oxygen systems as a source for emergency oxygen.

Equipment Design↗
PubMed1985

Direct evidence for brain-specific release of dopamine from a redox delivery system.

Dopamine (1) was transformed into a lipoidal redox chemical delivery system which crosses the blood brain barrier and is converted to a quaternary ammonium precursor of 1, thus "locking in" this ionized moiety. Systemic administration of this chemical delivery system for 1 increased concentrations of the major acid metabolite of 1, dihydroxyphenylacetic acid, (6) in several brain regions, and despite sustained inhibition of prolactin secretion, concentrations of 1 were unchanged. Inhibition of monoamine oxidase did not encourage the formation of 1 from this delivery system. When de novo synthesis of 1 was inhibited, however, regional brain concentrations of both 1 and dihydroxyphenylacetic acid acid were increased by systemic administration of the delivery system. This study provides direct evidence for the brain-specific delivery of 1 by a redox chemical delivery system and indicates that the 1 formed is delivered to sites which normally store newly biosynthesized 1.

Animals↗
PubMed2003

Rational design and engineering of delivery systems for therapeutics: biomedical exercises in colloid and surface science.

Engineering delivery systems of therapeutic agents has grown into an independent field, transcending the scope of traditional disciplines and capturing the interest of both academic and industrial research. At the same time, the acceleration in the discovery of new therapeutic moieties (chemical, biological, genetic and radiological) has led to an increasing demand for delivery systems capable of protecting, transporting, and selectively depositing those therapeutic agents to desired sites. The vast majority of delivery systems physically reside in the colloidal domain, while their surface properties and interfacial interactions with the biological milieu critically determine the pharmacological profiles of the delivered therapeutic agents. Interestingly though, the colloidal and surface properties of delivery systems are commonly overlooked in view of the predominant attention placed on the therapeutic effectiveness achieved. Moreover, the development and evaluation of novel delivery systems towards clinical use is often progressed by serendipity rather than a systematic design process, often leading to failure. The present article will attempt to illustrate the colloid and interfacial perspective of a delivery event, as well as exemplify the vast opportunities offered by treating, analysing and manipulating delivery systems as colloidal systems. Exploring and defining the colloid and surface nature of the interactions taking place between the biological moieties in the body and an administered delivery vehicle will allow for the rational engineering of effective delivery systems. A design scheme is also proposed on the way in which the engineering of advanced delivery systems should be practiced towards their transformation from laboratory inventions to clinically viable therapeutics. Lastly, three case studies are presented, demonstrating how rational manipulation of the colloidal and surface properties of delivery systems can lead to newly engineered systems relevant to chemotherapy, gene therapy and radiotherapy.

Biomedical Engineering↗
PubMed1997

[Development of a blood cardioplegia delivery system for children].

We have developed a blood cardioplegia delivery system for children. Essential points of a delivery system in pediatric cardiac surgery are (1) a small amount of priming volume of a delivery system, and (2) slow, steady infusion of a cardioplegic solution. We changed a heat exchanger to a smaller one for reduction of priming volume, and changed a roller pump tube to a smaller one for slow, steady infusion. Thus, priming volume of a delivery system has reduced from 180 to 100 ml, and we can infuse a cardioplegic solution at a steady rate less than 10 ml/min. Our clinical experience with this system suggests that this blood cardioplegia delivery system is useful for pediatric cardiac surgery.

Blood↗
PubMed1994

Development of an innovative nursing care delivery system.

In the reform of healthcare lies its renaissance, and in its challenges lie its opportunities. Faced with the changing needs of consumers, the evolving roles of care givers, technologic advances, and economic pressures, institutions are redesigning their physical facilities and systems of care delivery in preparation for a new era in healthcare. Innovative care delivery systems, developed to complement creative facility designs, will provide an approach to health-care that promotes administrative efficiency, patient/care giver satisfaction, and cost-effective use of resources. This article chronicles the development of a care delivery system for obstetric nursing, a blueprint for future healthcare at one institution.

Data Collection↗
PubMed2000

Skeletal drug delivery systems.

Selective drug delivery to any organ becomes very important in certain diseases and clinical manifestations, especially when the drug affects other exposed tissues adversely. The importance of selective drug action is still further increased when the affected part is poorly perfused. Although a network of blood vessels is present throughout skeletal tissue (or bone), it is not sufficient for immediate delivery of drugs to the desired site of action in the tissue and in sufficient amounts over appropriate time periods. Hence, selective drug delivery to the skeletal system has remained a great challenge to pharmaceutical scientists over the years. However, in the recent past, attention has been focused on the importance of skeletal drug delivery and the first Skeletal Drug Delivery System (SDDS) was introduced by Bucholz and Engelbrecht in 1970 for the delivery of drugs to skeletal tissues at a high concentration to achieve desirable therapeutic effects. SDDS is used to deliver the drug directly to skeletal tissue through self-setting cement, which also acts as a bone filler, thereby improving the therapeutic effectiveness of drugs in bone diseases. The present review highlights the applicability of various materials as bone fillers for the purpose of skeletal drug delivery.

Animals↗
PubMed2002

ATTEMPTS: a heparin/protamine-based delivery system for enzyme drugs.

A prodrug delivery system termed "Antibody Targeted, Triggered, Electrically Modified Prodrug-Type Strategy (ATTEMPTS)" has been developed to permit the antibody-directed administration of inactive enzyme drug including tissue-type plasminogen activator (tPA), and allow a subsequent triggered release of the active tPA at the target site. Cation-modified tPA (mtPA) was attached to a heparin-antifibrin complex via ionic interaction, and the active tPA can subsequently be released by the addition of protamine, a competitive heparin inhibitor. Anti-fibrin IgG was conjugated to heparin via an end-point attachment to form the heparin-antifibrin complex which provides the targeting efficiency of the final heparin/mtPA complex. Cation modification was performed by either chemical conjugation by linking (Arg)7Cys to tPA with N-succinimidy-3-(2-pyridyldithio) propionate or by recombinant DNA methods. Results show that the modification process did not significantly alter the specific activity of tPA with regard to plasminogen activation, fibrin-binding ability, and response toward fibrinogen. The complexes of both modified tPA-heparin did not yield any intrinsic catalytic activity owing to the blockage of the active site of tPA by the attached heparin. On the other hand, heparin-induced inhibition of modified tPA activity was reversed by adding protamine, which is similar to that of a prodrug delivery system. These results suggest that heparin/protamine-based enzyme delivery systems may be a useful tool to improve current enzyme therapeutic status, as well as thrombolytic therapy, by both regulating the release of active enzyme and aborting the associated systemic toxic effect. Currently, modification of enzyme drugs has been optimized by recombinant DNA technology assisted by computer simulation. In addition, the original strategy has been revised to obtain enhanced therapeutic efficacy.

Base Sequence↗
PubMed2006

Immunostimulatory colloidal delivery systems for cancer vaccines.

Cancer vaccine delivery is a multidisciplinary scientific field that is currently undergoing rapid development. An important component of cancer vaccines is the development of novel vaccine delivery strategies, such as colloidal immunostimulatory delivery systems. The importance of formulation strategies for cancer vaccines can be explained by the poor immunogenicity of tumour antigens. Colloidal vaccine delivery systems modify the kinetics, body distribution, uptake and release of the vaccine. This review explores recent research that is directed towards more targeted treatments of cancer through to colloidal vaccine delivery systems. Widely investigated carrier systems include polymeric micro- and nanoparticles, liposomes, archaeal lipid liposomes (archaeosomes), immune-stimulating complexes and virus-like particles. These systems are evaluated in terms of their formulation techniques, immunological mechanisms of action as well as the potential and limitations of such colloidal systems in the field of cancer vaccines.

Adjuvants, Immunologic↗
PubMed2002

Non-viral gene delivery systems.

Non-viral gene delivery systems have the potential to create viable pharmaceuticals from nucleic acids. These DNA delivery systems contain lipids and/or cationic polymers. In order for these systems to be developed into commercial products, several barriers must be overcome. These include obstacles in manufacturing, formulation and stability. In vivo, problems of extracellular non-specific interactions and intracellular trafficking to the nucleus are also encountered. Recent progress has been made in overcoming these issues.

Biological Transport, Active↗
PubMed2001

A novel pH- and time-based multi-unit potential colonic drug delivery system. I. Development.

A novel delivery system was developed for delivering drugs to the colon by selecting polymethacrylates with appropriate pH dissolution characteristics for the distal end of the small intestine and relying upon the relatively constant transit time of the small intestine. Pellets were prepared by powder layering of 5-aminosalicylic acid (5-ASA) on nonpareils (0.5-0.6 mm) in a conventional coating pan. Drug-layered pellets were coated with an inner layer of a combination of two pH-independent polymers Eudragit RL and RS (2:8), and an outer layer of a pH-dependent polymer, Eudragit FS. Scanning electron micrograph (SEM) pictures of the coated pellets showed the uniformity of both the coatings. The release profile of 5-ASA was studied in three phosphate buffers after a simulated gastric pre-soak for 2 h in pH 1.2 media. There was no drug release for 12 h at pH 6.5. There was a sustained release of 5-ASA for over 12 h both at pH 7.0 and 7.5 after a lag time at pH 7.0 and no lag time at pH 7.5. The release rate was faster at pH 7.5 than at pH 7.0. The delivery system demonstrated its potential for colonic delivery by resisting drug release until pH 6.5 and the combination of Eudragit RL and RS proved successful for the sustained delivery of 5-ASA at the expected pH of the colon.

Acrylic Resins↗
PubMed2000

Comparison of poly(acryl starch) and poly(lactide-co-glycolide) microspheres as drug delivery system for a rotavirus vaccine.

Drug delivery systems allowing controlled release of antigen are of particular interest in the development of vaccines. We have compared poly(acrylic starch) microspheres (PAS) and poly(lactide-co-glycolide) microspheres (PLG) as drug delivery systems for a rotavirus vaccine. The polymers are both biodegradable but have different degradation mechanisms and antigen release profiles. PAS are enzymatically degraded and have a continuous fast antigen release rate compared to the hydrolytically degraded PLG which release the incorporated antigen in a pulsatile manner. In this study mice were immunised intramuscularly and orally on three occasions with formalin-inactivated rotavirus (FRRV) incorporated in PAS and PLG and with FFRV alone. Serum and faeces samples were collected and analysed by ELISA for rotavirus specific IgG and IgA antibodies. A neutralising assay was also conducted on both serum and faeces antibodies. The two different polymer drug delivery systems induced different immune responses depending on administration route. PAS elicited significant antibody levels and neutralising effect after oral administration while PLG showed high antibody levels after intramuscular administration. The immune response appears to be dependent on the differences in antigen release and degradation mechanism for the two polymer systems.

Animals↗
PubMed2004

Modeling of drug release from polymeric delivery systems--a review.

Polymeric drug delivery platforms have been receiving increasing attention in the past decade. The pharmaceutical industry is evaluating modes of delivery for their prized therapeutics at every step of the design cycle. Not only can the drug delivery platform transport drug molecules effectively, it can also improve patient compliance, offer greater patient convenience, and extend product lifecycles as patents expire. A large number of successful drug delivery systems have been developed as a result of an almost arbitrary selection of constituents and configurations. However, the development of advanced drug delivery systems relies on a judicious and careful selection of components, configurations, and geometries, which can be facilitated through mathematical modeling of controlled release systems. Mathematical modeling aids in predicting the drug release rates and diffusion behavior from these systems by the solution of an appropriate model, thereby reducing the number of experiments needed. It also aids in understanding the physics of a particular drug transport phenomenon, thus facilitating the development of new pharmaceutical products. The objective of this article is to review the spectrum of mathematical models that have been developed to describe drug release from polymeric controlled release systems. The mathematical models presented in this article have been grouped under diffusion controlled systems, swelling controlled systems, and erosion controlled systems as proposed by Langer and Peppas. Simple empirical or semi-empirical models and complex mechanistic models that consider diffusion, swelling, and erosion processes simultaneously are presented.

Chemistry, Pharmaceutical↗