Showing papers on "Drug carrier published in 1981"

Magnetically-localizable, biodegradable lipid microspheres

Abstract: A drug carrier formulation consisting of magnetically-localizable, biodegradable lipid microspheres containing a magnetically-responsive substance, one or more diodegradable lipids and one or more nontoxic surfactants is described herein. There is also described a process for preparing such microspheres wherein the magnetically-responsive substance is wetted with surfactant and part of the lipids, then this material is added to the remaining lipids and heated to 90-100°C., water is added, the mixture is sonicated to obtain a microemulsion, which is then cooled and lyophilized to obtain the product.

The use of chitin and chitosan as drug carriers.

Abstract: The suitability of chitin and chitosan for use as vehicles for the sustained release of drugs was examined. Indomethacin and papaverine hydrochloride were used as model drugs in this evaluation. Sustained release of the drugs from the dried gels was obtained. Drugs dispersed in the chitosan gels were released at a constant rate (zero order). Chitin and chitosan could be useful vehicles for the sustained release of drugs.

Development of Biodegradable and Injectable Latices for Controlled Release of Potent Drugs

Abstract: A new dosage form designed to provide parenteral drug delivery over a prolonged period of time following a standard injection has been investigated using testosterone as the model drug. The drug carrier consists of a biodegradable, biocompatible polymer in which the drug is dispersed on a molecular level. The polymer itself is formulated as a pseudolatex with high solid content (40.0%). The formulation has a low viscosity (97 cps) which can be injected easily through a hypodermic needle. The histopathology study showed good tissue compatibility of the pseudolatices and in-vivo tests on rats confirmed a prolonged release of drug over a 14 day period. The stability of the biodegradable poly-d, l-lactic acid latex was found not to be significantly changed over 120 days of storage at room temperature (25°). A six month study showed a slight increase (10%) in the viscosity of the parenteral product when stored at room temperature. The increase was attributed to partial coalescence of the polymer partic...

Biomedical applications of magnetic fluids. ii. preparation and magnetic guidance of magnetic albumin microsphere for site specific drug delivery in vivo

Abstract: Magnetic guidance of magnetic albumin microsphere for site specific delivery was investigated in mice and rats. After intravenous injection in mice, magnetic microspheres with 1 and 3μm diameter size were localized and retained in the target-site (lung) by application of two permanent magnets to the lungs. Injection into the renal artery in rats also indicated that the 1-μm microspheres were concentrated in the kidney by a magnetic field. When the magnets were not applied, however, the microspheres following intravascular injection were concentrated mainly in the liver, regardless of the route of administration. Such preferential localization by magnetic means suggested that magnetic albumin microspheres could become effective drug carriers with site specificity for the delivery of chemotherapeutic agents in cancer therapy.

Poly(L-lysine) has different membrane transport and drug-carrier properties when complexed with heparin

Abstract: Methotrexate (MTX) conjugated to a Mr 3000 poly(L-Lys) markedly inhibits the growth of Pro-3 MtxRII5-3 Chinese hamster ovarian cells, a mutant line known to be drug resistant because of defective MTX transport. In these cells, membrane transport of [3H]MTX-poly(Lys) is sharply decreased by addition of 0.5- to 2.5-fold heparin but remains at 15-20% of control in 2.5- to 50-fold heparin excess. Heparin addition at first markedly inhibits but, at high concentration, restores the growth inhibitory effect of MTX-poly(Lys). In excess heparin, MTX-poly(Lys) is transported as a heparin complex. Because reduced transport (15-20%) is sufficient to cause a 90% inhibition of cell growth, MTX-poly(Lys) apparently gains pharmacologic potency when compared to heparin. This gain can be related to a greater inhibitory effect on dihydrofolate reductase and to a different mode of transport. The inhibitory effect of MTX-poly(Lys) on dihydrofolate reductase in vitro is increased nearly 100-fold in the presence of excess heparin but remains less than that of free MTX. Unlike that of MTX-poly(Lys), the transport of MTX-poly(Lys)-heparin has the characteristics and efficiency of a receptor-mediated process. It proceeds by endocytosis but is not, as in the case of uncomplexed conjugate, followed by the intracellular generation of pharmacologically active breakdown products that would account for cytotoxicity. These observations raise the possibility that at least part of the MTX-poly(Lys)-heparin reaches cellular dihydrofolate reductase in the form of macromolecular complexes that escape from entrapment in endocytotic structures. Our data illustrate a way to overcome drug resistance by taking advantage of the specific uptake of a macromolecular drug carrier. They offer a method of drug delivery in which heparin improves selectivity and decreases the unwanted toxicity inherent to polycationic carriers.

Liposomes as "targeted" drug carriers: a physical chemical perspective

Abstract: Over the last several years liposomes have increasingly caught the imagination of physical chemists, biologists, and medical scientists. In the last—mentioned context, they are being studied as carriers for selective drug delivery. In this lecture I will first give a brief overview of the possibilities and problems of liposomal carriers. Then I will discuss several instances in which physical chemical ideas are contributing directly to'the medical objectives. Finally, Iwill indicate remaining problem areas in need of additional physical chemical 'insight.

Tumor Chemoembolization: Target-Directed Drug Delivery or Tumor Embolization?

Abstract: To the Editor.— The article by Kato et al (1981;245:1123) suggests the potential of therapeutic angiography in cancer chemotherapy. The synthesis of tumor embolization with local drug delivery is a conceptual and perhaps practical advance. Other current approaches include angiographic embolization 1 or mechanical occlusion of tumor vessels and surgical strategies such as ligation of the hepatic artery 2 in combination with chemotherapy or radiation therapy. The article raises the question of what specifically is causing tumor regression—infarction of tumor or local release of drug. I agree with Vincent P. Chuang, MD, and Sidney Wallace, MD (1981; 245:1151), that Kato's results can be attributed primarily to embolization rather than local drug delivery. Direct infusion of chemotherapeutic agents into tumors (Chuang and Wallace) or drugs encapsulated in "drug carriers" 3 have had marginal success because there is little retention of drug in the tumor bed. The drug freely passes into the