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PubMed1983

[Iatrogenic pseudotumor of the skin induced by polyvinyl pyrrolidone].

A 65-year-old woman developed a prominent tumor-like swelling of the skin in the face and shoulder area after having received parenteral applications of a drug containing polyvinylpyrrolidone (PVP) (Depot-Impletol) for many years. Upon first examination the alterations appeared to represent a tumor of the adipose tissue. Subsequently, however, they were shown to result from excessive storage of high-molecular fractions of PVP in the reticulohistiocytic system. Storage of these fractions of PVP, which cannot be eliminated with urine, was also found in the interstitial tissue of adjacent muscles and in local lymph nodes. The histological picture resembles a thesaurismosis. The present report also describes enzyme histochemical and electron-microscopic findings. The electron-microscopic results are similar to those described by other authors in the few ultrastructural reports of PVP storage. The ultrastructural alterations in the capillary endothelium suggest a transendothelial transport mechanism for the incorporated substance.

Aged↗
PubMed1997

In vitro evaluation of flutamide-carrier systems. Part 1: Preparation and evaluation of flutamide systems with polyvinyl pyrrolidone and polyethylene glycol 4000 and 6000.

Coprecipitates were prepared using different ratios of flutamide with polyvinyl pyrrolidine (PVP), polyethylene glycol (PEG) 4000 and 6000. Drug solubility in carrier solutions, thin layer chromatography (TLC), differential scanning calorimetry (DSC), infra-red spectroscopy (IR), uniformity of drug content, drug dissolution from its respective systems and effect of aging on the physico-chemical parameters of stored flutamide-polymer system were studied. PEG 6000 was found to be the most efficient polymer in increasing both the solubility and the release rate of flutamide. Interaction was found to be complete in certain ratios of drug/polymer systems. The dissolution pattern of flutamide from all the prepared systems appeared to fit a first order mechanism. Physico-chemical parameters of flutamide/carrier systems were not influenced by storage.

Antineoplastic Agents, Hormonal↗
PubMed1976

[Nystatin and amphotericin B sorption complexes with polyvinyl-pyrrolidone in nonaqueous solvent systems].

Complexes of polyenic antibiotics with polyvinylpyrrolidone (PVP) can be used for preparing effective pharmaceutical forms soluble in water and consisting of fine dispersions. Studies were carried out; they are of great importance for revealing the mechanism of polyen interaction with neutral polymers, as well as for development of the technological processes for production of the pharmaceutical forms. The sorption isoterms of PVP with the molecular weight of 10 000 and 35 000 on nystatin and amphotericin B were obtained in the process of precipitation in the system of dimethylformamide-ethylacetate. The constants of the strength of the antibiotic binding with the polymer in a complex were calculated. It was shown that the complex strength increased with a rise in the relative amount of the precipitant in the system. The temperature dependence of the binding strength constant was studied. The process of the complex forming was shown to be exothermic, the activation energy of the complex being 26-30 kcal per a mole of the antibiotic. No significant differences in the binding strength of nystatin and amphotericin B were observed. On the basis of the experimental data, a scheme of the complex structure explaining the binding process by formation of a number of hydrogen bonds between the antibiotic hydroxyl groups and the PVP tertiaryamide groups is proposed.

Adsorption↗
PubMed1984

Assessment of the potential uses of liposomes for lymphoscintigraphy and lymphatic drug delivery. Failure of 99m-technetium marker to represent intact liposomes in lymph nodes.

The in vivo fate of subcutaneously injected neutral SUV liposomes in rats was examined using a membrane marker, 99mTc, and an aqueous marker, 125I-labelled poly(vinyl pyrrolidone). Liposomes with entrapped 125I-labelled poly(vinyl pyrrolidone) were labelled with 99mTc by the SnCl2 method. 99mTc-radioactivity was localized several-fold more in the primary and secondary regional lymph nodes than 125I-labelled poly(vinyl pyrrolidone)-radioactivity. Similarly, 99mTc-radioactivity appeared and was subsequently cleared from the circulation much more rapidly than 125I-labelled poly(vinyl pyrrolidone). The gel chromatography of the lymph node homogenate revealed that 60-70% of 125I-labelled poly(vinyl pyrrolidone)-radioactivity was in the liposome fractions, whereas only 3% of 99mTc-radioactivity was co-eluted with the liposomes. Thus, the two markers have different fates in the lymphatics, and the presence of all 99mTc-radioactivity does not represent the 60-70% of intact liposomes present in lymph nodes. Using the aqueous marker 125I-labelled poly(vinyl pyrrolidone), the lymph node localization of positive, negative and neutral small unilamellar vesicles was studied, and it was found that 125I-radioactivity was more localized from negative liposomes than from positive liposomes, which in turn was more localized than that from neutral liposomes. Thus, these findings differ from those reported earlier, where the authors used 99mTc as a liposomal marker. In vitro studies showed that liposomes of preparations containing 20 mol% cholesterol became 'leaky' to low-molecular-weight drugs, for example, methotrexate (Mr 454) to a much greater extent than with a large-molecular-weight substance, 125I-labelled poly(vinyl pyrrolidone) (Mr 30 000-40 000), when incubated with rat lymph at 37 degrees C. Using the two markers 99mTc and 125I-labelled poly(vinyl pyrrolidone) it was found that the localization of both radioactivities was reduced in lymph nodes draining lambda-carrageenan-treated footpads. In conclusion, it is suggested that liposomes can be used for the delivery of drugs to diseased lymph nodes, and it would be worthwhile examining the possibilities of using alternative methods of labelling liposomes with 99mTc rather than using the SnCl2 technique, or using other radionuclides as markers for gamma-scan imaging.

Animals↗
PubMed2001

Characterization of the solubility and dissolution properties of several new rifampicin polymorphs, solvates, and hydrates.

Based on reports that tuberculosis is on the increase, this investigation into the physicochemical properties of rifampicin when recrystallized from various solvent systems was undertaken. Rifampicin is an essential component of the currently recommended regimen for treating tuberculosis, although relatively little is known about its solubility and dissolution behavior in relation to its solid-state properties. A rifampicin monohydrate, a rifampicin dihydrate, two amorphous forms, a 1:1 rifampicin:acetone solvate, and a 1:2 rifampicin:2-pyrrolidone solvate were isolated and characterized using spectral, thermal, and solubility measurements. The crystal forms were relatively unstable because except for the 2-pyrrolidone solvate, all the hydrated or solvated materials changed to amorphous forms after desolvation. Fourier transform infrared (FTIR) analysis confirmed the favorable three-dimensional organization of the pharmacophore to ensure antibacterial activity in all the crystal forms except the 2-pyrrolidone solvate. In the 2-pyrrolidone solvate, the strong IR signals of 2-pyrrolidone interfered with the vibrations of the ansa group. The 2-pyrrolidone solvate was the most soluble in phosphate buffer at pH 7.4. This solvate also had the highest solubility (1.58 mg/ml) and the fastest dissolution in water. In 0.1 M HCl, the dihydrate dissolved the quickest. A X-ray amorphous form (amorph II) was the least soluble and had the slowest dissolution rate because the powder was poorly wettable and very electrostatic.

Antibiotics, Antitubercular↗
PubMed1998

Formulation and in vitro evaluation of polymeric films of diltiazem hydrochloride and indomethacin for transdermal administration.

Ethylcellulose-polyvinyl pyrrolidone films containing diltiazem hydrochloride and indomethacin were evaluated for their potential drug delivery at a controlled rate, using rat skin, to select a suitable formulation for the development of transdermal drug delivery systems. The influence of film composition, initial drug concentration, and film thickness on the in vitro drug release rate as well as drug permeation through rat abdominal skin were studied. Drug release studies were carried out employing the paddle over disk method and drug permeation through full thickness of the rat abdominal skin was tested using a modified Franz diffusion cell fastened with O-ring. The drug content of the film decreased at an apparent first-order rate, whereas the quantity of drug released was proportional to the square root of time. The release rates of both drugs increased linearly with increasing drug concentration and polyvinyl pyrrolidone fraction in the film, but was found to be independent of film thickness. The increase in release rate may be due to leaching of hydrophilic fraction of the film former which resulted in the formation of pores. It was also observed that the release of drugs from the films followed a diffusion-controlled model at low drug concentrations. A burst effect was observed initially, however, at high drug loading levels. This may be due to rapid dissolution of the surface drug followed by the diffusion of drug through the polymer network in the film. The in vitro skin permeation profiles showed increased flux values with increase of initial drug concentration in the film and also with the concentration of polyvinyl pyrrolidone. From this study, it is concluded that the films composed of ethylcellulose:polyvinyl pyrrolidone:diltiazem hydrochloride (8:2:2) and ethylcellulose:polyvinyl pyrrolidone:indomethacin (8:2:3) should be selected for the development of transdermal drug delivery systems, using a suitable adhesive layer and backing membrane, for potential therapeutic use.

Administration, Cutaneous↗
PubMed1982

The destruction of N-nitrosamides with 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiodiphosphetane-2,4-disulfide. Attempts to nitrosate thioamides.

The reaction between N-nitrosamides and 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide (LR) at low temperature (20-50 degrees C) gives the corresponding thioamides as the main products. In the reaction between N-nitroso-2-pyrrolidone and LR, dihydro-2-(3H)-thiophenone (III) is also isolated. Mechanistic considerations for the formation of III are presented. The nitrosation of thiono compounds gives the corresponding oxo analogues. N-Nitroso-2-pyrrolidone is obtained after nitrosation of 2-pyrrolidinethione. A kinetic investigation of this reaction has been performed using the theory of consecutive reactions with 2-pyrrolidone as an intermediate. The rate constants for these two reactions are found to be k1 = 0.055 s-1 for the formation of 2-pyrrolidone, using a first order plot of the change of 2-pyrrolidinethione; for the formation of N-nitroso-2-pyrrolidone, the rate constant obtained by computer simulation is k2 = 0.032 mol(-1)1 s-1.

Amides↗
PubMed1991

Effects of artificial tears on corneal epithelial permeability in dry eyes.

The aim of this study was to detect possible changes in the permeability of the corneal epithelium in dry eye patients treated with artificial tears. For this reason, corneal epithelial permeability was measured in 68 consecutive dry eye patients before and after 8 weeks of treatment with artificial tears by means of objective fluorophotometry (polyvinyl alcohol 1.4% + chlorobutanol 0.5%, 25 subjects; polyvinyl pyrrolidone 2% + benzalkonium chloride 0.005%, 25 subjects; polyvinyl pyrrolidone 2% without preservative, 18 subjects). Before treatment, the stromal fluorescein uptake of dry eyes was three times higher than that of healthy control eyes. Eight weeks after the beginning of treatment the corneal epithelial permeability of patients treated with polyvinyl alcohol 1.4% + chlorobutanol 0.5%, as well as of those treated with polyvinyl pyrrolidone 2% without preservative, was reduced significantly (-44.9% and -43.4%, respectively; P less than 0.001). However, patients who had been treated with polyvinyl pyrrolidone 2% + benzalkonium chloride 0.005% showed no significant change in corneal epithelial permeability after treatment (-7.9%; P = 0.3).

Cornea↗
PubMed1976

The interaction of four putative glutamate antagonists with glutamate and their effects on the toad spinal cord.

1. Four putative glutamate antagonists (L-glutamate diethyl ester, L-glutamate dimethyl ester, L-proline and 1-hydroxy-3-amino-pyrrolidone-2) were tested on the isolated hemisected toad spinal cord. 2. 1-hydroxy-3-amino-pyrrolidone-2 (10(-3)-10(-2) M) selectively antagonized the depolarizations evoked in both dorsal and ventral roots by applications of L-glutamate (5 X 10(-4) M). 3 1-hydroxy-3-amino-pyrrolidone-2 also antagonized the depolarizations evoked in both dorsal and ventral roots by stimulation of the adjacent dorsal root. 4. The dimethyl and diethyl esters of L-glutamate and L-proline had their own depolarizing actions on the dorsal and ventral roots, and neither potentiated nor antagonized the effects of L-glutamate. 5. The results with 1-hydroxy-3-amino-pyrrolidone-2 offer further evidence for the involvement of L-glutamate and L-aspartate in synaptic transmission in the amphibian spinal cord.

Animals↗
PubMed2004

Polyvinylpyrrolidone-drug conjugate: synthesis and release mechanism.

Covalent conjugates of polyvinylpyrrolidone (PVP) with para-nitroaniline (PNA) were synthesized as a model PVP-drug conjugate, and PNA release was evaluated in vitro. Pyrrolidone ring opening with subsequent t-BOC protection of the pyrrolidone nitrogen and reaction with PNA in methylene chloride (CH2Cl2) produced a PVP-PNA conjugate with 3% of the pyrrolidone groups modified. Rates of PNA release from N-deprotected conjugates were twofold greater than those that were N-protected, indicating participation of the pyrrolidone N in release. Additional studies with monomeric analogs supported intramolecular base catalysis rather than lactam formation as the mechanism of this involvement. The approach serves as a prototype for the conjugation of other drugs with primary and secondary amine functional groups with PVP, including peptides and proteins.

Chemistry, Pharmaceutical↗