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Biomedical subjects

P Maincent

Publications and source records attributed to P Maincent.

At least 55 records · Page 3Linked to original sources
PubMed1993

Poly(epsilon-caprolactone) nanocapsules in carteolol ophthalmic delivery.

In order to increase the ocular absorption of carteolol, this antiglaucomatous drug was incorporated into either nanoparticles (NP) or nanocapsules (NC). The polymer used was poly(epsilon-caprolactone) (PCL). The dosage forms were tested on intraocular hypertensive-induced rabbits. Results are presented as the chronological variations of the intraocular pressure (IOP) in comparison with the commercial aqueous solution (Carteol eye drops). The therapeutic results (decrease in IOP) were much more pronounced with carteolol incorporated into the colloidal carriers than with the commercial eye drops. Further, NC displayed a better effect than NP because the drug was entrapped in the oily core of the carrier, thus more readily available to the eye. The incorporation of the drug into nanocapsules produced a decline in the cardiovascular side effects in comparison with aqueous eye drops, thus showing that the undesired noncorneal absorption was reduced. In conclusion, colloidal suspension made of poly(epsilon-caprolactone) could offer a good opportunity for ophthalmic delivery of drugs.

Animals↗
PubMed1992

Lymphatic targeting of polymeric nanoparticles after intraperitoneal administration in rats.

Following intraperitoneal administration, the lymphatic targeting of polyacrylic nanoparticles has been evaluated in thoracic duct cannulated rats. The dosage forms administered consisted of carbon-14 polyhexylcyanoacrylate nanoparticles (PHCA) and polymethylmethacrylate (PMMA) nanoparticles. The carbon-14 concentrations were much higher in the excreted thoracic lymph than in the blood for both types of particles. The most dramatic results were found in the mediastinal nodes since the carbon-14 concentrations of rats receiving PHCA and PMMA nanoparticles by the ip route were 70- to more than 2000-fold higher than in the corresponding nodes of animals treated by the intravenous route. This potential lymphatic targeting could prove valuable in cancerology to treat tumors that metastasize in the peritoneal cavity or via lymphatic pathways such as colon carcinomas.

Animals↗
PubMed1991

The preparation and acute antihypertensive effects of a nanocapsular form of darodipine, a dihydropyridine calcium entry blocker.

We have addressed two problems associated with the use of dihydropyridine calcium entry blockers in antihypertensive therapy, namely, potent vasodilation and short half-lives, by incorporating the representative blocker, darodipine, into a nanocapsular vehicle. In awake, renovascular hypertensive rats, darodipine nanocapsules lowered blood pressure when given orally or intramuscularly, and the initial fall in blood pressure was less marked than that observed with the same dose of darodipine dissolved in polyethylene glycol 400 (PEG). Intramuscular administration of the nanocapsular form of darodipine had an antihypertensive effect which lasted for at least 24 hr.

Animals↗
PubMed1991

[Nanocapsules of beta-blocking agents: a new drug carrier in ophthalmology. Application to medical treatment of glaucoma in rabbits].

In order to reduce the lacrimal elimination and to increase the intraocular penetration of betaxolol after ocular administration, we prepared a new drug carrier, polycaprolactone nanocapsules, containing betaxolol in the base form. The instillation of nanocapsules containing only 0.1% of betaxolol into glaucomatous rabbit eyes induced a greater decrease of IOP in intensity, time and stability compared to the reduction of IOP induced after instillation of the commercial eye drops (Betoptic) containing 5 times more betaxolol (0.56%). This new pharmaceutical dosage form produces very interesting therapeutic effects with much lower drug concentrations than that commonly used in aqueous commercial eye drops; thus, systemic and local side effects could be minimized. All drugs used in medical treatments of eye diseases should be able to be included in this carrier. In addition, effective drugs not used because of their toxicity will become suitable for use at lower and safer doses.

Adrenergic beta-Antagonists↗
PubMed1990

Improvement of radioactive colloid binding by tumor cells.

Treatment of P388 leukemia cells with poly-DL-lysine (Poly-lys) considerably increases the binding of colloidal chromic phosphate (32P). This augmentation of the number of particles that are bound is in direct relationship with Poly-lys concentration, and very significantly with its degree of polymerization. Treatment with Poly-lys molecular weight 77,000 shows a 100% increase of binding with 200 micrograms and of 50% with 100 micrograms. Poly-lys M.W. 8,000 presents no significant increase, and for the other molecular weights the binding is intermediate.

Adsorption↗
PubMed1989

Enhancement of colloid uptake by tumor cell surface electrical charge modification.

Colloidal [51Cr]chromic phosphate uptake is considerably increased by preincubation of P388 ascites leukemia cells with poly(DL-lysine). The uptake increase is in direct relationship with the concentration and the degree of polymerization of poly(DL-lysine). The probable implication of cell surface electrical charge modification in these phenomena is discussed.

Animals↗
PubMed1986

Disposition kinetics and oral bioavailability of vincamine-loaded polyalkyl cyanoacrylate nanoparticles.

Hexyl cyanoacrylate nanoparticles loaded with vincamine as a drug model were prepared. Disposition kinetics and oral bioavailability of vincamine in rabbits were compared after administration of an aqueous solution of the drug and an aqueous colloidal suspension of nanoparticles. After intravenous administration, total body clearance of vincamine was equal for both dosage forms, but a longer half-life (X 2) and larger distribution volume (X 2) were observed with the suspension of nanoparticles. After oral administration, the bioavailability of vincamine was considerably greater for the drug loaded onto nanoparticles.

Administration, Oral↗
PubMed1984

Crystallinity and dissolution rate of tolbutamide solid dispersions prepared by the melt method.

The influence of cooling rate of solid dispersions prepared by the melt method was studied by X-ray diffraction and scanning electron microscopy. Tolbutamide was the model drug investigated, and the carriers included urea and polyethylene glycol 6000. Slow-cooled urea dispersions of tolbutamide demonstrated a complete lack of crystallinity, suggesting the formation of an amorphous material. The rapidly cooled dispersion showed peaks for urea and an absence of drug in the X-ray pattern, suggesting that a true molecular dispersion was formed. The X-ray patterns of rapid- and slow-cooled dispersions of tolbutamide and polyethylene glycol 6000 demonstrated that a physical mixture of drug and carrier resulted from both methods of dispersion preparation.

Chemical Phenomena↗
PubMed1984

Preparation and in vivo studies of a new drug delivery system. Nanoparticles of alkylcyanoacrylate.

Polyhexylcyanoacrylate nanoparticles have been prepared with vincamine as the model drug. These particles had an average size of 200 nm and adsorbed approximately 43% of vincamine. The adsorption of vincamine to nanoparticles modified the distribution of vincamine in tissues. After iv injection the distribution volumes were increased in comparison with an aqueous solution of drug. In comparison with an aqueous solution of drug, the absolute bioavailability of vincamine was also increased after an oral administration of nanoparticles.

Adsorption↗
PubMedDate not supplied

The role of ATP as a mediator in the action of iron complexes on cellular calcium homeostasis.

The effects of the interaction between low molecular weight iron complexes (citrate, lactate, and ATP complexes) with ATP and proteins, on the modification of Ehrlich carcinoma cell calcium homeostasis have been studied. In that modification the ferric-ATP complex shows much higher activity than the others. Sodium ATP, by iron translocation from citrate and lactate, increases their activity. This phenomenon implicates ATP as a mediator on the cellular activity of the complexes. Proteins, particularly ferritin, appear to moderately reduce their activity, whereas glutathione and ascorbic acid, acting as lipid peroxidation-inhibitors, show only a slight reduction of the iron complex's effects on cellular calcium uptake.

Adenosine Triphosphatases↗
PubMedDate not supplied

In vivo behaviour of low molecular weight iron complexes.

The in vivo distribution in mice of ferric citrate, ferric beta-glycerophosphate and ferric lactate complexes has been studied. There is a relationship between the 59Fe uptake by various tissues and the physicochemical characteristics of the complexes. Ferric lactate seems a useful preparation for iron deficiency therapy.

Animals↗
PubMedDate not supplied

Preparation and in vitro evaluation of heparin-loaded polymeric nanoparticles.

Nanoparticles of a highly soluble macromolecular drug, heparin, were formulated with two biodegradable polymers (poly-E-caprolactone [PCL] and poly (D, L-lactic-co-glycolic-acid) 50/50 [PLAGA]) and two nonbiodegradable positively charged polymers (Eudragit RS and RL) by the double emulsion and solvent evaporation method, using a high-pressure homogenization device. The encapsulation efficiency and heparin release profiles were studied as a function of the type of polymers employed (alone or in combination) and the concentration of heparin. Optimal encapsulation efficiency was observed when 5000 IU of heparin were incorporated in the first emulsion. High drug entrapment efficiency was observed in both Eudragit RS and RL nanoparticles (60% and 98%, respectively), compared with PLAGA and PCL nanoparticles (<14%). The use of the two types of Eudragit in combination with PCL and PLAGA increased the encapsulation efficiency compared with these two biodegradable polymers used alone; however, the in vitro drug release was not modified and remained low. On the other hand, the addition of esterase to the dissolution medium resulted in a significant increase in heparin release. The in vitro biological activity of released heparin, evaluated by measuring the anti-Xa activity by a colorimetric assay, was conserved after the encapsulation process.

Biodegradation, Environmental↗
PubMedDate not supplied

Microencapsulation of low molecular weight heparin into polymeric particles designed with biodegradable and nonbiodegradable polycationic polymers.

Owing to its lack of oral absorption, heparin has to be administered parenterally. However, parental administration has negative aspects such as multiple injections, possible infection, patient inconvenience, and high cost. Now, low molecular weight heparin (LMWH) is taking part in antithrombotic treatment and is proven to confer more advantages than unfractionated heparin. The aim of our present study was to formulate, by the w/o/w emulsification process, LMWH microparticles as potential oral carriers prepared with biodegradable (poly-epsilon-caprolactone and poly-lactic-co-glycolic acid) and nonbiodegradable polycationic polymers (Eudragit RS and RL), used alone or blended. The encapsulation efficiency ranged from 16 to 47% and was highly dependent on the presence of the positively charged polymers. In the same way, a low in vitro LMWH release was observed when Eudragit polymers composed totally or partially the polymeric matrix, compared with biodegradable polymers exhibiting higher LMWH release (40 and 60%). For each formulation, LMWH released from microparticles preserved its biological activity as shown by the antifactor Xa activity. Experiments performed with fluorescein-labeled LMWH showed the drug distribution in microparticles and may give information about the mechanisms controlling LMWH encapsulation and release.

Drug Compounding↗
PubMedDate not supplied

Preparation and characterization of ethylcellulose microspheres containing 5-fluorouracil.

Ethylcellulose microspheres containing 5-fluorouracil (5-FU) were prepared by a solvent evaporation technique using light mineral oil as the continuous phase. The drug was suspended in the acetone solution of the polymer. Three drug/polymer ratios (1/1, 1/2 and 1/3) were utilized. The microspheres were studied with respect to size, drug content and surface characteristics; the higher the polymer content, the smoother the microspheres. The drug was suspended in the polymer and the drug loading was important (more than 90%) with the three types of microspheres. In vitro dissolution studies in phosphate buffer showed that the 5-FU release was dependent on the drug/polymer ratio for the 400-500 microns granulometric fraction.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Preparation of silicone microspheres by emulsion polymerization: application to the encapsulation of a hydrophilic drug.

The objective of this work was to evaluate the ability of appropriate silicone elastomers to encapsulate hydrophilic compounds in microspheres prepared according to a multiphase emulsion-polymerization process. The particle size of the microspheres can be modified by controlling the usual emulsification parameters, such as the viscosity of the different phases, shear rates and surface activity properties of additives. The encapsulation efficiencies of a hydrophilic drug, propranolol hydrochloride, were very high but its release rates were very slow. Osmotic agents such as glycerol and propylene glycol did not enhance the release rate, whereas it was slightly increased by both sodium chloride addition and higher drug loading.

Chemistry, Pharmaceutical↗
PubMedDate not supplied

[The interchangeability of excipient formulations and the eventual consequences].

Excipients are used to prepare dosage forms in order to facilitate the administration and the efficacy of drugs through better handling of the manufacturing process and an increase in the stability of the dosage forms as well. They are produced, as for drugs, by lots and although they correspond to official Pharmacopoeian monographs, they may vary from batch to batch. This can alter the physico-chemical properties as well as their functionalities. Even for classical and non-critical tableting excipients, tablets prepared with the same excipient (microcrystalline cellulose) but originating from several suppliers may display very dramatic differences: the main difference concerns the in vitro dissolution rate which can consequently affect the bioavailability. Switching from one excipient to another is still possible but the similarity in behaviour of the dosage form must be demonstrated by relevant tests including functionality tests.

Biological Availability↗
PubMedDate not supplied

[The mechanisms of binding of active drugs to polyalkylcyanoacrylate nanoparticles].

Studies on colloidal carriers such as nanoparticles are generally based on the evaluation of the optimal amount of drug linked to the polymer matrix. This figure is obtained through the mathematical treatment of adsorption/incorporation isotherms. However, results of the literature show an obvious heterogeneity in the isotherms mathematical treatment. A theoretical review of the potential models of the sorption process of drugs will be used to compare the results previously published in the literature. An experimental and systematic approach will be proposed in order to compare more easily the studies from the different research teams and to evaluate the interactions between drugs and colloidal carriers.

Chemistry, Pharmaceutical↗