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Biomedical subjects

K Juni

Publications and source records attributed to K Juni.

At least 37 records · Page 2Linked to original sources
PubMed1991

In vivo and in vitro degradation of poly(3-hydroxybutyrate) in rat.

The inflammatory activity and biodegradation of poly(3-hydroxybutyrate) were examined. Poly(3-hydroxybutyrate) sheet did not cause any inflammation in the chorioallantoic membrane of the developing egg. The i.v. injection of 14C-labelled poly(3-hydroxybutyrate) granules showed that 86, 2.5 and 2.4% of the total radioactivity administered were distributed in the liver, spleen and lung, respectively, and the radioactivity decreased slowly but steadily in most tissues examined during 2 month. Crude extracts of rat tissues showed that the activity degraded the poly(3-hydroxybutyrate) granules in vitro.

Animals↗
PubMed1991

Controlled release of 5-fluoro-2'-deoxyuridine by the combination of prodrug and polymer matrix.

Poly(L-lactic acid) (L-PLA) microspheres containing 5-fluoro-2'-deoxyuridine (FUdR) or its ester prodrugs with saturated aliphatic acids (FUdR-Cn, n = 2, 3, 4, 5, 6, 8, 10 and 12) were prepared. The physicochemical and biological properties and antitumor activity of the L-PLA microspheres were studied. The lipophilicity of FUdR-Cn was increased by prolonging its acyl-promoieties. FUdR-C5, FUdR-C6, FUdR-C8, FUdR-C10 and FUdR-C12 showed almost complete incorporation into the microspheres, while incorporation of hydrophilic FUdR and FUdR-C2 was poor. The sustained release of FUdR from the microspheres containing FUdR-C4, FUdR-C5 and FUdR-C6 was obtained in the presence of esterase, and higher antitumor activity against P388 leukemia was observed in vivo. On the other hand, the release rates of FUdR from the microspheres containing FUdR-C10 and FUdR-C12 were very small, and their antitumor activity was much smaller than that of the free prodrug suspension. Effects of the susceptibility to enzymatic hydrolysis and the physiocochemical properties of prodrugs on the release profiles of FUdR from spheres were discussed.

Animals↗
PubMed1990

Ester prodrugs of zidovudine.

Ten novel ester prodrugs of zidovudine (azidothymidine; AZT) were synthesized with aliphatic acids (acetic-stearic), and the enzymatic regeneration of AZT from the prodrugs was investigated both in vitro and in vivo. The enzymatic hydrolysis rates of the AZT esters in the presence of mouse enzyme systems (plasma, liver, and intestine, and kidney) were highly dependent on the lengths of the acyl chains of the prodrugs. The caprate or caprylate of AZT showed the highest reactivity to three of the four enzyme systems; either the decrease or the increase in the acyl chain length resulted in the decrease of the reactivity to the enzymes. Zidovudine (AZT) and three of the prodrugs (acetate, caprate, and stearate) were administered to mice intraperitoneally, and the plasma concentrations of AZT and a corresponding prodrug were measured. The AZT concentrations in plasma following the acetate administration rapidly decreased with a half-life of 14.5 min. This tendency is similar to that shown in direct AZT administration. On the other hand, the concentrations following the caprate or stearate administration decreased slowly and were maintained for as long as 4 h after dosing. The prodrug concentrations in plasma after the prodrug administration were under the detection limit (0.01 micrograms/mL), except for acetate. The absence of the caprate and stearate in plasma may be attributed to the high hydrophobicity or favorable tissue distribution of the ester derivatives.

Animals↗
PubMed1990

Controlled release of 3',5'-diester prodrugs of 5-fluoro-2'-deoxyuridine from poly-L-lactic acid microspheres.

Poly-L-lactic acid (MW 6000) microspheres (PLA-MS) containing 5-fluoro-2'-deoxyuridine (FUdR) or four ester prodrugs of FUdR were prepared and examined with regard to the in vitro release kinetics. The incorporation efficiency of the lipophilic prodrugs into the PLA-MS was higher than that of FUdR or the hydrophilic prodrugs. The release of the lipophilic FUdR prodrugs from PLA-MS was sustained as compared with that of FUdR from PLA-MS. The release kinetics of the FUdR prodrugs appears to fit the Higuchi, Baker, and Lonsdale model in the early stage of the release process. The slope of the Baker and Lonsdale plots of the release of divaleryl-FUdR from PLA-MS decreased as the initial drug loading was decreased. The order of the release rates of FUdR prodrugs from PLA-MS with the same prodrug content was similar to that of the water solubilities of the prodrugs. These results suggest that the ester prodrugs could be released from PLA-MS by diffusion through water-filled capillaries or a series of pores rather than by diffusion through the PLA matrix.

Chemical Phenomena↗
PubMed1990

Enhanced delivery of zidovudine through rat and human skin via ester prodrugs.

In an attempt to improve the skin delivery characteristics of Zidovudine (AZT, azidothymidine), five aliphatic esters (acetate, butyrate, hexanoate, octanoate, and decanoate) of AZT were synthesized and assessed as prodrugs of AZT. While the water solubility of the esters is lower than that of AZT, the solubilities in isopropylmyristate (IPM) and the partition coefficients (n-octanol:buffer) are higher. Susceptibility to enzymatic hydrolysis in the rat skin homogenate increases as the acyl chain of the ester is lengthened. Among the esters, acetate (C2-AZT) and hexanoate (C6-AZT) showed 2.4- and 4.8-fold enhanced permeation in human skin from an apolar vehicle (IPM) relative to application of AZT itself, respectively.

Administration, Cutaneous↗
PubMed1990

Enhanced transdermal delivery of zidovudine in rats and human skin.

Zidovudine (azidothymidine, AZT), a potent antiviral agent acting on acquired immunodeficiency syndrome virus, was examined with regard to permeation through rat and human skin. A steady state plasma concentration of AZT after transdermal application in rats estimated from both pharmacokinetics data after i.v. administration and penetration rate through excised rat skin from 10% oleic acid (OA) aqueous solution shows penetration about 85 times higher compared to that from 10% OA would be needed for therapeutic efficacy. A mixed-solvent system consisted of 5% Sefsol-318 (S-318), 10% OA, 10% N-methyl-2-pyrrolidone (MP), 20% propylene glycol (PG) and water showed promising characteristics as a vehicle in terms of permeability of AZT through excised rat skin. The maximum flux of 0.41 mumol/cm2/h was observed in excised human skin after application of a gel formulation including S-318, OA, MP and PG. The result suggests a possible use of the gel formulation to gain an effective plasma concentration in humans.

Administration, Cutaneous↗
PubMed1990

Membrane permeation-controlled transdermal delivery system design. Influence of controlling membrane and adhesive on skin permeation of isosorbide dinitrate.

A membrane permeation-controlled transdermal delivery system (MC-TDS) of isosorbide dinitrate (ISDN), a model drug, was prepared from polyvinyl alcohol aqueous gel containing the drug, a membrane consisting of ethylene-vinyl acetate copolymer membrane and acrylic adhesive (EV-a). The permeability of ISDN through the EV-a membrane was 2.5 times higher than that through excised hairless rat skin. The ratio of plasma concentration of ISDN after application of MC-TDS on stripped (damaged) skin relative to intact skin was lower than that after application of Frandol tape-S, a marketed ISDN TDS, which suggests that the EV-a membrane might work as a control membrane for overall delivery rate of ISDN to the body. When MC-TDS stored at 30 degrees C for 13.5-48h was applied to the damaged skin, however, the initial plasma concentration of ISDN was very much higher than the expected therapeutic level and was not controlled by the EV-a membrane. The initial high plasma concentration of ISDN after application of the stored MC-TDS on the damaged skin was due to migration of ISDN from the reservoir to the adhesive during storage at 30 degrees C. The migration of drugs into the adhesive might be an important problem in developing efficient MC-TDS.

Administration, Cutaneous↗
PubMed1989

Studies on 2',3'-dideoxy-2',3'-didehydropyrimidine nucleosides. II. N4-benzoyl-2',3'-dideoxy-2',3'-didehydrocytidine as a prodrug of 2',3'-dideoxy-2',3'-didehydrocytidine (DDCN).

N4-Benzoyl-2',3'-dideoxy-2',3'-didehydrocytidine (Bz-DDCN) was synthesized as a novel prodrug of 2',3'-dideoxy-2',3'-didehydrocytidine (DDCN), which is a reverse transcriptase inhibitor and is considered to be a potential anti-acquired immunodeficiency syndrome agent. Chemical and enzymatic regeneration of DDCN from the prodrug has been investigated in both in vitro and in vivo experiments. Bz-DDCN regenerated DDCN under basic conditions (greater than pH 8), while cleavage of the N-glycosidic linkage and production of N4-benzoylcytosine were observed under acidic conditions (less than pH 6). DDCN was enzymatically regenerated from the prodrug in the presence of several enzyme preparations, including human plasma. DDCN and Bz-DDCN were intravenously administered to mice and the plasma concentrations of DDCN and the prodrug were measured. Though DDCN levels following direct DDCN administration decreased exponentially with a half-life of 14.5 min, the plasma levels of DDCN following the prodrug administration were sustained above 2 microM for over 3 h.

Animals↗
PubMed1989

Percutaneous absorption enhancer applied to membrane permeation-controlled transdermal delivery of nicardipine hydrochloride.

In the design of nicardipine hydrochloride-transdermal delivery systems (NC-TDS), the enhancing and regulating effects of penetration-enhancers and permeation controlling membranes were evaluated. Laurocapram (Azone) was selected as a model enhancer. Since its enhancing effect is considered to occur in the stratum corneum, its release from ethylene-vinyl acetate copolymers (EVAc), ethylene-vinyl alcohol copolymers (EVAl) or poly(2-hydroxyethylmethacrylate) (pHEMA) membranes was used as a criterion for membrane selection. The release rate was highest from pHEMA. Accordingly, a TDS consisting of a NC reservoir containing 1 w/v% Azone and a pHEMA membrane was prepared, and the effect of skin stripping on the plasma concentration of NC after NC-TDS administration was evaluated in rats. The increased ratio in drug plasma concentration caused by skin stripping was lower when the NC-TDS treatment was compared with a non-regulating NC-gel treatment. Our results suggest that the membrane permeation-controlled TDS of NC may be useful for long-term constant drug delivery with minimum dependence on skin conditions.

Administration, Cutaneous↗
PubMed1987

Selective anticancer effects of 3',5'-dioctanoyl-5-fluoro-2'-deoxyuridine, a lipophilic prodrug of 5-fluoro-2'-deoxyuridine, dissolved in an oily lymphographic agent on hepatic cancer of rabbits bearing VX-2 tumor.

3',5'-Dioctanoyl-5-fluoro-2'-deoxyuridine (FdUrd-C8), one of the lipophilic prodrugs of 5-fluoro-2'-deoxyuridine (FdUrd) was dissolved in an oily lymphographic agent (Lipiodol Ultra-Fluid), which had been studied as a carrier of the anticancer drug for hepatic cancer. The prodrug was administered into the left proper hepatic artery of rabbits bearing VX-2 tumor in the liver in order to examine the anticancer effects and possible adverse effects on nontumorous hepatic cells. Lipiodol or FdUrd-C8*Lipiodol selectively remained in the hepatic cancer area but disappeared from nontumorous parts of the liver 7 days after injection. Tumor growth rates in 1 week of the untreated group, a group given injections of 0.2 ml of Lipiodol alone, and groups given injections of 0.2 ml of Lipiodol containing 30, 50, 70, and 100 mg of FdUrd-C8 were 636, 436, 34.8, 14.9, -2.4, and -10.4% of the size at the time of treatment, respectively. Pathological observation also showed that FdUrd-C8 had a strong anticancer effect on VX-2 tumor growing in the liver of the rabbits. In contrast to the effect on the cancerous cells, that on nontumorous hepatic cells was very slight. In pathological observation, necrosis or degeneration of nontumorous hepatic cells was hardly observed. Plasma glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase levels temporarily rose 1 day after injection but returned to the initial levels within 7 days in all groups.

Animals↗
PubMed1987

Poly(hydroxy acids) in drug delivery.

Poly(hydroxy acids) so far have been examined for use in drug delivery in limited number, while the advantageous use of the polymers has been recognized due to their biodegradability and biocompatibility. Homo- and copolymers of lactic acid and glycolic acid have been studied in drug delivery by many workers, while homo- and copolymers of epsilon-caprolactone have been studied by only one group of workers. Although poly-hydroxybutyric acid had been found to be a naturally occurring polymer, examination as to the use of the polymer in drug delivery is rather recent and reports are still limited. In the present article, the use of poly(hydroxy acids) including homo- and copolymers of lactic acid and glycolic acid, polycaprolactone, and poly-beta-hydroxybutyric acid in drug delivery is reviewed. Physicochemical properties, biodegradability, and biocompatibility of the polymers, and evaluations in vitro and in vivo of specific dosage forms using the polymers, are included. The most recent work in our laboratories on the use of polyactic acid and poly-beta-hydroxybutyric acid is also included.

Biocompatible Materials↗