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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 103 (1981), S. 5614-5616 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: thermosensitive liposome ; cisplatin ; hyperthermia ; blood-drug level ; tumor-drug level ; targeting index ; drug release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract To evaluate the rate of drug release at the tumor and maximal drug targeting after administration of thermosensitive liposomes with hy-perthermia, a theoretical and experimental method was derived assessing the fraction of drug released from liposomes in a single pass through the heated tumor, F, and the drug targeting index when drug release occurs completely in response to heat (F = 1), DTImax. The F and DTImax were evaluated for four types of liposomes (LUV-1 and LUV-2, thermosensitive large unilamellar liposomes; LUV-3, a nonthermosensitive large unilamellar liposome; and SUV-1, a thermosensitive small unilamellar liposome) using reported data on blood liposome levels and tumor drug levels after the liposomes were administered to tumor bearing mice. DTImax values for LUV-1 and SUV-1 were approximately 6, while the value for LUV-2 with a relatively large systemic clearance was only 2.3. The F values for LUV-1, LUV-2, and SUV-1 with hyperthermia were 0.71, 1.17, and 0.34, respectively, whereas the values for these liposomes without hyperthermia and for LUV-3 with or without hyperthermia were nearly zero. These results confirm earlier findings that LUV-1 and LUV-2 release CDDP almost completely at the heated tumor and that the large DTI value obtained in LUV-1 (DTI = 4.6) was due to its high heat sensitivity and its small systemic clearance.
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  • 3
    ISSN: 1573-904X
    Keywords: leuprolide (leuprorelin) ; once-a-month injectable microspheres ; gonadotropin suppression ; steroidogenesis inhibition ; repeated administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Once-a-month injectable microspheres of leuprolide acetate prepared with copoly(DL-lactic/glycolic acid) using an in-water drying method were assessed for duration of the analogue release and pharmacological effects in rats after a single or repeated injection. The periodic challenge test revealed that a single injection of the microspheres caused a dramatic and persistent suppression of the ability of the pituitary–gonadal system to secrete gonadotropin and testosterone for over 5 weeks. The complete recovery of these functions was observed 10 weeks after the injection. The repeated injection of the microspheres at intervals of 2 or 4 weeks achieved persistent suppression of steroidogenesis after an initial transient flare-up and beneficially avoided the “acute-on-chronic response.” This depot formulation is expected to assure patient compliance and produce stronger therapeutic effects than the daily solution.
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  • 4
    ISSN: 1573-904X
    Keywords: leuprorelin (leuprolide) ; three-month depot microspheres ; sustained drug release ; pharmacological effects ; suppression of pituitary-gonadal axis ; rats and dogs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacological effects of leuprorelin three-month depot microspheres were investigated in rats and dogs. After s.c. and i.m. injection, the microspheres provided similar linear drug release and sustained serum drug levels for 3 months. Persistent suppression of serum LH, FSH (in rats) and testosterone (in rats and dogs) for over 16 weeks was achieved when the microspheres were given at a dose of 100 (rat) and 25.6 (dog) µg/kg/day. These hormone release responses upon periodic challenge tests revealed that a single injection of the microspheres caused dramatic suppression of the function of the pituitary-gonadal system for 15 weeks in rats. The growth of the genital organs was also suppressed dose-dependently by injection of the microspheres over 3 months; the strongest suppression was achieved at a dose of 100 µg/kg/day. This three-month depot formulation is expected to be more convenient than the one-month depot with improved patient compliance and therapeutic effects.
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  • 5
    ISSN: 1573-904X
    Keywords: cisplatin (CDDP) ; thermosensitive liposome ; intravenous administration ; rat ; blood level ; organ level ; systemic elimination ; reticuloendothelial system (RES) uptake ; systemic degradation ; CDDP release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The systemic degradation and reticuloendothelial system (RES) uptake of cisplatin (CDDP)-encapsulated thermosensitive liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and di-stearoylphosphatidylcholine (DSPC) (DPPC/DSPC = 9/1, 7/3, and 5/5, w/w) after intravenous administration to rats were examined by measuring the platinum (Pt) levels in the blood and RES (liver and spleen). The blood liposome level profile showed first-order rate elimination for each liposome administration. The elimination rate (K e1) was faster when the content of DSPC was lower (K e1: 1.3/hr for 9/1-liposomes, 0.7/hr for 7/3-liposomes, 0.5/hrfor5/5-liposomes). On the other hand, the RES liposome level profile showed distribution of liposomes followed by elimination therefrom. The RES level of the liposomes was lower when the content of DSPC was smaller (maximal level: 25% for 9/1-liposomes at 1 hr, 32% for 7/3-liposomes at 1 hr, 37% for 5/5-liposomes at 2 hr). The kinetic analysis demonstrated that the RES uptake rate (K res) was almost the same among the liposomes (0.4/hr), while the systemic degradation rate (K deg; K e1 − K res) became larger as the content of DSPC decreased (0.9/hr for 9/1-liposomes, 0.3/hr for 7/3-liposomes, and 0.1/hr for 5/5-liposomes) and that the RES liposome distribution amount was dependent not only on the K res but also on the K deg and the rate of RES liposome degradation. The K deg for each type of liposome corresponded with the systemic CDDP release rate.
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  • 6
    ISSN: 1573-904X
    Keywords: amorphous ; GPIIb/IIIa antagonist ; controlled release ; PLGA, microspheres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. We prepared injectable microspheres for controlled release of TAK-029, a water-soluble GPIIb/IIIa antagonist and discussed the characteristics of controlled release from microspheres. Methods. Copoly(dl-lactic/glycolic)acid (PLGA) microspheres were used for controlled release of TAK-029 [4-(4-amidinobenzoylglycyl)-3-methoxycarbonyl-2-oxopiperazine-l-acetic acid]. They were prepared with a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation technique using either a crystalline form or an amorphous form of the drug. Results. An amorphous form of TAK-029 gave more homogeneous S/O dispersion and higher viscosity than its crystalline form when added to dichloromethane solution of PLGA, resulting in a high drug entrapment into microspheres and a well-controlled release of the drug. Additions of sodium chloride into an external aqueous phase and L-arginine into an oil phase also increased entrapment of the drug, and reduced initial burst of the drug from the microspheres. The micro-spheres demonstrated a desirable plasma level profile in therapeutic range (20−100 ng/ml) for 3 weeks in rats after single subcutaneous injection. Conclusions. A well-controlled release of TAK-029, a water-soluble neutral drug, with small initial burst was achieved by utilizing its amorphous form as a result of possible interaction with PLGA and L-arginine.
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  • 7
    ISSN: 1573-904X
    Keywords: TNP-470 ; angiogenesis inhibitor ; medium-chain triglyceride ; intra-arterial injection ; rabbit VX-2 carcinoma ; CAM assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using rabbits bearing VX-2 carcinoma on the inner side of the leg, we examined the antitumor activity of a medium-chain triglyceride (MCT) solution of an angiogenesis inhibitor, TNP-470 (AGM-1470, 6-O-(N-chloroacetylcarbamoyl)-fumagillol), following administration into the femoral artery feeding the tumor. The MCT solution of TNP-470 (1 and 5 mg) strongly suppressed tumor growth following a single intra-arterial (i. a.) injection 2 or 3 weeks after tumor inoculation. Moreover, remarkable regression of well-developed tumors, those 4 weeks after inoculation, was obtained by i.a. injection of the MCT solution containing 20 mg of TNP-470 without any influence on body weight. The antitumor effects were potentiated by coad-ministration of doxorubicin or mitomycin C (MMC) in the solution or microspheres containing MMC. In a shell-less chorioallantoic membrane (CAM) assay, angiogenesis was inhibited when a droplet of the MCT solution containing 25 µg of TNP-470 was placed on the CAM for 2 days, suggesting that the prolonged antitumor effect resulted from the inhibition of tumor neovascularization by sustained drug release from the preparation. These results indicate that i. a. injection of the MCT solution of TNP-470 is promising for treating well-developed tumors.
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  • 8
    ISSN: 1573-904X
    Keywords: leuprorelin (leuprolide) ; three-month depot microspheres ; poly(DL-lactic acid) ; water-soluble oligomers ; glass transition temperature ; serum drug levels in rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract To obtain a three-month release injection of leuprorelin acetate, microspheres were prepared with copoly(DL-lactic/glycolic acid) or poly(DL-lactic acid) (PLA) using an in-water drying method, and drug release was evaluated. The content of water-soluble oligomers in the polymers was found to strongly affect the initial burst, and reducing the content to less than 0.1% was necessary to keep the first-day release below 10%. Drug loading of more than 15% also increased the initial drug release; the acceptable maximum loading was 12%. Elevation of the glass transition temperature of the microspheres was observed with an increase in drug loading. This suggests formation of a rigid structure, possibly with arrangement of the polymer around the drug cores like in a micelle. This structure provides a hydrophobic barrier against diffusion of the hydrophilic peptide, resulting in high trapping efficiency and long-term sustained release dependent on polymer erosion. The microspheres prepared with PLA having a m.w. of 12,000 to 18,000 provided linear sustained release and persistent serum levels of the drug in rats for over 3 months.
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  • 9
    ISSN: 1573-904X
    Keywords: leuprolide (leuprorelin) ; once-a-month injectable microspheres ; pharmacokinetics ; urinary excretion ; metabolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetic parameters of leuprolide acetate, a potent analogue of LH-RH, were determined in rats and dogs after i.v. and s.c. dosing with leuprolide solution. The effective human dose of once-a-month injectable microspheres of leuprolide was estimated to be about 3.2 to 8.1 mg analogue/month using these parameters. After microsphere injection at three different doses in rat serum leuprolide concentrations were sustained for over 4 weeks, and the AUCs and mean serum levels were linearly correlated with the dose. The serum levels and urinary excretion of the analogue in rats after repeated s.c. injection of the microspheres every 4 weeks exhibited similar profiles after each injection; no changes of the absorption and excretion of the analogue after the repeated injection could be demonstrated. The serum levels of the analogue metabolite (M-I) were 21% of the intact form 3 hr after injection of the microspheres but very low at the steady state after 1 to 4 weeks.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 14 (1986), S. 213-225 
    ISSN: 1573-8744
    Keywords: estimation of drug absorption rate ; staircase input ; multiexponential function ; absorption rate profile ; theophylline tablet ; initiation and termination of absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method affording direct estimation of the drug absorption rate from blood level data using arbitrary time intervals has been derived based on the staircase input principle. In the derivation, the drug was assumed to follow linear kinetics where the plasma concentration of the drug after an impulse input is expressed by a multiexponential function. Drug absorption was assumed to occur at a constant rate during each subsequent sampling interval. The absorption rate profiles obtained by the method using several numerical examples were expressed as a set of rectangular pulses. Divergence in the profiles reflected blood sampling measurement errors rather than errors due to the deconvolution. Smoothing of the rate profiles by calculating the mean of the absorption rates between adjacent time intervals gave realistic results. Absorption rate profiles for theophylline obtained by the method using published data gave information on the initiation and termination of the absorption as well as the extent of absorption from the dosage form.
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