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Biomedical subjects

J L Fox

Publications and source records attributed to J L Fox.

At least 145 records · Page 8Linked to original sources
PubMed1994

Stability of paclitaxel with ondansetron hydrochloride or ranitidine hydrochloride during simulated Y-site administration.

The stability of paclitaxel with either ondansetron hydrochloride or ranitidine hydrochloride during simulated Y-site injection at room temperature was studied. Triplicate test solutions of paclitaxel 0.3 and 1.2 mg/mL were admixed 1:1 with ondansetron 0.03 and 0.3 mg/mL (as the hydrochloride salt) or ranitidine 0.5 and 2.0 mg/mL (as the hydrochloride salt). Also, paclitaxel 1.2 mg/mL was admixed 1:1:1 with ondansetron 0.3 mg/mL and ranitidine 2.0 mg/mL. The solutions were stored in glass containers at room temperature, and samples were removed at zero, one, two, and four hours for immediate assay. At the time of the assay and before any dilution, each sample was visually inspected for clarity, color, and precipitation, and the pH was determined. Drug concentrations were measured by stability-indicating high-performance liquid chromatographic procedures. Throughout the study, more than 90% of the initial concentrations of paclitaxel, ondansetron, and ranitidine remained in the solutions. No precipitates, color changes, or haziness was seen. The changes in pH were minor. Paclitaxel in concentrations of 0.3 and 1.2 mg/mL was stable when mixed with either ondansetron (0.03 or 0.3 mg/mL, as the hydrochloride salt) or ranitidine (0.5 or 2.0 mg/mL, as the hydrochloride salt) and stored in glass containers for four hours. Paclitaxel 1.2 mg/mL was also stable when mixed with both ondansetron 0.3 mg/mL and ranitidine 2.0 mg/mL and stored in glass containers for four hours.

Chromatography, High Pressure Liquid↗
PubMed1994

A novel skeletal drug-delivery system using self-setting calcium phosphate cement. 3. Physicochemical properties and drug-release rate of bovine insulin and bovine albumin.

A novel drug-deliver device based on a self-setting bioactive cement formed from tetracalcium phosphate and dicalcium phosphate has been developed and tested in vitro using bovine insulin and bovine albumin as model polypeptide drugs. Equimolar mixtures of the calcium phosphate powders containing bovine insulin and bovine albumin were transformed into a hydroxyapatite cement after being mixed with a dilute phosphoric acid solution. X-ray diffraction and FT-IR spectra results suggested that the raw materials transformed into lower crystallinity of hydroxyapatite as it hardened. In vitro drug release from cement pellets into a 0.1 mol/L phosphate buffer at pH 7.40 and 37 degrees C continued for more than 3 weeks. Release from the drug-loaded cements followed the Higuchi model equation.

Bone Cements↗
PubMed1994

A novel skeletal drug-delivery system using self-setting calcium phosphate cement. 4. Effects of the mixing solution volume on the drug-release rate of heterogeneous aspirin-loaded cement.

The effect of the mixing solution volume was investigated on the in vitro drug-release rate of a novel drug-delivery device based on a self-setting bioactive calcium phosphate cement containing aspirin as a model drug. Equimolar mixtures of metastable calcium phosphate powders containing various proportions (3-40 w/w %) of seed hydroxyapatite crystals transformed into hydroxyapatite after being mixed with dilute phosphoric acid. The drug release from cement pellets in vitro into a 0.1 mol/L phosphate buffer at pH 7.40 and 37 degrees C by the rotating disk method continued for more than 1 week. The drug-release rate from the cement increased with increasing volumes of mixing solution. The relationship between the liquid/powder ratio and the porosity of the cement was a straight line, indicating that the cement porosity depended on the amount of the mixing solution, but was independent of the amount of seed crystals. Drug release from the cement followed the modified Fick's law, with the rate increasing with the amount of mixing solution, since the porosity depended on the amount. The tortuosity of the cements was estimated from the modified Fick's equation, and the relationships between the drug release rate and the tortuosity of the pore in the drug-loaded cement in the plots were nonlinear. The results suggested that the drug-release rates from the cement were controlled by the drug diffusion in the pores.

Aspirin↗
PubMed1994

A novel skeletal drug delivery system using self-setting calcium phosphate cement. 2. Physicochemical properties and drug release rate of the cement-containing indomethacin.

A novel drug delivery device based on a self-setting bioactive cement formed from tetracalcium phosphate and dicalcium phosphate has been developed and tested in vitro with indomethacin as a model drug. Equimolar mixtures of the calcium phosphate powders containing 2 and 5% of indomethacin were transformed into a hydroxyapatite after being mixed with a dilute phosphoric acid solution. X-ray diffraction and differential scanning calorimetry results suggested that indomethacin transformed into an amorphous form in the pores of the cement matrix as it hardened. In vitro drug release from cement pellets into a 0.1 mol/L phosphate buffer at pH 7.40 and 37 degrees C continued for > 3 weeks. Release from 2 and 5% drug-loaded cements followed the Higuchi model equation. The drug release profiles of 5% drug-loaded cements with different thicknesses (0.5, 1.0, and 1.5 g) overlapped up to 90% drug release, indicating that the drug concentration gradient in the pore was independent of the thickness of the cement as expected from the model equation.

Adsorption↗
PubMed1994

A novel skeletal drug delivery system using a self-setting calcium phosphate cement. 5. Drug release behavior from a heterogeneous drug-loaded cement containing an anticancer drug.

A novel drug delivery device based on a self-setting bioactive calcium phosphate cement formed from tetracalcium phosphate and dicalcium phosphate has been developed and tested in vitro using the anticancer agent 6-mercaptopurine (6-MP) as a model compound. X-ray diffraction results suggest that equimolar mixtures of the calcium phosphate salts were transformed into hydroxyapatite after being mixed with a dilute phosphoric acid solution, even in the presence of various amounts of 6-MP powder. The inclusion of 6-MP in the reaction mixture resulted in the formation of a homogeneous drug-containing cement. Alternatively, the drug was loaded after cement formation to produce a heterogeneous drug-containing pellet. In vitro drug release from both the homogeneous and heterogeneous drug-loaded cement pellets into simulated body fluid (pH 7.25, 37.0 degrees C) was measured using the rotating-disk method. Release from the homogeneous 5% drug-loaded cements did not obey the Higuchi equation. The release rate from the heterogeneous drug-loaded cements of different thicknesses (1, 2, and 3 mm) was a function of thickness, indicating that release kinetics could be controlled by the design of the cement formulation.

Antineoplastic Agents↗
PubMed1994

A novel skeletal drug delivery system using self-setting calcium phosphate cement. 7. Effect of biological factors on indomethacin release from the cement loaded on bovine bone.

The use of self-setting bioactive calcium phosphate cement containing indomethacin as a model drug in bovine bone was investigated by means of an in vitro drug release test, mercury porosimetry, and scanning electron microscopy (SEM). Calcium phosphate cements containing 2 and 5% indomethacin after being mixed with dilute phosphoric acid were applied to defect sites and the medullary cavity of bovine bone and transformed into hydroxyapatite. The in vitro drug release from the cement loaded on the defect site into a simulated body fluid (SBF) containing 2.5 mM Ca2+ and 1.0 mM HPO4(2+) or 0.1 M phosphate buffer at pH 7.25 and 37 degrees C continued for more than 3 weeks. The release profiles of the drug-loaded cements in phosphate buffer were linear using the Higuchi plot; however, that was not the case for SBF. The drug release in SBF was much lower than that in phosphate buffer. The total pore volume of the cement after the drug release test in SBF was lower than its initial value. However, the pore size of 0.1-0.01 microns after drug release in phosphate buffer was higher than that seen in SBF. The micropore distribution results suggested that hydroxyapatite crystallized from SBF and the pore volume in the cement decreased after drug release. However, in phosphate buffer it appeared to dissolve. The SEM observations for cements loaded on the bone after drug release in phosphate buffer suggested that there was a boundary layer between the cement and natural bone, but this was not the case in SBF, where the cement bonded with the natural bone. The drug release rates from the cement-loaded bone were significantly higher than those from cement loaded on the dissolution holder. The results suggested that cement formation and drug release were affected by the presence of protein from natural bone. The drug release rates from the cement loaded on the defective bone were slower than those from the medullary cavity.

Animals↗
PubMed1994

Heat-treatment-induced reduction in the apparent solubility of human dental enamel.

Holcomb and Young (1980) have shown a significant increase in human dental enamel (HE) structural order resulting from heat treatment in the temperature range of from 275 to 400 degrees C. Also, previous work in our laboratory had shown dramatic decreases in the initial dissolution rates (IDRs) of both carbonated apatite (CAP) heated at similar temperatures (from 300 to 500 degrees C) and HE exposed to CO2 laser irradiation for which calculated surface temperatures were in this same range. We hypothesize that thermal treatment shifts the apparent solubility distribution profile of HE toward lower apparent solubilities, paralleling the observed increased in crystal structural order and the decrease in IDRs. Powdered HE was heated in a furnace at temperatures ranging from 150 to 500 degrees C for 24 hours. The apparent solubility distributions of both heated and unheated HE powders were measured by equilibration for 24 hours in a series of partially saturated solutions simulating various amounts of HE dissolved in a pH 4.5 dissolution medium. The apparent solubility distribution for the unheated HE showed a peak at KHAP [the ion activity product based on the Ca10(PO4)6(OH)2 stoichiometry] of 10(121.0). Heat treatment shifted the apparent solubility distribution to lower solubilities. The peak KHAP values were approximately 10(124.8) at 200 degrees C; approximately 10(127.8) at 300 degrees C; and approximately 10(-129.1) from 400 to 500 degrees C. This approximately 8 orders of magnitude decrease in KHAP for HE heated at from 400 to 500 degrees C correlates with the previously observed reduction in the IDR driving force for laser-treated HE experiencing a similar surface temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Apatites↗
PubMed1994

Mechanochemical synthesis of bioactive material: effect of environmental conditions on the phase transformation of calcium phosphates during grinding.

The effect of environmental conditions on the crystalline transformation of metastable calcium phosphates during grinding was investigated using X-ray diffractometry and fourier transformed infrared spectroscopy. A mixture of CoA and dicalcium phosphate anhydrate (DCPA, CaHPO4) did not transform after grinding in air. On the other hand, CaO and dicalcium phosphate dihydrate (DCPD, CaHPO4 2H2O) were converted into a noncrystalline solid. Mixtures of DCPD and Ca(OH)2 transformed into low-crystallinity hydroxyapatite after grinding in air. When ground under N2, a mixture of Ca(OH)2 and DCPD did not transform into hydroxyapatite, whereas that of DCPD: Ca(OH)2: CaCO3 = 1:0.8: 0.2 did. The results of X-ray diffraction of FT-IR spectra suggested that the presence of carbon dioxide in the grinding system was necessary for transformation from metastable calcium phosphates to hydroxyapatite.

Air↗
PubMed1993

Comparison of three lasers on dental pulp chamber temperature change.

Previous studies have reported dental pulp chamber temperature changes using only one beam size per laser. This study was designed to evaluate the effects of beam size, wattage, and energy density on pulp chamber temperature changes of extracted human teeth for three lasers (CO 2, Argon, Nd:YAG). During laser irradiation of the outer enamel surface, a thermocouple was placed in the pulp chamber which measured and recorded the temperature changes. This was done for each combination of lasing dosimetry parameters. In all cases the recorded temperatures increased with the increase in beam size for a given energy density (J/cm 2) and wattage. Also, the recorded temperatures increased with increased energy density for a given wattage and beam size.

Dental Pulp Cavity↗
PubMed1993

Particle size effect of metastable calcium phosphates on crushing strength of self-setting bioactive calcium phosphate cement.

The resistance to crushing after a self-setting bioactive calcium phosphate cement, consisting of various particle sizes of tetracalcium phosphate (TECP), dicalcium phosphate dihydrate (DCPD) and hydroxyapatite (HAP), had hardened was tested after setting at 37 degrees C, 100% RH. X-ray diffraction suggested that the cement containing fine particles of DCPD and TECP was completely transformed to HAP, but that containing larger particles was not. Since particle size of both DCPD and TECP affected the dissolution rate, the crystal growth of HAP during cement formation depended on the specific surface area (Sw) of the raw materials. The crushing strength of the cement after hardening increased with an increase of its Sw.

Bone Cements↗
PubMed1993

Compatibility and stability of ondansetron hydrochloride, dexamethasone, and lorazepam in injectable solutions.

The stability of ondansetron hydrochloride, dexamethasone sodium phosphate, and lorazepam in 5% dextrose injection or 0.9% sodium chloride injection in polyvinyl chloride (PVC) minibags and glass bottles was studied. Triplicate solutions of 8 or 32 mg of ondansetron (as the hydrochloride salt) mixed with 20 mg of dexamethasone phosphate (as the sodium salt) with or without 2 mg of lorazepam were compounded in 50-mL PVC minibags and glass bottles containing either 5% dextrose injection or 0.9% sodium chloride injection and stored at 23-25 degrees C. Duplicate measurements were performed when drugs were added and at 1, 2, 4, 8, and 24 hours after addition. Samples of the 32-mg ondansetron admixtures were collected under aseptic conditions to inspect for precipitation and to count particles with a laser particle analyzer. Samples of all admixtures were evaluated for chemical stability by stability-indicating high-performance liquid chromatography. Ondansetron hydrochloride and dexamethasone were physically compatible and chemically stable for up to 24 hours under the study conditions. The concentration of lorazepam in PVC containers dropped below 90% of the original concentration within four hours. In addition, particle counts in lorazepam-containing solutions were higher when 0.9% sodium chloride injection was the diluent than when 5% dextrose injection was the diluent. In admixtures containing all drugs, ondansetron hydrochloride and dexamethasone sodium phosphate in 5% dextrose injection or 0.9% sodium chloride injection were stable for up to 24 hours when stored in PVC bags or glass bottles.(ABSTRACT TRUNCATED AT 250 WORDS)

Dexamethasone↗
PubMed1993

Stability of ondansetron hydrochloride injection in extemporaneously prepared oral solutions.

The stability of ondansetron hydrochloride in extemporaneously prepared oral solutions containing orange juice, cola, or cherry syrup was determined. Solutions were prepared by adding ondansetron hydrochloride to orange juice, cola, or cherry syrup to produce ondansetron concentrations of 0.267 and 0.067 mg/mL in orange juice or cola and 0.533 mg/mL in cherry syrup. The ondansetron concentration in orange juice and cola solutions was assayed at the time of preparation and at 30 minutes and one hour. The cherry syrup solution was stored at both 3-5 and 25-27 degrees C, with the ondansetron concentration being determined at the time of preparation and daily for seven days. All the solutions were prepared in triplicate. Ondansetron concentrations were measured by stability-indicating high-performance liquid chromatography. At each time interval, the mean ondansetron concentration remained > or = 97% of the initial measurement for all solutions. The appearance and color of the solutions did not change. Ondansetron hydrochloride was stable for at least one hour in orange juice or cola and at least seven days in cherry syrup.

Administration, Oral↗