Semi-automatic liquid chromatographic analysis of pamidronate in urine after derivatization with 1-naphthylisothiocyanate

Analysis of bisphosphonate using ultraviolet-visible spectroscopy based on modified phosphorus determination reagent

An improved phosphorous determination was developed using ethanol, phosphorus determination reagent (PDR) and Ultraviolet-visible spectroscopy (UV-Vis) for analyzing the bisphosphonates (BPs). The method was carried out under mild conditions without digestion, high temperature, high pressure, and other extreme conditions. Alcohols played an important role in this method. Without alcohol, this reaction system did not have a color reaction. Alendronate (ALN) and risedronate (RIS) were used to demonstrate the reliability of the improved phosphorous determination under different reaction conditions. The absorbance had an equal ratio of increase as well as a good trend line when the content of BPs increased. The improved phosphorous determination could be a new method to measure the drug content of BPs.

Bisphosphonate-based strategies for bone tissue engineering and orthopedic implants

Bisphosphonates (BPs) are a group of well-established drugs that are applied in the development of metabolic bone disorder-related therapies. There is increasing interest also in the application of BPs in the context of bone tissue engineering, which is the topic of this review, in which an extensive overview of published studies on the development and applications of BPs-based strategies for bone regeneration is provided with special focus on the rationale for the use of different BPs in three-dimensional (3D) bone tissue scaffolds. The different alternatives that are investigated to address the delivery and sustained release of these therapeutic drugs in the nearby tissues are comprehensively discussed, and the most significant published approaches on bisphosphonate-conjugated drugs in multifunctional 3D scaffolds as well as the role of BPs within coatings for the improved fixation of orthopedic implants are presented and critically evaluated. Finally, the authors' views regarding the remaining challenges in the fields and directions for future research efforts are highlighted.

Determination of bisphosphonate active pharmaceutical ingredients in pharmaceuticals and biological material: a review of analytical methods

Bisphosphonates is a class of chemical compounds finding extensive medical applications against bone disorders including osteoporosis, Pagets' disease, etc. Non-N-containing members include etidronate, clodronate and tiludronate, while N-containing bisphosphonates include active pharmaceutical compounds such as pamidronate, neridronate, olpadronate, alendronate, ibandronate, risedronate and zoledronate. The present study covers 20 years of analytical research on this group of compounds, focusing on bioanalytical and pharmaceutical QC applications. A wide range of analytical techniques is presented and critically discussed including among others liquid and gas phase separations, electrophoretic, electroanalytical, automated and enzymatic approaches.

Inhibition of bone healing by pamidronate in calvarial bony defects

OBJECTIVE

Pamidronate has been studied as a therapeutic drug for various osteopenic diseases. However, avascular osteonecrosis in the jawbone has been recently reported in patients receiving pamidronate. The objective of this study was to examine the effect of pamidronate on bone regeneration in a controlled animal model.

MATERIALS AND METHODS

To determine the effect of parmidronate on bone healing in a local bony defect area, a rabbit calvarial bony defect model was used and poly L-lactide-co-glycolide (PLGA) used as a drug carrier material. Four defect groups were made in each rabbit calvaria and the defects were treated as follows: untreated bony defect (group 1), PLGA only (group 2), 2 mg of pamidronate with PLGA (group 3), and 3 mg of pamidronate with PLGA (group 4). Bone healing was evaluated by radiography and histology at 1, 2, 4, 6, and 8 weeks after surgery.

RESULTS

In radiographic analysis, radiopacity was lower in pamidronate groups than non-operated rabbit calvarial bone at all observation points (P < .05). In histological analysis, the initial bone formation at 1 week was not different among groups, but it was much lower in the pamidronate groups than in the control or PLGA group after 2 weeks. Newly formed bone at 1 week underwent avascular necrosis after 2 weeks in both pamidronate groups. Avascular necrosis was not observed until 8 weeks in both topically applied pamidronate groups.

CONCLUSION

Collectively, pamidronate inhibits bone healing in rabbit calvarial bony defect and it may explain the avascular necrosis of the jaws in patients receiving pamidronate.

High-performance liquid chromatography method for determining alendronate sodium in human plasma by detecting fluorescence: Application to a pharmacokinetic study in humans

A high-performance liquid chromatographic (HPLC) method was developed using diethylamine (DEA) solid-phase extraction (SPE), 9-fluorenylmethyl derivative (FMOC) and fluorescence detection for quantifying alendronate in human plasma. Sample preparation involved a manual protein precipitation with trichloroacetic acid, a manual coprecipitation of the bisphosphonate with calcium phosphate and derivatization with 9-fluorenylmethyl chloroformate in citrate buffer at pH 11.9. Liquid chromatography was performed on a Capcell Pak C(18) column (4.6 mm x 150 mm, 5 microm particles), using a gradient method starting with mobile phase acetonitrile/methanol-citrate/pyrophosphate buffer (32:68, v/v). The total run time was 25 min. The fluorometric detector was operated at 260 nm (excitation) and 310 nm (emission). Pamidronate was used as the internal standard. The limit of quantification was 1 ng/ml using 3 ml of plasma. The intra- and inter-day precision expressed as the relative standard deviation was less than 15%. The assay was applied to the analysis of samples from a pharmacokinetic study. Following the oral administration of 70 mg of alendronate sodium to volunteers, the maximum plasma concentration (C(max)) and elimination half-life were 40.94 +/- 19.60 ng/ml and 1.67 +/- 0.50 h, respectively. The method was demonstrated to be highly feasible and reproducible for pharmacokinetic studies including bioequivalence test of alendronate sodium in humans.

Absorption of the oral bisphosphonate alendronate in osteoporotic patients with Crohn's disease

The absorption of bisphosphonates from the gut is poor. The question arises whether the absorption of alendronate, and thus its bioavailability, is further altered by the local inflammatory process in patients with Crohn's disease, thereby potentially affecting clinical outcome when used in the treatment of osteoporosis. To address this question, urinary excretion of alendronate was evaluated 3 months and 6 months after start of treatment with oral alendronate at a dose of 10 mg/day in 19 osteoporotic patients with stable Crohn's disease, 12 of whom had an intestinal resection. Biochemical parameters of bone turnover and BMD were also measured at start and at 6 months. Thirteen patients had been previously treated with glucocorticoids and five were currently using them. The average 24-h urinary excretion of alendronate was 0.5-0.6% of the dose administered, a figure comparable to that reported for osteoporotic patients without gut pathology. There was a significant decrease from baseline in urine N-telopeptides of collagen cross-links (NTx)/creatinine (60%) associated with an increase in lumbar spine BMD of already 2% after 6 months of treatment. Our data suggest that in patients with Crohn's disease, alendronate is adequately absorbed from the intestine and retained in the skeleton. This adequacy is confirmed by appropriate suppression of bone resorption and increase in lumbar spine BMD. These data hold significant implications for the clinical management of patients with Crohn's disease and osteoporosis.

Skeletal retention of bisphosphonate (pamidronate) and its relation to the rate of bone resorption in patients with breast cancer and bone metastases

Bisphosphonate pharmacokinetics may affect individual responses. Skeletal retention of pamidronate infused monthly to patients with bone metastases was highly variable (12-98%) and did not diminish with time, showing the capacity of the skeleton to retain large amounts of bisphosphonate. Relationships between skeletal retention of pamidronate and rate of bone resorption are complex and depend on previous treatment and the total amount of retained bisphosphonate.

INTRODUCTION

Bisphosphonates (BPs) given intravenously every 3-4 weeks are effective in the management of metastatic bone disease from breast cancer, but responses among patients vary, and it is not known whether current dose and dose intervals are appropriate for an individual patient. An influence of pharmacokinetics of BPs on antiresorptive action may contribute to this variation in response. To test this hypothesis, we determined the skeletal retention of intravenous pamidronate and its association to the rate of bone resorption in patients with bone metastases from breast cancer.

MATERIALS AND METHODS

In a cross-sectional study, 24-h urinary excretion of pamidronate and the biochemical marker of bone resorption N-terminal telopeptide of type 1 collagen and serum alkaline phosphatase were measured in 40 patients with bone metastases from breast cancer at the beginning, after 3-6 months, and after 1 year of treatment with intravenous pamidronate 90 mg every 3-4 weeks.

RESULTS AND CONCLUSIONS

Skeletal retention (dose--amount excreted into urine) 2 days after infusion varied between 12% and 98% (mean, 62%) of the administered dose, but there were no differences in retention between patients receiving pamidronate for the first time or after 3-6 months or after 1 year of treatment. Retention of pamidronate was related to the prevalent rate of bone turnover in previously untreated patients, whereas no such relationship was found in previously treated patients. Rate of bone resorption after treatment seemed to be related to the amount of pamidronate retained. During 1 year of treatment, retention of pamidronate remained constant, indicating no saturation of skeletal binding sites with treatment. The variability in retention among individual patients can be attributed to the number of available binding sites. This is related, however, to bone turnover only before the start of treatment. The apparent relationships between skeletal retention and antiresorptive effect could have implications for the design of optimal therapeutic regimens with BPs in patients with bone metastases from breast cancer.

A randomized, phase II trial of ketoconazole plus alendronate versus ketoconazole alone in patients with androgen independent prostate cancer and bone metastases

PURPOSE

Alendronate (AL), a potent oral bisphosphonate, blocks the secretion of matrix metalloproteinase-2 and the establishment of bone metastases in animal models. Ketoconazole (KT) has demonstrated activity in androgen independent prostate cancer (AIPC). In this study we determined whether KT plus AL produced acceptable disease responses compared with KT alone. As the experimental design, 72 patients with progressive AIPC metastatic to bone were randomized to receive KT (1,200 mg daily) plus hydrocortisone (H) (30 mg daily) with or without AL (40 mg daily). Prostate specific antigen (PSA) consensus criteria and radiographic scans were used to determine the proportion of patients with a PSA decrease, time to progression and response duration. The pharmacokinetics of KT and AL were characterized and changes in circulating angiogenic factors were assessed.

RESULTS

At a median potential followup of 23.9 months the proportion of patients with a greater than 50% decrease in PSA was similar in the KT/H/AL and KT/H, groups (50% and 47%, respectively). The median duration of response was 8.9 and 6.3 months in the KT/H/AL and KT/H groups, respectively (p = 0.125). Median progression-free survival was not significantly prolonged in the KT/H/AL group (4.6 vs 3.8 months, p = 0.27). There was no significant difference in overall survival between the 2 treatment arms but there was a trend toward improved survival in the KT/H arm (p = 0.074). Toxicity in the 2 groups was mild and there were no clear associations between changes in circulating angiogenic factor levels and clinical outcomes in either treatment arm.

CONCLUSIONS

There were no statistically significant differences in response rate, progression-free survival or overall survival between KT/H alone and KT/H plus AL treatment in patients with AIPC. The addition of AL to KT/H may increase the response duration with an acceptable safety profile compared with treatment with KT/H alone. However, the addition of AL offers no survival benefit in patients with AIPC.

Determination of alendronate in human urine as 9-fluorenylmethyl derivative by high-performance liquid chromatography

A high-performance liquid chromatographic method for the quantitation of alendronate as the 9-fluorenylmethyl derivative (FMOC) in human urine is presented. The sample preparation involved coprecipitation with calcium phosphate, separation on diethylamine (DEA) solid-phase extraction (SPE) cartridge and derivatization with 9-fluorenylmethyl chloroformate in citrate buffer pH 11.9. Liquid chromatography was performed on an octadecylsilica column (150 x 4.6 mm, 3 microm particles); a gradient method with starting mobile phase acetonitrile-methanol-citrate/pyrophosphate buffer (20:15:65 v/v) was employed. The total run time was 21 min. The fluorimetric detector was operated at the following wavelengths: 260 nm (excitation) and 310 nm (emission). Pamdronate was used as the internal standard. The limit of quantitation was 3.5 ng/ml using 5 ml of urine. Within-day and between-day precision expressed by relative standard deviation was less than 8% and inaccuracy did not exceed 9%. The assay was applied to the analysis of samples from a pharmacokinetic study.

Ion-pair solid-phase extraction

Solid-phase extraction (SPE) is a technique widely employed by analytical chemists. SPE cartridges are available in a wide variety of formats containing media with diverse chemistries. This paper will review ion-pair SPE, one of the less frequently applied, and presumably less well-known techniques. Advantages of this technique over more conventional reversed-phase or ion-exchange SPE include selectivity, compatibility with rapid evaporative concentration, and potential application to multiclass multiresidue analysis.

Semi-automatic liquid chromatographic analysis of olpadronate in urine and serum using derivatization with (9-fluorenylmethyl)chloroformate

The semi-automatic bioanalytical assays for olpadronate [(3-dimethylamino-1-hydroxypropylidene)bisphosphonate] involves a protein precipitation with trichloroacetic acid and a double co-precipitation with calcium phosphate for serum samples and a triple calcium co-precipitation for urine samples. These manual procedures are followed by an automated solid-phase extraction on a cation-exchange phase. The procedure is continued either directly, at high olpadronate levels in urine, or after off-line evaporation under nitrogen and reconstitution in water on the same robotic workstation. The continued automatic procedure comprehends derivatization with (9-fluorenylmethyl)chloroformate, ion-pair liquid-liquid extraction and ion-pair HPLC with fluorescence detection at 274/307 nm. The intra- and inter-day precisions for urine and serum samples are typically in the 5-8% range for different olpadronate concentrations [levels near the lower limit of quantification (LLQ) excluded]. The LLQ is 5 ng/ml olpadronate for a 2.5-ml urine sample and 10 ng/ml for a 1-ml serum sample, respectively.