alendronate, Fosamax
Effects of dose, sex, and age on the disposition of alendronate, a potent antiosteolytic bisphosphonate, in rats.

Lin JH, Chen IW, Duggan DE.

Merck Sharp & Dohme Research Laboratories, West Point, PA 19486.

Alendronate (4-amino-1-hydroxybutylidene-1,1-bisphosphonate), an antiosteolytic agent, is currently under investigation in the treatment of a variety of bone disorders. Earlier studies from this laboratory have demonstrated that systemically administered drug was rapidly taken up by bone tissue or excreted by the kidneys. Approximately 60 to 70% of the dose was taken up by the bone, and 30 to 40% was excreted in the urine. The purpose of this study was to determine the effects of dose, sex, and age on the disposition kinetics of alendronate using rats as an animal model. No evidence of saturation of drug uptake by the bone was observed in young rats when small, repetitive doses of alendronate were administered every 3 days for 21 days (total 35 mg/kg iv). However, less than proportional uptake by the bone was observed in young rats when single iv doses exceeded 10 mg/kg. Overall, a 500-fold increase in dose resulted in a 350-fold increase in drug concentration in bone. Nonlinear uptake of alendronate by bone was accompanied by simultaneous accumulation in noncalcified tissues at high doses. Less than 1% of the dose was found in noncalcified tissues at 24 hr after low doses (1 mg/kg iv), and 25% after high doses (30 mg/kg iv). Following iv administration, uptake of alendronate by the bone was lower in senescent rats than in young rats by a factor of 2 to 3. Bone uptake was lower in female rats than in male rats by about 30 to 40%, but this sex difference was only observed at low doses and in young rats.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1356720&dopt=Abstract alendronate Fosamax



alendronate, Fosamax
Renal handling of alendronate in rats. An uncharacterized renal transport system.

Lin JH, Chen IW, Deluna FA, Hichens M.

Merck Sharp & Dohme Research Laboratories, West Point, PA 19486.

Alendronate (4-amino-1-hydroxybutylidene-1,1-bisphosphonate), an antiosteolytic agent, is currently under investigation in the treatment of a variety of bone diseases. Earlier studies from this laboratory have demonstrated that systemically administered alendronate is rapidly either taken up by bone tissues or excreted by the kidney, and that renal excretion is the only route of elimination. The purpose of this study is to characterize the renal handling of alendronate in rats by standard clearance procedures with inulin as a marker of glomerular filtration rate. Alendronate is highly bound to rat serum protein. The excretion of alendronate by the kidney is concentration-and dose-dependent, and saturable, indicating that it is secreted by an active transport mechanism. The secretory mechanism exhibits limitation of transport, with an apparent Tm of approximately 25 micrograms/min/kg. However, high doses of cimetidine, quinine, probenecid, and p-aminohippuric acid had no effect on the renal excretion of alendronate, suggesting that alendronate is not secreted by anionic or cationic transport systems. In contrast, alendronate clearance is inhibited by etidronate, another bisphosphonate, in a dose-dependent manner, implying that these two bisphosphonates compete for an as yet uncharacterized renal transport system. As expected, the renal excretion of alendronate is drastically reduced in rats with acute renal failure. As a consequence of renal impairment, alendronate accumulates in plasma, and the concentration of the drug in bone tissues increases significantly.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1356743&dopt=Abstract alendronate Fosamax



alendronate, Fosamax
Determination of alendronate in pharmaceutical dosage formulations by ion chromatography with conductivity detection.

Tsai EW, Ip DP, Brooks MA.

Merck Sharp & Dohme Research Laboratories, West Point, PA 19486.

A method was developed and validated for the direct determination in pharmaceutical dosage formulations of alendronate, a non-chromophoric compound. It is based on the use of single-column ion chromatography with conductivity detection that obviates the need for the tedious chemical derivatization procedures that are required for UV and fluorescence detection. Diluted samples of 0.05 mg/ml were chromatographed directly on a Waters IC-Pak HR anion-exchange column or a Dionex OmniPac PAX-100 column with dilute nitric acid as the mobile phase followed by conductivity detection. The method was validated and shown to be precise, accurate and specific for the assay of alendronate in intravenous (i.v.) solution and tablet formulations. The ruggedness of the assay was studied by generating data from four different instruments. Also established was the equivalence between this method and a previously reported high-performance liquid chromatographic method with 9-fluorenylmethyl chloroformate derivatization and UV detection. Application of the method to the determination of alendronate in i.v. and tablet formulations is presented and the performances of the Waters IC-Pak HR and Dionex OmniPac columns are discussed.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1400839&dopt=Abstract alendronate Fosamax



alendronate, Fosamax
The bisphosphonate, alendronate, prevents bone loss in ovariectomized baboons.

Thompson DD, Seedor JG, Quartuccio H, Solomon H, Fioravanti C, Davidson J, Klein H, Jackson R, Clair J, Frankenfield D, et al.

Merck, Sharp and Dohme Research Laboratories, West Point, Pennsylvania.

We examined the effect of the amino bisphosphonate alendronate, administered IV every 2 weeks at 0.05 and 0.25 mg/kg for 1 year, on bone loss and parameters related to bone metabolism in ovariectomized baboons. Relative to non-OVX animals, the OVX baboons experienced increased bone turnover, reflected in biochemical and histomorphometric measurements, and bone loss assessed by dual-beam absorptiometry in the lumbar spine, which was similar to changes observed in ovariectomized women. Alendronate treatment maintained all parameters of bone turnover at control (nonovariectomized) levels and prevented the bone loss in a dose-dependent manner. We concluded that ovariectomized baboons offer a suitable model for the bone changes observed in ovariectomized women and that these changes can be prevented by sustained administration of an appropriate dose of this aminobisphosphonate.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1442209&dopt=Abstract alendronate Fosamax



alendronate, Fosamax
Improved determination of the bisphosphonate alendronate in human plasma and urine by automated precolumn derivatization and high-performance liquid chromatography with fluorescence and electrochemical detection.

Kline WF, Matuszewski BK.

Merck Research Laboratories, West Point, PA 19846.

An improved method for the determination of 4-amino-1-hydroxybutane-1,1-bisphosphonic acid (alendronate) in human urine and an assay in human plasma are described. The methods are based on co-precipitation of the bisphosphonate with calcium phosphates, automated pre-column derivatization of the primary amino group of the bisphosphonic acid with 2,3-naphthalene dicarboxyaldehyde (NDA)-N-acetyl-D-penicillamine (NAP) or cyanide (CN-) reagents, and high-performance liquid chromatography (HPLC) with electrochemical (ED) or fluorescence detection (FD). The feasibility of ED of the NDA-CN- derivative of aldendronate has been demonstrated, and a HPLC-ED assay in human urine has been validated in the concentration range 2.5-50.0 ng/ml. In order to eliminate the cyanide ion from the assay procedure, several other nucleophiles in the NDA derivatization reaction were evaluated. An NDA-NAP reagent was found to produce highly fluorescent derivatives of alendronate. The assay in urine based on NDA-NAP derivatization and HPLC-FD has been developed and fully validated in the concentration range 1-25 ng/ml. Based on the same NDA-NAP derivatization, an assay in human plasma with a limit of quantification of 5 ng/ml has also been developed. Both HPLC-FD assays were utilized to support various human pharmacokinetic studies with alendronate.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1478982&dopt=Abstract alendronate Fosamax



alendronate, Fosamax
Bisphosphonate action. Alendronate localization in rat bone and effects on osteoclast ultrastructure.

Sato M, Grasser W, Endo N, Akins R, Simmons H, Thompson DD, Golub E, Rodan GA.

Department of Bone Biology and Osteoporosis Research, Merck Sharp & Dohme Research Laboratories, West Point, Pennsylvania 19486.

Studies of the mode of action of the bisphosphonate alendronate showed that 1 d after the injection of 0.4 mg/kg [3H]alendronate to newborn rats, 72% of the osteoclastic surface, 2% of the bone forming, and 13% of all other surfaces were densely labeled. Silver grains were seen above the osteoclasts and no other cells. 6 d later the label was 600-1,000 microns away from the epiphyseal plate and buried inside the bone, indicating normal growth and matrix deposition on top of alendronate-containing bone. Osteoclasts from adult animals, infused with parathyroid hormone-related peptide (1-34) and treated with 0.4 mg/kg alendronate subcutaneously for 2 d, all lacked ruffled border but not clear zone. In vitro alendronate bound to bone particles with a Kd of approximately 1 mM and a capacity of 100 nmol/mg at pH 7. At pH 3.5 binding was reduced by 50%. Alendronate inhibited bone resorption by isolated chicken or rat osteoclasts when the amount on the bone surface was around 1.3 x 10(-3) fmol/microns 2, which would produce a concentration of 0.1-1 mM in the resorption space if 50% were released. At these concentrations membrane leakiness to calcium was observed. These findings suggest that alendronate binds to resorption surfaces, is locally released during acidification, the rise in concentration stops resorption and membrane ruffling, without destroying the osteoclasts.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1661297&dopt=Abstract alendronate Fosamax