RESUMO
A method based on single column ion chromatography with UV detection was developed for purity testing and assay of monosodium olpadronate. The analyte aqueous solution is precipitated with methanol to enhance the impurities/olpadronate molar ratio, thus improving purity determination at trace levels. The resulting solution is injected into a standard chromatographic system with UV detector in indirect mode with a Waters IC Pak HR column using diluted nitric acid as the mobile phase. The method was fully validated according to ICH guidelines for the determination of phosphite, phosphate, chloride and methanesulfonic acid in olpadronate being suitable for purity testing and assay.
Assuntos
Cloretos/análise , Cromatografia por Troca Iônica/métodos , Difosfonatos/análise , Mesilatos/análise , Fosfatos/análise , Fosfitos/análise , Sensibilidade e Especificidade , Espectrofotometria UltravioletaRESUMO
Paraneoplastic syndromes are rarely described in animal models. It may be useful to have a suitable experimental model to study the mechanisms by which they are produced. In this study, we describe a murine lung adenocarcinoma, P07, which presents hypercalcemia, leukocytosis and cachexia. We determined the presence of PTHrP in plasma as well as GM-CSF produced by P07 cells. TNF-alpha, which is responsible for cachexia, could neither be detected in serum nor in P07 cell supernatants. We conclude that this model, which shows paraneoplastic syndromes similar to those of lung tumor patients, should be useful to study the pathways and significance of these signs.
Assuntos
Adenocarcinoma/fisiopatologia , Neoplasias Pulmonares/fisiopatologia , Síndromes Paraneoplásicas/fisiopatologia , Adenocarcinoma/sangue , Adenocarcinoma/patologia , Alanina Transaminase/sangue , Fosfatase Alcalina/sangue , Animais , Aspartato Aminotransferases/sangue , Proteínas Sanguíneas/análise , Caquexia/fisiopatologia , Cálcio/sangue , Feminino , Fator Estimulador de Colônias de Granulócitos e Macrófagos/biossíntese , Hematócrito , Contagem de Leucócitos , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/patologia , Camundongos , Camundongos Endogâmicos BALB C , Síndromes Paraneoplásicas/sangue , Proteína Relacionada ao Hormônio Paratireóideo , Proteínas/análise , Células Tumorais CultivadasRESUMO
"In vitro" effects of disodium pamidronate on hydroxyapatite crystals morphology, and some "in vivo" data from bone powder of tibia and vertebrae from treated young and mature rabbits are here reported. Hydroxyapatite, synthesized following Rigoli et al method, and bone powder from rabbits were studied with X-ray, infrared and raman emission techniques for crystallographic analysis. Adsorption studies were also performed with a balanced solution of hydroxyapatite exposed to different times, 48, 120 and 168 hours and concentrations 1 x 10(-5) M, 3 x 10(-5) M, 8 x 10(-5) M y 1 x 10(-4) M of pamidronate. Infrared and raman spectrometry were not conclusive due to technical bias, but X-ray difractograms showed pure hydroxyapatite crystals in an hexagonal system. At constant time, pamidronate concentrations were varied, showing after 48 hours of exposition, a slight growth in the 002 plane, an aleatoric behavior in 213 and a marked increase in 004. After 120 hours, 002 plane is steady with a net growth in 004 and 213. After 168 hours, the 3 mentioned planes grow in proportion to pamidronate concentrations, tending to enlarge the crystal shape. Plane 13 markedly grow with pamidronate 8 x 10(-5) M a 1 x 10(-4) M, which are biologically high concentrations. Potentiometric assessments, in the 1 x 10(-5) to 1 x 10(-4) M range of concentrations show that bisphosphonate was completely adsorbed to the crystals. Additional "in vivo" observations showed changes in bone powder crystals isolated from pamidronate treated young animals, involving a growing of planes 002 and 211, in samples from both epiphysis and diaphysis, regarding untreated samples. Changes were more evident at epiphysis. In mature rabbits, it was shown a decrease in basal plane 002 and growing at 210, 211 and 310 with a trend to enlarge the crystal shape in diaphysis and to shorten it in vertebrate spongiosa. The "in vivo" doses are equivalent to those used by Ferretti et al. in intact rats with pamidronate low dose groups, showing an improvement of bone material properties and stiffness. Thus, it may rather be lower than the "in vitro" used concentrations. In concordance with above experimental conditions it can be concluded that bisphosphonates exert morphological changes in hydroxyapatite crystals, in a dose dependent manner, at least when high concentrations are used. In addition, it is postulated that changes observed on "in vivo" samples may be the result with other adaptative factors as for example the local mechanical usage. The latter data were limited, and should be studied with more details if an extrapolation to the bisphosphonate treated osteoporotic women is intended. Finally, it is suggested that any agent that changes BMU activity (all known anti-osteoporotic drugs) may potentially modify the quality of hydroxyapatite crystals, affecting in turn the bone resistance to fracture, independently from the quantity of bone mass gained. Thus, to help predicting the consequences on skeletal fragility, there is a need to know the direct or indirect effect of drugs on bone crystals.
Assuntos
Materiais Biocompatíveis , Difosfonatos/farmacologia , Durapatita/química , Animais , Cristalização , Pamidronato , Coelhos , Fatores de TempoRESUMO
Ovariectomy and immobilization in rats have demonstrated to be useful models for osteopenia and they are considered to mimic some aspects of human osteoporosis associated with a deficit of ovarian hormones and the absence of mechanical function (disuse of the bone). Pamidronate (APD) and Olpadronate (OLPA), a new dimethylated aminobisphosphonate, on a continuous oral scheme (APD: 8 and OLPA: 0.8 mg/kg/day) or on an intermittent parenteral scheme (APD: 1.25 and OLPA: 0.075 mg/kg every 15 days) did effectively prevent the trabecular bone loss caused by immobilization (unilateral sciaticectomy), by lack of ovarian stimuli (bilateral ovariectomy) or by both approaches. There were no signs of deterioration in the cortical bone mass. In a model of preestablished osteopenia, caused by estrogen deprivation, OLPA stopped the progression of the bone mass loss (0.5 mg/kg/i.v. every 15 days) and restored (0.30-0.60 mg/kg/i.v. every 15 days) the bone mineral density which had been affected (trabecular and cortical). The different activity of OLPA and APD on trabecular and cortical regions of long bones seems to accompany their different responses because of negative stimulus: better responses were more evident in the trabecular bone which proved to be more labile. In these "in vivo" models of OLPA's efficacy was similar to APD's but it was roughly 5-10 times more potent. OLPA has a high safety margin. Therefore, it could advantageously be used in those bone diseases which benefit with the use of bisphosphonates.
Assuntos
Densidade Óssea/efeitos dos fármacos , Doenças Ósseas Metabólicas/tratamento farmacológico , Osso e Ossos/efeitos dos fármacos , Difosfonatos/farmacologia , Análise de Variância , Animais , Doenças Ósseas Metabólicas/metabolismo , Osso e Ossos/metabolismo , Difosfonatos/metabolismo , Feminino , Masculino , Ovariectomia , Pamidronato , Ratos , Ratos WistarRESUMO
Bisphosphonates are a group of osteotropic substances able to modulate bone metabolism in different ways. They all display similar pharmacokinetic characteristics when administered in proportional dosages and assessed by similar methods. With the exception of olpadronate which is soluble in water, bisphosphonates have poor solubility, and may easily precipitate in the digestive media. In spite of their low digestive absorption (Bioavailability: 0.3-5%), they are effectively administered by oral route. Once in plasma they distribute rapidly, being uptaked by mineralized tissues, plasma proteins or eliminated by renal filtration in few minutes. The fraction retained in bones may be stored for long periods (from months up to 10 years depending on the compound) in an apparent inactive compartment. The risks of newly released molecules may be related to the potency of the drug. Within the clinical range of doses, bisphosphonates are not retained in soft tissues. This may explain the lack of extraskeletal collateral effects. Plasma blood levels are scarcely related to the clinical activity. Therefore, dosage may be guided better by biochemical markers of the bone disease than by the standard kinetic variables. On the other hand, dose is independent from age and/or body weight. Only renal impairment may induce additional dose adjustments.
Assuntos
Difosfonatos/farmacocinética , Animais , Disponibilidade Biológica , Difosfonatos/administração & dosagem , Difosfonatos/química , Humanos , Modelos LinearesRESUMO
Bisphosphonates regulate bone turnover by inhibiting osteoclastic bone resorption. Due to their pharmacodynamic and pharmacokinetic characteristics, bisphosphonates have a special pharmacotoxicological profile related to their high degree of specificity: low or non-existent distribution in soft tissues and strong affinity for calcified tissues. Some general conclusions may be drawn from the pre-clinical toxicological studies, whose main aim is to identify the toxicity target organ/s and estimate the safety margins of a "prospective therapeutic agent" in laboratory animals. They are based on our own results and on data from the available literature as regards various bisphosphonates: Alendronate, Clodronate, Etidronate, Olpadronate and Pamidronate. Generally, very high doses of bisphosphonates are required to produce in different levels and incidence various extra-skeletical toxic side effects: local reaction, hypocalcemia (and its consequences on the cardiovascular system and the possibility of tetany), affection of the dental structures and renal dysfunction. Most of side effects may be related to the low solubility in biological fluids, the formation of calcium complexes, the potent inhibitory effect of endogenous or induced bone resorption as well as to its main excretion pathway. Some other side effects (on the eye, lungs and liver), may be related to repeated excessive high doses. A safety margin of 200 to 300 : 1 between the "toxic" and "pharmacological" doses may be estimated if the total quantity of Olpadronate given to various animal species in toxicological studies and in pharmacodynamic experimental models (osteopenias due to estrogen deprivation or immobilization and retinoid-induced hypercalcemia) is considered. If the toxic doses in animals are related to the highest doses suggested for human beings, then the ratio increases from 300 to 1000 : 1 depending on the pathology and the route of administration. As regards their effect on the bone, experimental data with the new bisphosphonates suggest a significant dissociation between pharmacologically active doses and those ones producing defective mineralization. The excessive inhibition of bone remodelling, due to the use of high doses in normal animals, is the natural consequence of the pharmacological effect of this family of compounds. A bisphosphonate's toxic potential effect on bone should not be evaluated in normal animals but in particular situations with a high bone turnover. Furthermore, the doses should be adjusted in order to regulate the magnitude of bone remodelling inhibition so as to take it to a normal level without totally suppressing it. Potency, safety margins, doses and proper administration schemes, should be considered as key elements for the optimum use of the therapeutic potentiality of these compounds.
Assuntos
Densidade Óssea/efeitos dos fármacos , Remodelação Óssea/efeitos dos fármacos , Osso e Ossos/efeitos dos fármacos , Sistema Digestório/efeitos dos fármacos , Difosfonatos/toxicidade , Animais , Difosfonatos/administração & dosagem , Difosfonatos/farmacologia , Avaliação Pré-Clínica de Medicamentos , Humanos , Hipocalcemia/induzido quimicamente , Camundongos , Coelhos , RatosRESUMO
Oral nitrogen containing bisphosphonates (NCB) are effective drugs to inhibit bone metabolism turnover in osteoporosis and other bone diseases. Notwithstanding, some digestive disturbances create concern on the long term acceptance of the oral route. Side effects are mainly caused by low absorption and poor solubility in digestive content. Therefore the compound may precipitate and irritate the mucosas. Furthermore, the administered amount of a particular molecule, its intrinsic potency to irritate digestive walls and the degree of exposition to such sensitive tissue are other facts that combined, may determine the clinical tolerability. Thus, a single factor cannot predict the clinical tolerability. Pamidronate, alendronate and olpadronate are the main NCB under clinical usage. Alendronate is 10 times more potent than pamidronate but possesses a similar slight solubility (2.4 vs 3.0% W/V respectively). It also seems to be more (3 times fold) ulcerogenic in experimental assays. The current available pamidronate formulation protects from esophagus and gastric exposition. Up to now and until randomized clinical trials be performed the selection of the most tolerated aminobisphosphonate in clinical practice will depend on the interplay of many factors (table 1 shows a hypothetical view). Moreover, different patients may react dissimilarly depending on their sensitivity to a particular factor. Olpadronate is free-soluble (24% W/V), almost equipotent with alendronate (figure 1) and seems to lack relevant irritation potential, but clinical data is on its early phases and is still not available. Micronization of the bisphosphonate preparation may be of help to improve tolerability as shown with newer pamidronate oral formulations. The current clinical published data shows more or less the same safety profile for pamidronate (only when enteric coated capsules are used) as alendronate, with more than 90% of patients complying with long term treatments. Anyway the trials are not entirely comparable as said before. Some other pamidronate formulations proved to be intolerable and have not been accepted. Identifying the many factors of oral NCB's digestive tolerability may help with their clinical management. And in those countries where the two compounds are available they may alternatively be used in the sensitive patients. Finally, extra-digestive side effects, not commented in this article, should also be weighted when selecting a bisphosphonate.