Cytotoxic effects of pamidronate on monolayers of human intestinal epithelial (Caco-2) cells and its epithelial transport

Racial difference in bioavailability of oral ibandronate between Caucasian and Taiwanese postmenopausal women

Following 150 mg of oral ibandronate, Taiwanese females have greater serum and urine levels of this drug and bone resorption marker suppression than Caucasian women. These inter-ethnic differences seems to be partly explained by a 2.48-fold higher bioavailability of ibandronate in Taiwanese postmenopausal women.

INTRODUCTION

Interethnic differences in the pharmacokinetics of oral ibandronate for osteoporosis are unknown. We compared the disposition of oral ibandronate between Caucasian and Taiwanese postmenopausal women.

METHODS

Ibandronate 150 mg was administered to 35 Caucasian and 16 Taiwanese postmenopausal women in two separate phase 1 studies. Interethnic comparisons were performed to assess pharmacokinetic properties, including the area under the concentration-time curve (AUC), peak concentration (Cmax), elimination half-life, urinary drug recovery (Ae%), renal clearance (CLr), apparent total clearance (CL/F), and apparent volume of distribution (Vd/F).

RESULTS

The mean AUC, Cmax, and Ae% were 2.41-, 1.69-, and 2.95-fold greater in the Taiwanese than in the Caucasian subjects, and the average CL/F and Vd/F were 2.48- and 2.46-fold smaller. There were no significant differences in mean CLr and half-life between both groups. As bisphosphonates are not biotransformed but are mainly excreted in the urine, the total body clearance is close to the CLr. These results suggested a larger bioavailability in the Taiwanese group which resulted in the differences in the CL/F and Vd/F. Multiple linear regression analysis demonstrated ethnicity influences of the pharmacokinetic properties after adjusting for the other variables.

CONCLUSIONS

Bioavailability was largely responsible for the interethnic pharmacokinetic differences following oral administration of 150 mg ibandronate and seemed greater in the Taiwanese compared with the Caucasian subjects. Further dose-ranging studies are warranted to determine the optimal dosages of oral ibandronate in patients of Asian or Taiwanese ethnicity.

Combined Approach to Treat Medication-Related Osteonecrosis of the Jaws

Introduction: The proper therapeutic plan for medication-related osteonecrosis of the Jaw (MRONJ) is still lacking long-term data up to today. They were several high-technological appliances proposed for the different intervention steps, in addition to tissue repair promoters. The reason for proposing an integrated technique is justified, beyond better compliance of the patients associated to the pain and inflammation reduction and bleeding control, there is also achieving better hard and soft tissues healing. Methods: Patients diagnosed with bisphosphonates-related osteonecrosis of the jaws (BRONJ) at the Odontostomatology and Maxillo-Facial Surgery Unit of the Hospital of Piacenza undergone surgical intervention. The intervention was performed by using different devices: Piezosurgery for removing the necrotic bone tissue and for obtaining the bone specimen essential for histological analysis; Er:YAG laser (2940 nm) to vaporize necrotic hard tissue until reaching the bleeding bone; platelet-rich plasma (PRP) to stimulate hard and soft tissue healing; and finally diode laser (808 nm) to perform a biostimulation of the surgical site. Results: All treated patients demonstrated a good postoperative comfort even without using painkillers, no bleeding, and a fast healing process. Most of the patients (92.85%) reached complete healing with a minimum follow up at 6 months. Histological exams demonstrated a good quality without artifacts. Conclusion: Sequential utilization of different high-technologies devices during all the steps of MRONJ treatment allows to perform a faster and less invasive surgery with a more comfortable postoperative healing process and it may represent a new and original approach for treating this severe adverse event.

The influence of geranylgeraniol on human oral keratinocytes after bisphosphonate treatment: An in vitro study

This in vitro study analyzed the influence of geranylgeraniol (GGOH) on human oral keratinocytes (HOK) after exposure to bisphosphonates. HOK were incubated with four different bisphosphonates (clodronate, ibandronate, pamidronate, zoledronate) in two experimental set-ups: with and without GGOH. MTT and PrestoBlue assays were used to analyze HOK cell viability. HOK migration ability was examined with Boyden and Scratch assays, and Tunel and ToxiLight assays were used to detect the HOK apoptosis rate. No significant differences between the experimental set-ups, with and without GGOH, could be found for clodronate (p each >0.3). For the nitrogen-containing bisphosphonates, negative effects could be shown in the experimental set-ups without GGOH in all assays. In the GGOH experimental set-ups, the levels of HOK cell viability were significantly increased (MTT: p each ≤0.001; PrestoBlue: p each ≤0.012). The HOK migration ability was also greater (Boyden: p each <0.001; Scratch: p each ≤0.015). Regarding the apoptosis rate, reduced numbers of apoptotic HOK in the Tunel assay (p each <0.001) and decreased adenylate kinase release in the ToxiLight assay (p each ≤0.002) were observed. GGOH reversed the negative effects of bisphosphonates on HOK. These findings provide evidence that GGOH could be a promising treatment option for BP-ONJ.

Bisphosphonate associated osteonecrosis of the jaw: an update on pathophysiology, risk factors, and treatment

Osteonecrosis of the jaw in patients treated with bisphosphonates is a relatively rare but well known complication at maxillofacial units around the world. It has been speculated that the medication, especially long-term i.v. bisphosphonate treatment, could cause sterile necrosis of the jaws. The aim of this narrative review of the literature was to elaborate on the pathological mechanisms behind the condition and also to gather an update on incidence, risk factors, and treatment of bisphosphonate associated osteonecrosis of the jaw. In total, ninety-one articles were reviewed. All were published in internationally recognized journals with referee systems. We can conclude that necrotic lesions in the jaw seem to be following upon exposure of bone, for example, after tooth extractions, while other interventions like implant placement do not increase the risk of osteonecrosis. Since exposure to the bacterial environment in the oral cavity seems essential for the development of necrotic lesions, we believe that the condition is in fact chronic osteomyelitis and should be treated accordingly.

Eliminating the need for fasting with oral administration of bisphosphonates

Bisphosphonates are the major treatment of choice for osteoporosis, given that they are attached preferentially by bone and significantly reduce the risk of fractures. Oral bisphosphonates are poorly absorbed (usually less than 1% for nitrogen-containing bisphosphonates) and when taken with food or beverages create complexes that cannot be absorbed. For this reason, they must be taken on an empty stomach, and a period of up to 2 hours must elapse before the consumption of any food or drink other than plain water. This routine is not only inconvenient but can lead to discontinuation of treatment, and when mistakenly taken with food, may result in misdiagnosis of resistance to or failure of treatment. The development of an enteric-coated delayed-release formulation of risedronate with the addition of the calcium chelator, ethylenediaminetetraacetic acid (EDTA), a widely used food stabilizer, eliminates the need for fasting without affecting the bioavailability of risedronate or its efficacy.

Sarcoglycans and integrins in bisphosphonate treatment: immunohistochemical and scanning electron microscopy study

Osteonecrosis of the jaw is an adverse outcome associated with bisphosphonate treatment. Bisphosphonates are used in conjunction with antineoplastic chemotherapy for the treatment of hypercalcaemia associated with malignancy, lytic bone metastasis and multiple myeloma. However, it is not known if the osteonecrosis of the jaw lesion originates in the bone or whether it initiates in the gingival epithelium. Two bisphosphonates are commonly used in cancer treatment. One of these is pamidronate disodium, a second-generation bisphosphonate that differs from the first-generation drug because it inhibits bone resorption at a dose that does not affect bone mineralization. The other widely used BP, zoledronate, is a third-generation drug that is the most potent bisphosphonate in clinical use, showing strong anti-osteoclastic activity, similar to pamidronate. The aim of the present study was to evaluate the modifications of human oral mucosa and underlying bone in patients after treatment with these nitrogen-containing bisphosphonates for 24 and 36 months. We analyzed the structural damage of the oral mucosa and damage of the perilesional mandibular bone observing possible correlations from them. Our results allow to express two hypotheses about the mechanism responsible for these results relating to mandible matrix necrosis; first, an increased skeletal microdamage associated with turnover suppression occurred early in treatment and progress with longer treatment duration, second, opening damage in osteonecrosis of the jaw modifies structural morphology of gingival epithelium.

Potential therapeutic effects of oral bisphosphonates on the intestine

Bisphosphonates are the principal drugs prescribed for the prevention of osteoporotic fractures. They are bone specific but poorly absorbed. In oral formulations, almost 99% of the administered dose remains within the intestinal tract and reaches the small and large bowel. Although the nitrogen-containing bisphosphonates can irritate the distal esophageal/gastric mucosa, they improve drug-induced colitis in animal models and exhibit antitumor properties on intestinal cells in vitro. Several recent epidemiological studies provide evidence of a reduced risk of colorectal cancer in osteoporotic patients treated with oral bisphosphonates, notably alendronate. In this review, we will explore the possible mechanisms of action underlying these effects and raise the question of whether these agents might be used in the chemoprophylaxis against colorectal cancer.

Tooth extraction in patients on zoledronic acid therapy

OBJECTIVES

Surgical management of patients following zoledronic acid therapy is particularly difficult, since the dental extraction is the main cause of BRONJ.

METHODS

A case-control study was conducted on 176 patients treated with intravenous (IV) bisphosphonates for oncologic pathologies who also underwent dental extractions. The study was divided randomly into two groups: 91 were treated with Plasma Rich in Growth Factor Plasma (PRGF) (study group) and the other 85 were not treated with the growth factor preparation (control group).

RESULTS

Panoramic X-ray and computed tomography were performed both before and 60 months after surgery. By clinical and radiological diagnosis, BRONJ was diagnosed in only 5 patients in the control group at an average of 91, 6 days after tooth extraction.

CONCLUSIONS

We hypothesize that Plasma Rich in Growth Factor (PRGF) is important for the successful treatment of patients on bisphosphonates to restore the osteoblast/osteoclast homeostatic cycles via autologous cytokines. Moreover, this protocol reduces the risk of BRONJ when it is necessary to perform dental extractions in patients undergoing IV bisphosphonate treatment.

Novel therapy to reverse the cellular effects of bisphosphonates on primary human oral fibroblasts

PURPOSE

Osteonecrosis of the jaws (ONJ) is a clinical condition that is characterized by a nonhealing breach in the oral mucosa resulting in exposure of bone and has been increasingly reported in patients receiving bisphosphonate (BP) therapy. Although the pathogenesis and natural history of ONJ remain ill-defined, it appears that the oral soft tissues play a critical role in the development of this condition. We examined the effects of the nitrogen-containing BPs pamidronate and zoledronate on primary human gingival fibroblasts.

MATERIALS AND METHODS

Primary gingival fibroblasts were exposed to clinically relevant doses of pamidronate and zoledronate. Cellular proliferation was measured with an MTS/PMS reagent-based kit (Promega, Madison, WI), scratch wound assays were performed to measure cellular migration, and apoptosis was measured by use of terminal deoxynucleotidyl transferase-mediated dUTP-FITC end labeling and caspase assays. The BP-exposed cells were treated with 10-ng/mL recombinant human platelet-derived growth factor BB (rhPDGF-BB) and 50-μmol/L geranylgeraniol (GGOH).

RESULTS

Gingival fibroblasts are significantly more sensitive to inhibition of proliferation by zoledronate compared with pamidronate. Exposure of these cells to pamidronate but not zoledronate resulted in an increase in cellular apoptosis. Furthermore, exposure of gingival fibroblasts to pamidronate or zoledronate resulted in a decrease in cellular migration. We show that these defects are due to a loss of cell-substratum adhesion and a reduction of F-actin bundles. Finally, we show that the addition of rhPDGF-BB and GGOH in vitro is able to partially rescue the cell proliferation, migration, and adhesion defects.

CONCLUSION

The cytotoxic effects of BPs on oral fibroblasts and their significant reversal by the addition of GGOH and rhPDGF-BB provide both the potential mechanism and treatment options for ONJ.

Potential pathophysiological mechanisms in osteonecrosis of the jaw

Bisphosphonates are used in the treatment of hypercalcemia of malignancy, skeletal complications associated with metastastic bone disease, Paget's disease, and osteoporosis. Osteonecrosis of the jaw (ONJ) is a recently described clinical condition that has been associated with the use of nitrogen-containing bisphosphonates. Reports describing this entity first appeared in the literature in 2003. While there have been significant numbers of case reports and a limited number of retrospective and prospective studies examining risk factors associated with ONJ, the pathophysiology of this condition remains elusive. In this review, we explore proposed mechanisms underlying ONJ development and identify potential areas for future investigation.

Osteonecrosis of the jaw and the role of bisphosphonates: a critical review

Osteonecrosis of the jaw (ONJ), a condition characterized by necrotic exposed bone in the maxillofacial region, has been reported in patients with cancer receiving bisphosphonate therapy, and rarely in patients with postmenopausal osteoporosis or Paget disease of bone receiving such therapy. In the absence of a uniform definition, the American Academy of Oral and Maxillofacial Surgeons (AAOMS), the American Society for Bone and Mineral Research (ASBMR), and other groups have established similar diagnostic criteria for bisphosphonate-related ONJ, which is more commonly reported in patients with advanced malignancies with skeletal metastases who receive higher doses, and is more rarely reported in patients with osteoporosis and Paget disease who receive lower doses. However, a critical review of the literature reveals that the etiology of ONJ remains unknown, and to date no direct causal link to bisphosphonates has been established. Despite an increased awareness of ONJ and recent improvements in preventive strategies, patients and physicians alike continue to express concern about the potential risks of bisphosphonate treatment in both oncologic and nononcologic settings. Although much remains to be learned about this condition, including its true incidence in various patient populations, its pathophysiology, and optimal clinical management, evidence to date suggests that the positive benefits of bisphosphonates in patients with malignant bone disease, osteoporosis, or Paget disease outweigh the relatively small risk of ONJ.

Preparation and Evaluation of Floating Risedronate Sodium–Gelucire® 43/01 Formulations

Single and multi-unit floating matrices of risedronate sodium were prepared using Gelucire 43/01 by melt solidification and melt granulation technique, respectively. The controlled release floating matrices were evaluated for in vitro and in vivo floating ability and in vitro drug release. Effect of aging on Gelucire 43/01 was evaluated by hot stage microscopy (HSM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), in vitro floating ability, and in vitro drug release. Multi-unit system obtained has shown initial burst release, which was suppressed in single unit system. Both single- as well as multi-unit systems showed increase in rate of drug release on aging due to changes in the properties of the Gelucire 43/01. Multi-unit matrices obtained by melt granulation were relatively easier for scale up and advantageous if the initial burst release does not cause any significant clinical adversity.

Inhibition of oral mucosal cell wound healing by bisphosphonates

PURPOSE

Bisphosphonates (BPs) are a widely used class of drugs that are effective in the treatment and prevention of osteoporosis, hypercalcemia of malignancy, and bone metastases associated with multiple myeloma, breast cancer, and other solid tumors. In the past several years there have been numerous reports describing the occurrence of osteonecrosis of the jaws (ONJ) associated with these drugs. Whether the ONJ lesion initiates in the oral mucosa or derives from the underlying bone is not well understood. In this report we describe the effect of pamidronate, a second-generation BP, on oral mucosal cells.

MATERIALS AND METHODS

Murine oral keratinocytes were isolated and exposed to pamidronate at a range of clinically relevant doses. Cellular proliferation was measured using a MTS/PMS reagent-based kit and wound healing was examined with a scratch assay. To determine whether oral keratinocytes undergo apoptosis following exposure to pamidronate, TUNEL, caspase-3, and DAPI apoptosis assays were performed.

RESULTS

We show that BP pretreatment of oral mucosal cells inhibits proliferation and wound healing at clinically relevant doses, and that this inhibition is not due to cellular apoptosis.

CONCLUSIONS

To our knowledge this is the first report investigating the effect of nitrogen-containing BPs on oral mucosal cells. This study suggests that BPs inhibit oral keratinocyte wound healing which may play a significant role in the initiation of ONJ.

Influence of different calcic antagonists on the Caco-2 cell monolayer integrity or “TEER, a measurement of toxicity ?”

The purpose of this work was to investigate the interest of the TEER measurement, a quite simple measure, as an evaluation of toxicity, in function of time and level of drug in the experimental medium, for different anticalcic agents. The extend of the increase and decrease of TEER, was evaluated by measuring the TEERmax and calculating the TEER50 respectively. Three groups of compounds could be therefore considered. The first, characterized by a quite short period of TEER increase, followed by an extremely rapid decrease (high values of TEER50), included perhexiline and prenylamine. The most toxic compounds, the second one, characterized by the smallest variations of TEER, included verapamil and diltiazem. This group was related with the less toxic compounds, the third group, represented by bepridil, characterized by dependant-dose TEERmax and TEER50. Therefore, the TEER measurement appeared as a quite simple approach of comparative toxicity of anticalcic agents.

Effects of various absorption enhancers on transport of clodronate through Caco-2 cells

The major disadvantage concerning clinical use of bishosphonate drugs, like clodronate, is their poor and variable absorption after oral administration. The objective of this study was to assess the effects of four different absorption enhancers-palmitoyl carnitine chloride (PCC), N-trimethyl chitosan chloride (TMC), sodium caprate (C10), and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)-on the transport of clodronate using Caco-2 cell culture model. The transport experiments were performed in a normal (1.3mM) and in a minimum-calcium concentration (apically calcium-free medium and basolaterally 100 microM calcium concentration). In the normal calcium concentration, a strong enhancement in clodronate permeation was observed with the enhancers: EGTA (2.5mM), TMC (1.5% w/v), and PCC (0.2mM) increased the transport of 1mM clodronate 190-, 20-, and 10-fold, respectively, and the transport of 10mM clodronate 130-, 70-, and 35-fold. In the minimum-calcium concentration, the effects of the absorption enhancers on the transport of clodronate were not so potent: TMC, PCC, and EGTA caused 2- to 20-fold enhancement in clodronate permeation whereas C10 (10mM) was without any effect. According to the results, the permeation of clodronate through Caco-2 cells could be significantly promoted by the absorption enhancers, which cause widening of the tight junctions and, thus, increase the permeability of the paracellular route.

Cellular uptake and metabolism of clodronate and its derivatives in Caco-2 cells: a possible correlation with bisphosphonate-induced gastrointestinal side-effects

PURPOSE

To investigate possible reasons for the low frequency of GI side-effects of clodronate, even though clodronate is known to be metabolised into a cytotoxic nucleotide analogue (AppCCl(2)p) by many cell types. The effects of some lipophilic prodrugs of clodronate were also studied.

METHODS

The effects of clodronate and its lipophilic derivatives on the proliferation and viability of Caco-2 cells were examined using an MTT assay. The intracellular uptake of 14C-clodronate and the accumulation of a clodronate metabolite (AppCCl(2)p) in Caco-2 cells were evaluated using ion-pairing HPLC-ESI-MS.

RESULTS

Clodronate had little effect on growth of proliferating, or the viability of confluent, Caco-2 cells. The uptake of clodronate by Caco-2 cells was only about 0.04% of total clodronate. The potentially cytotoxic clodronate metabolite, AppCCl(2)p, was detected in Caco-2 cell extracts after 3 h of exposure. Dianhydride- and triPOM-clodronate were metabolised to AppCCl(2)p more efficiently and also affected the viability of Caco-2 cells more than clodronate.

CONCLUSIONS

Clodronate appears to be metabolised into a cytotoxic ATP-analogue (AppCCl(2)p) by any cell type capable of internalising the drug. However, the cytotoxicity depends on the degree of uptake of clodronate. Due to the very low initial uptake of clodronate by epithelial Caco-2 cells, they do not accumulate sufficient intracellular concentrations of AppCCl(2)p to affect cell function. This explains the low frequency of gastrointestinal side-effects caused by oral clodronate therapy.

Nitrogen-containing bisphosphonates induce apoptosis of Caco-2 cells in vitro by inhibiting the mevalonate pathway: a model of bisphosphonate-induced gastrointestinal toxicity

Bisphosphonates have become an important addition to the pharmacological armamentarium against postmenopausal osteoporosis. One of the major side effects of oral therapy with some nitrogen-containing bisphosphonates appears to be gastrointestinal (GI) intolerability, particularly esophageal irritation and ulceration. Because nitrogen-containing bisphosphonates can cause apoptosis in a variety of cell types in vitro, by inhibiting the mevalonate pathway, we hypothesized that the effect of these agents on the GI tract may be due to apoptosis or inhibition of growth of gut epithelial cells. A comparison between clodronate, etidronate, pamidronate, alendronate, and risedronate demonstrated that only the nitrogen-containing bisphosphonates were effective at inducing apoptosis or inhibiting proliferation of Caco-2 human epithelial cells in vitro, at concentrations of between 10 and 1000 micromol/L. The ability of nitrogen-containing bisphosphonates to cause apoptosis and inhibit Caco-2 cell proliferation was due to inhibition of the mevalonate pathway, because the addition of farnesol, oxidized low-density lipoprotein (LDL) cholesterol, or especially geranylgeraniol suppressed the effects. Furthermore, pamidronate, alendronate, and risedronate inhibited protein prenylation in Caco-2 cells, as determined by analysis of the processing of Rap1A, a prenylated small GTPase. These studies suggest that the effects of nitrogen-containing bisphosphonates observed in the GI tract may be due to inhibition of proliferation or apoptosis of gut epithelial cells, following loss of prenylated proteins and sterols.

Administration routes and delivery systems of bisphosphonates for the treatment of bone resorption

Geminal bisphosphonates (BPs) are a class of drugs considered to be stable analogs of pyrophosphate (P-O-P), a physiological regulator of calcification and bone resorption. A number of BPs have been approved for clinical use in Paget's disease, hypercalcemia of malignancy, and osteoporosis. The major disadvantage of the clinically utilized BPs is their poor oral absorption from the GI tract, typically less than 1% is absorbed. In addition, the BPs have been associated with adverse gastrointestinal effects in humans. The challenge for novel drug delivery systems is to achieve improved bioavailability and safety. In the first part of this review, we discuss the bioavailability of BPs, the effect of food on the absorption of BPs, the mechanism of BPs' absorption and the adverse gastrointestinal effects. In the second part of the review, various methods that have been used for improving the bioavailability of BPs are described. Dosage form strategies reviewed include the use of particular formulations for increasing oral absorption as well as decreasing adverse gastrointestinal effects, absorption enhancers, BP compounds and the solubility of their calcium complex/salts, and the prodrug approach. Because of the poor GI absorption, attempts have been made to enhance the bioavailability of BPs by several parenteral routes other than i.v. injections. Description of nasal administration, s.c. and i.m. injections, BP implants and targeted osteotropic delivery systems are reviewed.

Synthesis and preclinical pharmacology of 2-(2-aminopyrimidinio) ethylidene-1,1-bisphosphonic acid betaine (ISA-13-1)-a novel bisphosphonate

PURPOSE

To validate our hypothesis that a bisphosphonate (BP) having a nitrogen-containing heterocyclic ring on the side chain, and with no hydroxyl on the geminal carbon would possess increased activity, and better oral bioavailability due to enhanced solubility of its calcium complexes/salts and weaker Ca chelating properties.

METHODS

A novel BP, 2-(2-aminopyrimidinio)ethylidene-1, 1-bisphosphonic acid betaine (ISA-13-1) was synthesized. The physicochemical properties and permeability were studied in vitro. The effects on macrophages, bone resorption (young growing rat model), and tumor-induced osteolysis (Walker carcinosarcoma) were studied in comparison to clinically used BPs.

RESULTS

The solubility of the Ca salt of ISA-13-1 was higher, and the log beta(Ca:BP) stability constant and the affinity to hydroxyapatite were lower than those of alendronate and pamidronate. ISA-13-1 exhibited effects similar to those of alendronate on bone volume, on bone osteolysis, and on macrophages, following delivery by liposomes. ISA-13-1 was shown to have 1.5-1.7 times better oral absorption than the other BPs with no deleterious effects on the tight junctions of intestinal tissue.

CONCLUSIONS

The similar potency to clinically used BPs, the increased oral absorption as well as the lack of effect on tissue tight junction of ISA-13-1 warrant its further consideration as a potential drug for bone diseases.

The effects of nitrogen-containing bisphosphonates on human epithelial (Caco-2) cells, an in vitro model for intestinal epithelium

Nitrogen-containing bisphosphonates (N-PCP) are bisphosphonates with an increased antiresorptive potency. Aminobisphosphonates, N-PCPs with an amino group, can cause nonspecific gastrointestinal complaints. It is not known whether these side effects are specific for these bisphosphonates or for the whole class of N-PCPs. In this study, we investigated the effects of two aminobisphosphonates (pamidronate and alendronate) and a structurally similar N-PCP (olpadronate) and their three respective calcium complexes on the viability and the intracellular calcium concentration ([Ca2+]i) of cultured Caco-2 cells a model for intestinal epithelium. These cells were also examined for apoptosis or necrosis. In the presence of calcium, pamidronate and alendronate were toxic to the cells, with pamidronate being more toxic than alendronate. Olpadronate induced toxicity only at concentrations more than ten times higher than the toxic concentrations of pamidronate. In the absence of calcium definite signs of toxicity were observed only with pamidronate at clinically relevant concentrations. The complexes of pamidronate and alendronate with calcium were considerably less soluble than the olpadronate calcium complex. There were no signs of apoptosis. [Ca2+]i was transiently raised after treatment with the N-PCPs. Doses at which responses were seen were, respectively, 0.02 mM (pamidronate), 0.3 mM (alendronate), and 2 mM (olpadronate). The peak of response was slightly greater after pamidronate treatment than after alendronate or olpadronate, respectively. In conclusion pamidronate, either as an ion or as a calcium complex, is the most toxic of the bisphosphonates tested for Caco-2 cells. Alendronate was less toxic while olpadronate was the least toxic in presence of calcium. The solubility of the bisphosphonate complexes with calcium may account for these differences in toxicity.

Transepithelial transport of bepridil in the human intestinal cell line, Caco-2, using two media, DMEMc and HBSS

The purpose of this work was to study transepithelial transport of bepridil, an anticalcic agent, through monolayer cells Caco-2, using two experimental media with different chemical components. For experimentation, the measure of the transepithelial electrical resistance (TEER) allowed us to evaluate the state of cells; and the quantities of bepridil have been quantified using a gas chromatography/mass spectrometry system. First, when using the medium alone, without bepridil, Caco-2 cell integrity is, at least, maintained for 8 h using both media. However, for 24-h studies, only the DMEMc medium, rich in essential nutriments, allowed cell integrity to be maintained. Then, with bepridil in HBSS medium, the TEER measurement showed a dose-dependent toxic effect of bepridil, whereas in the DMEMc medium, the toxic effect was only found for the highest dose (12 microg). This difference is probably related to the high binding of bepridil to proteins of the DMEMc medium, therefore minimising the concentration of the free compound. The kinetics of bepridil result from two phenomena: first, an immediate passage of a slight part of bepridil through the cell barrier and second, a high retention of most of the bepridil dose in the cell level. The transfer of bepridil from the apical to the basolateral compartment appears quantitatively and kinetically different using DMEMc or HBSS medium. The retention of the compound in the 'filter with Caco-2 cells' compartment is higher in DMEMc medium (60% at 3 microg) than in HBSS medium (46% at 3 microg), and bepridil entering the basolateral compartment is delayed in the DMEMc medium. This study exhibits the importance of the selected medium on results and interpretation of data and the predominance of DMEMc to study the transport of lipophilic compounds highly retained in cells.

Comparison of the efficacy and bioequivalence of two oral formulations of tiludronate in the treatment of Paget's disease of bone

Tiludronate, an oral bisphosphonate used to treat Paget's disease of bone, is currently being studied as a treatment for osteoporosis. A multicenter, open-label, parallel-group study was performed to compare the efficacy of two tablet formulations of tiludronate in the treatment of Paget's disease. Eighty-eight patients with active Paget's disease were recruited. The diagnosis was based on radiologic evidence of bone lesions, and all patients included in the study had serum alkaline phosphatase (SAP) levels equal to or more than twice the upper normal value of the local laboratory that assayed the sample. Each patient received treatment with oral tiludronate 400 mg/d for 84 +/- 2 days; 39 patients received the previously tested tablet formulation 3C1, and 49 patients received formulation 9O1, which is prepared using an improved manufacturing technique. The objective of this study was to determine whether the two formulations have an equivalent therapeutic effect, the primary end point being SAP levels in both groups after 3 months of treatment. This equivalence is commonly assessed by comparing pharmacokinetic data; however, in previous studies of tiludronate, large intra-individual variability prevented statistically valid comparisons of the data. Therefore, in addition to pharmacokinetic data, biochemical and clinical response data were collected during the trial. The secondary objectives of the trial were to measure the plasma levels and to assess the efficacy and safety of the two tiludronate formulations. The relative pharmacologic activities of the two formulations were assessed by comparison of the confidence intervals of levels of SAP at monthly intervals. After 3 months of treatment, the 90% confidence interval of the difference between the formulations was included in the reference confidence interval. These findings suggest that the 9O1 and 3C1 formulations did not show a significant difference in therapeutic activity. Furthermore, after 3 months of treatment, the frequency of normalization of SAP levels was 30.6% in the 9O1 treatment group and 28.2% in the 3C1 treatment group. The percentage of patients responding to treatment (defined as a decrease in SAP levels of at least 50% from baseline) was 67.3% in the 9O1 treatment group and 69.2% in the 3C1 treatment group. Statistical analyses performed on the maximum and minimum plasma concentrations of tiludronate showed no significant differences between the two formulations. In this trial, the two tablet formulations of tiludronate demonstrated therapeutic and pharmacokinetic equivalence.

Bisphosphonates: a review of their pharmacokinetic properties

Bisphosphonates are a unique class of drugs. As a family, they are characterized pharmacologically by their ability to inhibit bone resorption, whereas, pharmacokinetically, they are classified by their similarity in absorption, distribution, and elimination. Although all bisphosphonates have similar physicochemical properties, their antiresorbing activities differ substantially. Activity is dramatically increased when the amino group is contained in the aliphatic carbon chain. For example, alendronate, an aminobisphosphonate, is approximately 700-fold more potent than etidronate, both in vitro and in vivo. In general, bisphosphonates are poorly absorbed from the gastrointestinal tract as a result of their poor lipophilicity. In vitro and in vivo studies have shown that bisphosphonates are absorbed from the gastrointestinal tract via paracellular transport. Systemically available bisphosphonates disappear very rapidly from plasma, and are partly taken up by the bone and partly excreted by the kidney. The relative contribution of these two processes to overall plasma elimination differs significantly among bisphosphonates. To date, all bisphosphonates studied show no evidence of metabolism. Renal excretion is the only route of elimination. Studies with alendronate in rats indicate that the drug is actively secreted by an uncharacterized renal transport system, and not by the anionic or cationic renal transport systems. Bisphosphonates bind preferentially to bones which have high turnover rates, and their distribution in bone is not homogeneous. After bone uptake, the bisphosphonates are liberated again only when the bone in which they are deposited is resorbed. Thus, the half-life of bisphosphonates in bone is very long, ranging among different species from 1 to 10 years, depending largely on the rate of bone turnover.