Novel Formulation Strategy to Improve the Feasibility of Amifostine Administration.

PURPOSE: Amifostine (AMF), a radioprotectant, is FDA-approved for intravenous administration in cancer patients receiving radiation therapy (XRT). Unfortunately, it remains clinically underutilized due to adverse side effects. The purpose of this study is to define the pharmacokinetic profile of an oral AMF formulation potentially capable of reducing side effects and increasing clinical feasibility. METHODS: Calvarial osteoblasts were radiated under three conditions: no drug, AMF, and WR-1065 (active metabolite). Osteogenic potential of cells was measured using alkaline phosphatase staining. Next, rats were given AMF intravenously or directly into the jejunum, and pharmacokinetic profiles were evaluated. Finally, rats were given AMF orally or subcutaneously, and blood samples were analyzed for pharmacokinetics. RESULTS: WR-1065 preserved osteogenic potential of calvarial osteoblasts after XRT to a greater degree than AMF. Direct jejunal AMF administration incurred a systemic bioavailability of 61.5%. Subcutaneously administrated AMF yielded higher systemic levels, a more rapid peak exposure (0.438 vs. 0.875 h), and greater total systemic exposure of WR-1065 (116,756 vs. 16,874 ng*hr/ml) compared to orally administered AMF. CONCLUSIONS: Orally administered AMF achieves a similar systemic bioavailability and decreased peak plasma level of WR-1065 compared to intravenously administered AMF, suggesting oral AMF formulations maintain radioprotective efficacy without causing onerous side effects, and are clinically feasible.

Two New Faces of Amifostine: Protector from DNA Damage in Normal Cells and Inhibitor of DNA Repair in Cancer Cells.

Amifostine protects normal cells from DNA damage induction by ionizing radiation or chemotherapeutics, whereas cancer cells typically remain uninfluenced. While confirming this phenomenon, we have revealed by comet assay and currently the most sensitive method of DNA double strand break (DSB) quantification (based on γH2AX/53BP1 high-resolution immunofluorescence microscopy) that amifostine treatment supports DSB repair in γ-irradiated normal NHDF fibroblasts but alters it in MCF7 carcinoma cells. These effects follow from the significantly lower activity of alkaline phosphatase measured in MCF7 cells and their supernatants as compared with NHDF fibroblasts. Liquid chromatography-mass spectrometry confirmed that the amifostine conversion to WR-1065 was significantly more intensive in normal NHDF cells than in tumor MCF cells. In conclusion, due to common differences between normal and cancer cells in their abilities to convert amifostine to its active metabolite WR-1065, amifostine may not only protect in multiple ways normal cells from radiation-induced DNA damage but also make cancer cells suffer from DSB repair alteration.

CCM-AMI, a Polyethylene Glycol Micelle with Amifostine, as an Acute Radiation Syndrome Protectant in C57BL/6 Mice.

Acute radiation syndrome results from radiation exposure, such as in accidental nuclear disasters. Safe and effective radioprotectants, mitigators, and treatment drugs must be developed as medical countermeasures against radiation exposure. Here, the authors evaluated CCM-Ami, a novel polyethylene glycol micelle encapsulated with amifostine, for its radioprotective properties after total-body irradiation from a 60Co source. Male C57BL/6 mice (6-8 wk old) were intravenously injected with 45 mg kg(-1) of CCM-Ami 90 min before exposure to 7.2 and 8.5 Gy irradiation at a dose rate of 0.04 Gy min(-1). Both survival benefit and hematopoietic protection were observed after prophylactic CCM-Ami administration when compared with the effects measured in excipient control and amifostine groups. Pharmacokinetic results showed that after the intravenous injection, the plasma concentration of WR-1065, the active form of amifostine, was higher in CCM-Ami-treated mice than in amifostine-treated mice. These findings suggest that CCM-Ami-mediated hematopoietic protection plays a key role in enhancing survival of mice exposed to radiation toxicity and thus indicate that CCM-Ami is a radioprotectant that can be used safely and effectively in nuclear disasters.

Ranking the Binding Energies of p53 Mutant Activators and Their ADMET Properties.

The guardian of the genome, p53, is the most mutated protein found in all cancer cells. Restoration of wild-type activity to mutant p53 offers promise to eradicate cancer cells using novel pharmacological agents. Several molecules have already been found to activate mutant p53. While the exact mechanism of action of these compounds has not been fully understood, a transiently open pocket has been identified in some mutants. In our study, we docked twelve known activators to p53 into the open pocket to further understand their mechanism of action and rank the best binders. In addition, we predicted the absorption, distribution, metabolism, excretion and toxicity properties of these compounds to assess their pharmaceutical usefulness. Our studies showed that alkylating ligands do not all bind at the same position, probably due to their varying sizes. In addition, we found that non-alkylating ligands are capable of binding at the same pocket and directly interacting with Cys124. The comparison of the different ligands demonstrates that stictic acid has a great potential as a p53 activator in terms of less adverse effects although it has poorer pharmacokinetic properties.

Design and evaluation of biodegradable enteric microcapsules of amifostine for oral delivery.

Amifostine is the first FDA approved cytoprotective and chemoprotective agent in the treatment of cancer. However, it is not used widely because of its ineffectiveness when administered orally. The objective of this study was to prepare and evaluate the radioprotective efficacy of orally active amifostine enteric microcapsules (amifostine mc). The microcapsules were prepared by spray drying technique using Eudragit L100-55, and the yield was more than 80%. The particle size and surface morphology were determined by particle analyzer and scanning electron microscopy. Thermal characterization and infrared spectroscopy were evaluated as well. In vitro release assay found that more than 60% amifostine was released during the first 4h and the cumulative release ratio was up to approximately 90% in 24h at 37°C. The radioprotective efficacy was determined by 30-day survival study in mice acutely exposed to 6 Gy γ-ray irradiation. The results showed that all dose groups of amifostine microcapsules could significantly improve survival animal numbers and time. Furthermore, tissue distribution studies indicated the concentrations of the active metabolite WR-1065 in mice tissues of microcapsule group were higher than that of oral amifostine group at 180 min (p<0.01). These results demonstrated that oral administration of amifostine microcapsules provided effective radioprotection compared to the bulk drug.

Feasibility study of the pharmacology of local application of amifostine (WR-2721) to the buccal mucosa in guinea pigs.

BACKGROUND/AIMS: We have undertaken this study to investigate the feasibility of topical application of the radioprotective compound WR-2721 to the buccal mucosa. METHODS: Saliva samples were collected from 5 volunteers and were reconstituted in 3 amifostine solutions. Measurements of amifostine and WR-1065 contents were performed at 6 different time points. Young-adult guinea pigs were topically administered amifostine 50 and 100 mg to each buccal mucosa. At 0, 15 and 30 min after application, the blood samples obtained from the heart and the buccal tissues were prepared for the analysis of amifostine and WR-1065. RESULTS: There was no significant difference between the 3 concentrations of amifostine in saliva in vitro at any of the 6 study time points (p > 0.05). No WR-1065 was detected in saliva. In the guinea pigs from groups A and B, there were significant differences in concentrations of amifostine and WR-1065 in the tissues between the 0-min and 15-min subgroups and between the 0-min and 30-min subgroups (p < 0.05). The concentrations of amifostine and WR-1065 from the 15-min and 30-min subgroups did not differ statistically (p > 0.05). CONCLUSIONS: It is feasible to administer topical amifostine (WR-2721) to mucosa to prevent radiation-induced oral mucositis, and systemic absorption is negligible. Relatively high concentrations of amifostine in human saliva in vitro were maintained, although some inconsistent changes are observed.

Ion-pair strategy for enabling amifostine oral absorption: rat in situ and in vivo experiments.

This study shows the effect of ion pair formation on intestinal absorption and oral bioavailability of amifostine. Amifostine is a prodrug used as a highly potent and selective radiotherapy and chemotherapy protectant but due to its low lipophilicity and charge at physiological pH range, its trans epithelial transport and its potential for oral drug delivery is very low. Ion pair formation with negatively charged counter ions was evaluated by in situ rat perfusion studies as a possible strategy to enhance intestinal absorption of amifostine. Succinic acid, phthalic acid and benzoic acid were used as counter ions. Rat intestinal perfusion studies confirmed a statistically significant increase in amifostine permeability in the presence of the counter ions in the order of succinic>phthalic>benzoic. Rat pharmacokinetic studies in vivo were performed to calculate oral absolute bioavailability of amifostine alone and with ion pairs in order to confirm the in situ perfusion results and the applicability of the ion pair approach. Intravenous and intraduodenal administrations were done in rats using a permanent jugular vein cannulation technique and a duodenal cannulation method to avoid drug degradation in stomach. In vivo oral bioavailability studies demonstrated a 20-30-fold increase in amifostine bioavailability with succinic acid depending on counter ion ratio and 10-fold increase with phthalic acid as ion pair. In summary ion pair strategy with succinic acid could enable amifostine oral administration on enteric coated formulations.

A phase I clinical and pharmacology study using amifostine as a radioprotector in dose-escalated whole liver radiation therapy.

PURPOSE: Diffuse intrahepatic tumors are difficult to control. Whole-liver radiotherapy has been limited by toxicity, most notably radiation-induced liver disease. Amifostine is a prodrug free-radical scavenger that selectively protects normal tissues and, in a preclinical model of intrahepatic cancer, systemic amifostine reduced normal liver radiation damage without compromising tumor effect. We hypothesized that amifostine would permit escalation of whole-liver radiation dose to potentially control microscopic disease. We also aimed to characterize the pharmacokinetics of amifostine and its active metabolite WR-1065 to optimize timing of radiotherapy. METHODS AND MATERIALS: We conducted a radiation dose-escalation trial for patients with diffuse, intrahepatic cancer treated with whole-liver radiation and intravenous amifostine. Radiation dose was assigned using the time-to-event continual reassessment method. A companion pharmacokinetic study was performed. RESULTS: Twenty-three patients were treated, with a maximum dose of 40 Gy. Using a logistical regression model, compared with our previously treated patients, amifostine increased liver tolerance by 3.3 ± 1.1 Gy (p = 0.007) (approximately 10%) with similar response rates. Peak concentrations of WR-1065 were 25 µM with an elimination half-life of 1.5 h; these levels are consistent with radioprotective effects of amifostine in patients. CONCLUSION: These findings demonstrate for the first time that amifostine is a normal liver radioprotector. They further suggest that it may be useful to combine amifostine with fractionated or stereotactic body radiation therapy for patients with focal intrahepatic cancer.

Radioprotective effect of Ocimum sanctum and amifostine on the salivary gland of rats after therapeutic radioiodine exposure.

The current study investigated the radioprotective effect of Ocimum sanctum on the salivary gland of rats administered radioiodine ((131)I) and compared its efficacy with a known radioprotectant, amifostine. The experimental rats were divided in four groups and sacrificed in three different batches at 1, 3, and 6 months of time interval after 18.5 MBq/100g (i.p.) (131)I exposure. Six months duration batch received (131)I exposure twice with the gap of 3 months. Two groups of experimental rats were presupplemented with O. sanctum (40 mg/kg for 5 days, orally) and amifostine (200 mg/kg, s.c) before (131)I exposure separately. Increased Technetium-99m-pertechnetate ((99m)TcO(4)(-)) uptake at 30 minutes post injection in salivary glands of only (131)I exposed rats may imply delay in clearance at 6 months of exposure in comparison to their counterparts sacrificed at 1 month. Parotid gland histology showed atrophy with lipomatosis in only (131)I exposed rats at 3 and 6 months of duration. O. sanctum and amifostine presupplemented and subsequently exposed to (131)I rats at 3 and 6 months duration exhibited comparable histopathology with controls. Our study indicates possible radioprotective effect of O. sanctum and amifostine against high-dose (131)I exposure.

Clinical pharmacokinetics of amifostine and WR1065 in pediatric patients with medulloblastoma.

PURPOSE: We evaluated the pharmacokinetics of amifostine and WR1065 in pediatric patients with newly diagnosed medulloblastoma to assess the influence of patient covariates, including demographics, clinical characteristics, and genetic polymorphisms, on amifostine and WR1065 pharmacokinetic parameters. EXPERIMENTAL DESIGN: We assessed the pharmacokinetics of amifostine and WR1065 in 33 children who received amifostine (1-minute infusion, 600 mg/m(2)) just before the start of and 3 hours into a 6-hour cisplatin infusion. Serial blood samples were collected after doses 1 (0 hour) and 2 (3 hours) of course 1. Amifostine and WR1065 were quantitated by high performance liquid chromatography with electrochemical detection. A pharmacokinetic model was simultaneously fit to amifostine and WR1065 plasma or whole blood concentration-versus-time data. The influence of demographic, biochemical, and pharmacogenetic covariates on amifostine and WR1065 disposition was evaluated. RESULTS: Body surface area was the primary size-based covariate for amifostine pharmacokinetics explaining 53% and 56% of interindividual variability in plasma and whole-blood amifostine clearance, respectively. The population-predicted values for amifostine clearance, volume, and apparent WR1065 clearance from the plasma data were 107 L/h/m(2), 5.53 L/m(2), and 30.6 L/h/m(2). The population-predicted values for amifostine clearance, volume, and apparent WR1065 clearance from whole blood data were 136 L/h/m(2), 7.23 L/m(2), and 12.5 L/h/m(2). CONCLUSIONS: These results support using body surface area for calculating doses of amifostine in children. Similar to data in adults, amifostine and WR1065 are rapidly cleared from plasma and whole blood in children.

Pharmacologic normal tissue protection in clinical radiation oncology: focus on amifostine.

BACKGROUND: Radiation toxicity is an important problem that limits treatment intensity and adversely affects patients' quality of life. Amifostine is a cytoprotector that can reduce toxicity and potentially improve the therapeutic ratio of radiotherapy. OBJECTIVE: To discuss the role of amifostine in modern radiotherapy and compare and contrast with alternative approaches to reducing radiation toxicity. METHODS: We conducted a literature search through Medline to identify randomized clinical trials pertaining to keyword 'amifostine'. We also consulted reviews, book chapters and selected articles regarding amifostine and normal tissue protection. RESULTS/CONCLUSION: Amifostine is an effective normal tissue protector with level I evidence supporting its use in head and neck and gynecologic cancers but studies in other disease sites, although promising, are inconclusive. Further study is needed to demonstrate conclusively the benefits of wider amifostine use.

Alternate delivery route for amifostine as a radio-/chemo-protecting agent.

Amifostine (ethiofos, WR-2721) is an organic thiophosphate prodrug that serves as an antineoplastic adjunct and cytoprotective agent useful in cancer chemotherapy and radiotherapy. The selective protection of certain tissues of the body is believed to be due to higher alkaline phosphatase activity, higher pH and vascular permeation of normal tissues. Amifostine is conventionally administered intravenously before chemotherapy or radiotherapy. It is approved by the Food and Drug Administration (FDA) to reduce cumulative renal toxicity associated with repeated administration of cisplatin in patients with advanced ovarian cancer. It was originally indicated to reduce the cumulative renal toxicity from cisplatin in non-small cell lung cancer although this indication was withdrawn in 2005. Amifostine is also FDA approved for patients with head and neck cancer to reduce the incidence of moderate to severe xerostomia in patients who are undergoing postoperative radiation treatment where the radiation port includes a substantial portion of the parotid glands. The potential of amifostine as a cytoprotective agent is unlikely to be fully realized if the method of administration is restricted to intravenous administration. Attempts have been made to develop non-invasive methods of delivery such as transdermal patches, pulmonary inhalers, and oral sustained-release microspheres. It is the goal of this article to explore non-intravenous routes of administration associated with better efficacy of the drug. This review will primarily focus on the variety of more recently studied (2002 and later) alternative modes for amifostine administration, including subcutaneous, intrarectal and oral routes.

Amifostine: the first selective-target and broad-spectrum radioprotector.

After several decades of preclinical and clinical research, the first approved radioprotective drug, amifostine, is being used in clinical practice. Amifostine has been shown to specifically protect normal tissues from damage caused by radiation and chemotherapy. An inactive prodrug, amifostine is converted to an active thiol by dephosphorylation by alkaline phosphatase in the normal endothelium. The hypovascularity and acidity of the tumor environment and the differential expression of alkaline phosphatase in normal and neoplastic tissues contribute to its cytoprotective selectivity. The cytoprotective mechanism of amifostine is complicated, involving free-radical scavenging, DNA protection and repair acceleration, and induction of cellular hypoxia. The U.S. Food and Drug Administration has approved the i.v. use of amifostine to reduce the cumulative renal toxicity associated with repeated administration of cisplatin in patients with advanced ovarian cancer and to reduce the incidence of moderate to severe xerostomia in patients undergoing postoperative radiation treatment for head and neck cancer, where the radiation port includes a substantial portion of the parotid glands. Nonetheless, amifostine has potential applications in many other oncologic settings. Novel schedules and routes of administration are under investigation and may further simplify the use of amifostine, reduce any undesired effects, and considerably broaden its applications. This review summarizes the clinical experience with amifostine and provides insight into future clinical directions.

Amifostina previene la toxicidad secundaria a la quimioterapia con shop, en pacientes ancianos con linfoma agresivo / Amifostine prevents toxicity secondary to chemotherapy shop in elderly patients with aggressive lymphoma

Objetivo: Determinar si amifostina puede efectivamente disminuir los efectos colaterales de la quimioterapia intensa en pacientes ancianos con linfoma maligno. nosotros realizamos un estudio rendomizado fase II B, comparando amifostina mas CHOP a dosis estándares versus CHOP. Pacientes y Métodos: Se incluyeron 34 pacientes (pts) mayores de 69 años, no tratados previamente, con linfoma maligno agresivo. Recibieron seis ciclos de A-Chop con amifostina 910 mg/m en día 1 más ciclofosfamida 750 mg/m, doxorubicina 50 mg/m vincristina 1.4 mg/m en dia 1 y prednisona 100 mg/día por 5 días, cada 3 semanas, versus 6 ciclos de CHOP solo. Resultados: 34 pts (18 A-CHOP versus 16 CHOP) fueron evaluables. Factores demográficos y pronósticos fueron similares entre ambos grupos. La tasa de respuesta fue 73,3 por ciento (RC 60 por ciento) para A-CHOP y 78.5 por ciento (RC 64 por ciento) para CHOP. En relación a tratamiento, fueron adminitrados 73/90 (81 por ciento) ciclos de A-CHOP y 69/84 (82 por ciento) de CHOP, la mediana de tratamiento fue 17,4 semanas con A-CHOP y 20.3 semanas con CHOP (p=0.05). Transfusión de glóbulos rojos fue necesario en 1/92 (1 por ciento) y 4/82 (5 por ciento) ciclos de A-CHOP y CHOP. Los ciclos de quimioterapia que requieron hospitalización fueron 4/92 (4 por ciento) y 11/82 (13 por ciento) con A-CHOP y CHOP (p=0.05). Episodios de neutropenia febril hubieron 3/92 con A-CHOP (3 por ciento) y 8/82 con (10 por ciento). Los días de hospitalización debido a toxicidad por quimioterapia fuern 21 para A-CHOP y 76 para CHOP. Conclusiones: Estos resultados muestran mejor tolerancia del régimen CHOP con amisfostina en pacientes mayores con linfoma.

Objective: To determine whether amifostine can effectively disminish the intensity of chemotherapy-related side effects, we conducted a randomized phase II-trial, comparing amifostine plus -dose CHOP (A-CHOP) versus CHOP, in elderly patients with agressive NHL. Patients and Methods: We included 34 previously untreated elderly (70 years)pts. The received 6 cycles of A-CHOP with amisfostine 910 mg / m on day 1 plus cyclophosphamide 750 mg / m², doxorubicin 50 mg / m vincristine 1.4 mg / m on day 1 and prednisone 100 mg / day for 5 days every 3 weeks, versus 6 cycles of CHOP alone. Results: 34 pts (18 A-CHOP CHOP versus 16) were evaluated. Demographic factors and prognosis were similar between both groups. The response rate was 73.3 per cent (60 per cent RC) for A-CHOP and 78.5 per cent (64 per cent RC) for CHOP. In relation to treatment were administrator 73/90 (81 per cent) cycles of A-CHOP and 69/84 (82 percent) of CHOP, the median was 17.4 weeks treatment with A-CHOP and 20.3 weeks with CHOP (p = 0.05). Red cell transfusion was necessary in 1 / 92 (1 per cent) and 4 / 82 (5 per cent) cycles of A-CHOP and CHOP. The cycles of chemotherapy were hospitalized 4 / 92 (4 per cent) and 11/82 (13 per cent) with A-CHOP and CHOP (p = 0.05). Had episodes of febrile neutropenia 3 / 92 with A-CHOP (3 per cent) and 8 / 82, (10 per cent). The days of hospitalization due to toxicity from chemotherapy fuern 21 for A-CHOP and 76 for CHOP. Conclusions: These results show better tolerance amisfostina CHOP regimen in elderly patients with lymphoma.

Phase I trial and pharmacokinetics of escalating doses of paclitaxel and concurrent hyperfractionated radiotherapy with or without amifostine in patients with advanced head and neck carcinoma.

BACKGROUND: Amifostine was developed to protect normal tissues from radiation exposure. The current study was undertaken to determine whether amifostine would allow the delivery of greater numbers of weekly paclitaxel treatments with concomitant, hyperfractionated radiotherapy in patients with advanced head and neck carcinoma. METHODS: Patients received radiation therapy twice daily using 1.6-gray (Gy) fractions up to a total of 70.4 Gy over an elapsed time of 6.5 weeks. All patients received paclitaxel 60 mg/m(2) once weekly starting on Day 1. The number of doses of paclitaxel was escalated from three to a maximum of six in groups of three patients. For the patients who received amifostine, a dose of 400 mg/m(2) was given intravenously over 15 minutes on Days 1-5, 8, 29-33, and 36. Patients underwent surgery for persistent tumor after radiotherapy. The plasma pharmacokinetics of paclitaxel were characterized during treatment with the first weekly dose to determine the effect of concurrently administered amifostine. RESULTS: Thirty-six patients were evaluable for this study. In the absence of amifostine, a maximum of four doses of paclitaxel were tolerated in combination with the radiotherapy. With amifostine, up to five doses of paclitaxel could be given. Generally, the treatment resulted in Grade 2 and 3 stomatitis. Overall, 69% of patients had a complete remission, and 29% had a partial remission. Both progression-free survival and overall survival were 66% at 30 months. Amifostine had no effect on the pharmacokinetics of paclitaxel. CONCLUSIONS: The administration of amifostine allowed the authors to give an additional dose of paclitaxel to patients who were undergoing hyperfractionated radiotherapy for head and neck carcinoma. This treatment regimen resulted in a high frequency of complete remissions and an excellent progression-free survival pattern without compromising the plasma kinetics of paclitaxel.

Amifostine (ETHYOL) protects rats from mucositis resulting from fractionated or hyperfractionated radiation exposure.

PURPOSE: The cytoprotective drug amifostine (Ethyol) protects rats from oral mucositis resulting from a single dose of gamma-irradiation. We expanded earlier studies to determine whether multiple doses of amifostine protect against fractionated or hyperfractionated radiation and whether the active metabolite of amifostine (WR-1065) accumulates in tissues upon repeated administration. METHODS AND MATERIALS: Rats received amifostine daily for 5 days in conjunction with a 1-week fractionated radiation schedule and were evaluated for oral mucositis. Rats also received amifostine before the am or pm exposure or b.i.d. in conjunction with hyperfractionated radiation. To determine the pharmacokinetics of WR-1065 after repeated dosing, amifostine was given 5 days a week for 1 or 3 weeks, and rat tissue and plasma were collected at intervals during and after treatment and analyzed for WR-1065. RESULTS: Amifostine protected rats from mucositis resulting from fractionated or hyperfractionated radiation. When the number of days of amifostine administration was reduced, protection was diminished. A dose of 100 mg/kg given in the morning or 2 doses at 50 mg/kg provided the best protection against hyperfractionated radiation. WR-1065 did not accumulate in tissues or tumor upon repeated administration. CONCLUSIONS: Amifostine prevented radiation-induced mucositis in a rat model; protection was dose and schedule dependent.

Oral delivery of spray dried PLGA/amifostine nanoparticles.

Amifostine (Ethyol, WR-2721) is a cytoprotective drug approved by the US Food & Drug Administration for intravenous administration in cancer patients receiving radiation therapy and certain forms of chemotherapy. The primary objective of this project was to develop orally active amifostine nanoparticles using spray drying technique. Two different nanoparticle formulations (Amifostine-PLGA (0.4:1.0 and 1.0:1.0)) were prepared using a Buchi B191 Mini Spray Dryer. A water-in-oil emulsion of amifostine and PLGA (RG 502) was spray dried using an airflow of 600 L h(-1) and input temperature of 55 degrees C. A tissue distribution study in mice was conducted following oral administration of the formulation containing drug-polymer (0.4:1.0). The efficiency of encapsulation was 90% and 100%, respectively, for the two formulations while the median particle sizes were 257 and 240 nm, with 90% confidence between 182 and 417 nm. Since amifostine is metabolized to its active form, WR-1065, by intracellular alkaline phosphatase, the tissue levels of WR-1065 were measured, instead of WR-2721. WR-1065 was detected in significant amounts in all tissues, including bone marrow, jejunum and the kidneys, and there was some degree of selectivity in its distribution in various tissues. This work demonstrates the feasibility of developing an orally effective formulation of amifostine that can be used clinically.

Preparation and in vitro characterization of amifostine biodegradable microcapsules.

The purpose of this project was to develop sustained release microcapsules of amifostine. The microcapsules were prepared using solvent evaporation technique. The effect of several formulation variables on the characteristics of the microcapsules was studied. The formulation variables studied were drug loading, polymer (polylactide-co-glycolide) (PLGA) concentration, and the amount of gelatin in the initial aqueous phase. The drug loading was studied at three different levels (5, 10, and 25 mg); the PLGA concentration was studied at two levels (500 and 1000 mg); and the amount of gelatin used ranged from 2 to 14 mg. In general, the microcapsules were less than 155 microm in diameter with median size between 50 and 80 microm. While the use of higher amounts of PLGA significantly increased the median size of the microcapsules, using higher amounts of amifostine had no significant effect, irrespective of the amount of PLGA. The use of gelatin, within the range 2-14 mg, did not show any significant effect on the particle size distribution. Scanning electron microscopy (SEM) of the microcapsules revealed that all nine formulations yielded spherical particles. The use of 500 mg PLGA with 10 or 25 mg amifostine yielded microcapsules with porous surfaces. The surface pores, however, were not present in microcapsules prepared using 1000 mg PLGA. The efficiency of encapsulation decreased significantly from 63 to 24% when the amount of amifostine increased from 5 to 25 mg in the formulations using 500 mg PLGA. Similarly, the efficiency of encapsulation decreased from 87 to 23% when the amount of PLGA was doubled to 1000 mg. An increase in the amount of amifostine in the formulation using 500 mg PLGA also resulted in a significant increase in initial drug release (from 20 to 62%) within the first hour. These results were consistent with the porous morphology of these microcapsules. In general, all batches of microcapsules showed 24-96 h sustained drug release.

Radioterapia y citoprotección. Mecanismo de acción. Bases

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Oral administration is as effective as intraperitoneal administration of amifostine in decreasing nitroxide EPR signal decay in vivo.

A rapid method to determine the systemic incorporation of amifostine has been sought in order to determine the effectiveness of different administration routes without the delay inherent in awaiting therapeutic results. Consistent changes in animal measurements of nitroxide signal decay were monitored using in vivo EPR at frequencies low enough to ensure uniform sensitivity to organs deep in 20-g C3H mice. Conditions included both co-administration of the amifostine with the carbamoyl-proxyl spin probe (CP) via i.p. injection (n=6) and oral administration (n=8) of the amifostine. These decreased the first order rate of decay of the CP EPR signal after a dose of 13.5 Gy radiation, by 23% and 18%, respectively. These changes were significantly different from the rate of decay of the CP EPR signal without amifostine, but were statistically indistinguishable from each other. These data demonstrate: (1) condition-dependent exponential decay of CP EPR signal allowing its use to determine systemic availability of a drug, and (2) that oral administration and i.p. injection of amifostine are both effective in affecting the CP EPR signal decay rate in a mouse model. This is a strong indicator of similar bioavailability in mice from both routes of administration.