Cost-effectiveness of ranibizumab compared with pegaptanib in neovascular age-related macular degeneration.

OBJECTIVE: To assess the cost-effectiveness of ranibizumab compared with pegaptanib in the treatment of patients with minimally classic/occult neovascular age-related macular degeneration (AMD), from a societal perspective in Spain. METHODS: We constructed a Markov model with five states defined by visual acuity (VA) in the better-seeing eye (Snellen scale): VA >20/40, < or =20/40 to >20/80, < or =20/80 to >20/200, < or =20/200 to >20/400, < or =20/400, and an additional death state. Two cohorts of patients were distributed along the VA states, and treated with either ranibizumab or pegaptanib. Transition probabilities assigned for movement between these states with both drugs were obtained from published randomized clinical trials. Medical costs related to AMD treatment and follow-up, medical costs related to AMD comorbidities, and non-medical-related costs were taken into account. Costs (2008 Euro), health outcomes (Quality-adjusted life years--QALYs), both discounted at a 3.5% annual rate, and incremental cost-effectiveness ratios (ICER: euro/QALY), were determined for a lifetime horizon in the base case analysis. Sensitivity analyses were conducted to explore different scenarios and assumptions in the model. RESULTS: Treating patients with varying degrees of visual impairment with monthly ranibizumab instead of pegaptanib was 71,206 euro more costly and provided 2.437 additional QALYs (29,224 euro/QALY). When administered on an as-needed basis, as in the Prospective Optical Coherence Tomography Imaging of Patients with Neovascular AMD Treated with Intraocular Ranibizumab (PrONTO) trial, the cost per QALY gained with ranibizumab was reduced to 4,623 euro. CONCLUSIONS: The cost per QALY gained with monthly ranibizumab compared with pegaptanib in the minimally classic/occult neovascular AMD population is just below the 30,000 euro threshold below which new drugs are sometimes regarded as cost-effective strategies in Spain. In this model, the key variables with greater impact on the cost-effectiveness results were the selected time horizon and the chosen extrapolation method, the source for data on pegaptanib efficacy and the number of ranibizumab injections. When administered on an as-needed basis, ranibizumab was a cost-effective strategy compared to pegaptanib in this population.

Cost-effectiveness of ranibizumab compared with photodynamic treatment of neovascular age-related macular degeneration.

OBJECTIVE: This study compared the cost-effectiveness of ranibizumab with that of photodynamic therapy (PDT) in the treatment of predominantly classic choroidal neovascularization secondary to age-related macular degeneration (AMD) from the perspective of a third-party payer in a Spanish setting. METHODS: We constructed a Markov model with 5 states defined by visual acuity (VA) in the better-seeing eye (Snellen scale), as follows: VA >20/40, 20/80, 20/200, 20/400, and

LC method for therapeutic drug monitoring of levetiracetam: evaluation of the assay performance and validation of its application in the routine area.

OBJECTIVES: An accurate and precise high-performance liquid chromatographic method using diode array detection for the determination of levetiracetam in human plasma has been developed and validated for use in pharmacokinetic studies. METHODS: A harmonized validation strategy based on the accuracy profiles was used to select the most appropriate regression model and to determine the limits of quantitation as well as the concentration range of the developed analytical procedure. On the other hand, the present paper also shows this validation approach as a suitable tool to guaranty the quality of the results obtained by the use of the analytical validated methodology for plasma levetiracetam determination in a routine setting and to ensure the risk of obtaining the future measurements outside the previously fixed acceptance limits. RESULTS: As pointed recently, the FDA, a weighted 1/x(2) quadratic regression model ranging from 0.53 to 107.00 mg/L was selected as the simplest calibration model that maximized the accuracy all over the range. Relative bias was <5%, assay imprecision was always <6% and mean extraction recovery from plasma was >90%. So, accuracy did not exceed the acceptance limits settled at + or - 20% according to the FDA or Washington conference regulatory requirements for bioanalytical methods. Internal quality control has been assessed over a 2 year time period. All controls were essentially found to provide levetiracetam concentrations within the target range according to the FDA. CONCLUSIONS: The validated analytical procedure complies with strongest regulatory standards. The validated method has a sufficiently rapid turnaround time and their results are good enough to enable the laboratory to routinely provide useful and accurate pharmacokinetic data in time to adjust patient regimens.

Ranibizumab for neovascular age-related macular degeneration.

PURPOSE: The pharmacology, pharmacokinetics, clinical efficacy, safety, pharmacoeconomics, and place in therapy of ranibizumab are reviewed. SUMMARY: Ranibizumab is the humanized fragment of the murine monoclonal antibody that binds all the active forms of the vascular endothelial growth factor, leading to the inhibition of the neovascular process underlying age-related macular degeneration (AMD). In animal studies, intravitreal administration of ranibizumab resulted in penetration of the drug into all layers of the retina and subsequent slow absorption into the systemic circulation. Improvement in visual acuity by 15 or more letters has been observed in 33.8-40.3% of patients treated with ranibizumab in pivotal clinical trials, compared with 5% of patients treated with sham injections and photodynamic therapy (PDT). The addition of PDT to ranibizumab has not been shown to offer any benefit in terms of efficacy and has been found to worsen ocular adverse reactions. The most common adverse ocular reactions reported in patients receiving ranibizumab during clinical trials include conjunctival hemorrhage, eye pain, vitreous floaters, increased intraocular pressure, and intraocular inflammation. Ranibizumab's efficacy in the treatment of neovascular AMD is well established; however, questions remain regarding the drug's optimal dosing strategy, duration of therapy, and combined therapy with other agents. While ranibizumab has been defined as the best available weapon against AMD, it is also the most expensive. CONCLUSION: The efficacy of ranibizumab in the treatment of AMD is well established, but more studies are needed to determine ranibizumab's optimal dosage interval, duration of therapy, and combined use with other agents.

Determination of 5-fluorouracil and its prodrug tegafur in plasma and tissue by high-performance liquid chromatography in a single injection: validation for application in clinical pharmacokinetic studies.

Tegafur, a prodrug of 5-fluorouracil (5-FU), is an oral fluorouracil antitumor drug used for the management of adenocarcinomas. It has an efficacy similar to that of intravenous 5-FU, with potential advantages in terms of convenience and quality of life for the patient and cost-effectiveness as compared with intravenous chemotherapy. The authors developed a high-performance liquid chromatography (HPLC) assay for the determination of tissue or plasma tegafur and 5-FU concentration in a single step extraction and a single HPLC injection. The retention times of 5-FU and tegafur were 5 and 16.5 minutes, respectively, and the internal standard retention times were 11.5 and 17.5 minutes for 5-bromouracil (5-BU) and beta-hydroxyethyltheophylline, respectively. The limit of quantification was 0.0125 microg/mL for 5-FU and 0.05 microg/mL for tegafur. The assay had good recovery (96.5% +/- 9.45% and 97.5% +/- 7.89% for 5-FU in plasma and tissue, respectively, and 88.5% +/- 12.17% and 104.9% +/- 8.77% for tegafur in plasma and tissue, respectively). Precision was good: the within-day and between-day standard deviation of the mean (RSD) for 5-FU (0.0125-5 microg/mL) and tegafur (0.5-150 microg/mL) was always <8%. The authors conclude that the method described here is ideally suited for the therapeutic monitoring of 5-FU and tegafur.

Methotrexate pharmacokinetics and survival in osteosarcoma.

BACKGROUND: The aim of this study was to analyze the relationship between exposure to high-dose methotrexate (HDMTX) and tumor response in terms of survival in children with osteosarcoma. PROCEDURE: This study included 44 patients (479 courses) who received a median dose of 5.92 g/m2 of MTX (interquartile range (IQR) 2.37 g/m2) in a 4-hr infusion. The mean area under the concentration-time curve (AUC) estimated by parametric methods (non-parametric expectation maximization, NPEM), and the mean concentration at the end of the infusion were considered to be the exposure parameters. Tumor response was recorded as disease-free survival (DFS), overall survival (OS), and histologic tumor response. The relationship between MTX exposure and survival parameters was analyzed by Cox regression. RESULTS: The group of 11 patients who were the least exposed to MTX (AUC <2,400 micromol/L hr) presented a high DFS, probably due to the shorter interval of time between MTX courses that led to a higher dose density. In patients with AUC >2,400 micromol/L hr, an increase in the AUC was related to an increase in the DFS. Significant differences were observed in the DFS between patients whose mean AUC was below or above 4,000 micromol/L hr (P=0.024), such that 4,000 micromol/L hr was considered as the minimum AUC to be aimed at for future patients. CONCLUSIONS: Dose density seems to be an important factor in osteosarcoma response, but this must be confirmed in further studies. In order to improve the response to osteosarcoma in children, it is recommended that the dose of MTX to be increased such as to obtain an AUC higher than 4,000 micromol/L hr.

Pharmacodynamics of high-dose methotrexate in pediatric patients.

OBJECTIVE: To establish a relationship between the pharmacokinetics of high-dose methotrexate (MTX) and toxicity in children of a pediatric oncology department and to reassess MTX concentrations at which the patients would be at high risk for toxic effects. METHODS: This study included 37 patients (227 treatment courses) who received a median dose of 4.87 g/m(2) of MTX in a 4-hour infusion. The population pharmacokinetic parameters of MTX were estimated by parametric (IT2B) and nonparametric methods (NPEM). Gastrointestinal, renal, and hematologic toxicity were evaluated. The relationship between pharmacokinetic parameters and toxicity was analyzed by logistic regression and multiple linear regression. RESULTS: Equations to predict hematologic and nonhematologic toxicity were obtained. An increase of 100 micro mol/L in the MTX peak concentration meant a 12% (p = 0.03) higher risk of vomiting; a significant delay in MTX elimination implied a 5.76-fold higher risk of mucositis (p < 0.001). An increase of 1 micro mol/L in the MTX concentration 24 hours after the end of the infusion (Cp(24h)) led to a 43% increase in the risk of renal toxicity (p < 0.001). Hematologic toxicity was significantly conditioned by the baseline leukocyte count and Cp(24h) (p < 0.001). CONCLUSIONS: The analysis of high-dose MTX pharmacokinetic/pharmacodynamic relationship to toxicity has led to equations able to predict toxicity that are easily applicable to daily practice. Cp(24h) >3.5 micro mol/L was confirmed as an indicator of high risk of toxicity.