A Cost-Effectiveness Framework for Amyotrophic Lateral Sclerosis, Applied to Riluzole.

OBJECTIVES: Reexamine cost-effectiveness of riluzole in the treatment of amyotrophic lateral sclerosis (ALS) in light of recent advances in disease staging and understanding of stage-specific drug effect. METHODS: ALS was staged according to the "fine'til 9" (FT9) staging method. Stage-specific health utilities (EQ-5D, US valuation) were estimated from an institutional cohort, whereas literature informed costs and transition probabilities. Costs at 2018 prices were disaggregated into recurring costs (RCs) and "one-off" transition/"tollgate" costs (TCs). Five- and 10-year horizons starting in stage 1 disease were examined from healthcare sector and societal perspectives using Markov models to evaluate riluzole use, at a threshold of $100 000/quality-adjusted life year (QALY). Probabilistic and deterministic sensitivity analyses were conducted. RESULTS: Mean EQ-5D utilities for stages 0 to 4 were 0.79, 0.74, 0.63, 0.54, and 0.46, respectively. From the healthcare sector perspective at the 5-year horizon, riluzole use contributed to 0.182 QALY gained at the cost difference of $12 348 ($5403 riluzole cost, $8870 RC and -$1925 TC differences), translating to an incremental cost-effectiveness ratio (ICER) of $67 658/QALY. Transition probability variation contributed considerably to ICER uncertainty (-30.2% to +90.0%). ICER was sensitive to drug price and RCs, whereas higher TCs modestly reduced ICER due to delayed tollgates. CONCLUSION: This study provides a framework for health economic studies of ALS treatments using FT9 staging. Prospective stage-specific and disaggregated cost measurement is warranted for accurate future cost-effectiveness analyses. Appropriate separation of TCs from RCs substantially mitigates the high burden of background cost of care on the ICER.

Protection of brain development by antenatal magnesium sulphate for infants born preterm.

Cerebral palsy (CP) remains the most significant neurological disorder associated with preterm birth. It disrupts quality of life and places huge cost burdens on society. Antenatal magnesium sulphate administration to females before 32 weeks' gestation has proven to be an effective intervention to reduce the rate of CP. In models of hypoxia, hypoxia-ischemia, inflammation, and excitotoxicity in various animal species, magnesium sulphate preconditioning decreased the resulting lesion sizes and inflammatory cytokine levels, prevented cell death, and improved long-term cognitive and motor behaviours. In humans, meta-analyses of five randomized controlled trials using magnesium sulphate as a neuroprotectant showed prevention of CP at 2 years. The benefit remained consistent regardless of gestational age, cause of preterm birth, and total dose received. Antenatal magnesium sulphate treatment is now recommended by the World Health Organization and by many obstetric societies. Its cost-effectiveness further justifies its widespread implementation. WHAT THIS PAPER ADDS: Neuroprotective effect of magnesium sulphate to reduce cerebral palsy in infants born preterm when administered to females at risk of imminent preterm birth. Neuroprotection regardless of gestational age, cause of preterm birth, and total dose. Antenatal magnesium sulphate treatment has good cost-effectiveness.

Bioactive stilbenes from Vitis vinifera grapevine shoots extracts.

BACKGROUND: Viticultural residues from commercial viticultural activities represent a potentially important source of bioactive stilbenes such as resveratrol. The main aim of the present study was therefore to isolate, identify and perform biological assays against amyloid-ß peptide aggregation of original stilbenes from Vitis vinifera shoots. RESULTS: A new resveratrol oligomer, (Z)-cis-miyabenol C (3), was isolated from Vitis vinifera grapevine shoots together with two newly reported oligostilbenes from Vitis vinifera shoots, vitisinol C (1) and (E)-cis-miyabenol C (2), and six known compounds: piceatannol, resveratrol, (E)-ε-viniferin (trans-ε-viniferin), ω-viniferin, vitisinol C and (E)-miyabenol C. The structures of these resveratrol derivatives were established on the basis of detailed spectroscopic analysis including nuclear magnetic resonance experiments. All the newly reported compounds were tested for their anti-aggregative activity against amyloid-ß fibril formation. Vitisinol C was found to exert a significant activity against amyloid-ß aggregation. CONCLUSION: Vitis vinifera grapevine shoots are potentially interesting as a source of new bioactive stilbenes, such as vitisinol C.

Efficacy, safety, and cost-effectiveness analysis of Cerebrolysin in acute ischemic stroke: A rapid health technology assessment.

This study conducts a rapid health technology assessment to systematically evaluate the effectiveness, safety, and cost-effectiveness of Cerebrolysin as an adjunctive therapy for acute ischemic stroke to provide evidence-based medicine for clinical decisions of Cerebrolysin. All systematic reviews/meta-analyses, pharmacoeconomic studies, and health technology assessment reports of Cerebrolysin for the treatment of acute ischemic stroke before August 17, 2023, were retrieved from PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, Wanfang, Weipu, Sinomed database and the official website of health technology assessment. According to the inclusion and exclusion criteria, 2 researchers independently carried out screening, data extraction, and quality evaluation and descriptively analyzed the results of the included studies. A total of 14 pieces of literature were incorporated, comprising 8 systematic reviews/meta-analyses and 6 pharmacoeconomic studies. In terms of effectiveness, compared to control groups, the use of Cerebrolysin as a treatment for acute ischemic stroke demonstrates certain advantages, including enhancement in total efficacy rate, neurological function, upper limb motor dysfunction, and facilitation of the recovery of activities of daily living. Especially in patients with moderate to severe acute ischemic stroke, Cerebrolysin has demonstrated the ability to enhance neurological function recovery and ameliorate disabilities. Regarding safety, adverse reactions were mild or comparable to those in the control group. The primary findings of economic studies reveal that advocating for the use of Cerebrolysin offers certain cost-effectiveness advantages. Cerebrolysin contributes to improved clinical efficacy and evaluation indexes while demonstrating favorable safety and economic benefits.

Magnesium sulphate for fetal neuroprotection: a cost-effectiveness analysis.

BACKGROUND: The aim of this study was to assess the cost-effectiveness of administering magnesium sulphate to patients in whom preterm birth at < 32+0 weeks gestation is either imminent or threatened for the purpose of fetal neuroprotection. METHODS: Multiple decision tree models and probabilistic sensitivity analyses were used to compare the administration of magnesium sulphate with the alternative of no treatment. Two separate cost perspectives were utilized in this series of analyses: a health system and a societal perspective. In addition, two separate measures of effectiveness were utilized: cases of cerebral palsy (CP) averted and quality-adjusted life years (QALYs). RESULTS: From a health system and a societal perspective, respectively, a savings of $2,242 and $112,602 is obtained for each QALY gained and a savings of $30,942 and $1,554,198 is obtained for each case of CP averted when magnesium sulphate is administered to patients in whom preterm birth is imminent. From a health system perspective and a societal perspective, respectively, a cost of $2,083 is incurred and a savings of $108,277 is obtained for each QALY gained and a cost of $28,755 is incurred and a savings of $1,494,500 is obtained for each case of CP averted when magnesium sulphate is administered to patients in whom preterm birth is threatened. CONCLUSIONS: Administration of magnesium sulphate to patients in whom preterm birth is imminent is a dominant (i.e. cost-effective) strategy, no matter what cost perspective or measure of effectiveness is used. Administration of magnesium sulphate to patients in whom preterm birth is threatened is a dominant strategy from a societal perspective and is very likely to be cost-effective from a health system perspective.

Improving Alzheimer's disease phase II clinical trials.

Over the past 30 years, many drugs have been studied as possible treatments for Alzheimer's disease, but only four have demonstrated sufficient efficacy to be approved as treatments, of which three are in the same class. This lack of success has raised questions both in the pharmaceutical industry and academia about the future of Alzheimer's disease therapy. The high cost and low success rate of drug development across many disease areas can be attributed, in large part, to late-stage clinical failures (Schachter and Ramoni, Nat Rev Drug Discov 2007;6:107-8). Thus, identifying in phase II, or preferably phase I, drugs that are likely to fail would have a dramatic impact on the costs associated with developing new drugs. With this in mind, the Alzheimer's Association convened a Research Roundtable on June 23 and 24, 2011, in Washington, DC, bringing together scientists from academia, industry, and government regulatory agencies to discuss strategies for improving the probability of phase II trial results predicting success when considering the go/no-go decision-making process leading to the initiation of phase III.

Cost-effectiveness analysis of the neuroprotective agent edaravone for noncardioembolic cerebral infarction.

BACKGROUND: The free radical scavenger edaravone has been reported useful for improvement in activities of daily living and for prevention of recurrent stroke in the edaravone versus sodium ozagrel in acute noncardioembolic ischemic stroke (EDO) trial. The aim of this report was to evaluate the cost-effectiveness of edaravone compared to the intravenous antiplatelet drug ozagrel sodium (ozagrel) for noncardioembolic stroke (non-CES) based on the EDO trial data. METHODS: A cost-effectiveness analysis was performed using the Markov model, which also incorporated the long-term course after the acute stage of non-CES. From the perspective of a health care payer, direct medical costs and nursing care costs were taken into account in the cost analysis. The quality-adjusted life year (QALY) served as an indicator of effectiveness. Simulation at 5 and 10 years after the onset of non-CES was carried out. The study involved 68-year-old patients with non-CES, selected against the EDO trial subject selection criteria. A 14-day treatment with edaravone 60 mg/day or ozagrel 160 mg/day was assumed as acute treatment for non-CES. RESULTS: The use of edaravone was associated with a reduction in total costs (0.51 million yen [$6,374] at 5 years and 0.64 million yen [$8,039]) at 10 years after the onset of non-CES) and improvement in QALYs (0.23 at 5 years and 0.38 at 10 years). Compared to ozagrel therapy, edaravone therapy was a cost-saving strategy for treating non-CES. CONCLUSIONS: Compared to ozagrel therapy, edaravone therapy for non-CES is not only useful from a clinical viewpoint, but also valuable from a socioeconomic perspective.

What does the developing brain tell us about neural diseases?

In a recently published report, the European Brain Council estimated that the annual cost of brain disorders is larger than the cost of all other disease areas combined, including cardiovascular diseases, cancer, and diabetes. The World Health Organization concluded that approximately one-third of the total burden of disease in Europe is attributable to brain disorders. Therefore, drug development for neural diseases should flourish and attract large pharmaceutical companies and smaller enterprises alike. However, this is far from being the case: industry is cutting down on research and investment in brain disorders in Europe. Political reasons may be contributing to this, but they do not constitute the only explanation. An important reason for the decreasing interest and investment is the lack of drug targets in neural diseases. In order to change this, greater efforts at understanding the etiologies and pathogenetic mechanisms of disorders of both the developing and the adult brain are required. We need to strengthen basic research to understand the brain in health and disease. A shift from translational to basic research is required to meet the need for drugs and therapies in the future. In support of this, I summarize some recent studies indicating that the developing brain has much to offer in this respect. The processes and genes involved in brain development are linked to the etiologies not only of neurodevelopmental but also of neurodegenerative diseases.

Two center, randomized pilot study of migraine prophylaxis comparing paradigms using pre-emptive frovatriptan or daily topiramate: research and clinical implications.

OBJECTIVE: To compare the efficacy and clinical benefit of 2 paradigms of migraine prevention using pre-emptive frovatriptan and daily topiramate. The study compares the paradigms of pre-emptive use of frovatriptan, a drug approved for acute migraine, and the daily use of topiramate, a Federal Drug Administration-approved and -accepted standard for migraine prophylaxis. BACKGROUND: Traditionally, preventive treatment of migraine required daily medication. However, recent studies suggest that pre-emptive prophylaxis may be beneficial to those migraineurs who can predict an attack of migraine based on premonitory symptoms and treat during that phase. METHODS: A total of 76 adult subjects with a diagnosis of migraine were screened for the study. During a 1-month baseline period, subjects demonstrated through a daily diary that they predicted at least 50% of migraine attacks during the premonitory phase and treated with their usual medication. Of these, 55 were randomized to either Group A (daily topiramate) or Group B (frovatriptan during premonitory symptoms); 44 completed the study. The treatment period lasted 2 months. The subjects answered the Migraine-Specific Quality of Life Questionnaire at randomization, and at Weeks 4 and 8. The revised Patient Perception of Migraine Questionnaire was answered 24 hours after taking frovatriptan (Group A, for break-through headaches; Group B, treatment during premonitory symptoms). RESULTS: The number of migraine attacks and headache days per month decreased significantly from baseline for both Groups A and B. Subjects in Group A had considerably more adverse events leading to study withdrawal than in Group B (18% vs 4%). Though this study was not powered to directly compare the efficacy of the 2 drugs, topiramate showed superiority over frovatriptan at Month 2 in reduction of headache days, which was a secondary end point in the study (P = .036). CONCLUSIONS: This pilot study demonstrated that statistical benefit for reduction of headache days over baseline for both pre-emptive frovatriptan and daily topiramate. Subjects utilizing pre-emptive frovatriptan experienced fewer adverse events leading to study withdrawal. Subjects utilizing daily topiramate had fewer headache days at Month 2.

Assessing the cost-effectiveness of the rivastigmine transdermal patch for Alzheimer's disease in the UK using MMSE- and ADL-based models.

OBJECTIVE: Assess long-term cost-effectiveness of rivastigmine patch in Alzheimer's disease (AD) management in the UK, using cognitive and functional models based on clinical trial efficacy data. METHODS: Incremental costs and Quality Adjusted Life Years (QALYs) associated with rivastigmine patch and capsule treatment versus best supportive care (BSC) were calculated using two economic models, one based solely on Mini-Mental State Examination (MMSE) scores, and one also incorporating activities of daily living (ADL) scores. The clinical pathway was populated with data from a clinical trial of rivastigmine patch (9.5 mg/24 h) and capsules (12 mg/day) versus placebo. Costs were based on the UK health and social care costs and basic UK National Health Service (NHS) prices. Disease progression was modelled beyond the trial period over 5 years using published equations to predict natural decline in AD patients. Base case costing variables included drugs, clinical monitoring, and institutionalization. RESULTS: The MMSE model estimated incremental costs per QALY of £10 579 for rivastigmine patch and £15 154 for capsule versus BSC. The MMSE-ADL model estimated incremental costs per QALY of £9114 for rivastigmine patch and £13 758 for capsules. The main difference between the models was a greater number of institutionalized days avoided for rivastigmine versus BSC estimated by the MMSE-ADL model. CONCLUSIONS: Both the MMSE and MMSE-ADL models suggest that rivastigmine patch and capsules are cost-effective treatments versus BSC. Incorporating ADL evidence makes a marginal but important difference to estimates in this case. Future economic evaluations of AD treatment should include measures of both cognition and functioning.

Economic evaluation of the impact of memantine on time to nursing home admission in the treatment of Alzheimer disease.

OBJECTIVE: An observational study showed that combining memantine with a cholinesterase inhibitor (ChEI) treatment significantly delayed admission to nursing homes in patients with Alzheimer disease (AD). Our study aimed to evaluate the economic impact of the concomitant use of memantine and a ChEI, compared with a ChEI alone, in a Canadian population of patients with AD. METHOD: A cost-utility analysis using a Markov model during a 7-year time horizon was performed according to a societal and Canadian health care system perspective. The Markov model includes the following states: noninstitutionalized, institutionalized, and deceased. The model includes transition probabilities for institutionalization and death, adjusted with mortality rates specific to AD. Utilities associated with institutionalization and noninstitutionalization were included. For the health care system perspective, costs of medication as well as costs of care provided in the community and in nursing homes were considered. For the societal perspective, costs of direct care and supervision provided by caregivers were added. RESULTS: From both perspectives, the concomitant use of a ChEI and memantine is a dominant strategy, compared with the use of a ChEI alone. On a per patient basis, there was a gain of 0.26 quality-adjusted life years with the treatment including memantine and cost decreases of Can$21 391 and Can$30 512, respectively, for the societal and health care system perspective. CONCLUSIONS: This economic evaluation indicates that institutionalization is the largest cost component in AD management and that the use of memantine, combined with a ChEI, to treat AD is a cost-effective alternative, compared with the use of a ChEI alone.

Cost-Effectiveness of Erythropoietin in Traumatic Brain Injury: A Multinational Trial-Based Economic Analysis.

The EPO-TBI multi-national randomized controlled trial found that erythropoietin (EPO), when compared to placebo, did not affect 6-month neurological outcome, but reduced illness severity-adjusted mortality in patients with traumatic brain injury (TBI), making the cost-effectiveness of EPO in TBI uncertain. The current study uses patient-level data from the EPO-TBI trial to evaluate the cost-effectiveness of EPO in patients with moderate or severe TBI from the healthcare payers' perspective. We addressed the issue of transferability in multi-national trials by estimating costs and effects for specific geographical regions of the study (Australia/New Zealand, Europe, and Saudi Arabia). Unadjusted mean quality-adjusted life-years (QALYs; 95% confidence interval [CI]) at 6 months were 0.027 (0.020-0.034; p < 0.001) higher in the EPO group, with an adjusted QALY increment of 0.014 (0.000-0.028; p = 0.04). Mean unadjusted costs (95% CI) were $US5668 (-9191 to -2144; p = 0.002) lower in the treatment group; controlling for baseline IMPACT-TBI score and regional heterogeneity reduced this difference to $2377 (-12,446 to 7693; p = 0.64). For a willingness-to-pay threshold of $US50,000 per QALY, 71.8% of replications were considered cost-effective. Therefore, we did not find evidence that EPO was significantly cost-effective in the treatment of moderate or severe TBI at 6-month follow-up.

High-dose methylprednisolone for acute traumatic spinal cord injury: A meta-analysis.

OBJECTIVE: Due to the continuing debates on the utility of high-dose methylprednisolone (MP) early after acute spinal cord injury (ASCI), we aimed to evaluate the therapeutic and adverse effects of high-dose MP according to the second National Acute Spinal Cord Injury Study (NASCIS-2) dosing protocol in comparison to no steroids in patients with ASCI by performing a meta-analysis on the basis of the current available clinical trials. METHODS: We searched PubMed and Cochrane Library (to May 22, 2018) for studies comparing neurologic recoveries, adverse events, and in-hospital costs between ASCI patients who underwent high-dose MP treatment or not. Data were synthesized with corresponding statistical models according to the degree of heterogeneity. RESULTS: We enrolled 16 studies (1,863 participants) including 3 randomized controlled trials (RCTs) and 13 observational studies. Pooled results indicated that MP was not associated with an increase in motor score improvement (RCTs: p = 0.84; observational studies: p = 0.44) and incidence of recovery by at least one grade on the American Spinal Injury Association Impairment Scale or Frankel (p = 0.53). Meanwhile, MP did not lead to better sensory recovery (p = 0.07). However, MP was associated with a significantly higher incidence of gastrointestinal hemorrhage (p = 0.04) and respiratory tract infection (p = 0.01). The difference in the overall in-hospital costs between MP and control groups was not statistically significant (p = 0.78). CONCLUSIONS: Based on the current evidence, high-dose MP treatment, in comparison to controls, does not contribute to better neurologic recoveries but may increase the risk of adverse events in patients with ASCI. Therefore, we recommend against routine use of high-dose MP early after ASCI.

[Pharmacoeconomic analysis of the neuroprotective medicines in the treatment of ischemic stroke]. / Farmakoékonomicheskii analiz neiroprotektorov, primeniaemykh v terapii ishemicheskogo insul'ta.

AIM: To perform a pharmacoeconomic analysis of the most frequently prescribed neuroprotective medicines for treating patients with mild ischemic stroke in the acute and early rehabilitation periods in the Russian Federation. MATERIAL AND METHODS: Three medical technologies were compared: ethylmethylhydroxypyridine succinate (mexidol), inosine + nicotinamide + riboflavin + succinic acid (cytoflavin) and a deproteinized hemoderivate of the blood of calves (actovegin). Cost minimization analysis, budget impact analysis and sensitivity analysis were performed based on the indirect comparison results. RESULTS: Efficacy analysis shows that mentioned above medicines have the same efficacy: mean difference mexidol is 0,2 (CI min 0,25; max 0,65), cytoflavin - 0,61 (CI min 0,23; max 0,99), actovegin 0,2 (CI min 0,18; max 0,22). The cost minimization analysis for the Russian Federation shows that mexidol therapy is associated with the lowest costs, while savings are observed both in the evaluation of total costs and separate components: intravenous ampoules and tablet forms. The savings in comparison with cytoflavin and actovegin are 231 RUB and 12,872 RUB, respectively. These savings will be enough to treat five patients with ischemic stroke (IS) with mexidol. Moreover, oral mexidol therapy is cheaper than the same dosage forms of cytoflavin and actovegin by 481 RUB and 3,164 RUB, respectively. This is an advantage for the treatment of population at the outpatient stage. Budget impact analysis has shown that the budget for the medicines for treating IS at the current distribution between treatment regimens, is estimated at 1.99 BN RUB. The increase in the proportion of patients receiving mexidol by 10% reduces total costs to 1.75 BN RUB, which is 240 M RUB less than current costs. With these savings 85 thousand patients with IS could be treated. The sensitivity analysis reveals that the result of the cost minimization analysis and the budget impact analysis remain stable when both the amount of the population and the cost of 1 mg of mexidol vary from -10% to + 10%. CONCLUSIONS: Mexidol has the same efficacy as alternatives. However mexidol is superior to cytoflavin and actovegin in terms of cost minimization analysis. The savings from one course of alternatives will cover costs of treatment of five patients with IS using mexidol. The increase in the proportion of patients receiving mexidol is associated with savings, which allows us to consider mexidol therapy of mild IS as budget-saving in the Russian Federation.

The cost-effectiveness of medication, laser trabeculoplasty, and trabeculectomy for treatment of open-angle glaucoma in South Korea.

OBJECTIVES: Open-angle glaucoma (OAG) imposes high disease burden in South Korea. Although various effective interventions are available to manage the progression of OAG, there is limited data on the cost-effectiveness of these treatment strategies in South Korea. METHODS: Using a Markov cohort model, we evaluated the cost-effectiveness of 3 major treatment strategies (medication, laser trabeculoplasty, and trabeculectomy) for South Korean patients with OAG. We projected a 25-year time horizon to study a hypothetical cohort of 10,000 patients of age 40 with mild OAG. The outcome measures were quality-adjusted life-years (QALYs) gained, cost from the societal perspective, and the incremental cost-effectiveness ratio (ICER) of medication, laser trabeculoplasty, and trabeculectomy. Interventions were evaluated at a willingness-to-pay (WTP) threshold of 30,000,000 KRW ($29,152) per QALY gained. Deterministic and probabilistic sensitivity analyses were conducted to address the model uncertainty. RESULTS: The mean costs for medication, laser trabeculoplasty, and trabeculectomy were 29,661,740 KRW, 17,34,1342 KRW, and 22,275,438 KRW, respectively. The mean QALYs gained were 15.7, 15.3, and 14.8 for medication, laser trabeculoplasty, and trabeculectomy, respectively. Surgery was strongly dominated because it generated fewer expected QALYs but incurred greater expected cost than laser. The ICER was 30,885,179 KRW per QALY for medication versus laser trabeculoplasty. Laser was cost-effective, however, at a lower WTP threshold of 21,000,000 KRW per QALY gained or below. The results were most sensitive to the progression rates from mild to moderate glaucoma under laser treatment. CONCLUSION: Under the WTP threshold of 30,000,000 KRW per QALY, medication was cost-effective compared with laser trabeculoplasty and trabeculectomy for treating mild OAG in South Korean population. Laser, however, can be a cost-effective alternative in more resource-limited settings.

Cost-minimization analysis comparing topiramate with standard treatments in migraine prophylaxis.

Migraine is a common disorder with a relatively high burden of disease from the perspective of both society and the individual patient. Optimizing the use of prophylactic treatment may decrease the frequency and severity of attacks thus reducing the burden of disease. In this regard, topiramate has been found to be as effective as propranolol in the prevention of migraine attacks. In the present study, a cost-minimization analysis was performed. Monthly preventive medication cost and price per migraine attack reduced were used as measures. In comparison with propranolol and flunarizine, topiramate was identified as being the most costly option for migraine prophylaxis with a monthly drug cost of USD 24.97-45.04 as compared with propranolol (USD 1.72-6.87) and flunarizine (USD 6.09-12.18). Current treatment options would appear to offer better value for money in achieving effective migraine prophylaxis unless additional benefits can be identified for topiramate in this patient group.

Is this neuroprotective drug good for my glaucoma patients? Some key factors in clinical decision-making.

Neuroprotection protects neurons from death after a primary insult, independent of that insult. Important clinical considerations include minimal interference with physiological processes, possible simultaneous or sequential treatment strategies, and most effective method of drug delivery. Clinicians' assessment of the neuroprotective value of any agent hinges on demonstration of efficacy by prospective randomized controlled trials. Use of a neuroprotectant will depend on the glaucomatous threat to a patient's visual function, as well as the agent's therapeutic index and its cost.