Efficacy and tolerability of the switch from a branded to a generic warfarin sodium product: an observer-blinded, randomized, crossover study

Examining therapeutic equivalence between branded and generic warfarin in Brazil: The WARFA crossover randomized controlled trial

OBJECTIVES

To determine whether the generic and branded warfarins used as anticoagulants in Brazil are therapeutic equivalents based on their international normalized ratio (INR) results.

METHODS

This crossover randomized controlled trial had four periods. We used the branded Marevan and two generic versions of warfarin sodium tablets, manufactured by União Química and Teuto laboratories, all purchased from retail drugstores. Eligible participants were outpatients from an anticoagulation clinic at a university hospital in São Paulo, Brazil. They had atrial fibrillation or flutter and had been using warfarin for at least 2 months with an INR therapeutic range of 2.0-3.0. Randomization was by numbered, opaque, sealed envelopes. Healthcare personnel and outcome assessors were blinded to treatments, but patients were not. The primary outcome was the variability in the INR (ΔINR) and secondary outcomes included mean INR. We accepted formulations as equivalent if the 95% confidence interval (CI) of the comparison of ΔINR between branded and generic formulations was within the limit of ±0.49.

RESULTS

One hundred patients were recruited and randomized to six sequences of treatment (four sequences with n = 17 and two sequences with n = 16). União Química generic warfarin had equivalent variability in the INR to Marevan (ΔINR +0.09 [95% CI -0.29 to +0.46], n = 84). Comparison between Teuto generic warfarin and Marevan was inconclusive (ΔINR +0.29 [95% CI -0.09 to +0.68], n = 84).

CONCLUSIONS

Marevan and União Química warfarin had equivalent therapeutic effectiveness and both could be confidently used for anticoagulation. The comparison between Marevan and TW was inconclusive and does not warrant a statement of equivalence. Our methods are especially important for comparing generic and branded drugs that raise concerns and may be subject of future investigations by regulatory agents.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02017197.

Are Generic Drugs Used in Cardiology as Effective and Safe as their Brand-name Counterparts? A Systematic Review and Meta-analysis

BACKGROUND

Previous systematic reviews (2008; 2016) concluded similarity in outcomes between brand-name and generic drugs in cardiology, but they included ≥ 50% comparative bioavailability studies, not designed or powered to detect a difference in efficacy or safety between drug types. We aimed to summarise best-evidence regarding the effectiveness and safety of generic versus brand-name drugs used in cardiology.

METHODS

For this systematic review of the literature, scientific databases (MEDLINE and EMBASE) were searched from January 1984 to October 2018. Original research reports comparing the clinical impact of brand-name versus generic cardiovascular drugs on humans treated in a real-life setting, were selected. Meta-analyses and subgroup analyses were performed. Heterogeneity (I²) and risk of bias were tested.

RESULTS

Among the 3148 screened abstracts, 72 met the inclusion criteria (n ≥ 1,000,000 patients, mean age 65 ± 10 years; 42% women). A total of 60% of studies showed no difference between drug types, while 26% concluded that the brand-name drug was more effective or safe, 13% were inconclusive and only 1% concluded that generics did better. The overall crude risk ratio of all-cause hospital visits for generic versus brand-name drug was 1.14 (95% confidence interval: 1.06-1.23; I²: 98%), while it was 1.05 (0.98-1.14; I²: 68%) for cardiovascular hospital visits. The crude risk ratio was not statistically significant for randomised controlled trials only (n = 4; 0.92 [0.63-1.34], I²: 35%).

CONCLUSION

The crude risk of hospital visits was higher for patients exposed to generic compared to brand-name cardiovascular drugs. However, the evidence is insufficient and too heterogeneous to draw any firm conclusion regarding the effectiveness and safety of generic drugs in cardiology.

Comparative Outcomes of Treatment Initiation With Brand vs. Generic Warfarin in Older Patients

The anticoagulant response to warfarin, a narrow therapeutic index drug, increases with age, which may make older patients susceptible to adverse outcomes resulting from small differences in bioavailability between generic and brand products. Using US Medicare claims linked to electronic medical records from two large hospitals in Boston, we designed a cohort study of ≥ 65-year-old patients. Patients were followed for a composite effectiveness outcome of ischemic stroke or venous thromboembolism, a composite safety outcome, including major hemorrhage, and a 1-year all-cause mortality outcome. After propensity score fine-stratification and weighting to account for > 90 confounders, hazard ratios comparing brand vs. generic warfarin initiators (95% confidence intervals) for the effectiveness, safety, and all-cause mortality outcomes, were 0.97 (0.65-1.46), 0.94 (0.65-1.35), and 0.84 (0.62-1.13), respectively. Results from subgroup analyses of patients with atrial fibrillation, CHADS-VASc score ≥ 3, and HAS-BLED score ≥ 3 were consistent with the primary analysis.

Design and rationale for the WARFA trial: a randomized controlled cross-over trial testing the therapeutic equivalence of branded and generic warfarin in atrial fibrillation patients in Brazil

Background

Warfarin is a commonly used anticoagulant. Whether a given dose of the different formulations of Brazilian warfarin will result in the same effect on the international normalized ratio (INR) is uncertain. The aim of the WARFA trial is to determine whether the branded and two generic warfarins available in Brazil differ in their effect on the INR.

Methods

WARFA is a cross-over RCT comparing three warfarins. The formulations tested are the branded Marevan® (Uniao Quimica/Farmoquimica) and two generic warfarin (manufactured respectively by Uniao Quimica Farmaceutica Nacional and Laboratorio Teuto Brasileiro). All of them were manufactured in Brazil, are available in all settings of the Brazilian healthcare system and were purchased from retail drugstores. Eligible participants had atrial fibrillation or flutter, had been using warfarin for at least 2 months with a therapeutic range of 2.0–3.0 and had low variability in INR results during the 1st period of the trial. Our primary outcome, for which we have an equality hypothesis, is the difference between warfarins in the mean absolute difference between two INR results, obtained after three and 4 weeks with each drug. Our secondary outcomes, that will be tested for inequality (except for the mean INR, which will be tested for equality), include the difference in the warfarin dose, and time in therapeutic range. Clinical events and adherence were also recorded and will be reported.

Discussion

To our knowledge, WARFA will be the first comparison of the more readily applicable INR results between branded and generic warfarins in Brazil. WARFA is important because warfarins are commonly switched between in the course of a chronic treatment in Brazil. Final results of WARFA are expected in May 2017.

Trial registration

ClinicalTrials.gov NCT02017197 . Registered 11 December 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-017-0584-4) contains supplementary material, which is available to authorized users.

Generic versus brand-name drugs used in cardiovascular diseases

This meta-analysis aimed to compare the efficacy and adverse events, either serious or mild/moderate, of all generic versus brand-name cardiovascular medicines. We searched randomized trials in MEDLINE, Scopus, EMBASE, Cochrane Controlled Clinical Trial Register, and ClinicalTrials.gov (last update December 1, 2014). Attempts were made to contact the investigators of all potentially eligible trials. Two investigators independently extracted and analyzed soft (including systolic blood pressure, LDL cholesterol, and others) and hard efficacy outcomes (including major cardiovascular adverse events and death), minor/moderate and serious adverse events. We included 74 randomized trials; 53 reported ≥1 efficacy outcome (overall sample 3051), 32 measured mild/moderate adverse events (n = 2407), and 51 evaluated serious adverse events (n = 2892). We included trials assessing ACE inhibitors (n = 12), anticoagulants (n = 5), antiplatelet agents (n = 17), beta-blockers (n = 11), calcium channel blockers (n = 7); diuretics (n = 13); statins (n = 6); and others (n = 3). For both soft and hard efficacy outcomes, 100 % of the trials showed non-significant differences between generic and brand-name drugs. The aggregate effect size was 0.01 (95 % CI -0.05; 0.08) for soft outcomes; -0.06 (-0.71; 0.59) for hard outcomes. All but two trials showed non-significant differences in mild/moderate adverse events, and aggregate effect size was 0.07 (-0.06; 0.20). Comparable results were observed for each drug class and in each stratified meta-analysis. Overall, 8 serious possibly drug-related adverse events were reported: 5/2074 subjects on generics; 3/2076 subjects on brand-name drugs (OR 1.69; 95 % CI 0.40-7.20). This meta-analysis strengthens the evidence for clinical equivalence between brand-name and generic cardiovascular drugs. Physicians could be reassured about prescribing generic cardiovascular drugs, and health care organization about endorsing their wider use.

The Impact of Generic Substitution on Health and Economic Outcomes: A Systematic Review

BACKGROUND

Generic drugs are considered therapeutically equivalent to their original counterparts and lower in acquisition costs. However, the overall impact of generic substitution (GS) on global clinical and economic outcomes has not been conclusively evaluated.

OBJECTIVE

To test whether (1) generics and original products yield the same health outcomes, and (2) generic therapies save economic resources versus original therapies.

METHODS

We performed a systematic literature review in Medline, Embase, and the Cochrane Database of Systematic Reviews to identify original studies that examine clinical or economic outcomes of GS. After standardized data extraction, reported outcomes were categorized as supporting or rejecting the hypotheses. Each reported outcome was assessed and accounted for supporting and opposing GS. One publication could provide multiple outcome comparisons.

RESULTS

We included 40 studies across ten therapeutic areas. Fourteen studies examined patients on de novo therapy; 24 studies investigated maintenance drug therapy, and two studies considered both settings. Overall, 119 outcome comparisons were examined. Of 97 clinical outcome comparisons, 67% reported no significant difference between generic drugs and their off-patent counterparts. Of 22 economic comparisons, 64% suggested that GS increased costs. Consequently, hypothesis (1) was supported but hypothesis (2) was not. We found no major differences among studies that investigated clinical outcomes with de novo or maintenance therapy.

CONCLUSION

The review suggests that clinical effects are similar after GS. However, economic savings are not guaranteed. More systematic research comparing clinical and economic outcomes with or without GS is needed to inform policy on the use of generic substitution.

Efficacy and Safety of Glaucoma Patients' Switch from a 2% Dorzolamide/0.5% Timolol Fixed-Combination Brand-Name Drug to Its Generic Counterpart

PURPOSE

To compare the efficacy and safety of the brand-name and generic 2% dorzolamide/0.5% timolol fixed-combination (DTFC) drugs in glaucoma patients.

METHODS

This was a prospective single-center study, in which patients using only the brand-name DTFC (Cosopt(®); Merck and Co, Inc.) drug and those using Cosopt with prostaglandin analogs (PGs) were enrolled. In the patients using Cosopt (Group A) and Cosopt with PGs (Group B), Cosopt was switched to its generic counterpart (Batidor(®); Bausch & Lomb, Inc.). The intraocular pressure (IOP) was measured before the switch and 4, 8, and 12 weeks after the switch in both groups. The questionnaire on the discomfort symptoms and on the discomfort score for the use of eye drops was answered by the patients in both groups before the switch and 12 weeks after the switch.

RESULTS

A total of 112 patients were enrolled in the study, 62 in Group A and 50 in Group B. The IOPs before the switch and 4, 8, and 12 weeks after the switch showed no statistical difference in both groups (P>0.05). There were higher incidences of bitter taste and blurring with Cosopt, and there was a higher incidence of headache with Batidor in both groups, but no significant differences (P>0.05) were noted. There was, likewise, no significant difference in the discomfort score between 2 drugs in both groups (P>0.05).

CONCLUSIONS

After the switch, the IOP-lowering effect of the generic drug Batidor was similar to that of the brand-name drug Cosopt in the monotherapy and combination therapy with PGs. No significant differences were found in terms of the discomfort symptoms and discomfort score between the 2 drugs.

Brand name versus generic warfarin: a systematic review of the literature

The use of generic drugs has become increasingly common in clinical practice. However, for drugs with a narrow therapeutic index, such as warfarin, there may be some concern regarding the definition of bioequivalence. Clinical studies that compared brand name and generic warfarin products provided conflicting results. Therefore, we performed a systematic review of the literature to better assess the characteristics of each generic warfarin product. Several sources were searched, including MEDLINE and EMBASE, electronic records of meetings' abstracts, and reference lists of included articles. Articles were considered relevant if they were original studies, enrolled patients receiving oral anticoagulant treatment, and compared any approved generic warfarin with brand name warfarin in at least one clinical, laboratory, or management outcome. Eleven studies, with a total of more than 40,000 patients, were included; five were randomized controlled trials, and six were observational studies. In three crossover trials evaluating the mean difference of the international normalized ratio (INR) after switching to the alternate formulation of warfarin, no statistically significant difference was found between patients randomly assigned to receive brand name or generic warfarin. The two other randomized trials found no significant differences in the magnitude or number of dosage changes between patients switched to brand name or generic warfarin. The results of the observational studies are more conflicting, suggesting different features for different generic warfarin products. In these observational studies, the time in the therapeutic range and the number of thromboembolic and hemorrhagic complications were similar in studies that compared the anticoagulation control before and after the switch to a generic warfarin product. In one observational study, however, a change in therapeutic INR control after the switch to generic warfarin was reported at the individual patient level. The results of our systematic review suggest that generic warfarin products may be as safe and effective as brand name products and that patients may be safely treated with these products. However, closer monitoring may be reasonable when switching brands, as variations in individual INR response may be seen.

Substituting Warfarin Products: What's the Source of the Problem?

Many clinicians have expressed concerns about the bioequivalence of warfarin products, and data suggest that substituting warfarin products may increase the risk of major bleeding and thromboembolic complications. Anecdotal reports and some retrospective studies have reported differences in anticoagulation control after a warfarin product substitution. But the best available evidence—prospective, randomized, blinded clinical trials—has failed to validate these observations. Indeed, interpatient and intrapatient variability in anticoagulation control observed before and after warfarin product substitution is very similar. So, while differences in product standardization, bioavailability, and bioequivalence make a convenient explanation, the problem lies elsewhere. Perhaps poor communication, fractionated systems of care, and errors are the culprits.

Comparing Generic and Innovator Drugs: A Review of 12 Years of Bioequivalence Data from the United States Food and Drug Administration

Background:

In the US, manufacturers seeking approval to market a generic drug product must submit data demonstrating that the generic formulation provides the same rate and extent of absorption as (ie, is bioequivalent to) the innovator drug product. Thus, most orally administered generic drug products in the US are approved based on results of one or more clinical bioequivalence studies.

Objective:

To evaluate how well the bioequivalence measures of generic drugs approved in the US over a 12-year period compare with those of their corresponding innovator counterparts.

Methods:

This retrospective analysis compared the generic and innovator bioequivalence measures from 2070 single-dose clinical bioequivalence studies of orally administered generic drug products approved by the Food and Drug Administration (FDA) from 1996 to 2007 (12 y). Bioequivalence measures evaluated were drug peak plasma concentration (Cmax) and area under the plasma drug concentration versus time curve (AUC), representing drug rate and extent of absorption, respectively. The generic/innovator Cmax and AUC geometric mean ratios (GMRs) were determined from each of the bioequivalence studies, which used from 12 to 170 subjects. The GMRs from the 2070 studies were averaged. In addition, the distribution of differences between generic means and innovator means was determined for both Cmax and AUC.

Results:

The mean ± SD of the GMRs from the 2070 studies was 1.00 ± 0.06 for Cmax and 1.00 ± 0.04 for AUC. The average difference in Cmax and AUC between generic and innovator products was 4.35% and 3.56%, respectively. In addition, in nearly 98% of the bioequivalence studies conducted during this period, the generic product AUC differed from that of the innovator product by less than 10%.

Conclusions:

The criteria used to evaluate generic drug bioequivalence studies support the FDA's objective of approving generic drug formulations that are therapeutically equivalent to their innovator counterparts.

Clinical equivalence of generic and brand-name drugs used in cardiovascular disease: a systematic review and meta-analysis

CONTEXT

Use of generic drugs, which are bioequivalent to brand-name drugs, can help contain prescription drug spending. However, there is concern among patients and physicians that brand-name drugs may be clinically superior to generic drugs.

OBJECTIVES

To summarize clinical evidence comparing generic and brand-name drugs used in cardiovascular disease and to assess the perspectives of editorialists on this issue.

DATA SOURCES

Systematic searches of peer-reviewed publications in MEDLINE, EMBASE, and International Pharmaceutical Abstracts from January 1984 to August 2008.

STUDY SELECTION

Studies compared generic and brand-name cardiovascular drugs using clinical efficacy and safety end points. We separately identified editorials addressing generic substitution.

DATA EXTRACTION

We extracted variables related to the study design, setting, participants, clinical end points, and funding. Methodological quality of the trials was assessed by Jadad and Newcastle-Ottawa scores, and a meta-analysis was performed to determine an aggregate effect size. For editorials, we categorized authors' positions on generic substitution as negative, positive, or neutral.

RESULTS

We identified 47 articles covering 9 subclasses of cardiovascular medications, of which 38 (81%) were randomized controlled trials (RCTs). Clinical equivalence was noted in 7 of 7 RCTs (100%) of beta-blockers, 10 of 11 RCTs (91%) of diuretics, 5 of 7 RCTs (71%) of calcium channel blockers, 3 of 3 RCTs (100%) of antiplatelet agents, 2 of 2 RCTs (100%) of statins, 1 of 1 RCT (100%) of angiotensin-converting enzyme inhibitors, and 1 of 1 RCT (100%) of alpha-blockers. Among narrow therapeutic index drugs, clinical equivalence was reported in 1 of 1 RCT (100%) of class 1 antiarrhythmic agents and 5 of 5 RCTs (100%) of warfarin. Aggregate effect size (n = 837) was -0.03 (95% confidence interval, -0.15 to 0.08), indicating no evidence of superiority of brand-name to generic drugs. Among 43 editorials, 23 (53%) expressed a negative view of generic drug substitution.

CONCLUSIONS

Whereas evidence does not support the notion that brand-name drugs used in cardiovascular disease are superior to generic drugs, a substantial number of editorials counsel against the interchangeability of generic drugs.

Analysis of the composition of 'original' and generic sevoflurane in routine use

BACKGROUND

Original sevoflurane (Sevofrane) contains a small amount of water, which can inhibit the production of hydrofluoric acid. Hydrofluoric acid is highly pungent, and sevoflurane that contains a high concentration of hydrofluoric acid is not suitable for volatile induction of anaesthesia. Recently, generic sevoflurane (Sevoness) has become available in some countries. The generic product is produced by a different method and kept in a different kind of bottle. We questioned whether the original and generic sevoflurane differed in their composition and thus might differ in their resistance to degradation.

METHODS

Sevoflurane from groups of three bottles of Sevofrane and three bottles of Sevoness was kept in the bottle at 24-37 degrees C for 2 weeks or in two kinds of vaporizer for 3 days, and the resulting contents measured by gas chromatography.

RESULTS

Both products contained sevoflurane concentrations exceeding 99.998%. Fluoride ion concentration did not differ between the products (0.043 ppm). The original sevoflurane contained more (0.07% w/v) water than the generic anaesthetic (0.003% w/v). Original sevoflurane contained 5 ppm compound A, 10 ppm sevomethylether, and 5 ppm of unknown materials. Generic sevoflurane contained 32 ppm hexafluoroisopropanol and 12 ppm of unknown materials. While stored in a vaporizer for 3 days, the water content in the original sevoflurane decreased by two-thirds but the water in the generic sevoflurane increased by a factor of three-fold.

CONCLUSIONS

Generic sevoflurane contains high-quality sevoflurane and only a small amount of fluoride ions, making it comparable with the original sevoflurane product.