Potential concerns about generic substitution: bioequivalence versus therapeutic equivalence of different amlodipine salt forms

Clinical Equivalence between Generic Versus Branded Antibiotics: Systematic Review and Meta-Analysis

Regulatory authorities authorize the clinical use of generic drugs (GD) based on bioequivalence studies, which consist of the evaluation of pharmacokinetics after a single dose in vitro or in healthy individuals. There are few data on clinical equivalence between generic and branded antibiotics. Our aim was to synthesize and analyze the available evidence on the clinical efficacy and safety of generic antibiotics compared to their original formulations. A systematic review was performed on Medline (PubMed) and Embase and validated through Epistemonikos and Google Scholar. The last search was conducted on 30 June 2022. Meta-analyses of clinical cure and mortality outcomes were performed. One randomized clinical trial (RCT) and 10 non-randomized intervention studies were included. No differences in clinical cure were observed between groups in the meta-analysis (OR = 0.89, 95% CI [0.61-1.28]; I² = 70%, p = 0.005). No difference was observed between groups when considering the use of carbapenems for overall mortality (OR = 0.99, 95% CI [0.63-1.55]; I² = 78%) or death associated with infections (OR = 0.79, 95% CI [0.48-1.29], I² = 67%). Most of the studies were observational, and the duration of follow-up, the characteristics of the participants, and the sites of infections were heterogeneous. Due to the uncertainty of the evidence, it is not possible to contraindicate the use of generics, which is an important strategy to expand access.

Who initiates price competition when generic entrants are introduced into the South Korean pharmaceutical market?

Background

Price competition has the potential to reduce health expenditures without hindering pharmaceutical innovation. However, empirical evidence on price competition after generic drugs are introduced is scarce. This study investigates product- and substance-level determinants of price competition following the entry of generics into the South Korean market.

Methods

We selected substances that were approved by the Ministry of Food and Drug Safety from 2000 to 2019, linked their corresponding pharmaceutical products, measured the degree of price competition under various scenarios, and utilized multilevel analysis to investigate the determinants of price competition.

Results

A total of 986 substances and 12,109 corresponding pharmaceutical products were identified. Only 11% of products were affected by price competition in the 10% scenario. However, the number increased to 43% when we measured price competition at the substance level. Major domestic manufacturers mainly initiated price competition at the product level, while foreign manufacturers were reluctant to initiate price competition. At the substance level, the maximum reimbursement price was a significant determinant of price competition.

Conclusion

Price competition at the product level is rare in South Korea. In contrast, the market is quite price competitive at the substance level. Policy options could be introduced to encourage "discounted generic" substitution in an effort to maximize the effects of price competition at the substance level. Major domestic manufacturers are essential in the introduction of discounted generics into the South Korean health system.

Public Health Outcomes May Differ After Switching from Brand-Name to Generic Angiotensin II Receptor Blockers

Background

It is unclear whether generics are as safe as brand-name drugs in cardiology. For public health surveillance purposes, we evaluated if switching from the brand-name losartan, valsartan, or candesartan impacted the occurrence of the following outcomes: emergency room (ER) consultations, hospitalizations, or death.

Study Design

This was a retrospective cohort study.

Methods

This study was conducted in the Quebec Integrated Chronic Disease Surveillance System, including healthcare administrative data of the population of Quebec, Canada. We included brand-name users of losartan, valsartan, or candesartan aged ≥ 66 years who had undergone ≥ 30 days of stable treatment on the brand-name drug prior to cohort entry (substitution time-distribution matching was used to prevent immortal time bias). Outcomes up to 1 year were compared between groups using multivariable Cox proportional hazards regression models (validity assumptions were verified).

Results

In our cohorts (losartan, n =15,783; valsartan, n =16,907; candesartan, n =26,178), mean age was 76–78 years, 59–66% were female, 90–92% had hypertension, and 13–15% had heart failure. Validity assumptions were violated for losartan only. For patients switched to generic valsartan, the hazard ratio (95% confidence interval) was 1.07 (0.99–1.14) for ER consultation, 1.26 (1.14–1.39) for hospitalization, and 1.01 (0.61–1.67) for death. The corresponding rates for candesartan were 1.00 (0.95–1.05), 0.96 (0.89–1.03), and 0.57 (0.37–0.88), respectively.

Conclusions

We observed an increased risk of hospitalizations for patients switched to generic valsartan, and a decreased risk of death for patients switched to generic candesartan, compared with those who continued taking the brand-name drug. The differences between generic and brand-name drugs may lead to some differences in public health outcomes, but this safety signal must be further studied using other cohorts and settings.

Electronic supplementary material

The online version of this article (10.1007/s40268-020-00307-2) contains supplementary material, which is available to authorized users.

Nontherapeutic equivalence of a generic product of imipenem-cilastatin is caused more by chemical instability of the active pharmaceutical ingredient (imipenem) than by its substandard amount of cilastatin

Background

We demonstrated therapeutic nonequivalence of “bioequivalent” generics for meropenem, but there is no data with generics of other carbapenems.

Methods

One generic product of imipenem-cilastatin was compared with the innovator in terms of in vitro susceptibility testing, pharmaceutical equivalence, pharmacokinetic (PK) and pharmacodynamic (PD) equivalence in the neutropenic mouse thigh, lung and brain infection models. Both pharmaceutical forms were then subjected to analytical chemistry assays (LC/MS).

Results and conclusion

The generic product had 30% lower concentration of cilastatin compared with the innovator of imipenem-cilastatin. Regarding the active pharmaceutical ingredient (imipenem), we found no differences in MIC, MBC, concentration or potency or AUC, confirming equivalence in terms of in vitro activity. However, the generic failed therapeutic equivalence in all three animal models. Its E_max against S. aureus in the thigh model was consistently lower, killing from 0.1 to 7.3 million less microorganisms per gram in 24 hours than the innovator (P = 0.003). Against K. pneumoniae in the lung model, the generic exhibited a conspicuous Eagle effect fitting a Gaussian equation instead of the expected sigmoid curve of the Hill model. In the brain infection model with P. aeruginosa, the generic failed when bacterial growth was >4 log₁₀ CFU/g in 24 hours, but not if it was less than 2.5 log₁₀ CFU/g. These large differences in the PD profile cannot be explained by the lower concentration of cilastatin, and rather suggested a failure attributable to the imipenem constituent of the generic product. Analytical chemistry assays confirmed that, besides having 30% less cilastatin, the generic imipenem was more acidic, less stable, and exhibited four different degradation masses that were absent in the innovator.

Clinical tolerability of generic versus brand beta blockers in heart failure with reduced left ventricular ejection fraction: a retrospective cohort from heart failure clinic

Background: Beta-blockers have been shown to decrease mortality and morbidity in heart failure with reduced ejection fraction (HFrEF) patients. However, the side effects are also dose-related, leading to the underdosing. Cost constraint may be one of the limitations of appropriate beta-blocker use; this can be improved with generic drugs. However, the effects in real life practice have not been investigated. Methods and results: This study aimed to compare the efficacy and safety of generic and brand beta-blockers in HFrEF patients. We performed a retrospective cohort analysis in HFrEF patients who received either generic or brand beta-blocker in Chiang Mai Heart Failure Clinic. The primary endpoint was the proportion of patients who received at least 50% target dose of beta-blocker between generic and brand beta-blockers. Adverse events were secondary endpoints. 217 patients (119 and 98 patients received generic and brand beta-blocker, respectively) were enrolled. There were no differences between groups regarding age, gender, etiology of heart failure, New York Heart Association (NYHA) functional class, left ventricular ejection fraction (LVEF), rate of receiving angiotensin converting enzyme inhibitor (ACEI), angiotensin recepter blocker (ARB), or spironolactone. Patients receiving brand beta-blockers had lower resting heart rate at baseline (74.9 and 84.2 bpm, p = .001). Rate of achieved 50% target dose and target daily dose did not differ between groups (40.4 versus 44.5% and 48.0 versus 55.0%, p > .05, respectively). Rate of side effects was not different between groups (32.3 versus 29.5%, p > .05) and the most common side effect was hypotension. Conclusion: This study demonstrated that beta-blocker tolerability was comparable between brand and generic formulations. Generic or brand beta-blockers should be prescribed to HFrEF patients who have no contraindications.

A comparison of the intrasubject variation in drug exposure between generic and brand-name drugs: a retrospective analysis of replicate design trials

AIMS

The aim of the present study was to investigate whether differences in total and peak drug exposure upon generic substitution are due to differences between formulations or to intrasubject pharmacokinetic variability of the active substance.

METHODS

The study was designed as a retrospective reanalysis of existing studies. Nine replicate design bioequivalence studies representing six drug classes - i.e. for alendronate, atorvastatin, cyclosporin, ebastine, exemestane, mycophenolate mofetil, and ropinirole - were retrieved from the Dutch Medicines Regulatory Authority.

RESULTS

In most studies, the intrasubject variability in total and peak drug exposure was comparable for the brand-name [in the range 0.01-0.24 for area under the concentration-time curve (AUCt ) and 0.02-0.29 for peak plasma concentration (Cmax ) on a log scale] and generic (0.01-0.23 for AUCt and 0.08-0.33 for Cmax ) drugs, and was comparable with the intrasubject variability upon switching between those drugs (0.01-0.23 for AUCt and 0.06-0.33 for Cmax ). The variance related to subject-by-formulation interaction could be considered negligible (-0.069 to 0.047 for AUCt and -0.091 to 0.02 for Cmax ).

CONCLUSION

In the investigated studies, the variation in total and peak exposure seen when a patient is switched from a brand-name to a generic drug is comparable with that seen following repeated administration of the brand-name drug in the patient. Only the intrasubject variability seems to play a crucial and decisive role in the variation in drug exposure seen; no additional formulation-dependent variation in exposure is observed upon switching. Thus, our data support that, for the medicines that were included in the present investigation, from a clinical pharmacological perspective, the benefit-risk balance of a generic drug is comparable with that of the brand-name drug.

Generic medicines and generic substitution: contrasting perspectives of stakeholders in Ireland

BACKGROUND

The Health (Pricing and Supply of Medical Goods) Act 2013 passed into law in July 2013 and legislated for generic substitution in Ireland. The aim of the study was to ascertain the knowledge and perceptions of stakeholders i.e. patients, pharmacists and prescribers, of generic medicines and to generic substitution with the passing of legislation.

METHODS

Three stakeholder specific questionnaires were developed to assess knowledge of and perceptions to generic medicines and generic substitution. Purposive samples of patients, prescribers and pharmacists were analysed. Descriptive quantitative and qualitative analyses were undertaken.

RESULTS AND DISCUSSION

A total of 762 healthcare professionals and 353 patients were recruited. The study highlighted that over 84% of patients were familiar with generic medicines and are supportive of the concept of generic substitution. Approximately 74% of prescribers and 84% of pharmacists were supportive of generic substitution in most cases. The main areas of concern highlighted by the healthcare professionals that might impact on the successful implementation of the policy, were the issue of bioequivalence with generic medicines, the computer software systems used at present in general practitioner (GP) surgeries and the availability of branded generics. The findings from this study identify a high baseline rate of acceptance to generic medicines and generic substitution among patients, prescribers and pharmacists in the Irish setting. The concerns of the main stakeholders provide a valuable insight into the potential difficulties that may arise in its implementation, and the need for on-going reassurance and proactive dissemination of the impact of the generic substitution policy.

CONCLUSION

The existing positive attitude to generic medicines and generic substitution among key stakeholders in Ireland to generic substitution, combined with appropriate support and collaboration should result in the desired increase in rates of prescribing, dispensing and use of generic medicines.

Consumers' perception of generic substitution in Iran

BACKGROUND

The growth of pharmaceutical expenditure and patients' out of pocket has motivated policy makers to encourage patients to substitution of brands medicines with their generic alternatives called generic substitution.

OBJECTIVES

As the patients are final decision makers to accept generic substitution, the aim of this study is to evaluate the patient perception about generic medicines and underlying factors which can promote the generic acceptance.

SETTING

The study was done in community pharmacies in Tehran, the capital city of Iran.

METHOD

A cross-sectional descriptive study inviting people purchasing their drug at community pharmacies were per-formed using a self-administrated anonymous questionnaire (N=1309).

MAIN OUTCOMES MEASURES

Besides the demographic section, 16 items of developed questionnaire were categorized to five main factors including: patients' perception about efficiency, safety and cost of generic medicines, patient trust on physicians and pharmacists' advice.

RESULTS

Findings of completed questionnaires showed among the aforementioned factors the physician has the first priority to encourage patients to use of generics medicines which followed respectively by pharmacist's role, cost of medicines, efficacy, and safety concerns.

CONCLUSION

In conclusion, the trust of Iranian's society on the physicians and pharmacists advice would create a credible opportunity to reduce pharmaceutical expenditures as well as patients' out of pocket by promotion of generic substitution.

Comparing recurrent antibiotic prescriptions in children treated with a brand name or a generic formulation

PURPOSE

The aim of this study was to investigate the rate of recurrent prescriptions and hospital admissions in children receiving a brand name or generic antibiotic prescription.

METHODS

The data source was a database of reimbursed prescriptions. Outpatient children/adolescents <18 years old (Lombardy Region, Italy) were included. The observational period was February-April 2010. A recurrence was defined as an antibiotic prescription occurring within 28 days after an index prescription. The rate of recurrent prescriptions and hospital admissions was calculated for generic/brand name formulations and for each age strata (0-5, 6-11, and 12-17 years old) for four antibiotics: amoxicillin, amoxicillin clavulanate, clarithromycin, and cefaclor. The percentage of therapy switches was calculated. Cochran-Mantel-Haenszel test was used to compare the age-adjusted outcomes.

RESULTS

In all, 17.5% (57 346) of children received at least one recurrent prescription. The rate of recurrent prescriptions was slightly lower in children receiving any generic (OR 0.96; 95%CI 0.93-0.98), compared with any brand name, antibiotic. The percentage of hospital admissions occurring in children initially treated with a brand name (1.01%; 95%CI 0.98-1.08) or generic (1.03%; 0.96-1.06) antibiotic was not different (p = 0.43). For children receiving amoxicillin clavulanate, the hospital admission rate was slightly higher in the brand name group (p = 0.002), while no differences were found for the other active substances.

CONCLUSIONS

Children treated with generic antibiotics had no worse safety and effectiveness outcomes when compared with those receiving brand name ones. These results provide additional evidence on the safety of generic antibiotics.

Generic drugs for hypertension: are they really equivalent?

Many antihypertensive drugs are now available in generic formulations at fractions of the cost of their branded counterparts. In the United States, marketing approval for generic medications is usually granted by the Food and Drug Administration on the basis of two simple studies involving dissolution rates and bioavailability in 24 - 36 healthy people, without data regarding antihypertensive efficacy, safety, or long-term outcomes. This process leaves many true disciples of "Evidence-Based Medicine" in a quandary: prescribe only brand-name medications that have been demonstrated in clinical trials to both lower blood pressure and prevent cardiovascular events, or instead recommend lower-priced generic agents that are usually supported by no such data. This review summarizes the current evidence that generic antihypertensive drugs are likely to be safe and effective, may increase the probability of medication availability and adherence for many patients, but, by law, must have a different physical appearance than the original product.

Comparative pharmacokinetic and pharmacodynamic evaluation of branded and generic formulations of meloxicam in healthy male volunteers

PURPOSE

The primary aim of the present study was to assess the pharmacokinetic bioequivalence between a generic formulation of meloxicam 15 mg tablets (Meloxicam Hexal) and its respective brand product (Mobic), in order to verify whether the generic product conforms to the regulatory standards of bioequivalence in the postmarketing setting. As a secondary exploratory aim, the pharmacodynamic effects of the two formulations were also evaluated by means of rating scales following hyperalgesia induced by cutaneous freeze injury.

SUBJECTS AND METHODS

A single 15 mg dose of generic or branded meloxicam tablets was administered to 24 healthy male volunteers in a crossover fashion. Plasma samples, collected for 24 hours after dosing, were assayed for meloxicam concentration by a validated highperformance liquid chromatography method.

RESULTS

THE ANALYSIS OF PHARMACOKINETIC PARAMETERS DID NOT SHOW ANY SIGNIFICANT DIFFERENCE BETWEEN THE TWO MELOXICAM FORMULATIONS: the 90% confidence intervals fell within the acceptance range of 80%-125% (0.84-1.16 for area under the curve [0-24], and 0.89-1.23 for peak concentration). No difference in the pharmacodynamic end point was observed between the two groups.

CONCLUSION

The pharmacokinetic profiles of the two meloxicam formulations confirm the regulatory criteria for bioequivalence; pharmacodynamic data indicate a similar antihyperalgesic effect. The two formulations can be used interchangeably in the clinical setting.

Associations between generic substitution and patients' attitudes, beliefs and experiences

BACKGROUND

Generic substitution has been implemented in many countries, but knowledge about patients' attitudes, beliefs and experiences is still sparse.

AIM

To assess associations between generic switching and patients' attitudes, beliefs and experiences with previous generic switching.

DESIGN AND SETTING

A cross-sectional study comprising questionnaire responses from 2,476 randomly selected patients aged 20 years or older and living in the Region of Southern Denmark, who had redeemed substitutable drugs.

METHODS

The questionnaire included items on beliefs about medicine, views on generic medicine and confidence in the healthcare system. Only prescriptions issued by the general practitioners were included. For each patient, we focused on one purchase of a generically substitutable drug (index drug). Patients were identified by means of a dispensing database.

RESULTS

Earlier generic switches within the index ATC code were statistically significantly associated with experience of a generic switch (adjusted OR 5.93; 95 % CI 4.70-7.49). Having had more than five earlier switches within other ATC codes and having negative views on generic medicines reduced the odds of experiencing a generic switch. No associations were found between generic substitution and gender, drug group, number of different drugs used by the patient, confidence in the health care system and beliefs about medicine in general.

CONCLUSION

Patients who had once experienced a generic switch were more likely to accept a future generic switch within the same ATC code. Negative views on generic medicines were negatively associated with switching, while beliefs about medicine and confidence in the healthcare system had no influence.

Should we have concerns with generic versus brand antimicrobial drugs? A review of issues

Objectives

To explore the issues involving generic versus brand antimicrobial drug products and provide an overview of assessments of equivalence and their potential relevance to health outcomes.

Methods

In April and May 2010, literature searches were performed in MEDLINE and EMBASE for studies involving antimicrobial drug products that convey equivalence or non-equivalence of generic and brand-name drugs.

Key findings

Sixty-six studies involving antibiotics, antifungals, antivirals and antimalarials were identified for analysis. The types of studies were categorized into microbial assays, pharmaceutical assays, bioequivalence and those that assess clinical endpoints. Studies varied markedly on equivalence measures between generic and brand drug products. Thirty-four of 66 (52%) were primarily bioequivalency studies with 30 of 34 (88%) demonstrating positive outcomes for equivalency. Two of 22 studies (9%) involved microbial and/or pharmaceutical assays for quality assurance testing and presented the largest disparity in equivalence. Ten studies compared outcomes of a clinical nature and concluded no significant difference in outcome between generic and brand products. Ten of 66 (15%) studies were published before 2000 and 11 (17%) were conducted in the USA.

Conclusions

In the USA, it is unlikely that use of generic antibiotics and antimicrobials pose a problem for patients with infectious diseases, where quality safeguards exist and patients are informed when generic substitution occurs. However, with expansion of international markets and questionable drug supply chains – particularly with the advent of the internet – consumers and providers should be aware of drug product quality differences that may impact patient outcomes.

[Influence of substitution of brand name for generic drugs on therapeutic compliance in hypertension and dyslipidemia]

OBJECTIVE

To determine therapeutic compliance when brand name amlodipine and simvastatin are substituted for generic drugs, and to determine patients' and physicians' opinions of this substitution.

PATIENTS AND METHODS

We performed an observational study with a control group, based on a review of the medical records in six primary care centers. Participants consisted of patients ≥ 40 years old initiating treatment with a brand name drug (initial period), which was later substituted by a generic drug (final period). The study subgroups consisted of patients with hypertension (amlodipine) or dyslipidemia (simvastatin). The main measures were comorbidity, compliance, treatment length, biochemistry determinations, and patients' and physicians' opinions (interviews). All patients received a brand name drug for a minimum of 1 year followed by a generic drug for a minimum of 1 year (minimum continuation/patient: 24 months).

RESULTS

There were 1,252 patients (groups: 49.5% amlodipine; 50.5% simvastatin). Patients treated with amlodipine (period comparison) showed better compliance (65.8 vs. 61.3%; p=0.037) and blood pressure control (48.5 vs. 45.8%; p=0.039) with the brand name drug. The percentages with simvastatin were 62.8 vs. 58.4% (p=0.041), respectively. A total of 73.6% of the physicians interviewed prescribed generic drugs and 59.2% believed that both types of drug had the same efficacy. Most of the patients interviewed (79.8%; CI: 74.3-85.3%) accepted the substitution; 55.3% (CI: 48.5-62.1%) received the appropriate information but 61.5% were confused by the different products. Lack of compliance was reported by 18.2%.

CONCLUSIONS

In patients receiving amlodipine or simvastatin, compliance decreased with time, independently of the change from a band name to a generic drug.

Biosimilars: controversies as illustrated by rhGH

Abstract Background and scope: Similar biological medicinal products, also called 'biosimilars', are copies of biopharmaceutical products whose patent has expired. Whether biosimilars are truly comparable and interchangeable with their reference biopharmaceutical products in terms of quality, efficacy and tolerability, is still a matter of debate. This review discusses the controversies related to the criteria for regulatory approval of biosimilars. These concerns are illustrated using recombinant human growth hormone (rhGH) biosimilars as an example.

METHODS

Publications on the regulatory approval of biosimilars in general and rhGH biosimilars in particular were searched in MEDLINE by exploding and combining the medical subject heading terms 'human growth hormone', 'efficacy' or 'safety' and the free-text words 'biosimilar', 'biopharmaceutical', 'similar biological medicinal product', 'follow-up biologic' or 'biogeneric'. Searches were limited to full-text English-language articles. The websites from the European Medicines Agency (EMA) and from the American Food and Drug Administration were also consulted. Regulatory status: To obtain regulatory approval of a biosimilar product by EMA, demonstration of comparability with an approved reference biopharmaceutical product in terms of quality, efficacy and tolerability is needed. Thus, comparative quality studies, non-clinical and clinical efficacy and tolerability studies are required. However, in contrast to the reference product, comparative non-clinical pharmacokinetics, safety pharmacology, reproduction toxicology, mutagenicity and carcinogenicity studies are not mandatory to obtain approval of a biosimilar. In addition, comparable efficacy and tolerability only needs to be established by one study in a single population during a limited time interval (12 months) and often allows extrapolation to all other approved indications of the reference product. Consequently, for the currently approved rhGH biosimilars, long-term efficacy and tolerability in all indications has not been proven to the same degree as for the reference products.

CONCLUSIONS

The validity of the current criteria for comparability and interchangeability of biosimilars and their reference products remains controversial. The authors conclude that long-term clinical investigations and systematic monitoring of the efficacy and tolerability of rhGH biosimilars in all indications are needed. In addition, the medico-economical environment should allow physicians to take a free and informed decision about the type of rhGH to be prescribed.