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The clinical equivalence of brand-name beta-blockers and their generic counterparts Posted 21/01/2011

The healthcare systems of the world are all under pressure to reduce costs and using generic substitution for the initially prescribed, more expensive equivalents is an obvious area to investigate. However, as a report reiterated in 2010, treatment decisions should not be based on economic grounds alone, for this would not be in the patient's best interest and would therefore be unethical. What is needed is an opinion based on the evidence available regarding therapeutic equivalence [1].

Beta-blockers have been used in cardiological treatment since the 1970s. They are routinely used to treat high blood pressure and/or one or more of the following conditions: angina, high heart rate, arrhythmia, heart failure and a history of previous heart attacks

Nine studies on the clinical equivalence of beta-blockers

Kesselheim et al. identified nine articles that compared clinical outcomes in generic and brand-name beta-blockers [2]. The drugs that these studies compared were metoprolol, atenolol, carvediol and propranolol. The long-acting metoprolol was evaluated in a double-blind randomised controlled trial in outpatients with stable angina and one retrospective cohort study of 3,649,285 insurance members with 49,673 subjects with claims data for beta-blockers in their statutory health insurance data over four years. This latter study identified patients prescribed with beta-blockers and found no differences in clinical outcomes after controlling for sociodemographic data and co-morbidities.

A randomised, double-blind controlled bioequivalency study with 12 subjects taking one dose of either tenormin or atenolol reported no significant differences in the drugs' ability to reduce heart rate and blood pressure. Another, similarly designed, bioequivalence study with 24 subjects also reported no difference in the clinical parameters of heart rate, blood pressure, PR segment length of the ECG or tolerability when taking either coreg or carvediol.

Tenormin was not found to be superior to its generic version in one randomised clinical trial and two bioequivalency studies when compared using the clinical endpoints of lowering heart rate and blood pressure. A retrospective cohort study of patients switching from short- to long-acting beta-blockers reported that, initially, more adverse effects occurred in patients taking the generic propranolol than those taking the brand-name Inderal, but this effect was extinguished when all patients were switched to long-acting Inderal. A later randomised controlled trial, funded by the National Institute of Health, found no clinical differences in patients taking the three versions of propranolol.

Conclusion

Although there are limitations in extrapolating the results of these, mainly small-scale, investigations, the empirical results obtained to date appear to demonstrate, not only the bioequivalence, but also the efficacy and safety of the lower cost generic versions of expensive brand-name prescription beta-blockers. However, future studies with an adequate design and power are required to prove actual equivalence.

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References

1. Johnston A. Challenges of therapeutic substitution of drugs for economic reasons: focus on CVD prevention. Curr Med Res Opin. 2010;26(4):871-8.

2. Kesselheim AS, Misono AS, Lee JL, Stedman MR, Brookhart MA, Choudry NK, et al. Clinical equivalence of generic and brand-name drugs used in cardiovascular disease: a systematic review and meta-analysis. JAMA. 2008;300(21):2514-26.

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