If you’ve ever picked up a prescription and noticed a different brand name on the box than what you expected, you might have wondered: Is this medicine the same? Will it work just as well?
In the UK, the NHS encourages prescribing generic medicines where possible.1 It’s a cost-saving measure that helps ensure the healthcare system remains sustainable. But many patients worry that switching from a well-known branded drug to a ‘generic’ might affect their treatment. Truth be told, it might not.
What is a generic medicine?
A generic medicine is a copy of a branded drug that is no longer protected by a patent.2 Once a branded drug’s patent expires, other companies can manufacture and sell the same medicine under a different name, usually at a lower cost. Generic medicines must meet the same strict strict UK regulatory and quality standards, which means they must:1
Contain the same active ingredient as the original
Be the same strength and form (tablet, capsule, liquid, etc.)
Have the same mechanism of action
In short, generic medicines must be “bioequivalent” to the branded version. This means they deliver the same amount of active ingredient into the bloodstream within a tight range of 80-125% compared to the original.3 This range is considered clinically insignificant in most cases, ensuring that generics are just as effective.
Why are generics cheaper?
Branded medicines are often more expensive because pharmaceutical companies spend years developing them, running clinical trials, and obtaining patents. They have a limited period of exclusivity to recoup those costs. Once that patent expires, generic manufacturers can enter the market without those hefty research expenses, meaning they can sell the drug at a fraction of the price.
The NHS saves hundreds of millions of pounds each year by using generic medicines whenever possible. In England, over 80% of prescriptions are written generically.4
Do generics work the same way?
For most people, yes. The key active ingredient is identical, meaning the therapeutic effect should be the same. However, there are some differences:
Inactive ingredients: Generic medicines may contain different fillers, colourings, or preservatives.5 While these usually don’t affect efficacy, they can trigger allergies or intolerances in some people.
Appearance: Certain patents prevent generic manufacturers from copying the shape or colour of branded drugs, which can sometimes confuse patients.
Mechanism: While the bioequivalence range is tightly controlled, some individuals may notice slight differences in how their body reacts—especially with medicines that have a narrow therapeutic index (more on this below).
When does it matter?
For most conditions, switching to a generic is straightforward and safe. However, there are cases where prescribing by brand is required:
1. Epilepsy
Anti-epileptic drugs (AEDs) must be prescribed by brand to ensure consistent blood levels.6 Even small variations in absorption between brands could increase the risk of seizures.
2. Controlled drugs
Strong painkillers (like morphine), sedatives, and medications for ADHD often require brand-specific prescribing to avoid fluctuations in drug levels that could lead to withdrawal symptoms or reduced effectiveness.2
3. Certain skin treatments and hormonal medicines
Hormone replacement therapies (HRT), contraceptive pills, and some topical treatments should be prescribed by brand to ensure consistent formulation and efficacy.7
The MHRA (Medicines and Healthcare products Regulatory Agency) advises doctors to be cautious when switching patients between brands of these types of medicines.
The controversy around generic substitution
In hospitals, pharmacists routinely swap out branded drugs for generics without issue. However, in GP surgeries and community pharmacies, the debate over whether pharmacists should be allowed to automatically substitute generic drugs remains contentious.2 Here’s why:
The NHS wants savings. Generic prescribing is one of the easiest ways to cut costs without compromising care.8
Some doctors and patients worry about differences.9 While regulators insist generics are just as good, some patients report feeling different side effects or noticing changes in effectiveness when switching.10
Pharmaceutical companies fight back. Drug companies argue that their branded products offer better reliability, leading them to push for brand loyalty among both prescribers and patients.11
The psychological effect
It’s worth noting that some patients perceive generic medicines as being “weaker” or “less effective” simply because they cost less. Studies show that people sometimes experience better results with branded drugs due to the placebo effect—believing a medicine is better can actually make it seem more effective.9,12
The numan take
For most people, generic medicines are just as safe and effective as their branded counterparts. The NHS promotes their use because they provide the same benefits at a lower cost, freeing up funds for other areas of patient care. The choice between them often comes down to cost, regulations, and individual patient needs. Your best bet is to stay informed, ask questions, and take charge of your own health.
References
Duerden MG, Hughes DA. Generic and therapeutic substitutions in the UK: are they a good thing? Br J Clin Pharmacol [Internet]. 2010;70(3):335–41. Available from: http://dx.doi.org/10.1111/j.1365-2125.2010.03718.x
Department of Health. The proposals to implement ‘generic substitution’ in primary care, further to the Pharmaceutical Price Regulation Scheme (PPRS) 2009. Consultation document 2010. Available at http://www.dh.gov.uk/en/Consultations/Liveconsultations/DH_110517 (last accessed 5 July 2010)
Committee for Proprietary Medicinal Products. Notes for Guidance on the Investigation of Bioavailability and Bioequivalence. London: European Medicines Evaluation Agency; 2001.
Department of Health. The proposals to implement ‘generic substitution’ in primary care, further to the Pharmaceutical Price Regulation Scheme (PPRS) 2009. Consultation document 2010. Available at http://www.dh.gov.uk/en/Consultations/Liveconsultations/DH_110517
Desai RJ, Sarpatwari A, Dejene S, Khan NF, Lii J, Rogers JR, et al. Comparative effectiveness of generic and brand-name medication use: A database study of US health insurance claims. PLoS Med [Internet]. 2019;16(3):e1002763. Available from: http://dx.doi.org/10.1371/journal.pmed.1002763
Colgan S, Faasse K, Martin LR, Stephens MH, Grey A, Petrie KJ. Perceptions of generic medication in the general population, doctors and pharmacists: a systematic review. BMJ Open [Internet]. 2015;5(12):e008915. Available from: http://dx.doi.org/10.1136/bmjopen-2015-008915
Figueiras MJ, Cortes MA, Marcelino D, Weinman J. Lay views about medicines: the influence of the illness label for the use of generic versus brand. Psychol Health [Internet]. 2010;25(9):1121–8. Available from: http://dx.doi.org/10.1080/08870440903137170
Moynihan R, Heath I, Henry D. Selling sickness: the pharmaceutical industry and disease mongering. BMJ [Internet]. 2002;324(7342):886–91. Available from: http://dx.doi.org/10.1136/bmj.324.7342.886
MacKrill K, Kleinstäuber M, Petrie KJ. The effect of rebranding generic medicines on drug efficacy and side effects. Psychol Health [Internet]. 2019;34(12):1470–85. Available from: http://dx.doi.org/10.1080/08870446.2019.1616088
