Has the name on your medicine changed, even though you take the same thing? You may have been given a generic – a medicine with the same active substance as the original brand – or a different brand. Here we explain what they have in common, how they can differ and what the rules are in pharmacies. We also show how to find medicines with the same active substance on this site.
The original (brand-name) medicine
The original medicine is usually licensed on the basis of full data on its quality, safety and effectiveness, including the results of clinical trials. The law calls it the reference medicinal product. On this page we call it the reference medicine: the medicine a generic is compared with.
The original medicine has a period of protection. Another company can apply for a generic licence once the original has been licensed for 8 years. The application can use the original company’s data. But the generic cannot be sold until 10 years after the original was licensed in the UK. The 10 years become 11 if a new use with a significant clinical benefit was added in the first 8 years. Patents can delay generics further.
Generic medicines
A generic contains the same active substance in the same form as the original medicine (for example a tablet). When the forms are compared, tablets and capsules that you swallow and that release the medicine straight away count as the same form. The company must show that the generic is bioequivalent. This means it gives comparable levels of the active substance in the blood. Different chemical forms of the same substance (for example different salts) count as the same substance. The exception is when they differ significantly in safety or effectiveness. The MHRA licenses a generic only if it meets strict safety and quality standards, like every medicine in the UK.
The NHS says generics are just as effective as the brand but cost far less, which is why the NHS uses them more often. The generic name of a medicine is the name of its active substance – for example “paracetamol” rather than a brand name such as Panadol.
A generic can differ from the original medicine in:
- its name, packaging, appearance and taste,
- its excipients (other ingredients) – these can matter for some people, for example with an allergy. The patient leaflet lists all the ingredients.
Prescriptions and the pharmacy
The NHS Specialist Pharmacy Service describes the rules like this. The NHS prefers to prescribe medicines by their generic name – the name of the active substance. Each active substance has only one generic name, but it may have many brand names. When your prescription gives the generic name, the pharmacist can give you any suitable product with that substance. So the brand or manufacturer may change from one prescription to the next.
When your prescription names a brand, a community pharmacist can normally give you only that brand – unless a Serious Shortage Protocol (SSP) applies.
Health ministers can issue an SSP when there is, or may be, a serious shortage of a prescription-only medicine in the UK or part of it. Each protocol says which medicines can be supplied instead, in which parts of the UK it applies and for how long. Under an SSP, the pharmacist can give you a different strength, form or quantity, or another medicine named in the protocol, without going back to the prescriber. They can only do this if you agree and they think it is right for you. Otherwise they refer you back to your prescriber.
For some medicines it matters which brand or manufacturer you take. In these cases the doctor prescribes a particular brand or manufacturer:
- The NHS Specialist Pharmacy Service lists medicines where the brand matters – for example ciclosporin, tacrolimus, lithium and some modified-release medicines (medicines that release the active substance slowly).
- The MHRA advises doctors to keep people who take certain epilepsy medicines (carbamazepine, phenobarbital, phenytoin and primidone) on one manufacturer’s product. For some other epilepsy medicines, the doctor decides together with the patient.
If the name or look of your medicine changes, ask your pharmacist what has changed. Two medicines with the same active substance may have different names. Make sure you are not taking both by mistake – you could take too much. For example, the NHS advises not to take paracetamol at the same time as other medicines containing paracetamol, such as cold and flu remedies.
Biological and biosimilar medicines
Biological medicines are made from, or come from, a biological source. They are large, complex molecules – for example insulins and vaccines. A biosimilar is a biological medicine that contains a version of the active substance of a medicine that is already licensed (the reference medicine). It is highly similar to the reference medicine, but it is not a generic: complex biological molecules cannot be made exactly the same.
According to the MHRA, a licensed biosimilar can be used instead of its reference medicine (or instead of another biosimilar of that medicine) with the same expected effect. The prescriber and the patient decide together whether to switch. A pharmacist must not swap a biological medicine without asking the prescriber (except under a Serious Shortage Protocol). The NHS Specialist Pharmacy Service, following MHRA advice, says biological medicines should be prescribed by brand name, so that the product is not switched by mistake.
Parallel imports
A medicine licensed in a country of the European Economic Area (the EU countries, Iceland, Liechtenstein and Norway) can be brought in and sold in the UK by an importer as a parallel import. It must have no therapeutic difference from the UK product. The importer needs a parallel import licence (PLPI) from the MHRA. The pack may be relabelled or repackaged. It must contain all the safety information of the UK product, and most packs must have braille.
Why medicines with the same active substance have different leaflets
Each licensed product must have its own leaflet. The leaflets of the original medicine and of generics can differ – for example in the name, the excipients or the look of the tablets. Read the leaflet that comes with your medicine.
How to find medicines with the same active substance on this site
- Active substance pages – in the list of active substances, each substance has a page with all the medicines on this site that contain it, alone or in a combination.
- “Still supplied” – for a medicine listed as discontinued or not available, this row shows other brands or manufacturers with the same active substance, strength and form in the NHS Dictionary of Medicines and Devices (dm+d).
- “Similar medicines” – this row shows medicines from the same or a related ATC group. Similar does not mean you can swap one for the other: ask your doctor or pharmacist before you change a medicine.
More guides: How to read a patient leaflet · Glossary · Medicine facts explained
Sources
We based this page on these documents and checked the facts against them on 4 November 2026. For each one we say what we took from it.
- The Human Medicines Regulations 2012, regulation 51B – a generic of a reference medicinal product authorised for at least 8 years, relying on its data; no sale before 10 years from the grant of the UK licence of the reference product, 11 years with a new indication of significant clinical benefit authorised in the first 8 years.
- MHRA: Types of application (legal basis), section 2.2 – a generic has the same active substance and pharmaceutical form as the reference product and is bioequivalent; dm+d editorial policy (DOCX) – bioequivalence shown by comparable blood levels; immediate-release oral forms count as the same form; salts, esters and other derivatives count as the same active substance unless they differ significantly in safety or efficacy.
- NHS: Medicines information – brand names versus generics: patents; the generic name is the name of the active ingredient, generics are just as effective but cost far less, licences are granted by the MHRA only if strict safety and quality standards are met, a changing name may mean a different brand or the generic.
- NHS Specialist Pharmacy Service: Prescribing by generic or brand name – the NHS policy of generic prescribing; one generic name, many brand names; prescribed by generic name = any suitable product, prescribed by brand = only that brand unless a Serious Shortage Protocol is in place; differences in name, appearance or taste; the MHRA advises that biological medicines are prescribed by brand name.
- NHS Specialist Pharmacy Service: Example medicines to prescribe by brand name – ciclosporin, tacrolimus, lithium, modified-release preparations.
- MHRA Drug Safety Update: Antiepileptic drugs – updated advice on switching between different manufacturers’ products – category 1 (carbamazepine, phenobarbital, phenytoin, primidone): keep the patient on a specific manufacturer’s product; category 2: decided by clinical judgement with the patient.
- The Human Medicines Regulations 2012, regulation 226A – Serious Shortage Protocols: issued by the Ministers when the UK or part of it is or may be in serious shortage of a prescription-only medicine; a different strength, quantity or form, another medicine or a similar biological medicine; the period and the parts of the UK where it applies; the pharmacist’s professional judgement; NHSBSA: Serious Shortage Protocols – the patient has to agree; NHSBSA: questions and answers (PDF) – pharmacists must otherwise dispense the prescription, referral back to the prescriber.
- MHRA: Guidance on the licensing of biosimilar products – definition of a biosimilar; interchangeable with the reference product and other biosimilars; switching decided by the prescriber with the patient; no substitution at the pharmacy without consulting the prescriber.
- NHS Specialist Pharmacy Service: Understanding biological and biosimilar medicines – biological medicines are made or derived from a biological source (insulins, vaccines); a biosimilar is highly similar to the reference product; prescribing by brand name.
- MHRA: Medicines – apply for a parallel import licence – parallel imports from the EEA with no therapeutic difference from the UK product, the PLPI licence, relabelling and repackaging, the safety information of the UK product, braille except for products given only by healthcare professionals; GOV.UK: Countries in the EU and EEA – the EEA includes the EU countries and also Iceland, Liechtenstein and Norway.
- MHRA: Medicines: packaging, labelling and patient information leaflets – each product authorised under a marketing authorisation must have its own leaflet.
- NHS: Paracetamol for adults – do not take it with other medicines containing paracetamol; Panadol as a brand of paracetamol.
- NHS Specialist Pharmacy Service: Understanding excipients in medicines – excipients can matter for some people; Human Medicines Regulations 2012, Schedule 27 – the leaflet gives the full composition.
This page explains the general rules for licensing and supplying medicines and does not replace advice from a doctor or pharmacist. Last updated 4 November 2026. Found a mistake? Email us at info@patient-info.co.uk.