Biosimilars

Overview

A biosimilar is a medicine designed to work in the same way as an existing 'biologic' medicine whose patent has expired. A biologic is a medicine made by living cells — often bacteria or specially grown animal cells — rather than mixed up from chemicals in a lab. Biologics are usually given by injection or a drip (infusion), and they are used for many long-term conditions, such as inflammatory arthritis, Crohn's disease and ulcerative colitis, psoriasis, some types of cancer, some kidney problems and some eye conditions. When the original maker's patent runs out, other companies can make a very close version of the same medicine. That close version is called a biosimilar. It is not an exact copy, because medicines grown in living cells can never be exactly identical. Instead, it is 'highly similar' — close enough that doctors and regulators expect it to work and behave in the same way for patients.

Yes. Biosimilars are now widely used in many countries, and more are being approved each year. Health services often encourage their use because they can cost less than the original medicine while offering the same expected benefits. If you are already on a biologic medicine, there is a good chance your clinic has talked about, or will talk about, biosimilars with you.

Biosimilars are relevant to anyone who takes, or may need, a biologic medicine. That includes people with inflammatory joint and skin conditions, inflammatory bowel disease, some kidney and blood conditions, some types of cancer, some eye conditions, and some hormone-related conditions. They can be used in adults, and sometimes in children and teenagers, depending on the medicine and the condition.

Symptoms

Common symptoms

• Most people notice no difference at all after starting or switching to a biosimilar — the aim is for it to feel the same as the original medicine.
• Some people get mild soreness, redness or a small bump where an injection is given. This usually settles on its own.
• Some people feel a little tired or fluey for a day after a drip (infusion). This is usually mild and passes.
• The symptoms of your underlying condition should follow the same pattern as before — improving if the medicine is working, or flaring if your disease is active.

Symptoms in children

• Children can be prescribed biosimilars for some conditions, using the same safety checks as the original medicine.
• Young children may be upset by injections or clinic visits — a numbing cream, a comfort toy, or a favourite song can help.
• Watch for soreness at the injection site, and mention any new or unusual symptoms to your child's care team.
• Children on biologic medicines are usually checked regularly for growth, blood counts and general wellbeing.

Symptoms in older adults

• Older adults are often taking several medicines at once, so it is worth asking your pharmacist to review them all together.
• Tiredness, a mild fever or feeling 'not quite right' after a dose is worth mentioning — it is easier to treat small problems early.
• Frailty and other health conditions do not mean biosimilars are unsuitable, but your care team may want to monitor you a little more closely.
• If you need help remembering doses or getting to appointments, ask about support — many clinics offer this.

Causes

Main causes

• Biologic medicines are protected by patents. When a patent runs out, other companies are allowed to make a highly similar version — a biosimilar.
• Making biologics is complex and expensive. Biosimilars create competition, which can lower prices and improve access.
• Regulators and health services support biosimilars because they can free up money to treat more patients.
• Biosimilars exist because biologics work well for many long-term conditions but can be costly to health systems and patients.

Risk factors

• Having had an allergic reaction to a biologic medicine in the past
• Being pregnant, planning a pregnancy, or breastfeeding — always discuss this with your team first
• Having an infection at the time a dose is due
• A weakened immune system, or taking other medicines that affect the immune system
• Recently having a vaccine, especially a live vaccine — check with your care team
• Travelling to countries where certain infections are common

When to see a doctor

See a doctor urgently if:

• You have a fever of 38°C or above, or feel hot and shivery
• You have signs of an infection — a cough, burning when passing urine, or a red, hot, spreading area of skin
• You have a severe reaction at an injection site, or any swelling of the face, lips or tongue
• You feel very unwell, dizzy, or unusually breathless
• You develop a new rash, severe headache, or changes in your vision

Book a routine appointment if:

• You are due a review of your treatment, or your clinic has offered you a switch to a biosimilar
• You have questions about how a biosimilar compares with your current medicine
• You are worried about side effects, even mild ones
• You are planning a pregnancy, or are going to travel or have a vaccine
• You have missed a dose, or are unsure how to store your medicine
• Your condition seems to be getting worse, or not improving as expected

Diagnosis

Biosimilars are not something you are 'diagnosed' with — they are medicines, and the question is whether one is right for you. Before a biosimilar can be prescribed, it must pass a strict approval process. Regulators look at the medicine's structure, how it behaves in the body, and results from studies in patients. They check that any differences from the original are so small they would not matter in real life. When you are offered a biosimilar, your doctor will consider your condition, how well your current treatment is working, any side effects you have had, national guidance, and cost and supply. Switching is normally done with your agreement, and your team should explain the reasons clearly.

Tests that may be done

• Lab studies comparing the biosimilar with the original medicine
• Studies in people to compare how well it works and how safe it is
• Ongoing monitoring of side effects once a medicine is in wide use
• Before or during treatment: blood tests to check your blood counts, liver and kidneys
• Screening for infections such as tuberculosis or hepatitis before starting some biologic medicines
• Regular checks of how active your condition is, such as joint counts, skin scores or bowel symptoms

What to expect at your appointment

You will usually have a conversation with your doctor, nurse or pharmacist about the medicine, including what it is, how it is given, and what to watch for. If you are switching from the original medicine, you may be seen a little more often at first so your team can check how you are doing. Expect questions about side effects, infections, vaccines and any travel plans. Write down your questions beforehand — it is easy to forget them in the appointment.

Treatment

Biosimilars are used in exactly the same way, and for the same conditions, as the original biologic medicines they are based on. They can be given as an injection under the skin, into a muscle, or as a drip (infusion) in a clinic or hospital. Sometimes you or a family member can be trained to give the injection at home. The dose and schedule are worked out by your care team based on your condition and how you respond. Biosimilars are not 'weaker' versions — they are designed to have the same effect.

Self-care at home

• Keep a simple record of your doses, and note any side effects with the date and time.
• Store your medicine as instructed — many need to be kept in a fridge, and some can be kept at room temperature for a limited time.
• Rotate injection sites and use clean hands and a clean site each time.
• Tell every healthcare professional you see that you are on a biologic medicine — including dentists, pharmacists and travel clinics.
• Ask your care team before having any vaccine, especially a live vaccine.
• Carry a card or note that lists your medicine and your clinic's contact details.
• Plan ahead for travel: ask about a travel letter, carrying medicines in hand luggage, and keeping them cool.
• Never stop or change your medicine because you feel better, or because you feel unwell — talk to your team first.

Medical treatments

Biosimilars are given by injection or infusion, usually on a set schedule, and are often used alongside other treatments such as anti-inflammatory medicines, steroid courses or pain relief. Your care team will decide the dose and how often you need it, and will adjust based on how your condition responds and how you tolerate it. Some clinics give the first dose under observation so any reaction can be spotted quickly. Regular reviews — including blood tests and checks of your symptoms — help make sure the treatment is working and remains safe. If a biosimilar does not suit you, your team can discuss other options.

Living with this condition

Most people fit biologic treatment around normal life. Injections can often be done at home on a day that suits you, and infusions are usually planned in advance so you can arrange time off work or school. Keep your medicine at the right temperature and keep a spare dose plan in mind for weekends and holidays, when clinics may be closed. It helps to know who to call if something goes wrong — write the number down or save it in your phone.

Lifestyle tips

• Keep your routine vaccinations up to date, after checking with your care team
• Wash your hands well and avoid close contact with people who have infections like chickenpox or shingles
• Take care with food hygiene — avoid raw or undercooked foods if your immune system is weaker
• Protect your skin from the sun, as some biologic medicines make you more sensitive to sunlight
• Avoid smoking, and limit alcohol, as both can affect how well long-term conditions are managed
• Keep a simple symptom diary so you can spot patterns and share them at appointments

Diet and exercise

There is no special diet or exercise plan for biosimilars themselves — the aim is a balanced, enjoyable way of eating that suits your condition and keeps your energy steady. Regular movement helps with joint stiffness, mood and sleep. Gentle activity such as walking, swimming, cycling or stretching is a good starting point. If you have a flare-up, scale back and rest, then build up again slowly. Ask your care team or a physiotherapist for guidance that fits your condition, and speak to your doctor before starting anything strenuous.

Mental health and emotional wellbeing

Long-term conditions and their treatments can bring worry, tiredness and low mood, and being asked to switch medicines can add uncertainty. Those feelings are very common and worth talking about. Mention them at your appointments — clinics can offer extra support, and some have psychologists or nurse specialists who help with the emotional side of treatment. If at any point you have thoughts of harming yourself, contact your local emergency number or a crisis line in your country straight away, and reach out to someone you trust.

Prevention

Biosimilars are medicines, not illnesses, so there is nothing to prevent. What you can do is use them safely: understand what you are taking, follow the storage and dose instructions, tell your care team about any side effects, and ask questions before any change. Good communication with your clinic is the best protection against problems.

Vaccines

Some biologic medicines affect how well your body responds to vaccines, and live vaccines are usually avoided while you are on them. Always check with your care team before booking any vaccination, including travel vaccines. It also helps to make sure the people you live with are up to date with their routine vaccines.

Screening programmes

Before starting some biologic medicines, your care team will check for infections that can become active later, such as tuberculosis and hepatitis. You may also be offered routine checks over time — blood counts, liver and kidney tests, and checks on how active your condition is. If you are due a cancer screening invitation, it is still worth attending; just let your clinic know.

Complications

If left untreated

• Stopping treatment without advice can let your underlying condition flare, which may lead to joint damage, bowel complications or other lasting problems
• Missing doses or stopping and starting can make the medicine work less well over time
• Untreated inflammation can affect sleep, mood, work and daily activities
• If you develop an infection while on treatment and ignore it, it can become serious — so early contact with your team matters

Long-term outlook

The outlook is generally positive. Biosimilars have been studied closely and are used safely in many countries around the world. For most people, they work as well as the original medicine, with the same kind of side effects. They also help health systems keep these effective treatments available to more people. If one medicine does not suit you, there are usually other options, and your care team will work with you to find the right one.

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