An mTOR inhibitor immunosuppressant
Sirolimus
An immunosuppressant used to prevent transplant rejection and in some rare conditions, monitored by blood tests.
What is Sirolimus?
Sirolimus is an immunosuppressant from the mTOR inhibitor group, used mainly to prevent rejection after a kidney transplant and in some rarer conditions. It works differently from the calcineurin inhibitors, calming a part of the immune system, but like them it increases the risk of infections. It has a narrow safety margin, so regular blood tests are needed to keep the level right and to watch for side effects such as raised blood fats, mouth ulcers and slower wound healing. It must be taken consistently in relation to food and grapefruit juice should be avoided.
Education and reference only. This is a plain-language guide to Sirolimus — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Sirolimus is an mTOR inhibitor, a type of immunosuppressant that blocks a different immune signal from ciclosporin and tacrolimus. It is used to stop the body rejecting a transplanted kidney and in some specific conditions, sometimes alongside or instead of a calcineurin inhibitor. It is taken as tablets or a liquid by mouth. Because it works on the immune system as a whole, it is a specialist medicine used under close supervision with regular blood tests.
How it works
Sirolimus blocks a protein called mTOR inside immune cells, which slows their growth and multiplication and so dampens the immune response that would otherwise attack a transplanted organ. Because mTOR is also involved in cell growth and healing, the medicine can slow wound healing and affect blood fats. As with other transplant medicines, a quieter immune system means a higher risk of infections. The amount in the blood matters, so treatment is guided by regular blood-level tests.
Company & origin
Originated / developed by: Generic (originally Pfizer).
An mTOR inhibitor used in the UK to prevent kidney transplant rejection and in some specific conditions.
Practical use
How to take Sirolimus
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it exactly as prescribed, at the same time each day and in a consistent way in relation to food.
- Avoid grapefruit and grapefruit juice, which can raise the level of sirolimus in your body.
- Attend all your blood tests, as these guide your dose and check for side effects.
- Tell your team well before any planned surgery, as sirolimus can slow wound healing and may be paused.
- Report mouth ulcers, leg swelling or signs of infection promptly, and never stop the medicine suddenly without advice.
- Tell every prescriber and pharmacist that you take sirolimus, as many medicines and grapefruit interact with it.
Weighing it up
Advantages & disadvantages of Sirolimus
Advantages
- Prevents transplant rejection by a different route from the calcineurin inhibitors, which can suit some people.
- May be useful where calcineurin inhibitors are causing kidney problems, as part of a tailored regimen.
- Available as tablets and liquid, with dosing guided by blood-level tests.
Disadvantages
- Has a narrow safety margin and needs regular blood tests and monitoring.
- Commonly raises blood fats and can cause mouth ulcers, leg swelling and slower wound healing.
- Increases the risk of infections and certain cancers, and interacts with many medicines and grapefruit.
Practical use
Good to know
Sirolimus has a narrow therapeutic range, so blood-level tests are central to keeping it safe and effective. It commonly raises the fats in the blood (cholesterol and triglycerides), which may need treating, and it can cause mouth ulcers, swelling of the legs and slower wound healing, so it is often paused around surgery. It increases the risk of infections and, with long-term use, certain cancers, so sun protection and prompt reporting of infections matter. It should be taken consistently in relation to food each day, and grapefruit juice should be avoided as it raises the level. Many other medicines interact with it, so always check before starting anything new, and never stop it suddenly without advice.
Who should not take it / use with caution
- People around the time of major surgery may need it paused because it slows wound healing.
- It is generally avoided in active untreated infections and used cautiously with very high blood fats.
- Those unable to attend regular monitoring blood tests are not suitable without arrangements in place.
Monitoring
- Regular blood tests to measure the sirolimus level and keep it within the target range.
- Checks of blood fats (cholesterol and triglycerides), kidney function and blood counts.
- Ongoing watch for infections, mouth ulcers, wound healing and other side effects.
Side effects
- Raised cholesterol and triglycerides, mouth ulcers, leg swelling and increased infection risk are common.
- Anaemia or low blood counts, joint pain, acne-like rashes and slower wound healing.
- Less commonly, lung inflammation and a higher risk of certain cancers with long-term use.
Key interactions
- Grapefruit juice and medicines such as some antifungals and certain antibiotics can raise its level.
- Other medicines, including some epilepsy drugs and St John's wort, can lower its level and risk rejection.
- Care is needed when combining it with calcineurin inhibitors or other medicines that affect the kidneys.
Available as: Tablets and oral liquid taken by mouth.
Answers
Sirolimus: frequently asked questions
How is sirolimus different from tacrolimus?
It is an mTOR inhibitor and blocks a different immune signal from the calcineurin inhibitors, which is why it can be chosen when those cause kidney problems.
Why does it raise my cholesterol?
Sirolimus commonly increases blood fats; your levels are monitored and may need treating with diet changes or other medicines.
Why should I tell my team before surgery?
Sirolimus can slow wound healing, so it is sometimes paused around planned operations to reduce problems.
Why do I keep getting mouth ulcers?
Mouth ulcers are a common side effect of sirolimus; tell your team, as they can advise on managing them.
Can I stop it if I feel well?
No. Stopping suddenly risks rejection of your transplant, so never change or stop it without specialist advice.
Authoritative sources
- BNF
- NICE CKS
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