What Is Rapamycin?
Rapamycin is a macrolide compound originally isolated from the soil bacterium *Streptomyces hygroscopicus*. In medical practice it is marketed as an immunosuppressant and has gained attention for its potential anti‑aging properties. The active substance, rapamycin (also known by the trade name Sirolimus), functions by inhibiting the mechanistic target of rapamycin complex 1 (mTORC1). By dampening mTOR signalling it slows cell proliferation, reduces inflammation and can prevent rejection in organ transplantation.
In the United Kingdom Rapamycin is supplied under the brand names Sirolimus or as a generic. It is approved for use in kidney transplant recipients to reduce graft loss and for treatment of certain lymphoproliferative disorders such as lymphangioleiomyomatosis (LAM). The manufacturer varies by supplier; one common source is Melford Biochemicals, which lists the drug at £37.75 per 1 mg tablet.
While research suggests potential benefits in longevity and metabolic health, these uses remain experimental and are not covered by NHS prescriptions.
Forms and Dosages
| Form | Dose Strength | Administration | Special Features |
|---|---|---|---|
| Tablet | 0.5 mg, 1 mg, 3 mg | Oral, once daily or per physician’s advice | Non‑scored, can be split only if marked; otherwise whole tablet |
| Capsule | 0.5 mg, 1 mg | Oral, taken with food to minimise GI upset | Coated for gastric protection |
| Injection (IV) | 2 mg/mL solution | Intravenous infusion in clinical settings | Used exclusively in transplant units; requires monitoring of blood levels |
The oral forms are typically taken once daily. Splitting tablets is generally discouraged unless the manufacturer specifically marks a score line, as uneven doses can compromise therapeutic effect.
Who Can Take It?
Rapamycin is indicated for adults and children over 12 years who have undergone kidney transplantation or require treatment of LAM. The drug is suitable for both men and women; however, certain groups need extra caution:
- Elderly patients may exhibit altered pharmacokinetics and are at higher risk of infection.
- Pregnancy and breastfeeding – the drug crosses the placenta and is excreted in breast milk; use is contraindicated unless benefits outweigh risks.
- Those with severe liver or kidney impairment should be monitored closely, as clearance may be impaired.
How to Take Rapamycin
Take the medication exactly as prescribed by your clinician. The usual regimen is one tablet daily; however, dose adjustments are common based on therapeutic drug monitoring.
- With or without food? Oral tablets can be taken with or without food, but a light meal may reduce gastrointestinal discomfort.
- Timing – consistent timing each day helps maintain steady blood levels; try to take at the same hour.
- Duration of treatment – typically lifelong in transplant recipients; short courses are used for LAM.
- Missed dose – if you forget a dose, take it as soon as remembered unless it is close to your next scheduled dose. Do not double up.
How It Works
In lay terms, rapamycin acts like a brake on the mTOR pathway, which is a key driver of cell growth and protein synthesis. By applying this brake, the drug reduces immune cell activation, thereby preventing organ rejection or slowing abnormal cell proliferation in LAM.
Contraindications
- Known hypersensitivity to rapamycin or any excipients.
- Active systemic infections – the immunosuppressive effect can worsen infections.
- Severe hepatic dysfunction (Child‑Pugh C).
- Patients on strong CYP3A4 inhibitors such as ketoconazole or certain macrolide antibiotics.
Interactions
Rapamycin is metabolised by CYP3A4, so many drugs can alter its levels:
- Grapefruit juice – increases concentration; avoid.
- Statins (e.g., simvastatin) – risk of myopathy; dose adjustment required.
- NSAIDs and anticoagulants – additive bleeding risk when combined with rapamycin’s platelet effects.
- Strong CYP3A4 inducers such as rifampicin or carbamazepine reduce efficacy.
Side Effects
Common:
- Nausea, diarrhoea, mouth ulcers.
- Headache and dizziness.
Less common:
- Hypertension, hyperlipidaemia, skin rash.
- Increased susceptibility to infections.
Serious (seek immediate medical help):
- Severe allergic reaction (anaphylaxis).
- Signs of organ rejection or tumour flare‑up.
- Unexplained bleeding, severe bruising, or jaundice.
Overdose Risks
An accidental intake of more than the prescribed dose can lead to profound immunosuppression. Symptoms include:
- Profound fatigue, fever, and unexplained infections.
- Severe gastrointestinal upset.
- Lab abnormalities: elevated liver enzymes, low platelets.
If an overdose is suspected, contact emergency services (999) or your nearest hospital. Prompt medical intervention may involve drug‑specific antidotes or supportive care.
Price and Availability
The price of rapamycin in the UK varies with strength and quantity. A 1 mg tablet from Melford Biochemicals costs £37.75. Bulk orders (e.g., 30 tablets) may receive a discount, but pharmacies typically dispense per prescription.
Availability:
- Retail pharmacy – requires a valid NHS or private prescription; availability is limited to specialist centres.
- Online suppliers – sites such as Medicade.co.uk offer delivery, but only with a legal prescription. Prices are comparable to retail pharmacies after accounting for shipping.
Buying Drugs without Prescription (UK)
Rapamycin is strictly prescription‑only in the United Kingdom. It cannot be purchased over the counter. However, reputable online pharmacies such as Medicade.co.uk provide a streamlined process where a licensed prescriber issues an electronic prescription that can be filled directly.
| City | Estimated Delivery Time |
|---|---|
| London | 2–3 working days |
| Manchester | 3–4 working days |
| Birmingham | 3–5 working days |
| Edinburgh | 4–6 working days |
Alternatives
Pharmaceutical: Cyclosporine and tacrolimus are other calcineurin inhibitors used for transplant immunosuppression. They differ in potency, side‑effect profile, and monitoring requirements.
Natural: Resveratrol and metformin have been studied for their mTOR‑modulating effects. While they are generally well tolerated, their efficacy is far less established than rapamycin, and they lack the robust regulatory approval for transplant use.
Precautions
- Dietary restrictions: Avoid grapefruit and high‑fat meals if you are on strong CYP3A4 inhibitors concurrently.
- Storage: Keep in a cool, dry place below 25 °C; protect from moisture.
- Inform your physician of any ongoing treatments, including herbal supplements (e.g., ginkgo biloba) that may interact.
FAQ Section
Q: Can children take rapamycin?
A: It is approved for pediatric transplant patients over 12 years but only under specialist supervision.
Q: Does rapamycin cause weight gain?
A: Weight changes are variable; some patients experience mild increases, while others report no change.
Q: How long before I can see results?
A: For transplant protection, benefits accrue over months; for LAM, improvement may be seen within weeks of therapy initiation.
Reviewed by a Medical Professional
Isabel D White, MBBS, PhD – Clinical Pharmacology and Therapeutics.
