Are Sirolimus and Rapamycin the same drug?

Yes, sirolimus and rapamycin refer to the same compound. Sirolimus is the name used for FDA-approved medications, while rapamycin was the original name given by researchers after its discovery. Clinically, this drug is widely used to prevent organ transplant rejection and is known for its role in inhibiting the mTOR (mechanistic target of rapamycin) pathway, which is essential in cell growth and immune regulation.

What Is Sirolimus (Rapamycin)?

Sirolimus is a macrolide compound classified as an immunosuppressant and mTOR inhibitor. Chemically, it is a natural macrocyclic lactone produced by the bacterium Streptomyces hygroscopicus. Its primary medical use is to suppress the immune system, especially in patients who have received organ transplants, to prevent rejection.

Brief History

• Discovery: Sirolimus was first isolated in 1972 from soil samples collected on Easter Island (Rapa Nui), which inspired the original name “rapamycin”.
• Development: Initially investigated as an antifungal agent, it was later found to have potent immunosuppressive and antiproliferative effects, leading to its use in medicine.
• Brand Names: Sirolimus is marketed under several brand names, most notably Rapamune. Other formulations include Fyarro (for certain cancers) and Hyftor (for topical use).

Why Are There Two Names?

While sirolimus and rapamycin are chemically identical, they are known by different names depending on the context. Understanding why this single compound has two names helps clarify how it is referenced in scientific research versus clinical practice. The distinction arises from naming conventions used in drug development and regulation.

• Rapamycin: This is the original name, derived from “Rapa Nui,” the native name for Easter Island, where the compound was discovered. It is commonly used in scientific literature and research contexts.
• Sirolimus: This is the International Nonproprietary Name (INN), adopted for regulatory and clinical use, including FDA approval. The INN system ensures each drug has a unique, globally recognized generic name for prescribing and labeling. “Sirolimus” is the term found on prescriptions, drug labels, and in clinical guidelines.

Both names refer to the exact same active compound. The difference is purely in naming conventions, not in the drug’s chemical structure or effects.

Summary

Sirolimus and rapamycin are two names for the same drug, a groundbreaking immunosuppressant and mTOR inhibitor with a unique history and important role in modern medicine.

See also:

Related medical questions

• What Is Sirolimus’s MOA (Mechanism of Action)?

Drug information

• Sirolimus Information for Consumers
• Sirolimus prescribing info & package insert (for Health Professionals)
• Side Effects of Sirolimus (detailed)
• Sirolimus user reviews (8)

Related support groups

• Sirolimus (2 questions, 10 members)
• Organ Transplant - Rejection Prophylaxis (4 questions, 19 members)

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