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Current uses and Contraindications for Rapamycin

Rapamycin, better known in medical circles as sirolimus or rapamune, is an immunosuppressant drug used for patients undergoing organ transplants. The drug helps to prevent the body’s rejection of the transplanted organ by temporarily suppressing the immune system of the patient. Rapamycin was approved by the FDA for use in September 1999. The average cost for a non-generic is $37 per 4mg, while the generic is $20 per 4m, although the generic is only distributed by orders from certain Canadian pharmacies. The pill should be taken once daily and be taken as soon as possible after an organ transplant.

Sirolimus was first discovered as a byproduct of the bacterium, Streptomyces hygroscopicus. According to PMID 1102 (PubMed Identifier), rapamycin is a macrocyclic polyketide which exhibits the properties of anti-fungal, anti-tumor, and immunosuppressant uses.

With regards to organ transplants, Rapamycin has been the most useful drug for kidney transplants. Unlike most immunosuppressant drugs, Sirolimus blocks the activation of T-Cells and B-Cells rather than the IL-2 cells that calcunuerin inhibitors such as tacrolimus block. The main advantage of rapamycin is the advantage of low toxicity toward the kidneys as opposed to the use of calcuneurin inhibitors, which are known to cause long-term impairing of kidney and renal function.

The optimal role and usage of rapamycin is still being determined as studies are still ongoing. The primary dangerous immediate side effect of rapamycin is thrombocytopenia, and other issues dealing with the healing of wounds.

Rapamycin is contraindicated in use for organ transplants such as lungs, heart, and liver, as the mortality rate rises dramatically when the drug is used in conjuction with or without a caclunuerin inhibitor.

The use of rapamycin also increases the risks of bodily infections, lymphoma, and certain types of cancers. Allergic reactions to the drug include: hives, difficulty breathing, and swelling of the face or throat. Other side effects include a fast heart rate, pain when breathing, feeling of faintness, coughing up of blood with or without mucus, feeling weak, and easy bruising or bleeding.

Ongoing studies and experimental uses of rapamycin are currently underway, primarily with studies using mice. According to PMC 1356 109, in January 2006 the lifespan of eukaryotes, in this case, mice were increased by 28-38% leading researchers to believe the drug may one day help as an anti-aging medication.

Researchers of rapamycin are also looking at its use to treat various kidney disorders such as autosomal dominant polycystic disease and tuberous sclerosis complex. The usefulness of rapamycin in these disorders is due to the anti-tumor properties that the drug exhibits. During experimentation it has been noted that withdrawal of the drug resulted in the regrowth of tumors.

The British Journal of Clinical Pharmacology, December 2010, said that rapamycin may inhibit HIV replication due to its known use in inhibiting T-cells and down-regulation of the CCR5 coreceptor. Research has also led to the possible usage of the drug in autism and Alzheimer’s, but research is early, and much more scientific study is necessary to establish any positive connections.

Sources:

MedLine Plus – http://www.nlm.nih.gov/medlineplus/druginfo/meds/a602026.html

PubMed – http://www.ncbi.nlm.nih.gov/pubmed/

RX List – Rapamune (Sirolimus) – http://www.rxlist.com/rapamune-drug.htm

Wikipedia – http://en.wikipedia.org/wiki/Sirolimus