Medications that Act on Microtubules in Humans and Parasites

Microtubules can be thought of as the supportive scaffolding inside of cells. These cellular elements give cells their shape and are essential in the movement of many types of cells from one location to another. There are drugs that act on microtubules in human cells and within parasites that are used for many common medical conditions. Medications that work on microtubules include Griseofulvin, Colchicine, Mebendazole, Thiabendazole, Vincristine and Vinblastine.

Griseofulvin is a medication that is effective only against dermatophytes. Common fungal infections such as ringworm and athlete's foot are caused by dermatophytes. Once Griseofulvin enters the dermatophyte, it works by attaching to tubulin, a molecule required for the formation of microtubules, and inhibits microtubule polymerization. The dermatophytes are thus unable to reproduce in the presence of Griseofulvin and eventually die.

Colchicine is a prescription drug used in the treatment of gout. It is effective both for acute attacks and in preventing flares of gout. Colchicine works by preventing the migration of polymorphonuclear neutrophils or "PMNs" which rely on microtubules for their cellular movement. Neutrophils normally migrate to gout affected joints and are largely responsible for the intense inflammatory symptoms that occur.

When Colchicine is used on a chronic basis for gout prophylaxis (prevention) there is a risk of agranulocytosis and/or aplastic anemia. Agranulocytosis is a condition of abnormally low levels of white blood cells called granulocytes. Aplastic anemia is a dangerous condition in which all types of blood cells drop to low levels due to decreased production within the bone marrow. Individuals who develop aplastic anemia while taking Colchicine will have low levels of white blood cells, red blood cells and platelets on a complete blood count test.

Mebendazole and Thiabendazole are antihelminthic prescription medications. These two drugs work by inhibiting microtubule formation in specific parasites known as helminths. The helminthes include pinworms (Enterobius vermicularis) and whipworms (Trichuris trichiura). When exposed to Mebendazole or Thiabendazole, the parasites slowly become immobile and eventually die.

Vincristine and Vinblastine are chemotherapeutic agents that bind to tubulin, a building block of microtubules, and thereby inhibit the polymerization of microtubules. These two powerful prescription drugs are commonly used in lymphoma patients and carry serious potential side effects. For example, Vincristine can cause a peripheral neuropathy, while Vinblastine can cause myelosuppression (inhibition of cell formation in the bone marrow).

By acting against the break down or build up of microtubules, the above medications have proven to be significantly useful in the treatment of a variety of illnesses. Cancers, parasitic infections and crystal deposition disorders are all effectively treated by microtubule targeted medications.

Source: Johannsen, E. MD. Pharmcards. 2nd Ed. LW&W. 2002.