What Is Thalidomide?

Thalidomide is a medication perhaps best known for causing birth defects. In the middle of the twentieth century it was commonly given to pregnant women as a treatment for morning sickness. When many babies were born with a congenital defect called phocomelia, the drug was withdrawn from the market. Due to the tragic consequences of this medication, many countries adopted stricter drug testing requirements. Over the years researchers have found new applications of thalidomide, using it as a cancer treatment or as a therapy for leprosy.

The mechanism of action of thalidomide is to work as an anti-angiogenic agent, meaning that it serves to inhibit the growth and development of new blood vessels. It also has activity as an immunomodulator, modifying the activity of the body’s immune system. In addition, the medication alters levels of various neurotransmitters in the brain, resulting in sedation.

The discovery of thalidomide dates to the early twentieth century. Researchers noted its ability to decrease nausea, relieve pain, cause sedation, and alleviate headaches. These early investigators considered the drug to be safe for administration to all people. Due to its perceived safety and its efficacy in relieving symptoms of morning sickness and insomnia, many pregnant women were given the medication during the 1950s and early 1960s.

Unfortunately, an adverse effect of the medication was soon discovered. A significant percent of pregnant women who took the medication gave birth to babies with phocomelia, which is a condition characterized by underdeveloped limbs, decreased intelligence, and absent pelvic bones. The development of these birth defects shocked the public, and led to the adoption of stricter drug regulation policies in many countries throughout the world.

Although the use of thalidomide has a tragic history, the drug has found new applications over the years. Researchers have utilized the drug's anti-angiogenic properties in treating conditions such as multiple myeloma. Patients affected with a certain type of leprosy, known as erythema nodosum leprosum, often benefit from taking the medication. Researchers have investigated using the medication in conditions including chronic graft-versus-host-disease, Crohn's disease, and chronic lymphocytic leukemia. Today, the drug is marketed under the brand name Thalidomid® when used to treat these conditions.

Common side effects of thalidomide include sedation, fatigue, constipation, and weakness. Patients taking the medication have an increased risk of developing blood clots. Due to the infamous adverse effect of causing birth defects, prescription of the medication is carefully regulated by many countries. In the US, patients given the medication must be educated on the risks and benefits of the therapy. Reproductive-age women on the medication must be on a fail-safe method of birth control and obtain regular pregnancy tests.