Thalidomide: From wonder drug to medical disaster.

24/02/2021

The tragic story of thalidomide is one of the most infamous cases of an apparent wonder drug turned medical disaster, the devastating consequences of which are still present today.

Where did thalidomide come from?

The drug was first released in 1957 by German pharmaceutical company Chemie Grünenthal, and marketed as a non-barbiturate, over-the-counter sedative. Soon after its release, it was found to be effective in treating colds, flu, nausea and morning sickness in pregnant women. This gave thalidomide its reputation as a ‘wonder drug’ and resulted in its increased popularity and widespread use.

Little did the physicians of the time know that prescribing thalidomide to pregnant women would result in one of the biggest medical disasters in modern history. Over 10,000 babies born to mothers who had used the drug experienced a range of severe health effects. In addition, a large number of miscarriages are also believed to have been caused by the drug.

How did this happen?

Modern drugs are subjected to multiple levels of drug testing in animal and clinical trials before they are approved for human use, but this kind of rigorous drug testing did not occur in the mid-twentieth century.

As a result, thalidomide was approved for use based largely on the results of one major test—the LD50 test (the lethal dose 50 test)—which measures toxicity. More specifically, it measures how quickly a substance will kill a group of 60–100 animals. Scientists found that it was almost impossible to give animals a lethal dose of the thalidomide, and as such, thalidomide was deemed safe for use across a range of demographics, including pregnant women. This tragic generalisation was made despite the absence of any specific tests on this particular group of people.

Dr Frances Oldham Kelsey, the FDA pharmacologist responsible for approving drug licenses in the USA, rejected the request for use and distribution of thalidomide across the US. She had concerns regarding reports of the peripheral neuropathy in those taking the drug, as well as its potential effects on the foetus given the lack of testing. Due to Dr Kelsey’s decision, the US was not directly involved in the thalidomide crisis.

In 1962, the Drug Efficacy Amendment was introduced to the FDA. This amendment requires drug companies to provide evidence that their drug is effective and safe before approval, and that drug advertising discloses all side effects.

Thalidomide is classed a teratogen and causes birth defects when taken by pregnant women.

What are the effects of thalidomide on the body?

Thalidomide affects multiple parts of the body, including the limbs, sight, hearing, internal organs and the brain.

A hallmark of thalidomide is upper limb phocomelia which is characterised by improper development of the long bones in the limbs. As a result, hands may be attached directly to the shoulders and feet to the pelvis. Fingers may also be missing or fused together.

Other health effects include the absence or malformation of the external ear, which can result in deafness or impaired hearing. Thalidomide-induced effects on the eye include small-sized eyes, absence of an eyeball and poor vision.

Is it ever safe to administer thalidomide to pregnant women?

Initially, the drug was believed to be harmful to the embryo only if taken 20 to 37 days after conception. It was considered safe when taken before or after this period. However, subsequent studies found that early exposure in rats induced miscarriage and late exposure led to brain damage. Hence, despite earlier evidence, there is no safe period to take the drug when pregnant.

Stopping the use of thalidomide

Since thalidomide had such a wide variety of effects on people, it took doctors, researchers and other medical professionals many years to find the connection between all these effects and the drug itself.

Due to widespread use of the drug—it was sold in 46 countries, under at least 37 different trade names—it took five years to match up the seemingly unrelated symptoms to a single cause.

Once the devastating side effects were revealed, thalidomide was pulled from German shelves in 1961 and soon after that the UK followed suit. Unfortunately, the drug remained in medicine cabinets across the world under its various trade names for many years.

Thalidomide was sold under various trade names, including Kevadon, Contergan and Thalomid.

What is thalidomide used for today?

Despite its controversial past, thalidomide is still used today—albeit not for the same reason or in the same way that it was once used.

Today, the drug is used to treat two major medical issues: leprosy and multiple myeloma, a type of blood cancer. Its anti-inflammatory properties make it suitable for the treatment of skin lesions created by leprosy. Its anti-angiogenic properties make it effective in preventing the growth and metastasis of cancerous tumours.

If a doctor decides that thalidomide is the right course of medication, patients receive an information pack and are required to sign a consent form agreeing to the terms of taking the drug. If a woman is taking the drug, she is required to use two forms of contraception and have regular pregnancy tests. If a man is taking thalidomide, he must wear a condom during sex.

The discontinuation of thalidomide due to its effects on pregnant women has sadly not put an end to babies being born with thalidomide-related health issues. In Brazil, where the drug is used to treat leprosy, as many as 1,000 people have been born with thalidomide syndrome since the drug was withdrawn from use among pregnant women in the 1960s.

According to Claudia Marques Maximino, President of the Brazilian Association of Thalidomide Syndrome Victims (ABPST), this is mostly due to illiteracy and lack of education. A drawing of a pregnant woman with a cross over it appears on the drug containers as a warning not to take thalidomide if pregnant. Unfortunately, some people misinterpreted this image to mean that the drug aided abortion. These people took the drug during pregnancy, hoping that it would induce miscarriage and this resulted in the thalidomide-effected births continuing in Brazil.

The thalidomide story is not a new one, and 63 years after the fact, it still serves as a devastating reminder of the importance of accurate and thorough drug testing.

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