Safety first

Before being used in humans, drugs undergo rigorous safety testing

It typically takes more than a decade for a new drug to go from initial research to use in the clinic. During this time, companies have to show that their drug actually does something beneficial and that it is safe.

There are a host of regulatory processes that have been set up to ensure these criteria are met before a drug is made available. They are designed to protect the public from harmful drugs and modern-day snake-oil salesmen. But no drug is entirely without side-effects, and medicines can themselves be a source of ill health.

While companies developing conventional medicines spend millions proving that their products work, there is no such regulation of complementary and alternative products (although various moves are being made to enhance quality control, which could help overcome the risk of contamination and batch-to-batch variation).

Snake-oil salesmen sold cure-all potions in the Wild West. The term is now used for anyone selling dubious medicines.

Use of animals in safety testing

The use of animals in safety testing is a key stage in drug development.

In 1937, US company S. E. Massengill used diethylene glycol, a sweet-tasting chemical, to prepare a new sulfa drug in syrup form. The sweet preparation had a sour aftertaste – more than 100 people, mostly children, died after taking it.

Although Massengill’s chemists studied the appearance, flavour and smell of their ‘elixir of sulfanilamide’, they did not test its toxicity; unfortunately, diethylene glycol is a poison. And although the thalidomide case is sometimes used as an argument against animal testing – it was shown to be safe in animals – in fact, the reverse is true. Despite being marketed as a remedy for morning sickness, it was never tested on pregnant animals to see whether it affected the fetus.

Both these cases led to a tightening up of drug-testing regulation. Animal testing determines whether the drug is non-toxic and whether it is absorbed by the blood, goes to the right part of the body, works effectively and is properly excreted. It can also reveal how it is metabolised – a single chemical may be converted into tens or even hundreds of metabolites in the body. Crucially, animal tests lessen the risk to human volunteers, the next stage in the drug development process.

Although there are alternatives that can substitute for some aspects of safety testing, nothing can yet model the complexity of a living organism.

So does animal testing perfectly predict what happens in people? No. Some drugs went through an animal screening stage yet still turned out to be toxic in humans. This is hardly surprising – rodents are similar to humans but obviously not identical. It is a question of reducing risk. The risk remains too high to leap from test-tube to human without the use of animal models.

Lead image:

Novartis AG/Flickr CC BY NC ND

About this resource

This resource was first published in ‘Drug Development’ in January 2008 and reviewed and updated in August 2014.

Drug Development
Education levels:
16–19, Continuing professional development