•  
  • History
  • Mission
  • Financial Information
•  
  • Join
  • Donate
  • Shop
  • Renew Membership
  • Estate Planning
•  

Animals in Scientific Research

Drug Development & Testing

One of the most commonly asked questions we receive is: “Would you take a drug that had never been tested on animals?”

Let’s examine some of the facts surrounding drug testing in animals and see if we can answer that question.

Medications are life-saving BUT:[1]

1. ADRs (adverse drug reactions) are the fourth leading cause of death
2. 15% of hospital admissions are caused by ADRs
1. 6.7% hospitalized patients suffer severe ADRs
3. Legal drugs kill approximately 100,000/yr. (More than all illegal drugs combined.)
4. ADRs cost the general public over $136 (US) billion in health care expenses
5. Most drugs are effective in 30-60% of patients
1. Some suffer severe side effects
2. In others, the drugs simply are not effective
6. It costs $802 million to bring a drug to market
1. 1 in 5000 drugs that pass animal tests make it to patients and it takes 15-20 years to get a drug to patients [1]
   

Drugs are, theoretically, supposed to hone in on a specific single target/molecule and leave all other targets alone. The problem is that often this is truer in theory than practice.

How often has your attention been grabbed by headlines that screamed: “Cancer Cured”, only to read on and find that the alleged cure had been wrought in nude mice? What happens to all these “cures”? The mythical land of animal-based-breakthroughs just doesn’t seem to exist. In light of the below, this should not come as a surprise.

Animals are used in drug development for basically two purposes: to determine if they are safe, and to determine if they are efficacious. Animal models fail on both accounts. As we will see, even members of the same species respond differently to the same drug and disease.

Good Drug / Bad Drug

What is it that makes a drug good and what makes it bad? RotaShield was a vaccine against rotavirus, a virus that causes roughly half million deaths per year. But one child out of 2500 children in the US suffered the side effect of intussusception (a potentially lethal bowel condition).

Worldwide, one child out of 200 children die from rotavirus so the risk benefit ratio was very favorable for children other than those in the US. But because the drug was not cost effective (since it could not be sold in the US) it was discontinued. Millions of children worldwide died as a result of not having the vaccine available.

Troglitazone (Rezulin) was very effective for many in controlling diabetes. But in others it caused liver failure. 

Thalidomide caused birth defects in thousands, but today is used as a cancer treatment for some.

Aspirin causes life threatening allergic reactions in some but for most is an excellent anti-inflammatory drug.

Penicillin likewise causes life threatening allergic reaction in some but has saved millions of lives.

Cisapride (Propulsid) was an effective drug for gastrointestinal disorders but caused some to suffer heart rhythm abnormalities leading to death.

Allen Roses, worldwide vice-president of genetics at GlaxoSmithKline (GSK), said fewer than half of the patients prescribed some of the most expensive drugs derived any benefit from them. "The vast majority of drugs - more than 90% - only work in 30 or 50% of the people." Most drugs had an efficacy rate of 50% or lower.[2]

Everything, including water and oxygen, is good for you provided it is given in the proper dose at the proper time. In the 16^th century Paracelsus said: “The dose determines the poison.” The same is true today. But today we should add a corollary: The genetic makeup also determines the poison.

Hopefully the above gives us a hint as to why experiments on animals do not make our drug supply safer or help us find cures for diseases such as cancer, AIDS, and stroke.

To further illustrate how small genetic differences can have a major impact on disease consider the following differences between individuals of different sex or race: Black women have a 50% higher incidence of breast cancer prior to age 35 than White women. They also have a greater probability of developing aggressive tumors and have the highest incidence of pre-menopausal cancer.

An article published in The New England Journal of Medicine in May 2001 revealed that Black people did not respond as well to medications known as ACE-inhibitors, medications routinely used to treat heart failure. One theory as to why this is the case is that Blacks have less nitric oxide, a chemical important in how ACE-inhibitors work. This theory led to the development of a medication named BiDil, a heart drug that increases the amount of nitric oxide. It appears to work very well in Blacks, but when given to Whites it worked no better than a placebo, as would be expected if Whites already had adequate amounts of nitric oxide.[3]

By examining the records of 786 patients, and then another 1,093 women and 1,355 men, scientists found that women treated with 5-FU-based chemotherapy for colorectal cancer, had more severe stomatitis and leukopenia compared with men.[4] There is more evidence that men and women do not react exactly the same way to medications.

Among 10 medications withdrawn from the US market between 1998 and 2001, eight were withdrawn secondary to side effects that occurred primarily in women.[5]

If humans differ so much between groups such as race or sex, how can we possibly expect animals of a different species to predict disease or drug response?

How Drugs Are Tested

Illustration

_______________________________________

[1] Nature Reviews Drug Discovery 2002;1:929