2.12: Clinical Trials
- Page ID
- 55703
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Results of test-tube and animal studies can be applicable to humans but, at some point, people must be tested. Such studies are usually major undertakings, very expensive, and take place only after the product or procedure has been tested for safety and effectiveness in test‑tube experiments and animal studies.
When heart disease was linked to high blood cholesterol, research focused on two questions: (1) Can high blood-cholesterol cause heart disease? (2) If healthy people lower their blood-cholesterol, will they lower their risk of heart disease? There’s now solid evidence that high blood-cholesterol can directly cause heart disease.
The question of whether heart disease could be prevented by lowering blood-cholesterol was harder to answer because it required clinical trials—also called intervention trials because researchers intervene to lower blood-cholesterol by diet, drugs, etc. Many clinical trials have shown that middle-aged people with high blood-cholesterol lower their risk of heart disease by lowering their blood-cholesterol. A nationwide goal has been to improve our diet and to identify and treat people with high blood-cholesterol before they show signs of heart disease.
Before a drug is submitted for approval, the Food and Drug Administration requires that clinical trials be undertaken in phases. In Phase I, the drug is tested for safety in a small group of people. In Phase II, the drug is tested for effectiveness in a larger group. In Phase III, the drug is tested for safety and effectiveness in a much larger group. Stock prices of drug companies often reflect how upcoming drugs are progressing in clinical trials. Information about current clinical trials can be found at clinicaltrials.gov
Some drugs that appear safe in clinical trials are later withdrawn because of unanticipated side effects. As in the aspirin study, drugs typically are tested on a very select group of subjects. When a drug is used in the general population, it’s used by many more people who vary much more in their state of health, reliability, etc. In “real life,” people forget to take a pill and take a double dose the next time, or take it with a variety of other pills and supplements. Also, the much larger group provides the statistical power to detect side effects that were undetectable in the smaller clinical trials.
One clinical trial with a completely unexpected result was to see if beta-carotene pills lowered the risk of lung cancer in smokers. Beta-carotene was expected to protect against cancer (it’s an antioxidant, and higher blood levels were linked to less cancer). The Finnish trial included more than 29,000 male smokers. The group taking the betacarotene got more lung cancer!
This shocking result was first thought to be a “fluke,” but a U.S. study published soon after of more than 18,000 male and female smokers, former smokers, or workers exposed to asbestors confirmed this finding. Taking beta-carotene as a dietary supplement isn’t the same as getting betacarotene in the fruits and vegetables associated with lower cancer rates.