Why can’t pharmaceutical companies produce drugs without side-effects?
Alida Bedford from Hampshire (Age: 55+)
Filed under: Al Cowell's Big Answers, Alan Morris' Big Answers, Andrew Chaytor's Big Answers, Answered Big Questions, Biology Big Questions, Carston Timmermann's Big Answers, Disease Big Questions, Medical Big Questions, age 55+
Most biological processes (including those in the human body) are fairly complex, with many different sub-processes that are closely interconnected. If we interfere at one point, for example by taking a drug, we change the equilibrium of the whole system and trigger a whole series of effects. Some of these may be desired, others may be considered side effects. But new ‘main’ effects of a drug sometimes emerge over time. At some point we observe that one of the effects which we used to view as side effects, may actually be quite useful. The older a drug, the more effects will become known. An example is aspirin, which as a side effect dilutes our blood and can be taken to prevent strokes and heart attacks.
All effective drugs have powerful biological effects and very often will have multiple actions – said to be pleiotypic effects, because the process(es) they influence is often complex. Inevitably then there will be effects which are undesirable. All pharmaceutical companies strive like mad to produce drugs with fewer or less severe side effects.
The example quoted by Dr Timmermann is aspirin, one of a wider class of drugs described as “cox inhibitors”. The role of cox is multiple, including control of inflammation (headache, fever) but also control of bleeding: so aspirin by inhibiting it reduces inflammation – good – but may enhance bleeding – often bad, especially for those with stomach ulcers. Pharma companies have developed “selective” cox inhibitors, which reduce inflammation but do not have the undesirable action on bleeding.
Another example is ACE inhibitors used to control blood pressure: these cause dry throat and coughing, but alternative drugs have been developed called angiotensin receptor antagonist which act in a similar way but do not cause the dry throat.
Alas very often the newer drugs just have a different set of side effects! For example one of the best known – notorious- selective cox inhibitors, very effective at relieving the symptoms of rheumatoid arthritis, was withdrawn because of unacceptably deleterious effects on the heart …
A drug may be active at a number of different ‘receptor’ types located at different sites within the body. The physiological response to the drug binding at sites other that that targeted may produce unwanted physiological responses that we call side effects.
Pharmaceutical companies are striving to make their new drugs as specific as possible. One reason for them conducting Clinical Trials is to determine what adverse effects or side effects may be present.
Clinical trials gradually increase the numbers of patients ‘trying’ the medicine, but it isn’t until the drug is licened to be prescribed into the whole population that the full range of side effects may become known. This is because there is a much greater range of genetic variations of physiology in the whole population. So as long as there ar genetic differences between patients, there will be differences in physiological responses – some adverse.
A drug is but a chemical that causes a biological response or in otherwords will change how the body works. Drugs can therefore cause changes that may be beneficial or detrimental to health.
Unfortunately, the site of action and effect of a drug may not be limited to the area requiring attention as mentioned by my learned colleagues above. Another good example is the commonly prescribed beta blockers (beta-adrenoceptor blockers) which block receptors found in the heart, blood vessels, bronchi in the lungs, pancreas and liver. The same receptor (which when activated causes a response) is found in each of these different parts of the body and thus the beta blocker drug blocks the receptor and response in each of these parts of the body. So although a drug may be given for heart problems it may also have effects elsewhere which may not be of benefit eg make asthma worse in some individuals.
In general we need to consider that all drugs potentially have unwanted side effects and therefore the benefits and risks of taking any drug will always be taken into account.
The tricky bit for the Pharmaceutical companies is to find chemicals where the beneficial effects far outstrip any unwanted or adverse effects.