Just because a drug is known to have side effects doesn’t mean everyone who takes the drug will experience any or all of them. The severity of side effects may also differ from person to person. Most people, most of the time, do not have to stop taking a drug because of side effects. For most therapeutic drugs, the benefits of taking them often outweigh the possibility of unpleasant or dangerous side effects – emphasis on the word “possibility”. Commonly, side effects will end once the drug is stopped but there are sufficient examples of drugs that may cause permanent problems to warrant caution and consideration.

Side effects occur because of the molecular/chemical reactions between the drug and the body. For example, medications used to treat depression may have an effect on a particular neurotransmitter (a chemical that is released by nerve endings to communicate with other nerves) involved in depression. Because the particular neurotransmitter may be involved in neural functions other than those involved in depression, every function the neurotransmitter affects may also be modified.

The occurrence or severity of a side effect depends on individual differences in people, the dose of the drug, the presence of disease, the presence of other drugs and duration of exposure. The role of the mind is important and expectation of a drug’s effects can modify those effects. Interestingly, side effects occur in patients taking a placebo during drug trials. Such trials are carried out in the same fashion as a blind taste test.

Because body systems are so interrelated, it is very difficult to find a drug that can accurately target only one system. Natural or herbal products are no better than pharmaceuticals in this respect. Their effects will depend on how their active ingredients (which are naturally occurring chemicals) interact with the body on the molecular level. A drug produced by a plant is therefore not inherently safer or better than one produced in a laboratory.

Knowledge is required to be able to choose a drug wisely. What is the evidence that a drug will have a desired effect? What is the evidence concerning side effects? The answers to these questions are critical to the safe use of any drug.