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Why Do Drugs Cause SIDE EFFECTS?

Updated on February 28, 2015

WARNING, reading this may cause...

  • Itchy, watery, burning, stinging eyes
  • Headache or migraine
  • Constipation
  • Diarrhea
  • Blurry vision or blindness
  • Dry Mouth
  • Nausea, vomiting
  • Ringing in the Ears
  • Weight gain or weight loss...but probably weight gain
  • Hair Loss or growth, whichever you think is worse
  • Gum Disease
  • Bad breath
  • Irreversible discoloration of the fingernails
  • A compulsion to curl up in a corner and scream for mercy
  • Generalized dysfunction of your functions
  • And, well, ummm, occasionally, death....

Does this sound familiar?

We have all heard the drug commercials. And it is not my intention to make light of what has been, for some, a very serious issue. But the list of side effects for many medications seem to reach nearly epic proportions. Why? How could ANY medicine possibly be marketed in the U.S. as SAFE that has so many possible side effects? Why do drugs cause side effects anyway?

Like Huey Lewis & the News, we all "want a new drug!"

This article is intended to be a brief explanation of WHY medications, intended for our benefit, also tend to cause so many side effects.

Is it ONLY prescription drugs that cause side effects?

First, let's make this clear: all drugs can cause side effects. All of them. If and when a manufacturer claims their product does NOT cause side effects...all they mean is that they do not have to record or report any side effects. That is all. Take any substance on the planet and give it to 500 people with a list of possible "side effects" for them to think about...and you know what will happen. Nearly everyone will find at least 1 side effect they think the substance caused. Some people will check every box on the list.

So, while I am not trying to minimize the seriousness of side effects, as patients we need to be aware of the truth about side effect reporting. Prescription drugs are held to a different standard. Vitamins, supplements, many OTC (over the counter) products, virtually any medicine you can order online or via an "1-800" not need to tell you about side effects. They don't research them. They don't record them. They don't report them.

Even placebos - pills that have NO active ingredients in them - can cause side effects. Because a "side effect" is ANYTHING a person says that they have experienced. Anything. Side effects do not HAVE to have any scientific explanation or rational relationship to the drug. A side effect is whatever you say or feel you have experienced as a result of the treatment. This is why the list of side effects reported by prescription manufacturers often seems longer than an Ayn Rand novel. They are required to collect such data, and are required to report it.

Why Side Effects?

There are chiefly 4 reasons why medications cause side effects:

1) Lack of specificity. The more specifically a drug can target a particular receptor or organ or pathogen or cell the fewer side effects (typically) we tend to experience. But developing drugs that have the capacity to target just 1 receptor (for example) and no others, is quite a challenge. For example, early in the development of a class of drugs known as "beta blockers" we discovered "propranolol." Now, propranolol was a great drug. It interacted with "Beta-1" receptors in the heart and vascular system, greatly reducing blood pressure and palpitations. The problem is that propranolol ALSO happened to interfere with "Beta-2" receptors which tended to cause difficulties in breathing, particularly for those with asthma. Not good. Over time, thankfully, we have developed better beta-blockers which are more specifically designed to target just Beta-1.

2) Shared Pathways. Sometimes a drug can be very specific, but the problem is that a particular cell or receptor might be involved in more than 1 process in our body. For example, we often have to warn patients about the possibility of constipation when taking narcotic pain relievers. Most narcotics target the "mu" receptors in our central nervous system to reduce pain. However, mu receptors are also located in our intestinal tract, and the result is a slowing down of our intestinal motility, leading to constipation. Bummer. Those on chronic pain reliever therapy must often use stool softeners and/or laxatives to aid in the process of normal bowel movements.

3) The Placebo Effect: It is well documented that we can often make ourselves believe we have experienced a side effect, simply because we have thought about it or anticipated it. If I tell you a drug may cause headaches...guess what...better take home some Tylenol too. A headache is more likely to occur. Scientifically, this has been called the "expectancy theory."

4) Unknown: Maybe it isn't fair to call the "unknown" a specific category of reasons for the side effects of medications. However, this is so often the case that it demands some recognition. For example, a Mayo Clinic study seems to show some correlation between a particular drug used to treat Parkinson's Disease, known as pramipexole, and compulsive gambling. Somehow, individuals not previously addicted to gambling, found the impulse to gamble almost uncontrollable while taking this drug. Why? No one knows. And it is so rare, that we probably never will (at least in my lifetime).


Someone once said "Most men die of their remedies, rather than their maladies." Maybe, given the long list of side effects from drugs these days, they weren't too far off.

I remember a cartoon of a doctor talking to a patient. The doctor said "Don't worry, once the side effects of this drug kick won't even remember what was originally wrong with you!"

I realise that for many people, the side effects of drugs are no laughing matter. However, the fact is, side effects are still only a problem in a minority of cases. The uniqueness of each individual person, and our conditions, makes it difficult to predict which (if any) side effect you might experience. However, just remember, the fact that a treatment claims to have "no side effects" is simply untrue and unfair. All treatments, even non-treatments (like placebos) cause side effects. It just depends who you ask....



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    • hscchemistry profile image

      hscchemistry 5 years ago from Sydney, Australia

      Nice hub on drugs and their side effects - I do approve of this :D

    • TahoeDoc profile image

      TahoeDoc 5 years ago from Lake Tahoe, California

      Excellent and insightful. Love to see reliable, useful medical information on the Internet!

    • writer20 profile image

      Joyce Haragsim 5 years ago from Southern Nevada

      I take a beta blocker and quiet a number of R/A drugs.

      Voted up and interesting.