What Are Side Effects (Adverse Effects)? What Causes Side Effects?

Editor's Choice
Main Category: Public Health
Also Included In: Pharmacy / Pharmacist
Article Date: 28 Jul 2010 - 9:00 PST

email to a friend   printer friendly   opinions  

A side effect, also known as an adverse effect, adverse event, or undesirable secondary effect is when a treatment goes beyond the desired effect and causes a problem; the treatment, which may be a medication, surgical procedure or some kind of therapy has an undesirable secondary effect which occurs in addition to the desired therapeutic effect.

Experts say that side effects vary for each patient, and depend largely on their general health, the state of their disease, age, weight, and gender.

With medications (drugs), if side effects do occur they will tend to do so either when the patient starts taking them, or when dosages are changed. Side effects are also more likely to occur at the end of treatment than in the middle. Doctors can sometimes help reduce the severity of side effects by reducing the drug dosage.

Some cancer treatments, such as chemotherapy or radiotherapy (or a combination of the two) can cause fatigue, nausea, vomiting, hair loss, mouth sores and a lower blood cell count - these are side effects. The aim of the therapy - its desired therapeutic effect - is to either destroy the cancer, reduce the size of the tumor, or slow its progression.

Side effects are a common cause of non-compliance (non-adherence) - when the patient stops following the doctor's instructions. They might not continue taking a medication when they should, or discontinue a specific exercise to strengthen a limb because the activity resulted in pain.

The term undesirable side effect is more specific than side effect. For example - imagine a fictitious drug for elderly people for the treatment of insomnia which also improved the eyesight of 3% of those who took it; this could be classed as a side effect, even though whoever experienced improved eyesight would not complain about it. However, the term side effect is mainly used with a negative meaning. For it to have a positive meaning, the speaker would have to explain what the benefit was - if they didn't, the listener would most likely imagine undesirable things.

The terms adverse effects, adverse events or undesirable side effects are unambiguous.

When a medication is approved and goes on the market, the drug manufacturer has to list all its known side effects. In most countries, side effects have to be reported, investigated in human trials (clinical trials) and included into the patient information that accompany drugs and medical devices that are sold to the public.

Iatrogenesis - adverse events may sometimes be referred to as iatrogenic. This means they were generated by a physician or treatment; adverse events or complications resulting from medical treatment or advice. The adverse event could have been caused by actions by health care professionals as well as providers of complementary and alternative medicine.

A distinction is made between AEs (adverse events) and SAEs (serious adverse events) in clinical trials. SAEs are adverse events such as death, birth defects, complications that require hospitalization, or permanent damage.

A complication - in medicine this is an unfavorable development of a disease/condition, or a medical treatment. It has a similar meaning to side effect when referring to surgery and some other therapies. But a complication can also be the result of not receiving treatment. For example, a complication of untreated hypertension (high blood pressure) can be heart attack or stroke. In this case, it is not a side effect. Put simply, a complication can mean an undesirable side effect, but only sometimes.

Adverse events (complications) from surgery

The most common complications from surgery include:

• Cardiovascular risks
• Changes in local blood flow
• Constipation
• DVT (deep vein thrombosis) and pulmonary embolism
• Erectile dysfunction (e.g. after a prostatectomy, when the prostate gland is removed)
• Hemorrhage (bleeding)
• Infection
• Inflammation
• Loss of function
• Nerve damage
• Scarring

When a doctor recommends surgery, the possible complications have to be weighed up against the expected benefits. For example, an amputation will result in the loss of a limb; there are also the possible risks from surgery and anesthesia - however, if the patient's gangrene is advanced, the procedure will prevent a life-threatening condition; it will probably save the patient's life.

Keyhole surgery (laparoscopic surgery) has significantly reduced the likelihood of many surgery complications.

Adverse events from radiation therapy (radiotherapy)

As radiotherapy inevitably damages some healthy cells most patients will experience side effects. Their severity and duration will depend on which part of the body is targeted, the radiation dose, and the speed of recovery of the damaged cells. The intended therapeutic benefit of radiotherapy is the destruction of cancerous cells. Side effects may include:

• Fatigue - the most common symptom. If doctors determine that it is caused by anemia (lack of red blood cells) they may order a blood transfusion. Gentle exercise can sometimes help.
• Diarrhea - especially if the beams are aimed at the abdomen. Symptoms tend to appear a few days after the start of treatment, and will go away a few weeks later.
• Heart disease - a risk if the beam hits the heart, as may be the case with breast cancer treatment, if the tumor is on the left side.
• Nausea - can occur at any time during treatment, or shortly afterwards.
• Muscle and joint stiffness - there may also be swelling in the affected area.
• Sore skin - patients should avoid scented soaps, scratching, and rubbing. The affected skin should be shielded from too much sunlight. In some cases there may be skin burns.
• Drop in sex drive (libido) - this may affect male or female patients if the beams are aimed at the pelvic area. Males may have erectile dysfunction if prostate cancer is being treated. Women may experience narrowing of the vagina, as well as dryness.
• Infertility - if beams are aimed at the pelvic area there is a risk of infertility or early menopause for female patients. Risk is lower for males, but still exist.
• Loss of appetite, swallowing difficulties - fatigue and nausea are usually accompanied by lack of appetite. Patients who had beams aimed at their head, neck or chest may have swallowing difficulties.
• Xerostomia (dry mouth) - especially if the beams are aimed at the head, neck or mouth.
• Alopecia - hair falls out (temporary).

Side effects from vaccinations

Side effects may be caused by the way the vaccine was biologically prepared, especially if attenuated pathogens or toxins were needed. An attenuated vaccine uses the pathogen (the germ that causes the disease), the pathogen is much less virulent, however, it is still alive.

Common vaccine side effects include:

• Fever
• A general feeling of being unwell (malaise)
• Skin reactions at the vaccination site. In rare cases there may be eczema vaccinatum, a complication experienced by patients with eczema or atopic dermatitis.

Side effects from diagnostic procedures

Diagnostic procedures may be invasive or non-invasive. There may be allergic reactions, bleeding, perforation of the intestinal wall (from a colonoscopy). There is a risk that a cancer biopsy may cause some of the cancer to break off, enabling it to spread beyond the immediate tumor area ("seeding" of the tumor).

Side effects from chemotherapy

Most people immediately link chemotherapy with uncomfortable side effects. However, side-effect management has improved considerably over the last twenty years. Many side effects that were once inevitable can be either prevented or well controlled today.

Possible side effects may include:

• Alopecia - hair loss (temporary). Some chemotherapies don't cause hair loss.
• Cognitive problems - problems with attention span, memory, comprehension, reasoning, judgment, and multitasking. Affects about 20% of patients.
• Diarrhea
• Fatigue
• Hearing impairment
• Infertility - the man's sperm may be damaged. Some women may become infertile. In most cases this is temporary
• Loss of appetite
• Low blood platelet count (thrombocytopenia) - blood clotting problems
• Low red blood cell count - anemia
• Low white blood cell count - increasing susceptibility to infections
• Moodiness
• Mucositis - inflammation of the mucous membrane
• Nausea - experienced by over half of all patients.
• Vomiting - experienced by over half of all patients.
• Reduced libido - less interest in sex.
• Skin and nails - skin may become dry and sore. Nails may become brittle and flaky.
• Constipation

Side effects from medications (drugs, medicines)

Drug side effects are closely linked to dosage, which may be altered.

Drug interaction - a side effect may also be caused by a substance which affects the activity of a drug. The substance may raise or reduce the effect of a drug - sometimes it may even cause a completely different action to occur.

Drug-drug interactions is when one drug alters the action of another drug (if the patient is taking two drugs).

Drug-food interactions occur when a particular food alters what the drug should be doing.

Drug-herb interactions refer to interactions caused by herbs.

A good doctor or pharmacist should be able to avoid unpleasant side effects caused by drug interactions.

A problem today is that some OTC (over-the-counter) medications, which are bought by lay people, may also interact with substances - the consumer, not being a health care professional, runs the risk of experiencing side effects. For example, St. John's Wort (Hypericum perforatum), an OTC medication in several countries used for the treatment of mild depression, can clash with many prescription medications.

In some developing nations where prescription drugs can be bought without prescriptions, the risk of drug-drug interactions is greater.

The most common non-severe or mild side effects from taking drugs include (there are many more, these are the most common):

• Constipation
• Dermatitis
• Diarrhea
• Dizziness
• Drowsiness
• Dry mouth
• Headache
• Insomnia
• Malaise
• Moodiness, irritability, confusion, anxiety or agitation
• Nausea
• Erectile dysfunction (some antidepressants)

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

• Additional
• References
• Citations