Adverse drug reactions (adverse effects) are any unwanted effects of a drug. There is no universal scale for describing or measuring the severity of an adverse drug reaction. Assessment is largely subjective. Reactions can be described as
Mild or moderate adverse drug reactions do not necessarily mean that people must stop taking a drug, especially if no suitable alternative is available. However, doctors are likely to reevaluate the dose, frequency of use (number of doses a day), and timing of doses (for example, before or after meals; in the morning or at bedtime). Other drugs may be used to control the adverse drug reaction (for example, a stool softener to relieve constipation).
Mild adverse drug reactions
Moderate adverse drug reactions
Moderate reactions include
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Rashes (especially if they are extensive and persistent)
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Visual disturbances (especially in people who wear corrective lenses)
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Muscle tremor
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Difficulty with urination (a common effect of many drugs in older men)
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Any perceptible change in mood or mental function
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Certain changes in blood components, such as a temporary, reversible decrease in the white blood cell count or in blood levels of some substances, such as glucose
Also, reactions that are usually described as mild are considered moderate if the person experiencing them considers them distinctly annoying, distressing, or intolerable.
Severe adverse drug reactions
Severe reactions include those that may be life threatening (such as liver failure, abnormal heart rhythms, certain types of allergic reactions), those that result in persistent or significant disability or hospitalization, and those that cause birth defects. Severe reactions are relatively rare. People who develop a severe reaction usually must stop using the drug and must be treated. However, doctors must sometimes continue giving high-risk drugs (for example, chemotherapy to people with cancer or immunosuppressants to people undergoing organ transplantation). Doctors use every possible means to control a severe adverse drug reaction.
Lethal adverse drug reactions
Lethal reactions are those in which a drug reaction directly or indirectly caused death. These reactions are typically severe reactions that were not detected in time or did not respond to treatment. Lethal reactions can be the reasons that some drugs are withdrawn from the market (such as troglitazone and terfenadine).
More Information
The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
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American Association of Poison Control Centers: Access to information on a variety of poisons, an emergency helpline (1-800-222-1222), and tips on prevention.
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FDA Adverse Event Reporting System: Access to Questions and Answers on FDA's Adverse Event Reporting System (FAERS).
