Managing Common Drug Side Effects

Medically reviewed by Carmen Pope, BPharm. Last updated on Nov 23, 2020.

Overview

Every drug has side effects. How vulnerable you are to these side effects depends on many different factors, which can be generally grouped as patient-related, drug-related, and environmentally or socially-related. Find out if you have any characteristics that will increase your susceptibility to drug-related reactions, and what you can do to manage some of these possible side effects.

Risk of Developing Side Effects

Every one of us is unique. However, certain individual factors make some of us more likely to develop side effects than others.

The most significant of these factors is age. The very young and the very old are ALWAYS more susceptible to unwanted reactions.

Children are not small adults. The way their bodies absorb metabolize and eliminate drugs differs from adults, and this is especially true in babies. Younger children tend to absorb medicine more slowly from the stomach but have faster intramuscular (IM) absorption rates. In early life, they have a higher body water to lipid ratio and a larger liver to bodyweight ratio. Liver enzymes are immature as is their kidney function. In addition, the permeability of their blood-brain barrier (the layer of cells that restricts the passage of substances from the bloodstream to the brain) is higher.

Older adults typically take more medicines and studies have shown they are twice as likely to go to ED because of an adverse drug event and seven times more likely to be hospitalized. They are more likely to be on medicines with a narrow margin between being effective or toxic such as warfarin, insulin, digoxin, and anti-seizure medications. Their bodies tend to have more fat and less water which may increase the duration of effect of certain drugs. In addition, metabolism in the liver and excretion through the kidneys is typically reduced. Their brains are also more sensitive to the sedating effects of drugs, and pre-existing problems, such as dizziness, eye, and ear problems, may be exacerbated increasing the risk of falls.

Individual Factors That Also Increase Risk

Several other factors also play a significant role in the likelihood of side effects. Some notable examples include:

Genetics: Pharmacogenetics is the name given to the study of how your genes influence your reaction to drugs and genetic factors account for 20-95% of patient variability. This field of pharmacology is rapidly evolving and testing for liver enzyme variations becoming more widespread. For example, codeine requires metabolism through CYP2D6 for conversion to one of its active metabolites, morphine. 5-10% of people are poor metabolizers - which means that in these people, very little codeine is converted to morphine which results in insufficient pain relief. However, 1-2% of people are ultra-rapid metabolizers and more codeine is converted into morphine than normal, resulting in a higher risk of toxic reactions including respiratory depression.
Kidney function If your kidneys are not functioning at full capacity, then side effects are more likely if you are taking drugs that are excreted through the kidneys. Some other drugs may lose their effectiveness when kidney function is reduced.
Gender: Females have a lower activity of certain hepatic enzymes, a higher body fat to water ratio, and a decreased clearance of drugs through the kidneys than men. Studies have shown the incidence of drug-induced liver toxicity, gastrointestinal side effects, allergic skin reactions, and long QT syndrome is higher in females.

Drug-Related Factors

Drug-related influences include:

The dose of the drug: The higher the dosage the greater the risk of side effects
The formulation used: For example, inhaled steroids directly target the lungs and produce fewer side effects than oral steroids that have more of a body-wide effect
How the drug is absorbed, metabolized, distributed, and eliminated
Other medicines that are being taken at the same time.

Environmentally or Socially Related Influences

Environmentally or socially-related influences include:

Level of alcohol intake: Alcohol can intensify some side effects such as drowsiness, confusion, changes in blood pressure, abnormal behavior, respiratory depression, and nausea and vomiting
Smoking: The hepatic enzymes CYP 1A2 and 2B6 are induced by cigarette smoking. These enzymes metabolize several clinically important drugs (such as clozapine, olanzapine, and methadone), which means an abrupt cessation of smoking can increase blood levels of these drugs. Nicotine replacement therapy does not influence enzyme activity
Diet: Several medicines interact with foods. For example; atorvastatin with grapefruit, green leafy vegetables and warfarin, natural black licorice and lithium, salt and potassium supplements and ACE inhibitors, and tyramine-containing foods and MAOI antidepressants
Level of hydration: Dehydration can increase the risk of side effects of some medicines. Some medicines that shouldn't be taken by a person who is dehydrated include ACE inhibitors, NSAIDs, metformin, and diuretics
Level of understanding about a medicine: Side effects are more likely if instructions are not clear, or a person is confused as to why they are taking a medicine; both of which may result in a wrong dosage being taken.

List of Common Drug Side Effects

The following table lists some of the more commonly encountered drug-related side effects and suggestions for their management.

Allergic Reactions

Potentially could occur with any medication. Symptoms range from a mild rash to a severe anaphylactic reaction (including facial and throat swelling, difficulty breathing and a widespread rash).