Drug interactions occur when one drug in the body affects another drug that a
person is taking. The interaction can take many forms, and may be helpful or
harmful. Drugs that are known to interact are sometimes given together in order
to have a positive effect.
What is the information for this topic?
Drug interactions can cause serious problems. The more drugs a person takes,
the more likely a drug interaction is. Drug interactions can occur with many
types of substances. These include prescription medications, over-the-counter
medications, herbal remedies, and
vitamins. Homeopathic remedies and recreational drugs, such as
alcohol, tobacco, and illegal drugs, can also interact.
Effects of drug interactions
Drug interactions can happen in the following ways:
Drug A increases the effect of drug B. This can make drug B more likely to
cause side effects or toxic effects. For example, ketoconazole, a medication
used to treat fungal infections, can increase the levels of a blood-thinning
medication called warfarin.
Drug A decreases the effect of drug B. This may make drug B less effective
or even ineffective. For example, an antibiotic called rifampin can cause birth control pills to be broken down
too quickly. A woman taking both of these medications risks becoming
Drug A and drug B have additive effects, which can be helpful or harmful.
For example, both aspirin and warfarin thin the blood. In
some situations, taking both medications may be beneficial. But in other cases,
it may lead to an increased risk of serious bleeding.
Drug A and drug B have opposite effects. This may cause an unpredictable
response. For example, people on medication to control high blood pressure must be
careful if they take ephedrine for nasal congestion because it
can raise blood pressure.
How drugs interact
There are several ways in which drug interactions can take place. Drug A might
interfere with the way drug B is absorbed into the bloodstream through the
gut. Or drug A might block the metabolism, or the breakdown, of drug B by the
liver. Drug A might block drug B from being eliminated from the urine. Drugs
can also interact at the cell level. For example, one drug may push the other
drug off the cell and make it less effective. There are a number of other kinds
When a new medication is prescribed, a person should tell his or her
healthcare provider what other drugs he or she is taking. To avoid serious
drug interactions, it's important to
mention medications that have been prescribed by other healthcare providers.
A person cannot afford to be quiet
about taking birth control pills,
over-the-counter medications, herbal
remedies and complementary therapies, or illegal drugs. All drugs and
substances are important to mention.
The American Society of Anesthesiologists recently issued a warning about the
potential side effects and interactions of herbal remedies with medications used before,
during, and after surgery. The group recommends discontinuing all
herbal supplements at least two weeks before planned surgery.
An individual who takes over-the-counter medications should read the warning
labels on the package. Sometimes, important drug interactions are listed
on the box. Those who take prescription medications should ask their healthcare
providers before taking new medications or herbal remedies. A pharmacist can be consulted when buying
over-the-counter medications to be sure that they do not interact with
A good way to help reduce the risk of drug interactions is to get all
prescriptions filled at the same pharmacy. That way the pharmacist will have a
complete record of all the medications the person is taking. The pharmacist can
make sure there are no potentially dangerous interactions. This is especially
important for people who are treated by more than one healthcare provider.
There are hundreds of possible drug interactions. The list grows longer every
year. It's wise to check for possible drug interactions before any new
substance is taken.