Revised: 4 July 2013
Medicines are used for:
- controlling illness
- treating the symptoms of specific conditions (eg, pain killers)
- preventing patients becoming unwell.
All medicines can cause adverse reactions in some people. Adverse reactions can range from
headaches and upset stomach to more serious reactions such as liver or kidney injury. Some adverse
reactions can be predicted, but some adverse reactions occur unexpectedly once many people take the medicine
(eg, severe allergy). Most people take medicines without suffering any serious adverse reactions.
The best way to know what the possible adverse reactions might be is to read the
Medicine Data Sheet and/or
Consumer Medicine Information available
on the Medsafe website.
More about finding medicine
What is meant by a common or rare adverse reaction?
The chance of having an adverse reaction can be described as:
- Very common- this means that 1 in every 10 people taking the medicine are likely to have the adverse
- Common – this means that between 1 in 10 and 1 in 100 people may be affected.
- Uncommon – this means that between 1 in 100 and 1 in 1,000 people may be affected.
- Rare- means that between 1 in 1,000 and 1 in 10,000 people
may be affected
- Very rare – means that fewer than 1 in 10,000 people may be affected.
If an adverse reaction affects 1 person in every 10,000 people taking it, then 9,999 people out of 10,000
are not expected to have that adverse reaction.
How can I reduce the risk of adverse reactions?
- Always take medicines as advised by a pharmacist, doctor or
prescriber (eg, some medicines
that can cause drowsiness are best taken at night).
- If the medicine is bought always follow the directions on the package.
- Never take medicines prescribed for other people.
- Never take more medicine than recommended.
- Be careful about mixing medicines. Some medicines, including
complementary medicines and medicines bought
in a pharmacy or supermarket should not be taken together. Patients taking prescription medicines should
discuss with their pharmacist whether any medicines available over-the-counter should be avoided.
- Be careful about taking medicines with alcohol or certain foods.
- Patients should always tell their doctor if they are taking medicines bought in a pharmacy,
supermarket (including complementary medicines and food supplements).
Do adverse reactions always come on straight away?
It depends on the medicine and the person.
In general adverse reactions are most likely to happen soon after medicines are started or after
increasing the dose. Other reactions can occur after long term use; patient's doctors can monitor for these
reactions to prevent them occurring (eg, blood tests with warfarin).
Some adverse reactions will go away if the medicine is continued. However, any concerns should be
discussed with a doctor or pharmacist.
Can I report an adverse reaction?
Anyone living in New Zealand who thinks they may have experienced an adverse reaction due to a medicine
can report this to the
Centre for Adverse Reactions Monitoring (CARM).
CARM informs Medsafe of any medicine related safety issues detected.
How to report an adverse reaction
What suspected adverse reactions have been reported to CARM for my medicine(s)?
You can find information on reports of suspected adverse reactions
to medicines reported to CARM using the Suspected Medicine Adverse Reaction Search (SMARS).
Medsafe publishes communications about safety concerns through the
early warning system.
Suspected Medicine Adverse Reaction Search (SMARS)
More about the Trans-Tasman early warning system