Medicines and Drowsiness
There are some medicines that you can buy over-the-counter
(OTC) from your pharmacy or a supermarket that
have the potential to cause drowsiness. This includes
medicines that you might take for:
- Allergies such as hayfever
- Anti-nausea treatments
- Medicines for gastrointestinal upsets
It is vital that
you read the instructions before taking
any medicine; this includes the leaflet
inside the box as well as the information
on the outside of the packaging.
If you are taking medication that can
cause drowsiness you should not drive
or operate machinery.
If you have any queries or are unsure
you should ask your pharmacist before
taking any medicine.
Different substances affect people differently
so something that might not cause you drowsiness
could affect another person.
Predominantly it is antihistamines that can cause
drowsiness. Among these there are two main types;
the first generation that lead to most drowsiness
and the second generation antihistamines that
have less potential to cause sleepiness.
Other substances that have been reported to have
the potential to cause drowsiness include hyoscine that is used
for travel sickness.
This group of antihistamines, which have been
in use for longer, is well known to have the potential
to cause sleepiness.
Below is a list first generation antihistamines,
known to cause sleepiness, which are ingredients
in some OTC medicines such as allergy treatments,
anti-nausea medicines, cough
and decongestant treatments.
Make sure you check with your pharmacist before
taking any OTC medicine whether it could make
you sleepy. If so you should not drive or operate
This group of antihistamines is more recent –
they were mainly developed as alternatives that
would cause less drowsiness than first generation
Four antihistamines in this group are available
to the public as ingredients in OTC medicines.
Some people will however still experience drowsiness
when using this group of antihistamines so should
still be aware that they could do so. You should
therefore not drive or operate machinery when
taking OTC medicines with these ingredients.
These antihistamines that are featured in some
OTC medicines include:
- Levocabastine (Only present in nasal spray
or eye drop formats. Faint possibility of drowsiness
if both used together, but nasal sprays and
eye drops containing this ingredient should
only be used together under medical supervision.)
Muscarinic receptors can regulate gut motility.
One muscarinic antagonist is available over-the-counter.
This is hyoscine and it is featured in products
for the treatment of motion sickness and in painkillers
for stomach pain. It can cause drowsiness and
you should not drive or operate machinery if you
are taking a medicine featuring this ingredient.
Taking more than one OTC medicine at the
same time can cause side effects and you
should consult your pharmacist before
Sedative effects can be heightened by
drinking alcohol so if you are on OTC
medicines avoid alcohol – if you
do drink be aware that you may experience
is a directory of medicines and food supplements
that are available 'over the counter' (OTC) from
your pharmacist. The links below will take you
to pages detailing products which may help treat
or relieve the following symptoms:
Direct and NHS 24 (in Scotland) - The gateway to health information
on the internet. Contains a list of information on health, including
features, healthy living, healthcare guide, conditions
and treatments and frequently asked questions.